bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of surface transition layers on the phase diagrams and the pyroelectric properties of ferroelectric thin films
Authors: Oubelkacem A. , Esssaoudi I. , Ainane A. , Saber M. , Dujardin F. , Gonzalez J. 
Published: April 2009

AbstractBy taking into account surface transition layers STLs and single surface transition layer SSLs (introduced for comparison), the phase‐transition and pyroelectric properties of ferroelectric thin films described by the transverse Ising model (TIM) are discussed in the framework of the effective‐field theory, based on the probability distribution technique. We discuss an N ‐layer film of simple cubic symmetry with nearest‐neighbor exchange interaction in which the exchange‐interaction strength is assumed to be different from the bulk values in surface layers. We derive and illustrate expressions for the phase‐transition and pyroelectric profiles. We demonstrate that the phase transition depends more strongly on intra‐layer interaction than inter‐layer interaction and the ferroelectricity of a film will disappear at a critical STL thickness if the intra‐layer and inter‐layer interactions are weak. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Release of potassium sorbate from active films of sodium alginate crosslinked with calcium chloride
Authors: Zactiti E. M. , Kieckbusch T. G. 
Published: April 2009

AbstractThe release of potassium sorbate from alginate films was evaluated considering different active agent concentrations in the film and three levels of alginate crosslinking. The mechanism involved in the diffusional process was investigated using the Power Law Model. The results indicated that potassium sorbate diffusion in alginate films has characteristics of Fickian and non‐Fickian behaviour. Effective diffusion coefficients obtained using the solution in series derived from Fick's Second Law are close to values obtained by the short‐time solution, indicating that the influence of swelling on effective diffusivity, although perceptible, is small, allowing the use of an average effective diffusivity. The values of effective diffusivity found indicate that alginate films have a potential use as systems for release of active substances. Copyright © 2009 John Wiley & Sons, Ltd.
Ensemble estimation of background‐error variances in a three‐dimensional variational data assimilation system for the global ocean
Authors: Daget N. , Weaver A. T. , Balmaseda M. A. 
Published: April 2009

AbstractThis paper studies the sensitivity of global ocean analyses to two flow‐dependent formulations of the background‐error standard deviations (σb) for temperature and salinity in a three‐dimensional variational data assimilation (3D‐Var) system. The first formulation is based on an empirical parameterization of σb in terms of the vertical gradients of the background temperature and salinity fields, while the second formulation involves a more sophisticated approach that derives σb from the spread of an ensemble of background states. The ensembles are created by explicitly perturbing both the surface fluxes (wind stress, fresh water and heat) used to force the model and the observations (temperature and salinity profiles) used in the assimilation process. The two formulations are compared in two cycled 3D‐Var experiments for the period 1993‐‐2000. In both experiments, the observation‐error standard deviations (σo) are geographically dependent and estimated from a model‐data comparison prior to assimilation. An additional 3D‐Var experiment that employs the parametrized σb but a simpler σo formulation, and a control experiment involving no data assimilation, were also conducted and used for comparison.All 3D‐Var experiments produce a significant reduction in the mean and standard deviation of the temperature and salinity innovations compared to those of the control experiment. The largest differences between the two σb formulations occur in the upper 150 m, where the parametrized σb are notably larger than the ensemble σb. In this region, the innovation statistics are slightly better for the parametrized σb. Statistical consistency checks indicate that both schemes underestimate σb, the underestimation being stronger with the ensemble formulation. The error growth between cycles, however, is much reduced with the ensemble σb, suggesting that the analyses produced with the ensemble σb are in better balance than those produced with the parametrized σb. This claim is supported by independent data comparisons involving model fields not directly constrained by the assimilated temperature and salinity profiles. In particular, sea‐surface height (SSH) anomalies in the northwest Atlantic and zonal velocities in the equatorial Pacific are clearly better with the ensemble σb than with the parametrized σb. Results also show that while some aspects of those variables are improved with data assimilation (SSH anomalies and currents in the central and eastern Pacific), other aspects are degraded (SSH anomalies in the northwest Atlantic, currents in the western Pacific). Areas for improving the ensemble method and for making better use of the ensemble information are discussed. Copyright © 2009 Royal Meteorological Society
Achieving super‐resolution X‐ray imaging with mobile C‐arm devices
Authors: Bodensteiner C. , Darolti C. , Schweikard A. 
Published: April 2009

AbstractBackgroundThe term super‐resolution refers to the process of combining a set of low‐resolution images into a high‐resolution image using image processing methods. This work is concerned with the reconstruction of high‐resolution X‐ray images. Specifically, we address the problem of acquiring X‐ray images from multiple, very close view points.MethodsWe propose to use a novel experimental robotic C‐arm device to create high‐resolution X‐ray images. For this purpose, we suggest different strategies for acquiring multiple low‐resolution images, and we provide the steps to achieve acquisition‐error compensation. Compared to visible light images, X‐ray images have the particularity that parallax effects render super‐resolution very difficult. Using the acquired multi‐frame data, we evaluate recent well‐known super‐resolution reconstruction algorithms. The same algorithms are evaluated based on synthetic 3D phantom data and real X‐ray images.ResultsIn experiments with both synthetic and real projection data, we successfully reconstruct up to four times higher‐resolution images. These images reveal structures and details which are not perceivable in the low‐resolution images.ConclusionsThe advantage of super‐resolution techniques for X‐ray is the potential reduction of radiation dose for patients and medical personnel. Potential medical applications include the diagnosis of early‐stage osteoporosis and the detection of very small calcifications. Copyright © 2009 John Wiley & Sons, Ltd.
Analytical formulation to compute QFT bounds: The envelope method
Authors: Martín‐Romero Juan José , Gil‐Martínez Montserrat , García‐Sanz Mario 
Published: April 2009

AbstractThis paper describes an analytical formulation to compute quantitative feedback theory (QFT) bounds in one‐degree‐of‐freedom feedback control problems. The new approach is based on envelope curves and shows that a QFT control specification can be expressed as a family of circumferences. Then, the controller bound is defined by the envelope curve of this family and can be obtained as an analytical function. This offers the possibility of studying the QFT bounds in an analytical way with several useful properties. Gridding methods are avoided, resulting in a lower computational effort procedure. The new formulation improves the accuracy of previous methods and allows the designer to calculate multivalued bounds. Copyright © 2009 John Wiley & Sons, Ltd.
Examination of the interface of a model adhesive joint by surface analysis: a study by XPS and ToF‐SIMS
Authors: Abel Marie‐Laure , Watts John F 
Published: April 2009

AbstractModel samples of the interface of an adhesive joint containing small levels of aminopropyl triethoxysilane (APS) have been prepared in order to examine the interface formed with an aluminium substrate. X‐ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectrometry (ToF‐SIMS) have been used to analyse and image the interface region in between the aluminium and an epoxy adhesive in order to ascertain the reactions by the organosilane which is present as a minor component within the system.It was found that APS was present at the interface between the adhesive and the substrate and that it had reacted with the substrate forming a covalent bond and was also crosslinked within the adhesive. Evidence of near to full hydrolysis of APS is also present within the spectra. Copyright © 2009 John Wiley & Sons, Ltd.
Film characteristics of anodic oxidized AZ91D magnesium alloy by applied power
Authors: Jang Yong Seok , Kim Yu Kyoung , Park IL Song , Lee Sook Jeong , Lee Min Ho , Yoon Jeong Mo , Bae Tae Sung 
Published: April 2009

AbstractThis study examined the film characteristics of an anodized AZ91D magnesium alloy by varying the direct current and pulse frequency conditions. In order to evaluate the effect of the pulse frequency on film formation, anodic oxidation was carried out by applying direct current and pulse current at a current density of 300 mA/cm2. Compared with the sample groups treated with the direct current, a large number of small arcs were generated continuously on the film treated with the pulse current and the film formation rate was found to increase. Homogeneous and compact pores were formed with increasing frequency, and the rate of formation was increased rapidly to the arrival voltage. The film thickness increased and the surface roughness decreased with increasing anodic oxidation time at a fixed frequency of 125 Hz. However, treatment for more than 3 min led to decomposition of the oxidized film onto the previously formed film, which caused an increase in the number of cracks and pores within the film. The most uniform and smallest pores were acquired when the surface was anodized for 3 min at a current density and frequency of 300 mA/cm2 and 125 Hz, respectively. X‐ray diffraction revealed the formation of MgO and Mg2SiO4 peaks, with a relative decrease in peak intensity for the MgO and Mg substrate. The Vickers hardness value was higher on the treated groups than on the untreated group, and the potentiodynamic polarization test revealed satisfactory corrosion resistance through a decrease in corrosion density and a large improvement in the corrosion potential. Copyright © 2009 John Wiley & Sons, Ltd.
Post‐oxidizing effects on surface characteristics of salt bath nitrocarburized AISI 02 tool steel type
Authors: Fares M. L. , Chaoui K. , Le Coze J. 
Published: April 2009

AbstractThe effect of post‐oxidizing treatment on the characteristics of modified surface layers produced by salt bath nitrocarburizing on the industrial American Iron and Steel Institute (AISI) 02 tool steel types is investigated. Nitrocarburizing treatment is performed for 6 h and 8 h at 570 °C and post‐oxidizing treatment for 30, 60 and 90 min at 520 °C, using argon–steam mixture. Formed layers are characterized by their basic properties such as thickness layer, depth, surface hardness and wear resistance. Detailed estimation of the modified metal surface quality, in terms of chemical composition, formed phases, microstructures and diffusion mechanisms are performed by metallographic techniques, EDX, X‐ray diffraction, scanning electron microscopy (SEM) and glow discharge optical electron spectroscopy (GDOES). The corrosion resistance was investigated in 0.4 M H2SO4 solutions, using steady‐state electrochemical polarization methods. The obtained results revealed the existence of a superficial oxide layer which consists of magnetite (Fe3O4) and hematite (Fe2O3) and the presence of an ε‐phase associated with a small amount of γ′‐phase. Important improvements in wear, microhardness and corrosion resistance occur after these treatments and it is specifically concluded that the sole application of a nitrocarburizing treatment does not significantly ameliorate the corrosion resistance of the as‐received steel. In fact, post‐oxidation treatment contributes to increase corrosion resistance by forming a dense magnetite layer and at the same time, it partially covers the compound layer pores. Copyright © 2009 John Wiley & Sons, Ltd.
In‐situ spectroelectrochemical study of the growth process of a lead decanoate coating as corrosion inhibitor for lead surfaces
Authors: Dowsett Mark , Adriaens Annemie , Schotte Bart , Jones Gareth , Bouchenoire Laurence 
Published: April 2009

AbstractWe have monitored the growth of lead decanoate coatings in real time using electrochemical impedance spectroscopy (EIS) and synchrotron X‐ray diffraction in a unique environmental cell. The measurements involved the immersion of lead substrates in a 0.05 M sodium decanoate solution and the simultaneous collection of spectroscopic and electrochemical data as the coating deposits. In separate experiments, the surface morphology was investigated with SEM. The stratigraphy and thickness of layers after 6 h of treatment (≅1.5 µm) was determined using RBS and ultra low energy SIMS combined with surface profilometry. Weight‐gain measurements were also carried out. Overall, the results are consistent with an initially parabolic process, due simply to diffusionally limited two‐dimensional growth across the surface from nucleation sites. This becomes linear over time as one‐dimensional vertical growth sets in at full coverage (layer closure). The X‐ray data and the microscopy show that the coating consists of fine, interlocking, randomly oriented flake‐shaped crystals, with no obvious epitaxial relationship to the lead substrate. The growth rate of the coating and its corrosion resistance are extremely sensitive to preparation method of the NaC10 solution in ways which are still under investigation. Copyright © 2009 John Wiley & Sons, Ltd.
EIS study on passive films of AISI 304 stainless steel in oxygenous sulfuric acid solution
Authors: Lai Weiya , Zhao Wenzhen , Wang Feng , Qi Chengzhu , Zhang Jun 
Published: April 2009

AbstractElectrochemical impedance spectroscopy (EIS) and Kramers–Kronig (K–K) transforms were made on American Iron and Steel Institute (AISI) 304 stainless steel (SS) in naturally aerated sulfuric acid solution at room temperature. The K–K relations testify that the systems under investigation comply with the linearity, causality, and stability constraints of linear system theory (LST) and thereby validate the EIS data. The polarization resistance decreased with removing of passive film and pitting formed in the passive layer, due to layer thinning or pitting caused by chloride. The impedance data for 304 SS with passive films can be accurately modeled using individual components of the equivalent circuits. The polarization resistances (Rp) of the 304 SS can be confirmed by Nyquist plots and estimated from the anodic polarization curves. The reaction model of the dissolution‐passivation process of 304 SS in acid solution is proposed. Copyright © 2009 John Wiley & Sons, Ltd.
Phenanthroline method for quantitative determination of surface carboxyl groups on carboxylated polystyrene particles with high sensitivity
Authors: Dai Jie , Liu Yanmei , Li Jun , Lu Ziyang , Yang Wensheng 
Published: April 2009

AbstractThis study developed a phenanthroline method for quantitative determination of surface carboxyl groups on carboxylated polystyrene (PS‐COOH) particles based on the coordination between the carboxyl groups and Fe2+. The ratio of the carboxyl groups, which is determined by conductometric titration method, to Fe2+ coordinated with the particles, which is determined by phenanthroline method, is 4.7, i.e. nCOOH = 4.7 × ΔnFe2+. The Lambert–Beer law is obeyed in the range of 0–60 × 10−9 mol/ml for the amount of surface carboxyl on the particles. The detection limit of the method is 2 nmol COOH/ml. The average standard deviation of the experiments is 4.4%. The relative deviation of the data obtained with this method is lower than 7% compared with that obtained with the conductometric titration method. The weight of the sample necessary for phenanthroline method is only about 0.1% of that necessary for conductometric titration method. It has been demonstrated that the phenanthroline method is suitable for quantitative determination of low amount of surface carboxyl groups on PS‐COOH particles due to its high sensitivity. Copyright © 2009 John Wiley & Sons, Ltd.
Measures of between‐cluster variability in cluster randomized trials with binary outcomes
Authors: Thomson Andrew , Hayes Richard , Cousens Simon 
Published: April 2009

AbstractCluster randomized trials (CRTs) are increasingly used to evaluate the effectiveness of health‐care interventions. A key feature of CRTs is that the observations on individuals within clusters are correlated as a result of between‐cluster variability. Sample size formulae exist which account for such correlations, but they make different assumptions regarding the between‐cluster variability in the intervention arm of a trial, resulting in different sample size estimates. We explore the relationship for binary outcome data between two common measures of between‐cluster variability: k, the coefficient of variation and ρ, the intracluster correlation coefficient. We then assess how the assumptions of constant k or ρ across treatment arms correspond to different assumptions about intervention effects. We assess implications for sample size estimation and present a simple solution to the problems outlined. Copyright © 2009 John Wiley & Sons, Ltd.
The k‐in‐a‐row up‐and‐down design, revisited
Authors: Oron Assaf P. , Hoff Peter D. 
Published: April 2009

AbstractThe percentile‐finding experimental design known variously as ‘forced‐choice fixed‐staircase’, ‘geometric up‐and‐down’ or ‘k‐in‐a‐row’ (KR) was introduced by Wetherill four decades ago. To date, KR has been by far the most widely used up‐and‐down (U&D) design for estimating non‐median percentiles; it is implemented most commonly in sensory studies. However, its statistical properties have not been fully documented, and the existence of a unique mode in its asymptotic treatment distribution has been recently disputed.Here we revisit the KR design and its basic properties. We find that KR does generate a unique stationary mode near its target percentile, and also displays better operational characteristics than two other U&D designs that have been studied more extensively. Supporting proofs and numerical calculations are presented. A recent experimental example from anesthesiology serves to highlight some of the ‘up‐and‐down’ design family's properties and advantages. Copyright © 2009 John Wiley & Sons, Ltd.
Visualizing covariates in proportional hazards model
Authors: Karvanen Juha , Harrell Frank E. 
Published: April 2009

AbstractWe present a graphical method called the rank‐hazard plot that visualizes the relative importance of covariates in a proportional hazards model. The key idea is to rank the covariate values and plot the relative hazard as a function of ranks scaled to interval [0, 1]. The relative hazard is plotted with respect to the reference hazard, which can be, for example, the hazard related to the median of the covariate. Transformation to scaled ranks allows plotting of covariates measured in different units in the same graph, which helps in the interpretation of the epidemiological relevance of the covariates. Rank‐hazard plots show the difference of hazards between the extremes of the covariate values present in the data and can be used as a tool to check if the proportional hazards assumption leads to reasonable estimates for individuals with extreme covariate values. Alternative covariate definitions or different transformations applied to covariates can be also compared using rank‐hazard plots. We apply rank‐hazard plots to the data from the FINRISK study where population‐based cohorts have been followed up for events of cardiovascular diseases and compare the relative importance of the covariates cholesterol, smoking, blood pressure and body mass index. The data from the Study to Understand Prognoses Preferences Outcomes and Risks of Treatment (SUPPORT) are used to visualize nonlinear covariate effects. The proposed graphics work in other regression models with different interpretations of they‐axis. Copyright © 2009 John Wiley & Sons, Ltd.
A model selection approach to analysis of variance and covariance
Authors: Alber Susan A. , Weiss Robert E. 
Published: April 2009

AbstractAn alternative to analysis of variance is a model selection approach where every partition of the treatment means into clusters with equal value is treated as a separate model. The null hypothesis that all treatments are equal corresponds to the partition with all means in a single cluster. The alternative hypothesis correspond to the set of all other partitions of treatment means. A model selection approach can also be used for a treatment by covariate interaction, where the null hypothesis and each alternative correspond to a partition of treatments into clusters with equal covariate effects. We extend the partition‐as‐model approach to simultaneous inference for both treatment main effect and treatment interaction with a continuous covariate with separate partitions for the intercepts and treatment‐specific slopes. The model space is the Cartesian product of the intercept partition and the slope partition, and we develop five joint priors for this model space. In four of these priors the intercept and slope partition are dependent. We advise on setting priors over models, and we use the model to analyze an orthodontic data set that compares the frictional resistance created by orthodontic fixtures. Copyright © 2009 John Wiley & Sons, Ltd.
Direct Transdifferentiation of Stem/Progenitor Spermatogonia Into Reproductive and Nonreproductive Tissues of All Germ Layers
Authors: Simon Liz , Ekman Gail C. , Kostereva Natalia , Zhang Zhen , Hess Rex A. , Hofmann Marie-Claude , Cooke Paul S. 
Published: April 2009

Abstract
Pluripotent stem cells have great clinical potential for tissue regeneration/repair in humans. The use of embryonic stem (ES) cells is ethically controversial, leading to searches for other sources of pluripotent stem cells. Testicular spermatogonial stem cells (SSCs) produce the spermatogenic lineage. Under in vitro conditions, SSCs have the ability to give rise to pluripotent ES-like cells. We hypothesized that stem/progenitor spermatogonia could directly transdifferentiate into different tissue types if they were recombined with inductive mesenchymes from fetal/neonatal organs using a tissue separation/recombination methodology and grown in vivo. Green fluorescent protein transgenic mice were used to track cell lineages. Our results indicate that stem/progenitor spermatogonia recombined with the appropriate mesenchyme can directly transdifferentiate in vivo into tissues of all germ layers, including prostatic, uterine, and skin epithelium. In addition, transdifferentiated tissue expressed molecular, histological, and functional markers of the appropriate epithelium. The ability of stem/progenitor spermatogonia to directly generate various epithelia emphasizes their clinical potential, and if adult human SSCs have similar properties, this may have applications in human regenerative medicine.
Disclosure of potential conflicts of interest is found at the end of this article.