bluuebunny/crossref_metadata_2025 huggingface dataset:
A level set based model for damage growth: The thick level set approach
Authors: Moës N. , Stolz C. , Bernard P.‐E. , Chevaugeon N.
Published: December 2010

In this paper, we introduce a new way to model damage growth in solids. A level set is used to separate the undamaged zone from the damaged zone. In the damaged zone, the damage variable is an explicit function of the level set. This function is a parameter of the model. Beyond a critical length, we assume the material to be totally damaged, thus allowing a straightforward transition to fracture. The damage growth is expressed as a level set propagation. The configurational force driving the damage front is non‐local in the sense that it averages information over the thickness in the wake of the front. The computational and theoretical advantages of the new damage model are stressed. Numerical examples demonstrate the capability of the new model to initiate cracks and propagate them even in complex topological patterns (branching and merging for instance). Copyright © 2010 John Wiley & Sons, Ltd.
Synthesis and phase‐separation behavior of α,ω‐difunctionalized diblock copolymers
Authors: Werner Saija , Pospiech Doris , Jehnichen Dieter , Eckstein Kathrin , Komber Hartmut , Friedel Peter , Janke Andreas , Näther Franziskus , Reuter Uta , Voit Brigitte , Taurino Rosa , Messori Massimo
Published: December 2010

A series of diblock copolymers of n‐pentyl methacrylate and methyl methacrylate (PPMA/PMMA BCP) with one or two terminal functional groups was prepared by sequential anionic polymerization of PMA and MMA using an allyl‐functionalized initiator and/or and end‐capping with allyl bromide. Allyl functional groups were successfully converted into OH groups by hydroboration. The morphology in bulk was examined by temperature‐dependent small‐angle X‐ray measurements (T‐SAXS) and transmission electron microscopy (TEM) showing that functional groups induced a weak change in d‐spacings L0 as well as in the thermal expansion behavior. T‐SAXS proved that the lamellar morphologies were stable over multiple heating/cooling cycles without order‐disorder transition (ODT) until 300 °C. While non‐functionalized BCP formed parallel lamellae morphologies, additional OH‐termination at the PMMA block forced in very thin films (ratio between film thickness and lamellar d‐spacing below 1) the generation of perpendicular lamellae morphology through the whole film thickness, as shown by Grazing‐incidence small‐angle X‐ray scattering experiments (GISAXS) measurements. Functionalized BCP were successfully used in thin films as templates for silica nanoparticles in an in‐situ sol–gel process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Synthesis of backbone thermo and pH dual‐responsive hyperbranched poly(amine‐ether)s through proton‐transfer polymerization
Authors: Pang Yan , Zhu Qi , Zhou Dongliang , Liu Jinyao , Chen Yan , Su Yue , Yan Deyue , Zhu Xinyuan , Zhu Bangshang
Published: December 2010

Stimuli‐responsive hyperbranched polymers have attracted great attention in recent years because of their wide applications in biomedicine. Through proton‐transfer polymerization of triethanolamine and 1,2,7,8‐diepoxyoctane with the help of potassium hydride, a series of novel backbone thermo and pH dual‐responsive hyperbranched poly(amine‐ether)s were prepared successfully in one‐pot. The degrees of branching of the resulting polymers were at 0.40–0.49. Turbidity measurements revealed that hyperbranched poly(amine‐ether)s exhibited thermo and pH dual‐responsive properties in water. Importantly, these responsivities could be readily adjusted by changing the polymer composition as well as the polymer concentration in aqueous solution. Moreover, in vitro evaluation demonstrated that hyperbranched poly(amine‐ether)s showed low cytotoxicity and efficient cell internalization against NIH 3T3 cell lines. These results suggest that these backbone thermo and pH dual‐responsive hyperbranched poly(amine‐ether)s are promising materials for biomedicine. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Atom transfer radical polymerization using activators regenerated by electron transfer of acrylonitrile in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate
Authors: Chen Hou , Chen Lingfang , Wang Chunhua , Qu Rongjun
Published: December 2010

Atom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile (AN) was first approached with 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium tetrafluoroborate ([ecemim][BF4]) as reaction medium and tin(II) bis(2‐ethylhexanoate) (Sn(EH)2) as reducing agent in the presence of air. When compared with in bulk, an obvious increase of polymer isotacticity was observed for ARGET ATRP of AN in 1‐(1‐ethoxycarbonylethyl)‐3‐methylimidazolium hexafluorophospate ([ecemim][PF6]), the reaction rate of ARGET ATRP of AN in [ecemim][PF6] was higher and the polymerization process was better controlled. The block copolymer polyacrylonitrile‐block‐poly(methyl methacrylate) with molecular weight at 69,750, distribution at 1.34, and isotacticity at 0.36 was successfully obtained in [ecemim][PF6]. [Ecemim][PF6] and the catalyst system were recycled and reused and had no effect on the living nature of polymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Kinetics of electron induced desorption of hydrogen in nanostructured porous silicon
Authors: Ruano G. D. , Ferron J. , Arce R. D. , Koropecki R. R.
Published: December 2010

We found that nanostructured porous silicon obtained by anodization desorbs hydrogen under electron bombardment. The kinetics of this electron‐induced effusion can be explained neither in terms of thermal processes nor by direct transference of energy from the impinging electron to the SiH bonds. We show that short lived‐large energy fluctuations (SLEFs), occurring during bimolecular recombination processes of carriers produce both, a midgap increment of the density of electronic defect states and hydrogen desorption.
Influence of the doping concentration on crystallographic pore growth on n‐type InP and GaAs
Authors: Leisner Malte , Dorow‐Gerspach Daniel , Carstensen Jürgen , Föll Helmut
Published: December 2010

The growth of crystallographical pores (crysto pores) in n‐type InP and GaAs has been investigated in detail in this work. The dependence on several experimental parameters, like the substrate doping concentration ND, the etching current density j, nucleation, and etching time lead to a large amount of data. It could be shown that the data can be consistently understood in the framework of a simple model for crysto pore growth developed earlier by the authors. The stochastic nature of the model allowed for its implementation into 3‐dimensional Monte‐Carlo simulations, which were already able to reproduce the major features of crysto pores, as well as many detailed results. In this framework, this work serves as expansion of the parameter space which is subjected to the simulations, since the aforementioned parameters serve as free input parameters for the simulations. First results indicate that the main model parameters, the branching probabilities at pore tips and walls (ktips and kwall) are higher for InP as compared to GaAs. This effect has been interpreted as caused by a stronger passivation of GaAs surfaces by HCl in comparison to InP.
The use of porous silicon layers in thin‐film silicon solar cells
Authors: Van Hoeymissen Jan , Depauw Valerie , Kuzma‐Filipek Izabela , Van Nieuwenhuysen Kris , Payo Maria Recaman , Qiu Yu , Gordon Ivan , Poortmans Jef
Published: December 2010

In the quest for lowering the manufacturing cost of silicon solar cells, imec has been working successfully on two crystalline Si ‘thin‐film’ cell concepts. In a first concept, a 20 µm‐thin Si solar cell is epitaxially grown on top of a porous Si‐based Bragg‐type reflector which is electrochemically etched in a low‐cost UMG Si substrate. Large area solar cells with efficiencies of 15.2% have been made, using (semi‐)industrial processing tools. This clearly demonstrates that this cell concept has almost reached the stage of industrial application. In a second, longer‐term approach, a 1–5 µm‐thin, stand‐alone mono‐crystalline film is created based on the controlled annealing of an ordered macroporous silicon layer (the ‘Epi‐free’ process). With this very thin Si layer, a simple proof‐of‐concept solar cell has been made exhibiting an efficiency of 4%. By optimizing the cell process in terms of light trapping and passivation, efficiencies over 15% can be expected from this technology.
Macro and quasi‐mesoporous silicon by self‐assembling and metal assisted etching
Authors: Boarino L. , Enrico E. , De Leo N. , Celegato F. , Tiberto P. , Sparnacci Katia , Laus M.
Published: December 2010

The combination of two recent techniques developed in the last years demonstrates the possibility to obtain regular and semi‐ordered macro and mesopores on any type of silicon substrates and with holes diameter ranging from 800 to 60 nm and less. Self‐assembling of polystyrene nanospheres (PSNS) is obtained by floating technique, then the 2D crystal is lifted on a silicon substrate with a 30 nm silver thin film deposited by thermal evaporation or sputtering. The nanospheres are then reduced in diameter by reactive ion etching (RIE) in oxygen plasma, then the samples are exposed to Ar ions sputter‐etching (SE) for thin film structuration. At this point of the process the polystyrene nanosphere mask is removed and a metal assisted etching (MAE) of few minutes is performed. Ordered and regular pores of diameters ranging from 500 to 60 nm have been obtained.

magnified image

Macropores (450 nm) obtained by self‐assembly nanolithography and metal assisted etching.
Characteristics of SnSe and SnSe2 thin films grown onto polycrystalline SnO2‐coated glass substrates
Authors: Guillén C. , Montero J. , Herrero J.
Published: December 2010

Tin selenide thin films have been prepared by selenization of sputtered tin layers and have been analyzed comparatively onto bare and SnO2‐coated glass substrates. In particular, the effects of the selenization temperature and the polycrystalline substrate nature on the stoichiometry and physical properties of the layers were investigated. X‐ray diffraction was used to determine the crystalline phases and their structure, scanning electron microscopy to observe the surface topography, energy‐dispersive X‐ray analysis to establish the film composition, and spectrophotometry to determine the optical absorption, all these properties correlated to the experimental parameters. By using polycrystalline tin oxide coatings it is possible to achieve a significant crystalline enhancement for the SnSe and SnSe2 phases identified, being the Se:Sn atomic proportion, as well as the optical absorption, highly dependent on the selenization temperature apart from the substrate nature.
Manipulation of absorption in Si thin films with ordered nanostructures
Authors: Lu Yalin , Reinhardt Kitt
Published: December 2010

Silicon thin film solar cells have attracted an increasing attention because of the potential to provide clean energy at relatively low cost. Currently, their performances are limited by poor light absorption and low efficiency carrier collection. In this research with a goal to enhance the light absorption, integration with metallic surface nanostructures to thin film silicon solar cells was investigated. Large, broadband, and polarization‐insensitive light absorption enhancement was verified. The enhancement was explained by a few possible mechanisms such as the planar cavity resonance, surface plasmonic resonance (SPR), planar waveguide coupling, etc. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hall mobility drops in disordered boron‐doped Czochralski silicon compensated by thermal donors activation
Authors: Veirman J. , Dubois S. , Enjalbert N. , Garandet J. P. , Heslinga D. R. , Lemiti M.
Published: December 2010

We investigated the variation of majority carrier Hall mobility in Boron‐doped Electronic‐Grade Silicon progressively compensated by Double Thermal Donors. We show a strong reduction in Hall mobility around full compensation in both p‐ and n‐type Si. We relate this drop in mobility to a rising inhomogeneity of the electrostatic potential associated with increasing compensation, as revealed by minority carrier diffusion length mapping. Two consequences of this inhomogeneity are considered to explain our data: 1) a physical scattering of carriers by submicronic non‐uniformity of the electrostatic potential and 2) a bias in the determination of the Hall mobility in highly compensated Si. We show that the Hall Effect is indeed affected at high compensation level by the large‐scale inhomogeneity in carrier density related to non‐uniform dopant distributions. In parallel, we also discuss the possible existence of microscopic variations in dopants distribution that could lead to physical reductions in mobility. We eventually suggest suitable experiments that could reveal them. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantumchemical simulation of diffusion in alloys: diffusion of interstitial oxygen atoms in Si1‐xGex
Authors: Gusakov Vasilii
Published: December 2010

In the present work the results of theoretical analysis of the process of diffusion of covalently bonded atoms (interstitial oxygen atoms) in Si1‐xGex alloys are presented. The diffusion coefficient (activation energy and preexponential factor) was calculated by means of quantumchemical simulations (NDDO PM5) and the dependences of the activation energy and preexponential factor on Ge atoms concentration (x) were analyzed with the use of the percolation theory. It is shown that a significant decrease in the diffusion coefficient of interstitial oxygen atoms in Si1‐xGex (x<0.05) compared to the value in pure silicon is caused not only by changes in activation energy but also by a decrease of the preexponential factor. The alloy‐induced decrease in the preexponential factor is associated with removal of the degeneracy of the number of equivalent diffusion paths. The dependences obtained describe well experimentally observed changes in the diffusion coefficient of interstitial oxygen atoms and in the formation rate of oxygen‐related thermal donors in Si1‐xGex alloys. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phosphorous gettering in acidic textured multicrystalline solar cells
Authors: Montesdeoca‐Santana A. , Jiménez‐Rodríguez E. , González‐Díaz B. , Díaz‐Herrera B. , Rinio M. , Borchert D. , Hernández‐Rodríguez C. , Guerrero‐Lemus R.
Published: December 2010

The influence of phosphorus gettering is studied in this work applied to an acidic textured multicrystalline silicon substrate. The texturization was achieved with an HF/HNO3 solution leading to nanostructures on the silicon surface. It has been demonstrated in previous works that this textured surface decreases the reflectance on the solar cell and increases the surface area improving the photon collection and enhancing the short circuit current. The present study investigates the effect on the minority carrier lifetime of the phosphorous diffusion when it is carried out on this textured surface. The lifetime is measured by means microwave photoconductance decay and quasi steady state phototoconductance devices. The diffused textured wafers are used to fabricate solar cells and their electrical parameters are analyzed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study on different textured surfaces passivated with amorphous silicon
Authors: Montesdeoca‐Santana A. , Ziegler J. , Lindekugel S. , Jiménez‐Rodríguez E. , Keipert‐Colberg S. , Müller S. , Krause C. , Borchert D. , Guerrero‐Lemus R.
Published: December 2010

In this work it is studied the influence of different texturizations on minority carrier lifetime of n‐type Fz silicon wafers passivated with thin amorphous silicon layers (a‐Si:H). For amorphous‐crystalline silicon based heterojunction solar cells a good light trapping is essential. Therefore a front side texturization is needed as it can increase the photocurrent due to its low reflectance. The interface between the amorphous emitter and the crystalline base plays an important role for two reasons: firstly, the micromorphic surface topology can generate different deposition regimes that results in different lifetimes, and secondly, the nanomorphic structure also show influences on the lifetime. We compare two different types of wet chemical texturizations by different carbonate solutions and a plasma texturization subsequently covered by a thin layer of a‐Si:H by means of plasma‐enhanced chemical vapor deposition. The surface morphology produced by the texturization on the silicon wafers is analyzed by scanning electron microscopy and atomic force microscopy. The quality of the passivation of the textured silicon surface by the a‐Si:H deposition is evaluated by measuring minority carrier lifetimes with a microwave photo‐conductance decay and quasi steady state photo‐conductance devices. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variation in the structure and optical properties of polymorphous silicon thin films using dichlorosilane as silicon precursor
Authors: Remolina A. , Hamui L. , Monroy B. M. , García‐Sánchez M. F. , Ponce A. , Picquart M. , Santana G.
Published: December 2010

Polymorphous silicon thin films were obtained by plasma enhanced chemical vapor deposition using dichlorosilane as silicon precursor. The RF power and the dichlorosilane to hydrogen flow rate ratio were varied to obtain different crystalline fractions and average sizes of silicon nanocrystals embedded in the amorphous silicon matrix. Microscopy images confirmed the existence of nanocrystallites with averages sizes between 2 and 6 nm. Broader size distributions were obtained with increasing RF power. Raman results confirmed that different nanocrystalline fractions (from 12% to 54%) can be achieved in these films by regulating the selected growth parameters. The optical band gap calculated by the Tauc model from UV‐visible transmittance measurements varies between 1.8 to 2.3 eV. The relationship between the optical properties is discussed in terms of the different nanostructures of the samples. Depending on their absorption properties and effective band gap, these materials can be suitable for application in thin film solar cell devices (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optoelectronic enhancement of monocrystalline silicon solar cells by porous silicon‐assisted mechanical grooving
Authors: Ben Rabha Mohamed , Mohamed Seifeddine Belhadj , Dimassi Wissem , Gaidi Mounir , Ezzaouia Hatem , Bessais Brahim
Published: December 2010

One of the most important factors influencing silicon solar cells performances is the front side reflectivity. Consequently, new methods for efficient reduction of this reflectivity are searched. This has always been done by creating a rough surface that enables incident light of being absorbed within the solar cell. Combination of texturization‐porous silicon surface treatment was found to be an attractive technical solution for lowering the reflectivity of monocrystalline silicon (c‐Si). The texturization of the monocrystalline silicon wafer was carried out by means of mechanical grooving. A specific etching procedure was then applied to form a thin porous silicon layer enabling to remove mechanical damages. This simple and low cost method reduces the total reflectivity from 29% to 7% in the 300 ‐ 950 nm wavelength range and enhances the diffusion length of the minority carriers from 100 µm to 790 µm (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ulrich Gösele – 35 years of research: From defects and diffusion to nanomaterials
Authors: Zacharias Margit
Published: December 2010

Quite inconceivable for all his friends, colleagues and co‐workers Prof. Ulrich Gösele, Director of the Max Planck Institute of Microstructure Physics at Halle/Saale, died unexpectedly on November 8th 2009. We mourn for Ulrich Gösele as an outstanding scientist who was all the time full of new ideas. With 650 papers and a similar number of conference papers, more than 20.000 citations in 2009 and an impressive H factor of 67 at the time of his dead, he put his foot prints actually into a number of fields in physics and material science. His opinions were widely sought by scientists as well as politics. He was an advisor for local and state government, changing the scientific and innovative perspective of the Halle/Saale area. He did not fail to give advice to the best of his knowledge. And even if not all agreed with all of his opinions, his statements were mostly going to the core of the topic. It was inspiring talking to him. He had a deep sense of responsibilities for the sources entrusted to him, being its funding or peoples. From my own experience I can say, that in all the long discussions we had during the years I had the pleasure to be in his institute, I enjoyed his spirit in science but also how he was able to give confidence for the research plans we had (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Robust non‐parametric one‐sample tests for the analysis of recurrent events
Authors: Rebora Paola , Galimberti Stefania , Valsecchi Maria Grazia
Published: December 2010

One‐sample non‐parametric tests are proposed here for inference on recurring events. The focus is on the marginal mean function of events and the basis for inference is the standardized distance between the observed and the expected number of events under a specified reference rate. Different weights are considered in order to account for various types of alternative hypotheses on the mean function of the recurrent events process. A robust version and a stratified version of the test are also proposed. The performance of these tests was investigated through simulation studies under various underlying event generation processes, such as homogeneous and nonhomogeneous Poisson processes, autoregressive and renewal processes, with and without frailty effects. The robust versions of the test have been shown to be suitable in a wide variety of event generating processes. The motivating context is a study on gene therapy in a very rare immunodeficiency in children, where a major end‐point is the recurrence of severe infections. Robust non‐parametric one‐sample tests for recurrent events can be useful to assess efficacy and especially safety in non‐randomized studies or in epidemiological studies for comparison with a standard population. Copyright © 2010 John Wiley & Sons, Ltd.
Correcting for misclassification for a monotone disease process with an application in dental research
Authors: García‐Zattera M. J. , Mutsvari T. , Jara A. , Declerck D. , Lesaffre E.
Published: December 2010

Motivated by a longitudinal oral health study, we evaluate the performance of binary Markov models in which the response variable is subject to an unconstrained misclassification process and follows a monotone or progressive behavior. Theoretical and empirical arguments show that the simple version of the model can be used to estimate the prevalence, incidences, and misclassification parameters without the need of external information and that the incidence estimators associated with the model outperformed approaches previously proposed in the literature. We propose an extension of the simple version of the binary Markov model to describe the relationship between the covariates and the prevalence and incidence allowing for different classifiers. We implemented a Bayesian version of the extended model and show that, under the settings of our motivating example, the parameters can be estimated without any external information. Finally, the analyses of the motivating problem are presented. Copyright © 2010 John Wiley & Sons, Ltd.
Simultaneous confidence bounds for relative risks in multiple comparisons to control
Authors: Klingenberg B.
Published: December 2010

We discuss the construction of asymptotic simultaneous upper confidence limits that jointly bound relative risks formed by comparing several treatments to a control. Motivated by a vaccine study, we investigate the performance of several methods under such settings. Inverting the minimum of score statistics, together with estimating the correlation matrix of these statistics under the null gives simultaneous coverage rates closest to the nominal level. In typical settings of vaccine studies, this method proves to be the most powerful of the ones considered, but computationally simpler alternatives are also worth exploring when the number of comparisons is large. Simultaneous lower and two‐sided confidence intervals are also considered. All procedures can be implemented and evaluated using freely available and general R code. Copyright © 2010 John Wiley & Sons, Ltd.
Summary ROC curve based on a weighted Youden index for selecting an optimal cutpoint in meta‐analysis of diagnostic accuracy
Authors: Rücker Gerta , Schumacher Martin
Published: December 2010

Established approaches for analyzing meta‐analyses of diagnostic accuracy model the bivariate distribution of the observed pairs of specificity Sp and sensitivity Se, thus accounting for across‐study correlation. However, it is still a matter of debate how to define a summary ROC (SROC) curve. It was recently pointed out that the SROC curve is in principle unidentifiable if only one (Sp, Se) pair per study is known. We evaluate an alternative approach, modeling the study‐specific ROC curves based on the assumption of linearity in logit space. A setting is considered in which the pair (Sp, Se) that is selected for publication in a particular study maximizes a weighted Youden index λSe+(1−λ)Sp with a given weight λ.This leads to a fixed slope (1−λ)/λ of the ROC curve in (1−Sp, Se), equivalent to a slope of (1−λ)Sp(1−Sp)/(λSe(1−Se)) for the corresponding straight line in logit space. While the slope depends on the variance ratio of the underlying distributions, the intercept is a function of the mean difference. Our approach leads in a natural way to a new, model‐based proposal for a summary ROC curve. It is illustrated using an example from the literature. Copyright © 2010 John Wiley & Sons, Ltd.
A semiparametric estimator of survival for doubly truncated data
Authors: Moreira Carla , de Uña‐Álvarez Jacobo
Published: December 2010

Doubly truncated data are often encountered in the analysis of survival times, when the sample reduces to those individuals with terminating event falling on a given observational window. In this paper we assume that some information about the bivariate distribution function (df) of the truncation times is available. More specifically, we represent this information by means of a parametric model for the joint df of the truncation times. Under this assumption, a new semiparametric estimator of the lifetime df is derived. We obtain asymptotic results for the new estimator, and we show in simulations that it may be more efficient than the Efron–Petrosian nonparametric maximum likelihood estimator. Data on the age at diagnosis of childhood cancer in North Portugal are analyzed with the new method. Copyright © 2010 John Wiley & Sons, Ltd.
Frequentist performance of Bayesian inference with response‐adaptive designs
Authors: Lecoutre Bruno , Derzko Gérard , ElQasyr Khadija
Published: December 2010

In controlled clinical trials, where minimizing treatment failures is crucial, response‐adaptive designs are attractive competitors to 1:1 randomized designs for comparing the success rates ϕ1and ϕ2of two treatments. In these designs each new treatment assignment depends on previous outcomes through some predefined rule. Here Play‐The‐Winner (PW), Randomized Play‐The‐Winner (RPW), Drop‐The‐Loser, Generalized Drop‐the‐Loser and Doubly adaptive Biased Coin Designs are considered for new treatment assignments. As frequentist inference relies on complex sampling distributions in those designs, we investigate how Bayesian inference, based on two independent Beta prior distributions, performs from a frequentist point‐of‐view. Performance is assessed through coverage probabilities of interval estimation procedures, power and minimization of failure count. It is shown that Bayesian inference can be favorably compared to frequentist procedures where the latter are available. The power of response‐adaptive designs is generally very close to the power of 1:1 randomized design. However, failure count savings are generally small, except for the PW and Doubly adaptive Biased Coin designs in particular ranges of the true success rates. The RPW assignment rule has the worst performance, while PW, Generalized Drop‐the‐Loser or Doubly adaptive Biased Coin Designs may outperform other designs depending on different particular ranges of the true success rates. Copyright © 2010 John Wiley & Sons, Ltd.
Meta‐analysis of diagnostic test data: A bivariate Bayesian modeling approach
Authors: Verde Pablo E.
Published: December 2010

In the last decades, the amount of published results on clinical diagnostic tests has expanded very rapidly. The counterpart to this development has been the formal evaluation and synthesis of diagnostic results. However, published results present substantial heterogeneity and they can be regarded as so far removed from the classical domain of meta‐analysis, that they can provide a rather severe test of classical statistical methods. Recently, bivariate random effects meta‐analytic methods, which model the pairs of sensitivities and specificities, have been presented from the classical point of view. In this work a bivariate Bayesian modeling approach is presented. This approach substantially extends the scope of classical bivariate methods by allowing the structural distribution of the random effects to depend on multiple sources of variability. Meta‐analysis is summarized by the predictive posterior distributions for sensitivity and specificity. This new approach allows, also, to perform substantial model checking, model diagnostic and model selection. Statistical computations are implemented in the public domain statistical software (WinBUGS and R) and illustrated with real data examples. Copyright © 2010 John Wiley & Sons, Ltd.
Endoscopic placement of a new short‐term biodegradable pancreatic and biliary stent in an animal model: a preliminary feasibility study (with videos)
Authors: Itoi Takao , Kasuya Kazuhiko , Abe Yuta , Isayama Hiroyuki
Published: December 2010

Background and purpose

Recently, biodegradable pancreatic stents have been designed and placed in vivo and in vitro. The aim of this study is to investigate the feasibility of endoscopic stenting using the novel, braided, self‐expandable, biodegradable, pancreatic and biliary stent in a pig model.

Methods

A braided, self‐expandable, biodegradable stent was endoscopically placed into the pancreatic duct and bile duct in 4 pigs. Eventually, necropsy was performed to evaluate the stent placement after the procedure.

Results

Pancreatic and biliary stents were successfully inserted and easily deployed across the papilla into the main pancreatic duct and bile duct, respectively, in all the animals under endoscopic and fluoroscopic guidance. Necropsy performed immediate following stent placement, found that stents had been placed across the papilla and stent expansion had occurred in all cases.

Conclusions

Although this stent is not radiopaque and the number of cases was small in this experimental study, endoscopic stenting using this novel, braided, self‐expandable, biodegradable, pancreatic and biliary stent was feasible in the pig model. Further animal studies to evaluate the short‐term patency, tissue reactivity and degradability of the stents are warranted.
Toxic response caused by a misfolding variant of the mitochondrial protein short‐chain acyl‐CoA dehydrogenase
Authors: Schmidt Stinne P. , Corydon Thomas J. , Pedersen Christina B. , Vang Søren , Palmfeldt Johan , Stenbroen Vibeke , Wanders Ronald J. A. , Ruiter Jos P. N. , Gregersen Niels
Published: December 2010

Background

Variations in the gene ACADS, encoding the mitochondrial protein short‐chain acyl CoA‐dehydrogenase (SCAD), have been observed in individuals with clinical symptoms. The phenotype of SCAD deficiency (SCADD) is very heterogeneous, ranging from asymptomatic to severe, without a clear genotype–phenotype correlation, which suggests a multifactorial disorder. The pathophysiological relevance of the genetic variations in the SCAD gene is therefore disputed, and has not yet been elucidated, which is an important step in the investigation of SCADD etiology.

Aim

To determine whether the disease‐associated misfolding variant of SCAD protein, p.Arg107Cys, disturbs mitochondrial function.

Methods

We have developed a cell model system, stably expressing either the SCAD wild‐type protein or the misfolding SCAD variant protein, p.Arg107Cys (c.319 C > T). The model system was used for investigation of SCAD with respect to expression, degree of misfolding, and enzymatic SCAD activity. Furthermore, cell proliferation and expression of selected stress response genes were investigated as well as proteomic analysis of mitochondria‐enriched extracts in order to study the consequences of p.Arg107Cys protein expression using a global approach.

Conclusions

We found that expression of the p.Arg107Cys variant SCAD protein gives rise to inactive misfolded protein species, eliciting a mild toxic response manifested though a decreased proliferation rate and oxidative stress, as shown by an increased demand for the mitochondrial antioxidant SOD2. In addition, we found markers of apoptotic activity in the p.Arg107Cys expressing cells, which points to a possible pathophysiological role of this variant protein.
Early Complications of Volar Plating of Distal Radius Fractures and Their Relationship to Surgeon Experience
Authors: Ward Christina M. , Kuhl Taften L. , Adams Brian D.
Published: December 2010

Background

Fractures of the distal radius are among the most common fractures in adults. Recently, there has been a trend towards open reduction and internal fixation of these fractures through a volar approach. The purpose of this study was to assess the early complications of volar locking plate fixation of distal radius fractures with an emphasis on defining the relationship between surgeon experience and incidence of complications.

Materials and Methods

Following IRB approval, we conducted a retrospective chart review of the initial 96 distal radius fractures (92 patients) treated by open reduction and internal fixation of distal radius fracture using a volar locked plate. Our outcome measurements were incidence of postoperative complications and radiographic loss of reduction.

Results

Twenty-two complications occurred in 21 patients. Of these, five complications (5%) required surgical treatment or hospitalization. Seventeen complications (18%) required no surgical intervention or hospitalization. Transient nerve dysfunction was the most common complication, accounting for 12 of 22 complications. The first 30 patients experienced significantly more complications than those treated later in the series ( p=0.03). There was a trend towards increased incidence of complications in cases where more than 10 days elapsed between injury and surgery or where supplementary Kirschner wire fixation was used. There was no correlation between patient age, sex, severity of fracture, or presence of ulnar styloid fracture and the development of complications or loss of reduction.

Discussion

The incidence of complications decreased significantly with increased surgeon experience, suggesting that many of these early complications are avoidable.
The Role of Fairness in Modelling Customer Choice
Authors: Mathies Christine , Gudergan Siegfried P.
Published: December 2010

Some business practices of service firms have the potential to negatively affect customer demand because they are perceived as unfair. We discuss how fairness concerns can influence customer choice, and propose a conceptualisation embedded in expected utility theory that accounts for fairness judgments. The intended contributions are (1) to advance the literature on customer decision making by combining expected utility theory with justice (fairness) theory; (2) to provide a conceptual framework capturing fairness in customer choice; and (3) to propose a research agenda concerning fairness in customer decision making.
Investigation of an Argyre basin ring structure using Mars Reconnaissance Orbiter/Compact Reconnaissance Imaging Spectrometer for Mars
Authors: Buczkowski Debra L. , Murchie Scott , Clark Roger , Seelos Kim , Seelos Frank , Malaret Erick , Hash Christopher
Published: December 2010

The Argyre basin, a large impact basin in the southern highlands of Mars, excavates early Noachian geologic units and thus is an ideal probe of the compositional layering of ancient highland crust. A ring structure defined by circumferential graben is believed to represent the outermost topographic scarp of the basin. Two distinct layers in the fluvially dissected highland plains unit Npld have been exposed by the ring graben in northwest Argyre: a lower unit enriched in high‐calcium pyroxene and an upper unit showing laterally extensive occurrences of phyllosilicates, including chlorite and iron‐magnesium smectite. These phyllosilicates closely follow the unit contact between unit Npld and Hpl3 in this region; the Hesperian‐aged Hpl3 caprock directly covers unit Npld. Two nearby knobs also show phyllosilicate‐bearing materials over a high‐Ca pyroxene‐enriched unit, although the knobs are located in regions mapped as Npl1 and Nplh. From these observations, we suggest that an extensive layer of phyllosilicates underlying a layer of high‐Ca pyroxene‐bearing rock existed in the region prior to the Argyre impact. These materials were thrown up by the impact event and deposited as an inverted flap. This inverted flap of ejecta was then cut by the circumferential graben that formed as the transient Argyre crater collapsed, exposing the materials.
Northward intensification of anthropogenically forced changes in the Atlantic meridional overturning circulation (AMOC)
Authors: Zhang Rong
Published: December 2010

Extensive modeling studies show that changes in the anthropogenic forcing due to increasing greenhouse gases might lead to a slowdown of the Atlantic meridional overturning circulation (AMOC) in the 21st century, but the AMOC weakening estimated in most previous modeling studies is in depth space. Using a coupled ocean atmosphere model (GFDL CM2.1), this paper shows that in density space, the anthropogenically forced AMOC changes over the 21st century are intensified at northern high latitudes (nearly twice of those at lower latitudes) due to changes in the North Atlantic Deep Water (NADW) formation. In contrast, anthropogenically forced AMOC changes are much smaller in depth space at the same northern high latitudes. Hence projecting AMOC changes in depth space would lead to a significant underestimation of AMOC changes associated with changes in the NADW formation. The result suggests that monitoring AMOC changes at northern high latitudes in density space might reveal much larger signals than those at lower latitudes. The simulated AMOC changes in density space under anthropogenic forcing can not be distinguished from that induced by natural AMOC variability for at least the first 20 years of the 21st century, although the signal can be detected over a much longer period.
Mechanism of inverted‐chirp infrasonic radiation from sprites
Authors: de Larquier Sebastien , Pasko Victor P.
Published: December 2010

Farges and Blanc (2010) reported inverted‐chirp infrasonic signals with high frequencies arriving before low frequencies, possibly emitted by sprite discharges and observed on the ground at close range (<100 km) from the source. In the present work a parallel version of a 2‐D FDTD model of infrasound propagation in a realistic atmosphere is applied to demonstrate that the observed morphology of infrasound signals is consistent with general scaling of diameters of sprite streamers inversely proportionally to the air density. The smaller structures at lower altitudes radiate higher infrasonic frequencies that arrive first at the observational point on the ground, while the low frequency components are delayed because they originate at lower air densities at higher altitudes. The results demonstrate that strong absorption of high frequency infrasonic components at high altitudes (i.e., ∼0.2 dB/km for 8 Hz at 70 km) may also contribute to formation of inverted‐chirp signals observed on the ground at close range.
Nonlinear evolution of EMIC waves in a uniform magnetic field: 2. Test‐particle scattering
Authors: Bortnik J. , Thorne R. M. , Omidi N.
Published: December 2010

The trajectories of individual proton test particles are computed as they traverse a temporally and spatially evolving electromagnetic ion cyclotron (EMIC) wavefield. This EMIC wavefield is simulated using a hybrid code, which is described in a companion paper, with parameters representative of those found in the dawnside outer magnetosphere (L ∼ 9). The scattering of a representative group of hot protons (E0 = 4 keV, α0 = 60°) and cool protons (E0 = 30 eV, α0 = 20°) is analyzed in configuration space, velocity space, E, α, and phase. Results indicate that the hot protons are scattered by the EMIC wave in a manner consistent with resonant wave‐particle interactions, that they are constrained to move along single‐wave characteristic curves, and that the particles experience moderate phase bunching. On the other hand, the cool protons are not scattered by the EMIC wave resonantly and experience strong phase bunching, which results in large positive advective motion in both E and α, as well as large relative diffusion. The phase bunching and heating of the cool proton population is consistent with observations of cool, heavy‐ion heating in space, and the phasing of the particle v⊥ and EMIC wave's E field is consistent with a previously described mechanism known as electric phase bunching, which results in efficient energization of cool particles.
Comprehensive ground‐based and in situ observations of substorm expansion phase onset
Authors: Walsh A. P. , Rae I. J. , Fazakerley A. N. , Murphy K. R. , Mann I. R. , Watt C. E. J. , Volwerk M. , Forsyth C. , Singer H. J. , Donovan E. F. , Zhang T. L.
Published: December 2010

In this paper, we present comprehensive ground‐based and space‐based in situ geosynchronous observations of a substorm expansion phase onset on 1 October 2005. The Double Star TC‐2 and GOES‐12 spacecraft were both located within the substorm current wedge during the substorm expansion phase onset, which occurred over the Canadian sector. We find that an onset of ULF waves in space was observed after onset on the ground by extending the AWESOME timing algorithm into space. Furthermore, a population of low‐energy field‐aligned electrons was detected by the TC‐2 PEACE instrument contemporaneous with the ULF waves in space. These electrons appear to be associated with an enhancement of field‐aligned Poynting flux into the ionosphere which is large enough to power visible auroral displays. The observations are most consistent with a near‐Earth initiation of substorm expansion phase onset, such as the Near‐Geosynchronous Onset (NGO) substorm scenario. A lack of data from further downtail, however, means other mechanisms cannot be ruled out.
Fold geometry at Sheep Mountain anticline, Wyoming, constructed using airborne laser swath mapping data, outcrop‐scale geologic mapping, and numerical interpolation
Authors: Lovely Peter , Zahasky Christopher , Pollard David D.
Published: December 2010

Constraints available at the Earth's surface on the geometry of geologic folds often are discontinuous, consisting of scattered bedding surface outcrops representing the position and orientation of different stratigraphic surfaces. For this reason, characterization of fold geometry from surface data, by methods such as sequential balanced cross sections, remains a subjective and interpretive process. We present a new method for modeling the geometry of kilometer‐scale folds using dense, precise topographic data available from airborne laser swath mapping (ALSM), outcrop‐scale geologic mapping, and a reproducible numerical interpolation method that is free of subjectivity. Geologic mapping at Sheep Mountain anticline, Wyoming, enables the association of hundreds of thousands of ALSM data points with 14 weathering‐resistant bedding surfaces from seven different stratigraphic units ranging in age from Mississippian to Cretaceous. These data, supplemented by several hundred strike and dip measurements constraining local orientation of folded strata, are projected to the stratigraphic position of a single surface and used as constraint for a smoothed minimum curvature spline interpolation to generate a continuous representation of fold geometry. Both strengths and weaknesses of the new method are discussed in the context of comparison between the new surface model and an existing model constructed by traditional methods.
Magneto‐photophoresis and mesospheric particles
Authors: Rohatschek H. , Horvath H.
Published: December 2010

So far, levitation of solid particles in the atmosphere by photophoretic forces has been attributed exclusively to gravito‐photophoresis. In this paper attention is drawn to magneto‐photophoresis, a motion of ferromagnetic particles related to a magnetic field during their irradiation by light. In regions showing an approximately vertically directed magnetic field, magneto‐photophoretic levitation is likewise possible. Laboratory experiments with particles produced by an arc discharge in air between iron electrodes have quantitatively shown magneto‐photophoretic levitation. Using these results, we show that magneto‐photophoresis can be an essential factor for the formation and persistence of particle layers. Under conditions of illumination by the sun, magneto‐photophoretic levitation takes place with particles having sizes around and below 0.1 μm whereas gravito‐photophoresis occurs for particle sizes around 1 μm.
Modeling the interaction between flow and highly flexible aquatic vegetation
Authors: Dijkstra J. T. , Uittenbogaard R. E.
Published: December 2010

Aquatic vegetation has an important role in estuaries and rivers by acting as bed stabilizer, filter, food source, and nursing area. However, macrophyte populations worldwide are under high anthropogenic pressure. Protection and restoration efforts will benefit from more insight into the interaction between vegetation, currents, waves, and sediment transport. Most aquatic plants are very flexible, implying that their shape and hence their drag and turbulence production depend on the flow conditions. We have developed a numerical simulation model that describes this dynamic interaction between very flexible vegetation and a time‐varying flow, using the sea grass Zostera marina as an example. The model consists of two parts: an existing 1DV k‐ɛ turbulence model simulating the flow combined with a new model simulating the bending of the plants, based on a force balance that takes account of both vegetation position and buoyancy. We validated this model using observations of positions of flexible plastic strips and of the forces they are subjected to, as well as hydrodynamic measurements. The model predicts important properties like the forces on plants, flow velocity profiles, and turbulence characteristics well. Although the validation data are limited, the results are sufficiently encouraging to consider our model to be of generic value in studying flow processes in fields of flexible vegetation.