bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterned Immobilization of a Luminescent Ru(II) Complex in Polymer Films Using the Photoreaction of Benzyl thiocyanate: Toward Color Emission Tuning of Electroluminescent Devices
Authors: Koepplmayr Thomas , Cardinale Massimiliano , Rath Thomas , Trimmel Gregor , Rentenberger Stephan , Zojer Egbert , Kern Wolfgang , Griesser Thomas
Published: February 2012

This contribution deals with the patterned immobilization of a highly luminescent Ru(II) complex in thin polymer films. Photosensitive polymers bearing benzyl thiocyanate groups in the side chain undergo a photoisomerization reaction upon irradiation with UV light. This photoreaction leads to the formation of isothiocyanate groups, which readily react with primary amino groups. We report on the immobilization of a highly luminescent Ru(II) complex in the illuminated areas of a norbornene based polymer by means of this photoreaction. In combination with lithographic techniques, patterned, luminescent polymer films are realized. A novel approach for tuning the electroluminescence of polyfluorene‐based organic light‐ emitting diodes by the immobilization of this Ru(II) complex in the emission layer is suggested.
Cultural Adaptation, Validity, Reliability and Responsiveness of the Swedish Version of the Effective Musculoskeletal Consumer Scale (EC‐17)
Authors: Bremander Ann , Wikström Ingegerd , Larsson Ingrid , Bengtsson Maria , Hagel Sofia , Strömbeck Britta
Published: February 2012

Background

Endorsed by the Outcome MEasures in Rheumatoid Arthritis in Clinical Trials (OMERACT) group, The Effective Consumer Scale (EC‐17) was developed in English for patients with musculoskeletal diseases to assess the skills and perceptions important for participating in and managing health care. The objective of this study was culturally to adapt the questionnaire into Swedish and to study its psychometric properties.

Methods

After translation of the questionnaire into Swedish, two different groups of outpatients from two specialist rheumatology departments participated in the study. Face validity was assessed, together with internal consistency, test–retest and responsiveness of the questionnaire. Construct validity was assessed using the Arthritis Self‐Efficacy Scale (ASES), and responsiveness to a five day educational intervention was analysed using the standardized response mean (SRM).

Results

Analyses were based on 124 patients with inflammatory rheumatic diseases, of whom 50 attended the intervention. Data quality met the requirements, with missing values <5%, and floor and ceiling effects <15%. Item total correlations were all >0.4, ranging from 0.49 to 0.88. Cronbach's alpha was 0.93 and 0.95 for the two groups. The test–retest correlation (ICC2.1) was 0.94, and there was a significant improvement as a result of the intervention, with an SRM of 0.43. However, the questionnaire had a higher construct validity with the ASES subscale ‘other symptoms’ than hypothesized a priori (rs 0.75).

Conclusion

The Swedish version of the EC‐17 met the required recommendations for face validity, internal consistency, test–retest reliability and responsiveness. Its construct validity needs to be further established, and the questionnaire needs further testing in different groups of patients and in different interventions. Copyright © 2012 John Wiley & Sons, Ltd.
The Sinc‐Galerkin method for solving an inverse parabolic problem with unknown source term
Authors: Shidfar A. , Babaei A.
Published: February 2012

The inverse problem of determining an unknown source term depending on space variable in a parabolic equation is considered. A numerical algorithm is presented for recovering the unknown function and obtaining a solution of the problem. As this inverse problem is ill‐posed, Tikhonov regularization is used for finding a stable solution. For solving the direct problem, a Galerkin method with the Sinc basis functions in both the space and time domains is presented. This approximate solution displays an exponential convergence rate and is valid on the infinite time interval. Finally, some examples are presented to illustrate the ability and efficiency of this numerical method. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013
Kesterites—a challenging material for solar cells
Authors: Siebentritt Susanne , Schorr Susan
Published: February 2012

Kesterite materials (Cu2ZnSn(S,Se)4) are made from non‐toxic, earth‐abundant and low‐cost raw materials. We summarise here the structural and electronic material data relevant for the solar cells. The equilibrium structure of both Cu2ZnSnS4 and Cu2ZnSnSe4 is the kesterite structure. However, the stannite structure has only a slightly lower binding energy. Because the band gap of the stannite is predicted to be about 100 meV lower than the kesterite band gap, any admixture of stannite will hurt the solar cells. The band gaps of Cu2ZnSnS4 and Cu2ZnSnSe4 are 1.5 and 1.0 eV, respectively. Hardly any experiments on defects are available. Theoretically, the CuZn antisite acceptor is predicted as the most probable defect. The existence region of the kesterite phase is smaller compared with that of chalcopyrites. This makes secondary phases a serious challenge in the development of solar cells. Copyright © 2012 John Wiley & Sons, Ltd.
Preparation of side‐chain liquid crystalline Azopolymers by CuAAC postfunctionalization using bifunctional azides: Induction of chirality using circularly polarized light
Authors: Royes Jorge , Rebolé Javier , Custardoy Laura , Gimeno Nélida , Oriol Luis , Tejedor Rosa M. , Piñol Milagros
Published: February 2012

Well‐defined side‐chain liquid crystal azopolymers have been synthesized by click chemistry of poly(propargyl methacrylate) with bifunctional liquid crystalline azides to produce materials with large degrees of functionalization. A polymeric scaffold having pendant alkyne groups was prepared by atom transfer radical polymerization (ATRP) and postfunctionalized by copper(I)‐catalyzed azide‐alkyne cycloaddition (CuAAC) using homo‐ and heterobifunctional azides. The azides are derivatives of 2,2‐bis(hydroxymethyl)propanoic acid (bis‐MPA) containing photoresponsive azobenzene and/or liquid crystalline biphenyl moieties. The approach is a convenient alternative to increase the density of functional units in side‐chain polymers having moderate polymerization degrees and to modulate the properties of the final material. The article describes the synthesis, characterization, and liquid crystalline properties of the obtained polymers. The effect of the chemical structure and the possible cooperative effects between functional units in the photo‐induction of chirality are also evaluated. A switchable photo‐transference of chirality from the circularly polarized light (CPL) to material has been achieved. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Basic ionic liquid/FeCl3·6H2O as an efficient catalyst for AGET ATRP of methyl methacrylate
Authors: Deng Zhijun , Qiu Lihua , Bai Liangjiu , Zhou Yinxia , Lin Bencai , Zhao Jie , Cheng Zhenping , Zhu Xiulin , Yan Feng
Published: February 2012

A basic ionic liquid, 1‐butyl‐3‐methyl imidazolium hydroxide ([Bmim]OH), was synthesized and used as the additives in an iron‐mediated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) of methyl methacrylate in bulk and solution, using FeCl3·6H2O as the catalyst, ethyl 2‐bromoisobutyrate as the initiator, vitamin C (Vc) as the reducing agent, and tetrabutylammonium bromide or tetra‐n‐butylphosphonium bromide as the ligand. Catalytic amount of [Bmim]OH could enhance the polymerization rate and produce poly(methyl methacrylate) with controllable molecular weights and narrow molecular weight distributions (Mw/Mn = 1.3–1.4). The nature of controlled/“living” free radical polymerization in the presence of basic ionic liquid was further confirmed by chain‐extension experiments. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Polynorbornene dicarboximide/amine functionalized graphene hybrids for potential oxygen barrier films
Authors: Lee Daewoo , Choi Myeon‐Cheon , Ha Chang‐Sik
Published: February 2012

In this work, we prepared polynorbornene dicarboximide (PND)/amine functionalized graphene (AFG) hybrids in N,N‐dimethylacetamide (DMAc). The AFG was synthesized by modifying graphene oxides (GO) with amine groups. The AFG sheets were well‐dispersed in DMAc and randomly distributed throughout the PND matrix in the hybrid films, which enhanced the mechanical and oxygen barrier properties of the PND/AFG hybrid films. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Bioreducible and core‐crosslinked hybrid micelles from trimethoxysilyl‐ended poly(ε‐caprolactone)‐S‐S‐poly(ethylene oxide) block copolymers: Thiol‐ene click synthesis and properties
Authors: Wang Yu‐Jing , Dong Chang‐Ming
Published: February 2012

Bioreducible and core‐crosslinked hybrid micelles were for the first time fabricated from biodegradable and biocompatible trimethoxysilyl‐terminated and disulfide‐bond‐linked block copolymers poly(ε‐caprolactone)‐S‐S‐poly(ethylene oxide), which were prepared by combining thiol‐ene coupling reaction and ring‐opening polymerization. The molecular structures, physicochemical, self‐assembly, and bioreducible properties of these copolymers were thoroughly characterized by means of FTIR, 1H NMR, gel permeation chromatography, differential scanning calorimetry, wide‐angle X‐ray diffraction, dynamic light scattering (DLS), and transmission electron microscopy. The core‐crosslinking sol‐gel reaction was confirmed by 1H NMR, and the core‐crosslinked hybrid micelles contained about 3 wt % of silica. The bioreducible property of both uncrosslinked and core‐crosslinked micelles in 10 mM 1,4‐dithiothreitol (DTT) solution was monitored by DLS, which demonstrated that the PEO corona gradually shedded from the PCL core. The anticancer doxorubicin drug‐loaded micelles showed nearly spherical morphology compared with blank micelles, presenting a DTT reduction‐triggered drug‐release profile at 37 °C. Notably, the core‐crosslinked hybrid micelles showed about twofold drug loading capacities and a half drug‐release rate compared with the uncross‐liked counterparts. This work provides a useful platform for the fabrication of bioreducible and core‐crosslinked hybrid micelles potential for anticancer drug delivery system. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Synthesis of [CH2C(CO2Et)2CH2Ar]n polymers and their unique optical properties by through‐space interactions between Ar and CO groups
Authors: Hoshino Tohru , Watanabe Jun‐ichi , Kudo Masaru , Sakai Edo , Funyu Shigeaki , Ishitsuka Ken‐ich , Okamoto Sentaro
Published: February 2012

Polymers of type [CH2C(CO2Et)2CH2Ar]n (Ar = 1,4‐phenylene, 2,6‐naphthylene, 9,10‐anthrylene, or 1,4‐phenylene‐ethynylene‐1,4‐phenylene) were synthesized by alkylation of diethyl malonate with XCH2ArCH2X (X = Cl or Br). These polymers exhibited unexpectedly enhanced UV absorption and strong, broad, bathochromically shifted fluorescence spectra compared with the parent Ar compounds. The origin of these photophysical characteristics was postulated to be a configuration interaction between the π→π* excitation of the aromatic moiety and the n→π* excitation of the carbonyl moiety on the trimethylene tether via intramolecular charge transfer. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Effects of salt and temperature on single‐chained cationic surfactant/oligodeoxynucleotide vesicle formation
Authors: Guo Xia , Cui Bo , Li Yang , Ding Jiatong
Published: February 2012

Recently, we found oligodeoxynucleotide could induce single‐chained cationic surfactant to organize into vesicles. In this article, we will report the effects of NaCl and temperature on the surfactant/oligodeoxynucleotide vesicle formation. A moderate content of NaCl can facilitate vesicle formation and high content of NaCl makes vesicle degraded. The enhanced hydrophobic interaction between surfactant and oligodeoxynucleotide with NaCl plays a key role for facilitating vesicle formation. Moreover, surfactant/oligodeoxynucleotide vesicles tend to aggregate at high temperature and the change is irreversible. However, the presence of NaCl makes this change reversible. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Optical polarization and anisotropic gain characteristics in semipolar and nonpolar InGaN quantum well lasers
Authors: Yamaguchi Atsushi A. , Kojima Kazunobu
Published: February 2012

By using a new simple theoretical approach, the previously‐reported experimental results of the polarization properties in semipolar and nonpolar InGaN quantum wells (QWs) were analyzed. On the basis of the k·p‐perturbation theory, we derived a useful analytical expression for describing the polarization properties of these QWs, and used this expression to analyze experimental data reported from various research groups. All the reported data are successfully fitted by the analytical expression, and realistic prediction of polarization properties is possible for unexplored substrate orientation and In composition. Based on these analyses, it is predicted that the optical gain characteristics favourable for laser diodes with cleaved‐facet cavity mirrors would appear in the green‐InGaN QWs on the lower‐angle semipolar planes (30° ∼ 40° inclined from the c‐plane). (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anion modulation epitaxy (AME), an alternative growth strategy for group III‐nitrides
Authors: Goff Lucy E. , Foxon C. Thomas , Staddon Christopher R. , Kent Anthony J. , Campion Richard P.
Published: February 2012

In this paper we report a new strategy for growth of group III‐nitrides by Plasma‐Assisted Molecular Beam Epitaxy (PA‐MBE), which we term Anion Modulation Epitaxy (AME). In this modified growth method, the nitrogen flux is interrupted periodically to build up a group III surface concentration. This leads to enhanced mobility and thus improved morphology compared to growth using conventional PA‐MBE. Direct comparison of GaN samples grown at equivalent temperature by PA‐MBE and AME show the advantages of this improved growth procedure (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A 600 V AlGaN/GaN Schottky barrier diode on silicon substrate with fast reverse recovery time
Authors: Hsin Yue‐Ming , Ke Tsung‐Yu , Lee Geng‐Yen , Chyi Jen‐Inn , Chiu Hsien‐Chin
Published: February 2012

Lateral AlGaN/GaN Schottky barrier diodes on silicon (111) substrate have been fabricated and characterized. The Hall measurement shows the mobility of 1430 cm2/V‐s with a sheet carrier density of 9.8 × 1012 cm‐2 for the AlGaN/GaN structure. The specific on‐state resistance (Ron) is 1.27 mΩ‐cm2, while the forward turn‐on voltage is 1.43 V at the current density of 100 A/cm2 for device with Schottky‐to‐ohmic distance of 10 μm. The measured reverse breakdown voltage (VB) at room temperature is up to 600 V without edge termination. The figure‐of‐merit, (VB)2/Ron, is 302.7 MWcm‐2, and fast reverse recovery time is observed for device switched from a forward current density of 720 A/cm2 to a reverse bias of 30 V with di /dt of 60 A/μs. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characteristics of epitaxial lateral overgrowth AlN templates on (111)Si substrates for AlGaN deep‐UV LEDs fabricated on different direction stripe patterns
Authors: Mino Takuya , Hirayama Hideki , Takano Takayoshi , Tsubaki Kenji , Sugiyama Masakazu
Published: February 2012

We investigated the characteristics of epitaxial lateral overgrowth (ELO) AlN templates fabricated on Si substrates which are applicable to AlGaN‐based deep ultraviolet (DUV) light‐emitting diodes (LEDs). ELO‐AlN layers were grown on stripe‐patterned thin AlN seed‐layer directly deposited on (111)Si substrates by using an ‘NH3 pulsed‐flow multi‐layer (ML) growth’ technique. A 4 µm‐thick ELO‐AlN layer with stripe pattern along <10‐10> direction of AlN can be coalesced successfully. We achieved marked reduction of crack and threading dislocation density (TDD) in the ELO AlN layers. In fact, the (10‐12) full width at half maximum (FWHM) of the X‐ray diffraction ω‐scan rocking curves (XRCs) of ELO‐AlN template on Si substrate was reduced to be 980 arcsec. These results show that the combination of NH3 pulsed‐flow ML growth and ELO method is effective to fabricate high‐quality AlN templates on Si substrates. Moreover we fabricated 256‐278 nm AlGaN quantum well (QW) DUV LEDs on the low TDD ELO‐AlN templates on Si, and achieved single‐peak operations under room temperature (RT) cw current injection. The low cost AlGaN based DUV LEDs on Si substrates is expected to be integrated with Si based electric devices on the same chips. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optically pumped UV lasers grown on bulk AlN substrates
Authors: Wunderer T. , Chua C. L. , Northrup J. E. , Yang Z. , Johnson N. M. , Kneissl M. , Garrett G. A. , Shen H. , Wraback M. , Moody B. , Craft H. S. , Schlesser R. , Dalmau R. F. , Sitar Z.
Published: February 2012

Sub‐300 nm optically pumped ultraviolet lasers were realized on low‐defect‐density (0001) AlN substrates fabricated from single crystalline AlN boules. The AlxGa1–xN/AlyGa1–yN hetero‐structures were grown by metal‐organic vapor phase epitaxy near atmospheric pressure. The high structural quality of the pseudomorphically deposited films was confirmed by X‐ray reciprocal space mappings and time‐resolved photoluminescence (PL) studies of the multiple quantum well emission.

The initial PL‐decay times for a sample emitting at 267 nm were 0.87 ns and 1.14 ns for T = 295 K and T = 14 K, respectively. Laser resonators with a length of about 1 mm were formed by cleaving the AlN crystal to obtain m‐plane mirror facets. Lasing was demonstrated for various wavelengths between 267 and 291 nm with the threshold power density as low as 126 kW/cm2 for the shortest attempted wavelength. The laser emission was TE polarized for all emission wavelengths. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simple near‐infrared photodetector based on charge transfer complexes formed in molybdenum oxide doped N,N′‐di(naphthalene‐1‐yl)‐N,N′‐diphenyl‐benzidine
Authors: Wu S. H. , Lo M. F. , Chen Z. Y. , Ng T. W. , Hu X. , Mo H. W. , Wu C. , Li W. L. , Lee C. S.
Published: February 2012

We have demonstrated a simple near‐infrared (NIR) photodetector (PD) based on charge transfer complex (CTC) formed in molybdenum trioxide (MoO3) doped N,N′‐di(naphthalene‐1‐yl)‐N,N′‐diphenyl‐benzidine (NPB), which shows a photocurrent of about 0.35 A/cm2 at –3 V under 980 nm illumination. The existence of CTC formation promotes photocurrent generation which is investigated by comparison with MoO3 doped 2‐methyl‐9,10‐di(2‐naphthyl)anthracene (MADN) film which has no CTC absorption. It can be evolved that this kind of simple‐structure photodetector has potential application in the near‐infrared (NIR) detection area. It is shown in this Letter that although both MoO3 and NPB have larger energy gaps of about 3 eV and weak absorption in the NIR region, the charge transfer complexes formed by mixing the two materials show an extra absorption band and good photoelectric response in the NIR region.

magnified image

(© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multilevel latent variable models for global health‐related quality of life assessment
Authors: Kifley Annette , Heller Gillian Z. , Beath Ken J. , Bulger David , Ma Jun , Gebski Val
Published: February 2012

Quality of life (QOL) assessment is a key component of many clinical studies and frequently requires the use of single global summary measures that capture the overall balance of findings from a potentially wide‐ranging assessment of QOL issues. We propose and evaluate an irregular multilevel latent variable model suitable for use as a global summary tool for health‐related QOL assessments. The proposed model is a multiple indicator and multiple cause style of model with a two‐level latent variable structure. We approach the modeling from a general multilevel modeling perspective, using a combination of random and nonrandom cluster types to accommodate the mixture of issues commonly evaluated in health‐related QOL assessments—overall perceptions of QOL and health, along with specific psychological, physical, social, and functional issues. Using clinical trial data, we evaluate the merits and application of this approach in detail, both for mean global QOL and for change from baseline. We show that the proposed model generally performs well in comparing global patterns of treatment effect and provides more precise and reliable estimates than several common alternatives such as selecting from or averaging observed global item measures. A variety of computational methods could be used for estimation. We derived a closed‐form expression for the marginal likelihood that can be used to obtain maximum likelihood parameter estimates when normality assumptions are reasonable. Our approach is useful for QOL evaluations aimed at pharmacoeconomic or individual clinical decision making and in obtaining summary QOL measures for use in quality‐adjusted survival analyses. Copyright © 2012 John Wiley & Sons, Ltd.
On the covariance of two correlated log‐odds ratios
Authors: Bagos Pantelis G.
Published: February 2012

In many applications two correlated estimates of an effect size need to be considered simultaneously to be combined or compared. Apparently, there is a need for calculating their covariance, which however requires access to the individual data that may not be available to a researcher performing the analysis. We present a simple and efficient method for calculating the covariance of two correlated log‐odds ratios. The method is very simple, is based on the well‐known large sample approximations, can be applied using only data that are available in the published reports and more importantly, is very general, because it is shown to encompass several previously derived estimates (multiple outcomes, multiple treatments, dose–response models, mutually exclusive outcomes, genetic association studies) as special cases. By encompassing the previous approaches in a unified framework, the method allows easily deriving estimates for the covariance concerning problems that were not easy to be obtained otherwise. We show that the method can be used to derive the covariance of log‐odds ratios from matched and unmatched case‐control studies that use the same cases, a situation that has been addressed in the past only using individual data. Future applications of the method are discussed. Copyright © 2012 John Wiley & Sons, Ltd.
Predictive power to assist phase 3 go/no go decision based on phase 2 data on a different endpoint
Authors: Hong Shengyan , Shi Li
Published: February 2012

One of the most critical decision points during drug development is to make a phase 3 go/no go decision after a phase 2 proof of concept trial is conducted. It is particularly challenging in oncology drug development where oftentimes the primary endpoint for phase 3 trial is overall survival (OS), but the phase 2 proof of concept trial is powered only for an early endpoint, typically progression‐free survival (PFS), whose relationship to OS is often unclear. We propose the use of predictive power to assist the phase 3 go/no go decision by evaluating the strength of actual observed phase 2 efficacy effects in terms of how likely it will predict the chance of OS success in the subsequent phase 3 trial. The formula is provided for calculation of predictive power based on either observed PFS effect only, or observed OS effect only, or both. An example is provided to compare these three predictive powers, which shows that when there is little prior information about PFS and OS, the predictability based on the observed phase 2 PFS effect is low and not sensitive to the size of the trial and extent of the observed PFS effect, and it also has limited added value to the predictability based on the observed phase 2 OS effect. Therefore, one should be cautious of inherently high risk of making a phase 3 go/no go decision based on phase 2 PFS outcome alone and should take the phase 2 OS data into consideration whenever possible. Copyright © 2012 John Wiley & Sons, Ltd.
A pathway analysis method for genome‐wide association studies
Authors: Shahbaba Babak , Shachaf Catherine M. , Yu Zhaoxia
Published: February 2012

For genome‐wide association studies, we propose a new method for identifying significant biological pathways. In this approach, we aggregate data across single‐nucleotide polymorphisms to obtain summary measures at the gene level. We then use a hierarchical Bayesian model, which takes the gene‐level summary measures as data, in order to evaluate the relevance of each pathway to an outcome of interest (e.g., disease status). Although shifting the focus of analysis from individual genes to pathways has proven to improve the statistical power and provide more robust results, such methods tend to eliminate a large number of genes whose pathways are unknown. For these genes, we propose to use a Bayesian multinomial logit model to predict the associated pathways by using the genes with known pathways as the training data. Our hierarchical Bayesian model takes the uncertainty regarding the pathway predictions into account while assessing the significance of pathways. We apply our method to two independent studies on type 2 diabetes and show that the overlap between the results from the two studies is statistically significant. We also evaluate our approach on the basis of simulated data. Copyright © 2012 John Wiley & Sons, Ltd.
A mixed non‐homogeneous hidden Markov model for categorical data, with application to alcohol consumption
Authors: Maruotti Antonello , Rocci Roberto
Published: February 2012

Hidden Markov models (HMMs) are frequently used to analyse longitudinal data, where the same set of subjects is repeatedly observed over time. In this context, several sources of heterogeneity may arise at individual and/or time level, which affect the hidden process, that is, the transition probabilities between the hidden states. In this paper, we propose the use of a finite mixture of non‐homogeneous HMMs (NH‐HMMs) to face the heterogeneity problem. The non‐homogeneity of the model allows us to take into account observed sources of heterogeneity by means of a proper set of covariates, time and/or individual dependent, explaining the variations in the transition probabilities. Moreover, we handle the unobserved sources of heterogeneity at the individual level, due to, for example, omitted covariates, by introducing a random term with a discrete distribution. The resulting model is a finite mixture of NH‐HMM that can be used to classify individuals according to their dynamic behaviour or to estimate a mixed NH‐HMM without any assumption regarding the distribution of the random term following the non‐parametric maximum likelihood approach. We test the effectiveness of the proposal through a simulation study and an application to real data on alcohol abuse. Copyright © 2012 John Wiley & Sons, Ltd.
Identifying representative trees from ensembles
Authors: Banerjee Mousumi , Ding Ying , Noone Anne-Michelle
Published: February 2012

Tree‐based methods have become popular for analyzing complex data structures where the primary goal is risk stratification of patients. Ensemble techniques improve the accuracy in prediction and address the instability in a single tree by growing an ensemble of trees and aggregating. However, in the process, individual trees get lost. In this paper, we propose a methodology for identifying the most representative trees in an ensemble on the basis of several tree distance metrics. Although our focus is on binary outcomes, the methods are applicable to censored data as well. For any two trees, the distance metrics are chosen to (1) measure similarity of the covariates used to split the trees; (2) reflect similar clustering of patients in the terminal nodes of the trees; and (3) measure similarity in predictions from the two trees. Whereas the latter focuses on prediction, the first two metrics focus on the architectural similarity between two trees. The most representative trees in the ensemble are chosen on the basis of the average distance between a tree and all other trees in the ensemble. Out‐of‐bag estimate of error rate is obtained using neighborhoods of representative trees. Simulations and data examples show gains in predictive accuracy when averaging over such neighborhoods. We illustrate our methods using a dataset of kidney cancer treatment receipt (binary outcome) and a second dataset of breast cancer survival (censored outcome). Copyright © 2012 John Wiley & Sons, Ltd.
A nonparametric test for equality of survival medians
Authors: Rahbar Mohammad H. , Chen Zhongxue , Jeon Sangchoon , Gardiner Joseph C. , Ning Jing
Published: February 2012

In clinical trials, researchers often encounter testing for equality of survival medians across study arms based on censored data. Even though Brookmeyer and Crowley introduced a method for comparing medians of several survival distributions, still some researchers misuse procedures that are designed for testing the homogeneity of survival curves. These procedures include the log‐rank, Wilcoxon, and Cox models. This practice leads to inflation of the probability of a type I error, particularly when the underlying assumptions of these procedures are not met. We propose a new nonparametric method for testing the equality of several survival medians based on the Kaplan–Meier estimation from randomly right‐censored data. We derive asymptotic properties of this test statistic. Through simulations, we compute and compare the empirical probabilities of type I errors and the power of this new procedure with those of the Brookmeyer–Crowley, log‐rank, and Wilcoxon methods.

Our simulation results indicate that the performance of these test procedures depends on the level of censoring and appropriateness of the underlying assumptions. When the objective is to test homogeneity of survival medians rather than survival curves and the assumptions of these tests are not met, some of these procedures severely inflate the probability of a type I error. In these situations, our test statistic provides an alternative to the Brookmeyer–Crowley test. Copyright © 2012 John Wiley & Sons, Ltd.
Measurements of Solidus and Liquidus Temperatures of CaOAl2O3SiO2 and CaOMgOAl2O3SiO2 Slags with MnO Additions
Authors: Wang Lijun , Taniguchi Yoshinori , Seetharaman Seshadri
Published: February 2012

The present work was carried out with a view to re‐examine the phase diagram aspects of CaOAl2O3SiO2 and CaOMgOAl2O3SiO2 slags with MnO additions. The aim was to confirm the homogeneous liquid range necessitated for sulfide capacities measurements of the above‐mentioned slags. The liquidus and solidus temperatures of these slags were measured by DSC and X‐ray radiograph techniques. The experimental results were compared with the liquidus and solidus temperatures obtained from literature (Slag Atlas) and commercial softwares ThermoCalc and FactSage. The results indicate that there is good agreement between the experimental values and those retrieved from literature and the commercial software in the case of the ternary system CaOAl2O3SiO2. For the CaOMgOMnOAl2O3SiO2 system, significant deviations were observed between the different sources. The present observations indicate that X‐ray radiography can be a very useful tool in estimating the solidus temperatures of slags while DSC would complement the information with respect to liquidus temperatures.
Vergabe, Tragwerksplanung und Montage der Brücke über die IJssel, Niederlande
Authors: Bos Bertus , Casper Hans‐Joachim , Simon Tamàs , van Kessel Frank , Wiltink Remco
Published: February 2012

Mit der Hanzelijn, einer 50 km langen, zweigleisigen Neubaustrecke zwischen Zwolle und Lelystad am IJsselmeer, entsteht in den Niederlanden eine leistungsfähige Verbindung für den Eisenbahnverkehr zwischen dem Norden des Landes und dem Ballungsgebiet um Amsterdam und Rotterdam im Westen. Wesentlicher Bestandteil dieser Baumaßnahme ist der Neubau der 930 m langen Eisenbahnüberführung über die IJssel. Das Brückenbauwerk ist der Siegerentwurf eines Design and Build Wettbewerbes und herausragendes Beispiel für architektonisch ansprechenden Eisenbahnbrückenbau.

Award, structural design and erection of the bridge across the IJssel, Netherlands. The ‘Hanzelijn’, a 50 km long double‐tracked newly built railway line between Zwolle and Lelystad at the IJsselmeer, is presently built in the Netherlands creating an efficient railway connection between the north and the conurbations of Amsterdam and Rotterdam in the west.

Essential part of the project is the new construction of the 930 m long railway bridge over the IJssel. The bridge is the winning design of a design and build competition and an outstanding example of architecturally appealing railway bridge construction.
Eisenbahnüberführung Simmerbach – Pilotprojekt in VFT‐Rail‐Bauweise mit externer Bewehrung
Authors: Seidl Günter , Mensinger Martin , Koch Eckart , Hugle Franz
Published: February 2012

Die DB Netz AG hat das erste Brückenbauprojekt in Verbundbauweise mit externer Bewehrung auf der Strecke Bingen–Saarbrücken erstellt und erste Erfahrungen gesammelt. Die neuartige Bauweise sieht einen Überbau im Prinzip der direkten Schienenbefestigung vor. Die Tragstruktur ist ein Querschnitt mit externer Bewehrung aus Walzträgern, die durch Verbunddübel mit dem Fertigteil schubfest verbunden ist. Nur eine Wochenendsperrpause stand bei diesem Pilotprojekt zur Verfügung, um die 140 Jahre alten Stahltrogbrücken zu ersetzen. Gleichzeitig wurden die Auflagerbänke der Pfeiler‐ und Widerlager erneuert. Seit Ende Oktober 2011 rollt der Verkehr über die beiden neuen Überbauten mit je 12,75 m Spannweite.

Report on the railway overpass Simmerbach, Germany – Pilot project in VFT‐Rail construction method with external reinforcement. The German Railway Company DB Netz AG put the first bridge structure using a composite structure with external reinforcement into operation and is gaining experience on the railway link Bingen‐Saarbrücken. The new construction method implements a superstructure based on the non‐ballast slab‐track system. The structure contains a cross‐section with external reinforcement manufactured out of rolled sections which are fixed to the precasted element by composite dowels.

The close‐off interval of one weekend was available for that project to replace the 140 years old trough bridges out of steel. The pier head and the support part of the abutments were renewed contemporaneously. The two innovative superstructures with a span of 12,75 m each have been in service since end of October 2011.
Rückbau der Rheinbrücke Wesel
Authors: Enders Walter , Sprinke Peter , Hamme Markus , Scheuer Franz‐Josef
Published: February 2012

Nach der Inbetriebnahme der neuen Niederrheinbrücke bei Wesel ist die alte Rheinbrücke, eine dreifeldrige, 344 m lange Stahlfachwerkkonstruktion, jeglicher Funktion enthoben und rückzubauen. Da die Schifffahrt auf dem Rhein in diesem Abschnitt von wesentlicher verkehrlicher Bedeutung ist, waren im Rahmen der Planung Sperrungen des Wasserweges zu minimieren bzw. auszuschließen. Um den gestellten Anforderungen der Wasserschifffahrtsbehörden gerecht zu werden, wurde ein spezielles Rückbaukonzept entwickelt und in mehreren Planungsschritten für die Ausschreibung optimiert. Dass Rückbauplanungen höchste Ansprüche an die entwerfenden Ingenieure stellen, wird in der Vorstellung zum Rückbau der Rheinbrücke deutlich.

Planning the deconstruction of the bridge over the Rhine at Wesel, Germany. Following the opening of the new bridge over the River Rhine at Wesel, the old bridge, a three‐span, 344 m long, steel truss structure, is completely redundant and must be taken down. As this stretch of the Rhine is crucial to shipping, the planning work had to ensure that interruptions to river traffic were ruled out or at least minimised. In order to comply with the requirements of the shipping authorities, a bespoke deconstruction concept was devised and optimised for the tender in several stages. The following article describing the deconstruction of this bridge reveals the great demands placed on design engineers when planning such work.
Zhengzhou Yellow River road‐cum‐railway bridge, China
Authors: Gao Zongyu
Published: February 2012

Zhengzhou Yellow River road‐cum‐railway bridge accommodates both the Beijing–Guangzhou passenger railway line and the Zhengzhou–Xinxiang inter‐city highway, which cross the Yellow River at Zhengzhou, China (Fig. 1). The bridge is 9177 m long and has two distinct sections[1]: the first is a six‐pylon continuous steel‐concrete composite truss extradosed bridge with a span arrangement of 120 5 ¥168 120 m; the second is a continuous steel‐concrete composite truss with a span arrangement of 5 ¥120 m. The main bridge has a double deck, with a six‐lane carriageway on the upper deck and a twin‐track railway on the lower deck. An inclined truss structure is used for the main bridge superstructure. The upper deck is of concrete, the lower deck uses orthotropic steel solution. The analysis revealed that the main bridge has good rigidity and favourable service conditions for high‐speed trains. The main steel truss was constructed by incremental launching.
Gellan gum/cassava starch mixtures in water systems and in milk systems
Authors: Coronato Rafael , Biasutti Eliza A. R. , Carvalho Carlos W. P. , Grossmann Maria V. E.
Published: February 2012

Cassava starch is an important ingredient in various foods. However, when processed, it develops some properties that are unsuitable for many industrial applications, such as unstable viscosity and excessive cohesiveness. To reduce those disadvantages, one alternative is a mixture of starch with hydrocolloids. The aim of this study was to evaluate the effect of 0:05, 0.1, 0.2, or 0.3% w/v gellan gum on the physical properties of pastes and gels of cassava starch in water and in milk systems. Differential scanning calorimetry (DSC), pasting properties, the texture profile, and the microstructure of gels were studied. The addition of gellan gum dispersions to the water system (WS) and the milk system (MS) gave rise to pastes with higher viscosity and, in the case of MS, with lower thermal and shear stability (higher breakdown). The addition of gellan gum had a greater textural effect on the MS, in which the addition of gellan at concentrations of 0.1 and 0.3% increased adhesiveness and decreased springiness of gels. Microscopy revealed a more uniform gel structure in the MS compared with the WS. Starch gelatinization temperatures were higher in MS than in WS.
Estimation of seismic demands of steel frames subjected to near‐fault earthquakes having forward directivity and comparing with pushover analysis results
Authors: Soleimani Amiri F. , Ghodrati Amiri G. , Razeghi H.
Published: February 2012

High statistics of damages in modern structures (buildings structured based on new codes) exposed to near‐fault earthquake illustrates the necessity of more studies on this kind of earthquake effects on the structures. A specification of near‐fault earthquakes is the directivity effects. Existing records of near‐fault quakes containing directivity effects including records of Iran and abroad were modified and used for linear time history analysis of three steel moment frames (5, 8 and 12 story frames), and the results were compared with nonlinear time history analysis and pushover analysis of far‐fault quakes in this paper. The results showed that these records (near fault) motivate high modes of the structure, and especially for the 12‐story structure, high response was detected, but none of these results made the frames collapse. By comparing nonlinear dynamic analysis (time history) with nonlinear static analysis (pushover), it was concluded that various lateral load patterns in pushover cannot cover the time history result needs. Load distribution pattern based on the first vibration mode covers these demands in the lower floors, but in higher floors, this method is not applicable. Copyright © 2012 John Wiley & Sons, Ltd.
Neurodevelopmental delay in small babies at term: a systematic review
Authors: Arcangeli T. , Thilaganathan B. , Hooper R. , Khan K. S. , Bhide A.
Published: February 2012

Objective

Being small for gestational age (SGA) or having fetal growth restriction (FGR) may be associated with poorer neurodevelopmental outcomes compared to being appropriate for gestational age (AGA). The aim of this paper was to evaluate the existence and magnitude of decrease in neurodevelopmental scores in SGA and FGR infants born at term from a systematic review of the existing literature.

Methods

Studies of neurodevelopment in SGA/FGR babies were identified from a search of the internet scientific databases. Studies that included preterm births and those that did not define absolute indices of standardized cognitive outcome were excluded. SGA was defined as birth weight below the 10th centile for gestation and FGR as the same birth‐weight standard with abnormal umbilical artery Doppler ultrasound or evidence of abnormal placentation on pathology specimen studies. Effect size was calculated as the standardized mean difference between neurodevelopment scores of controls and SGA/FGR children.

Results

There were 28 studies of SGA, with a total of 7861 SGA and 91 619 control AGA babies, and three studies of FGR, with a total of 119 FGR and 49 control AGA babies. Data synthesis showed that standardized neurodevelopmental scores in SGA babies were 0.32 SD (95% CI, 0.25–0.38) below those for normal controls, though with heterogeneity between studies (I2 = 68.3%). Insufficient data were available for FGR babies.

Conclusion

The findings of the study demonstrate that among babies born at term, being SGA is associated with lower scores on neurodevelopmental outcomes compared to AGA controls. A trial designed to evaluate the effects of intervention in small fetuses born at term in order to improve the neurodevelopmental outcome is urgently needed. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Spatiotemporal image correlation‐derived volumetric Doppler impedance indices from spherical samples of the placenta: intraobserver reliability and correlation with conventional umbilical artery Doppler indices
Authors: Welsh A. W. , Hou M. , Meriki N. , Martins W. P.
Published: February 2012

Objective

Volumetric impedance indices derived from spatiotemporal image correlation (STIC) power Doppler ultrasound (PDU) might overcome the influence of machine settings and attenuation. We examined the feasibility of obtaining these indices from spherical samples of anterior placentas in healthy pregnancies, and assessed intraobserver reliability and correlation with conventional umbilical artery (UA) impedance indices.

Methods

Uncomplicated singleton pregnancies with anterior placenta were included in the study. A single observer evaluated UA pulsatility index (PI), resistance index (RI) and systolic/diastolic ratio (S/D) and acquired three STIC‐PDU datasets from the placenta just above the placental cord insertion. Another observer analyzed the STIC‐PDU datasets using Virtual Organ Computer‐aided AnaLysis (VOCAL) spherical samples from every frame to determine the vascularization index (VI) and vascularization flow index (VFI); maximum, minimum and average values were used to determine the three volumetric impedance indices (vPI, vRI, vS/D). Intraobserver reliability was examined by intraclass correlation coefficients (ICC) and association between volumetric indices from placenta, and UA Doppler indices were assessed by Pearson's correlation coefficient.

Results

A total of 25 pregnant women were evaluated but five were excluded because of artifacts observed during analysis. The reliability of measurement of volumetric indices of both VI and VFI from three STIC‐PDU datasets was similar, with all ICCs ≥ 0.78. Pearson's r values showed a weak and non‐significant correlation between UA pulsed‐wave Doppler indices and their respective volumetric indices from spherical samples of placenta (all r ⩽ 0.23). VOCAL indices from specific phases of the cardiac cycle showed good repeatability (ICC ≥ 0.92).

Conclusion

Volumetric impedance indices determined from spherical samples of placenta are sufficiently reliable but do not correlate with UA Doppler indices in healthy pregnancies. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Effect of letrozole on uterine artery Doppler flow indices prior to first‐trimester termination of pregnancy: a randomized controlled trial
Authors: Lee V. C. Y. , Yeung T. W. Y. , Tang O. S. , Ng E. H. Y. , Yeung W. S. B. , HO P. C.
Published: February 2012

Objective

We previously demonstrated that a sequential regimen of letrozole and misoprostol resulted in a marked reduction in the serum estradiol concentration and in a higher efficacy of first‐trimester termination of pregnancy than misoprostol alone. The aim of this study was to evaluate the effect of letrozole on uterine artery Doppler flow indices during early pregnancy.

Methods

This was a randomized controlled trial. Thirty women requesting termination of pregnancy up to 63 days' gestation were randomized into two groups: a letrozole group receiving 10 mg of letrozole, daily, for 3 days, and a control group receiving a placebo for 3 days. Serum estradiol, progesterone and human chorionic gonadotropin (hCG) concentrations were measured before drug administration and then daily for 6 days. Ultrasound scanning for fetal viability and measurement of the pulsatility (PI) and resistance (RI) indices of the uterine arteries was performed before drug administration, and then on day 3 and day 7 after starting letrozole or placebo. All pregnancies were terminated by surgical evacuation on day 7 or day 8.

Results

Uterine artery PI and RI decreased significantly in the letrozole group, but not in the control group. Serum estradiol concentrations were significantly lower in the letrozole group than in the control group from day 2 onwards. Serum progesterone and hCG concentrations were comparable for the two groups throughout the 7 days. There were significantly more women in the letrozole group with vaginal bleeding.

Conclusion

We have demonstrated that the use of letrozole in the first trimester of pregnancy suppresses serum estradiol levels but results in an increase in blood flow to the uterus. Further studies should be carried out to elucidate the mechanism of letrozole pretreatment in medical abortion. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.
Can we identify the limits of the puborectalis/pubovisceralis muscle on tomographic translabial ultrasound?
Authors: Kashihara H. , Shek K. L. , Dietz H. P.
Published: February 2012

Objective

In order to determine the relative locations of puborectalis/pubovisceralis (PR/PV) and iliococcygeus (IC) muscles, we undertook an analysis of four‐dimensional (4D) ultrasound datasets obtained after suburethral sling placement.

Methods

This was a retrospective analysis of ultrasound volume data obtained in 110 women after undergoing the Monarc suburethral sling procedure. Tomographic ultrasound imaging (TUI) was performed with eight slices in the axial plane, from 5 mm below to 12.5 mm above the plane of minimal hiatal dimensions. Hyperechogenic tape material was rated as absent, present or as producing an anechoic acoustic shadow overlying the muscle in each slice.

Results

Slices 7 and 8 virtually always showed evidence of the implant or its acoustic shadow on the pelvic sidewall (98% for slice 8 and 96% for slice 7), suggesting that these slices are located at the level of the obturator foramen. This implies that these slices do not generally contain PR/PV muscle, but rather IC muscle.

Conclusion

On standardized tomographic imaging of the levator hiatus and muscle, slices located ≥ 1 cm over the plane of minimal dimensions are very likely to contain IC muscle rather than PR/PV muscle. Copyright © 2012 ISUOG. Published by John Wiley & Sons, Ltd.