bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical anisotropy of A‐ and M‐plane InN grown on free‐standing GaN substrates
Authors: Schley P. , Räthel J. , Sakalauskas E. , Gobsch G. , Wieneke M. , Bläsing J. , Krost A. , Koblmüller G. , Speck J. S. , Goldhahn R. 
Published: March 2010

AbstractWurtzite A‐ and M‐plane InN films were grown by molecular beam epitaxy (MBE) on free‐standing GaN substrates. Spectroscopic ellipsometry (SE) in the photon energy range from 0.56 up to 15 eV was applied in order to determine the ordinary and extraordinary complex dielectric function (DF) of InN. A distinct optical anisotropy was found over the whole energy range. The extraordinary absorption edge in comparison to the ordinary one is shifted to higher energies confirming previous studies. The investigations in the upper vacuum‐ultraviolet (VUV) spectral range (9.5–15 eV) yielded transition energies for four critical points (CPs) of the band structure (BS) which have not been observed so far.
The role of InGaN interlayers on the microstructure of InN epilayers grown via metal organic vapour phase epitaxy
Authors: Kadir Abdul , Ganguli Tapas , Gokhale M. R. , Shah A. P. , Bhattacharya Arnab 
Published: March 2010

AbstractA detailed study on the influence of an InGaN interlayer between the GaN buffer and InN epilayer on the microstructural properties of the InN layer is reported. Using high‐resolution X‐ray diffraction measurements the mosaicity of MOVPE grown InN epilayers deposited directly on c‐plane sapphire, on GaN buffer layers, and on different InGaN interlayers have been compared. Generally the angle of tilt and hence the screw dislocation density in the InN epilayers can be controlled by growth conditions, while the angle of twist, corresponding to the edge dislocation density is usually weakly dependent on growth conditions. However, for a given layer thickness the edge dislocation density can be significantly reduced by the insertion of an InGaN interlayer.
Electron ionization and electrospray ionization mass spectrometric study of a series of isomeric N‐chloro(or bromo)benzyl‐substituted (E)‐2′(3′‐ or 4′)‐hydroxy‐4‐stilbazole halides
Authors: Prukała Dorota , Prukała Wiesław , Sikorski Marek 
Published: March 2010

AbstractThe electron ionization (EI) mass spectra and electrospray ionization (ESI) mass spectra of a series of isomeric N‐chlorobenzyl‐ and N‐bromobenzyl‐substituted (E)‐2′(3′ or 4′)‐hydroxy‐4‐stilbazole chlorides and bromides (1–12) were recorded. The fragmentation pathways of all of the compounds and the characteristic fragment ions formed by EI‐MS were studied by means of B/E and B2/E constant linked‐scanning techniques. The formation of ions originating from preionization reactions, characteristic of quaternary halides under EI‐MS conditions, such as the elimination of chloro‐ or bromobenzyl halides, dehydrohalogenation or substitution reactions, is explained. As soft ionization methods cause no such degradation reactions, the ESI‐MS spectra of the studied compounds were also obtained for comparison. We thus demonstrated the applicability of EI‐MS even in cases when preionization takes place, as long as such secondary processes are properly accounted for. Copyright © 2010 John Wiley & Sons, Ltd.
Electrospray ionization mass spectrometric analysis of newly synthesized α,β‐unsaturated γ‐lactones fused to sugars
Authors: Madeira Paulo J. Amorim , Rosa Ana Margarida , Xavier Nuno M. , Rauter Amélia P. , Florêncio M. Helena 
Published: March 2010

AbstractKnowledge of the fragmentation mechanisms of lactones and their behaviour under electrospray ionization (ESI) conditions can be extended to larger and more complex natural products that contain an α,β‐unsaturated γ‐lactone moiety in their structure. Moreover, little is known about the gas‐phase behaviour of α,β‐unsaturated γ‐lactones linked or fused to sugars. Therefore, five α,β‐unsaturated γ‐lactones (butenolides) fused to a pyranose ring, recently synthesized compounds with potential relevance regarding their biological properties, were investigated using ESI‐MS and ESI‐MS/MS in both positive and negative ion modes. Their fragmentation mechanisms and product ion structures were compared. It was observed that two isomers could be unambiguously distinguished in the negative ion mode by the fragmentation pathways of their deprotonated molecules as well as in the positive ion mode by the fragmentation pathways of either the protonated or the sodiated molecule.Fragmentation mechanisms are proposed taking into account the MS/MS data and semi‐empirical calculations using the PM6 Hamiltonean. The semi‐empirical calculations were also very useful in determining the most probable protonation and cationization sites. Copyright © 2010 John Wiley & Sons, Ltd.
The application of multiplexed, multi‐dimensional ultra‐high‐performance liquid chromatography/tandem mass spectrometry to the high‐throughput screening of lysosomal storage disorders in newborn dried bloodspots
Authors: Kasper David C. , Herman Joseph , De Jesus Victor R. , Mechtler Thomas P. , Metz Thomas F. , Shushan Bori 
Published: March 2010

AbstractLysozomal storage disorders are just beginning to be routinely screened using enzyme activity assays involving dried blood spots and tandem mass spectrometry (MS/MS). This paper discusses some of the analytical challenges associated with published assays including complex sample preparation and potential interference from excess residual substrate. Solutions to these challenges are presented in the form of on‐line two‐dimensional chromatography to eliminate off‐line liquid‐liquid extraction (LLE) and solid‐phase extraction (SPE), the use of ultra‐high‐performance liquid chromatography (UHPLC) to separate excess substrate from all other analytes and multiplexed sample introduction for higher throughput required of a population screening assay. High sensitivity, specificity and throughput were demonstrated using this novel method. Copyright © 2010 John Wiley & Sons, Ltd.
In situ lipid dip‐pen nanolithography under water
Authors: Lenhert Steven , Mirkin Chad A. , Fuchs Harald 
Published: March 2010

AbstractLipids form the structural and functional basis of biological membranes, and methods for studying their self‐organization in well‐defined nano‐ and micro‐scale model systems can provide insights into biology. Using lipids as an ink for dip‐pen nanolithography (lipid DPN) permits the rapid nanostructuring of multicomponent model lipid membrane systems, but this technique has so far been limited to air. Here we demonstrate that lipid DPN can be carried out under water with single tips or parallel arrays. Using the same tip for deposition and imaging in aqueous solution permits imaging of self‐spreading lipid bilayer spots in situ and quantification of the nanoscale spreading kinetics in real time by means of lateral‐force microscopy. Furthermore, using fluorophore‐labeled phospholipids, we directly observed, by confocal laser scanning microscopy, a two‐phase (oil in water) meniscus formed around the contact point between the DPN tip and surface, gaining insights into the mechanisms of the ink transport. The methods described here provide a new tool and environment for high‐resolution studies of lipid nanodynamics and molecular printing processes in general. SCANNING 32: 15–23, 2010. © 2010 Wiley Periodicals, Inc.
Adding local components to global functions for continuous covariates in multivariable regression modeling
Authors: Binder H. , Sauerbrei W. 
Published: March 2010

AbstractWhen global techniques, based on fractional polynomials (FPs), are employed for modeling potentially nonlinear effects of several continuous covariates on a response, accessible model equations are obtained. However, local features might be missed. Therefore, a procedure is introduced, which systematically checks model fits, obtained by the multivariable fractional polynomial (MFP) approach, for overlooked local features. Statistically significant local polynomials are then parsimoniously added. This approach, called MFP + L, is seen to result in an effective control of the Type I error with respect to the addition of local components in a small simulation study with univariate and multivariable settings. Prediction performance is compared with that of a penalized regression spline technique. In a setting unfavorable for FPs, the latter outperforms the MFP approach, if there is much information in the data. However, the addition of local features reduces this performance difference. There is only a small detrimental effect in settings where the MFP approach performs better. In an application example with children's respiratory health data, fits from the spline‐based approach indicate many local features, but MFP + L adds only few significant features, which seem to have good support in the data. The proposed approach may be expected to be superior in settings with local features, but retains the good properties of the MFP approach in a large number of settings where global functions are sufficient. Copyright © 2010 John Wiley & Sons, Ltd.
A weighted Cox model for modelling time‐dependent exposures in the analysis of case–control studies
Authors: Leffondre Karen , Wynant Willy , Cao Zhirong , Abrahamowicz Michal , Heinze Georg , Siemiatycki Jack 
Published: March 2010

AbstractMany exposures investigated in epidemiological case–control studies may vary over time. The effects of these exposures are usually estimated using logistic regression, which does not directly account for changes in covariate values over time within individuals. By contrast, the Cox model with time‐dependent covariates directly accounts for these changes over time. However, the over‐sampling of cases in case–control studies, relative to controls, requires manipulating the risk sets in the Cox partial likelihood. A previous study showed that simple inclusion or exclusion of future cases in each risk set induces an under‐ or over‐estimation bias in the regression parameters, respectively. We investigate the performance of a weighted Cox model that weights subjects according to age‐conditional probabilities of developing the disease of interest in the source population. In a simulation study, the lifetime experience of a source population is first generated and a case–control study is then simulated within each population. Different characteristics of exposure are generated, including time‐varying intensity. The results show that the estimates from the weighted Cox model are much less biased than the Cox models that simply include or exclude future cases, and are superior to logistic regression estimates in terms of bias and mean‐squared error. An application to frequency‐matched population‐based case–control data on lung cancer illustrates similar differences in the estimated effects of different smoking variables. The investigated weighted Cox model is a potential alternative method to analyse matched or unmatched population‐based case–control studies with time‐dependent exposures. Copyright © 2010 John Wiley & Sons, Ltd.
Threshold regression for survival data with time‐varying covariates
Authors: Lee Mei‐Ling Ting , Whitmore G. A. , Rosner Bernard A. 
Published: March 2010

AbstractTime‐to‐event data with time‐varying covariates pose an interesting challenge for statistical modeling and inference, especially where the data require a regression structure but are not consistent with the proportional hazard assumption. Threshold regression (TR) is a relatively new methodology based on the concept that degradation or deterioration of a subject's health follows a stochastic process and failure occurs when the process first reaches a failure state or threshold (a first‐hitting‐time). Survival data with time‐varying covariates consist of sequential observations on the level of degradation and/or on covariates of the subject, prior to the occurrence of the failure event. Encounters with this type of data structure abound in practical settings for survival analysis and there is a pressing need for simple regression methods to handle the longitudinal aspect of the data. Using a Markov property to decompose a longitudinal record into a series of single records is one strategy for dealing with this type of data. This study looks at the theoretical conditions for which this Markov approach is valid. The approach is called threshold regression with Markov decomposition or Markov TR for short. A number of important special cases, such as data with unevenly spaced time points and competing risks as stopping modes, are discussed. We show that a proportional hazards regression model with time‐varying covariates is consistent with the Markov TR model. The Markov TR procedure is illustrated by a case application to a study of lung cancer risk. The procedure is also shown to be consistent with the use of an alternative time scale. Finally, we present the connection of the procedure to the concept of a collapsible survival model. Copyright © 2010 John Wiley & Sons, Ltd.
Bayesian methods for meta‐analysis of causal relationships estimated using genetic instrumental variables
Authors: Burgess Stephen , Thompson Simon G. ,   CRP CHD Genetics Collaboration
Published: March 2010

AbstractGenetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta‐analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C‐reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes. Copyright © 2010 John Wiley & Sons, Ltd.
High‐Concentration Solvent Exfoliation of Graphene
Authors: Khan Umar , O'Neill Arlene , Lotya Mustafa , De Sukanta , Coleman Jonathan N. 
Published: March 2010

AbstractA method is demonstrated to prepare graphene dispersions at high concentrations, up to 1.2 mg mL−1, with yields of up to 4 wt% monolayers. This process relies on low‐power sonication for long times, up to 460 h. Transmission electron microscopy shows the sonication to reduce the flake size, with flake dimensions scaling ast−1/2. However, the mean flake length remains above 1 µm for all sonication times studied. Raman spectroscopy shows defects are introduced by the sonication process. However, detailed analysis suggests that predominately edge, rather than basal‐plane, defects are introduced. These dispersions are used to prepare high‐quality free‐standing graphene films. The dispersions can be heavily diluted by water without sedimentation or aggregation. This method facilitates graphene processing for a range of applications.
Shape‐Dependent Cytotoxicity and Proinflammatory Response of Poly(3,4‐ethylenedioxythiophene) Nanomaterials
Authors: Oh Wan‐Kyu , Kim Sojin , Yoon Hyeonseok , Jang Jyongsik 
Published: March 2010

AbstractPoly(3,4‐ethylenedioxythiophene) (PEDT) is recognized as one of the most promising conducting polymers for future applications in the fields of electronics, optics, energy storage/conversion, and biomedical science. The toxicity of PEDT could be considered to affect the potential for its widespread application. Herein, the cytotoxicity and proinflammatory response of PEDT nanomaterials of three different shapes toward human lung fibroblast (IMR90) and mouse alveolar macrophage (J774A.1) cells are investigated. The shape‐dependent toxicity of the PEDT nanomaterials is evaluated by examining cell morphological change, cytotoxicity, apoptosis/necrosis, oxidative stress, and immune response. The cytotoxicity and apoptosis of the nanomaterials increase with their decreasing aspect ratio in both cell lines. The formation of reactive oxygen species in cells treated with PEDT nanomaterials is dependent on the shape and concentration of the nanomaterial. Proinflammatory cytokines, such as interleukin‐1, interleukin‐6, and tumor necrosis factor α from macrophages, are induced by PEDT nanomaterial‐treated cells.
Produktion, Eigenschaften und Tragverhalten von thermisch gebogenen Floatgläsern für das Bauwesen – Erstprüfung und werkseigene Produktionskontrolle im Rahmen des Zulassungsverfahrens
Authors: Ensslen Frank , Schneider Jens , Schula Sebastian 
Published: March 2010

AbstractGebogene Gläser werden zunehmend in der Architektur eingesetzt. Da im Bauwesen bislang keine Produktnormen für gebogene Gläser existieren, ist es notwendig, Qualitätskriterien für die Herstellung und das Inverkehrbringen über eine allgemeine bauaufsichtliche Zulassung oder über eine Zustimmung im Einzelfall zu regeln. Der vorliegende Beitrag gibt einen Überblick über das Herstellverfahren, die mechanischen Eigenschaften und das Tragverhalten thermisch gebogener Floatgläser. Besonders werden die Inhalte für die Erstprüfung und werkseigene Produktionskontrolle im Rahmen des Zulassungsverfahrens vorgestellt.Production, properties and structural behaviour of bent glasses – Initial testing and production control within the scope of the approval procedure. The market of bent architectural glass is continuously increasing. Due to a lack of product standards in construction engineering, quality standards for manufacturing and handling have to be checked by a general technical approval or individually for each case and project. This article gives an overview about the production, mechanical properties and the structural behavior of bent glasses. The initial testing and production control is specified.
Hybride Glasträger als Fassadenelemente
Authors: Weller Bernhard , Meier Anja , Weimar Thorsten , Menkenhagen Jochen , Koschecknick Kai 
Published: March 2010

AbstractGlasträger ermöglichen ein erhöhtes Maß an Transparenz in Fassadenkonstruktionen. Die Anwendung erfordert allerdings stets die umfassende Betrachtung der spezifischen Eigenschaften von Glas, wie beispielsweise die Sprödigkeit und die fehlende Resttragfähigkeit. Auch bei Glasträgern aus Verbund‐Sicherheitsglas, die einige Eigenschaften verbessern, ist der Verlust der Tragfähigkeit nach einem Bruch aller Einzelscheiben nicht auszuschließen. Zur Vermeidung des Bruches werden daher bei der Bemessung erhöhte Sicherheitsfaktoren eingesetzt. Die hier vorgestellten hybriden Glasträger zeigen eine Lösung, die Resttragfähigkeit von Glasträgern mittels geklebter Stahlelemente zu erhöhen. Es werden die durchgeführten Vierpunkt‐Biegeversuche zur Bestimmung der Tragfähigkeit und Resttragfähigkeit an Stahl‐Glas‐Trägern mit unterschiedlichen Querschnittsgeometrien erläutert. Anschließend erfolgt die Beschreibung der numerischen Berechnungen und deren Verifizierung basierend auf den experimentellen Untersuchungen.Glass Beams as Structural Members in Facades. Glass as a structural member enables a higher degree of transparency in facades. However, the application always requires a comprehensive consideration of the specific properties of glass, such as the brittleness and lack of residual bearing capacity. Even with laminated glass beams, which improve several properties, the loss of load‐bearing capacity after breakage of each individual pane can not be excluded. Increased safety factors are used in the design to avoid the breakage. The hybrid beams presented show a solution to increase the residual bearing capacity of glass beams using bonded steel elements. The conducted four‐point bending tests are discussed for the purpose of the determining of the structural strength and post‐breakage behaviour of the beams with different cross‐sectional geometries. Subsequently, the description of the numeric simulations and their verification based on the experimental investigations is illustrated.
Erfahrungen mit Netzwerkbogenbrücken im Eisenbahnbrückenbau
Authors: Gauthier Peter , Krontal Ludolf 
Published: March 2010

AbstractIn den vergangenen zwei Jahren wurden bei der DB AG mehrere Eisenbahnüberführungen als Netzwerkbogenbrücken errichtet. Die Bauweise zeichnet sich vor allem durch eine effektive, wirtschaftliche und ästhetische Tragkonstruktion aus. An den Bauwerksentwurf, die Ausführungsplanung und die Bauausführung sind aufgrund des komplexen Tragverhaltens und der schwierigeren Geometrie hohe Anforderungen zu stellen. Die Erfahrungen bei der Planung und dem Bau der Netzwerkbogenbrücken im Eisenbahnbrückenbau werden im nachfolgenden Aufsatz aufgeführt und anhand von Beispielen erläutert.Experiences with Network arches for railway bridges. In the past two years several railroad bridges were established as Network arch bridges by DB AG. The construction method is characterized for the bridge construction particularly by an effective, an economical and aesthetically a carrying construction. Considering complex carrying behavior and more difficult geometry high demands on basic design, detailed design and construction works are to be made. The experiences when planning and building of the network arch bridges in the railway bridge construction are specified in the following article and described on the basis of examples.
Umgang mit genieteten Bahnbrücken von hohem kulturellem Wert
Authors: Brühwiler Eugen , Hirt Manfred A. 
Published: March 2010

AbstractZunehmende Bahnlasten können die Weiterverwendung genieteter Bahnbrücken, die oftmals hohe kulturelle Werte aufweisen, in Frage stellen. Beim Umgang mit genieteten Bahnbrücken sind neben technischen und wirtschaftlichen Kriterien auch denkmalschützerische Aspekte zu berücksichtigen. Über die letzten 20 Jahre wurden die Kenntnisse über das Trag‐ und Ermüdungsverhalten von genieteten Bahnbrücken wesentlich erweitert, so dass heute eine wirklichkeitsnahe Überprüfung dieser Bauwerke möglich ist. Dieser Kenntnisstand ist in den in der Schweiz bald veröffentlichten SIA Normen über den Umgang mit bestehenden Tragwerken enthalten. Anhand von drei Beispielen wird aufgezeigt, dass bei der Erhaltung genieteter Bahnbrücken von hohem kulturellem Wert die Interessen von Bahnunternehmen und Denkmalschutz übereinstimmen.Dealing with riveted railway bridges of high cultural value. The continuing use of riveted railway bridges may be questioned because of increasing train loads. Riveted bridges often possess high cultural values and, consequently, aspects of cultural heritage have to be considered in addition to technical and economic issues when dealing with riveted railway bridges. Over the last 20 years, knowledge on the structural and fatigue behavior of riveted railway bridges have been significantly improved allowing nowadays for realistic examination of these bridges. This stateof‐ the‐art is comprised in the soon to be released SIA codes on existing structures. Three examples illustrate that interests of railway companies and cultural heritage coincide when dealing with riveted railway bridges of high cultural value.