bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring mitochondrial metabolism in rat brain in vivo using MR Spectroscopy of hyperpolarized [2‐13C]pyruvate
Authors: Park Jae Mo , Josan Sonal , Grafendorfer Thomas , Yen Yi‐Fen , Hurd Ralph E. , Spielman Daniel M. , Mayer Dirk
Published: April 2013

Hyperpolarized [1‐13C]pyruvate ([1‐13C]Pyr) has been used to assess metabolism in healthy and diseased states, focusing on the downstream labeling of lactate (Lac), bicarbonate and alanine. Although hyperpolarized [2‐13C]Pyr, which retains the labeled carbon when Pyr is converted to acetyl‐coenzyme A, has been used successfully to assess mitochondrial metabolism in the heart, the application of [2‐13C]Pyr in the study of brain metabolism has been limited to date, with Lac being the only downstream metabolic product reported previously. In this study, single‐time‐point chemical shift imaging data were acquired from rat brain in vivo. [5‐13C]Glutamate, [1‐13C]acetylcarnitine and [1‐13C]citrate were detected in addition to resonances from [2‐13C]Pyr and [2‐13C]Lac. Brain metabolism was further investigated by infusing dichloroacetate, which upregulates Pyr flux to acetyl‐coenzyme A. After dichloroacetate administration, a 40% increase in [5‐13C]glutamate from 0.014 ± 0.004 to 0.020 ± 0.006 (p = 0.02), primarily from brain, and a trend to higher citrate (0.002 ± 0.001 to 0.004 ± 0.002) were detected, whereas [1‐13C]acetylcarnitine was increased in peripheral tissues. This study demonstrates, for the first time, that hyperpolarized [2‐13C]Pyr can be used for the in vivo investigation of mitochondrial function and tricarboxylic acid cycle metabolism in brain. Copyright © 2013 John Wiley & Sons, Ltd.
Effect of obesity onset on pendular energy transduction at spontaneous walking speed: Prader–willi versus nonsyndromal obese individuals
Authors: Malatesta Davide , Vismara Luca , Menegoni Francesco , Grugni Graziano , Capodaglio Paolo
Published: April 2013

Objective

To compare the mechanical external work (Wext) and pendular energy transduction (Rstep) at spontaneous walking speed (Ss) in individuals with Prader–Willi syndrome (PWS) versus subjects with nonsyndromal obesity (OB) to investigate whether the early onset of obesity allows PWS subjects to adopt energy conserving gait mechanics.

Design and Methods

Wext and Rstep were computed using kinematic data acquired by an optoelectronic system and compared in 15 PWS (BMI = 39.5 ± 1.8 kg m−2; 26.7 ± 1.5 year) and 15 OB (BMI = 39.3 ± 1.0 kg m−2; 28.7 ± 1.9 year) adults matched for gender, age and BMI and walking at Ss.

Results

Ss was significantly lower in PWS (0.98 ± 0.03 m s−1) than in OB (1.20 ± 0.02 m s−1; P < 0.001). There were no significant differences in Wext per kilogram between groups (PWS: 0.37 ± 0.04 J kg−1 m−1; OB: 0.40 ± 0.05 J kg−1 m−1; P = 0.66) and in Rstep (PWS: 69.9 ± 2.9%; OB: 67.7 ± 2.4%; P = 0.56). However, Rstep normalized to Froude number (Rstep/Fr) was significantly greater in PWS (6.0 ± 0.6) than in OB (3.8 ± 0.2; P = 0.001). Moreover, Rstep/Fr was inversely correlated with age of obesity onset (r = −0.49; P = 0.006) and positively correlated with obesity duration (r = 0.38; P = 0.036).

Conclusion

Individuals with PWS seem to alter their gait to improve pendular energy transduction as a result of precocious and chronic adaptation to loading.
Local aggregation effect of CNT on the vibrational behavior of four‐parameter continuous grading nanotube‐reinforced cylindrical panels
Authors: Pourasghar A. , Yas M.H. , Kamarian S.
Published: April 2013

Free vibrations analysis of four‐parameter continuously graded nanocomposite cylindrical panels reinforced by randomly oriented straight and local aggregation single‐walled carbon nanotubes (CNTs) are presented based on three‐dimensional theory of elasticity. The material properties of continuously graded carbon nanotube‐reinforced composites (CG‐CNTRCs) are estimated through the Eshelby–Mori–Tanaka approach based on an equivalent fiber. The generalized differential quadrature method as an efficient and accurate numerical tool is used to discretize the governing equations and impediment the boundary conditions. One of the contributions of this work is to illustrate the influence of the four parameters of power‐law distributions on the vibration behavior of functionally graded orthotropic cylindrical panels reinforced by nanotube. The properties of CG‐CNTRC are affected by its microstructure, especially the degree of CNT aggregation that is described by an aggregation coefficient. It is shown the degree of aggregation canseriously reduce the effective stiffness and frequency parameter. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
Electrical and thermal properties of polyethylene/silver nanoparticle composites
Authors: Jouni Mohammad , Boudenne Abderrahim , Boiteux Gisèle , Massardier Valérie , Garnier Bertrand , Serghei Anatoli
Published: April 2013

The concentration dependence of specific heat, electrical and thermal conductivities of nanocomposites based on high‐density polyethylene (HDPE) filled with silver nanoparticles have been investigated. The composites filled with high filler content show high electrical and thermal conductivities. The dielectric relaxation spectroscopy was used to investigate the electrical properties in the studied systems. The scaling law of electrical percolation was used for an exact estimation of the percolation threshold (Pc). A low electrical percolation threshold was found in the investigated composites. The rule of mixture was sufficient for the prediction of the specific heat dependence of HDPE–Ag nanocomposites as a function of the weight filler content. The basic models of the thermal conductivity have a tendency to underestimate the measured values for the low and high filler concentrations. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
Halloysite nanotube reinforced biodegradable nanocomposites using noncrosslinked and malonic acid crosslinked polyvinyl alcohol
Authors: Qiu Kaiyan , Netravali Anil N.
Published: April 2013

Halloysite nanotubes (HNTs) based thin membrane‐like fully biodegradable nanocomposites were produced by blending individualized HNT dispersion with polyvinyl alcohol (PVA). Stable individualized HNT dispersion was obtained using several separation techniques, sequentially, prior to blending with PVA. PVA was crosslinked using malonic acid (MA) as crosslinker and phosphoric acid as catalyst, to increase the mechanical and thermal properties of HNT–PVA nanocomposites. Crosslinking was also intended to make PVA water‐insoluble and hence more useful in commercial applications. Examination of the composites indicated that HNTs were uniformly dispersed in both PVA as well as crosslinked PVA. Excellent mechanical properties of the HNT–PVA nanocomposites were achieved. These nanocomposites are intended to be composted at the end of their life rather than ending up in landfills as most of today's traditional petroleum based non‐biodegradable plastics. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
Natural Language Processing to identify pneumonia from radiology reports
Authors: Dublin Sascha , Baldwin Eric , Walker Rod L. , Christensen Lee M. , Haug Peter J. , Jackson Michael L. , Nelson Jennifer C. , Ferraro Jeffrey , Carrell David , Chapman Wendy W.
Published: April 2013

Purpose

This study aimed to develop Natural Language Processing (NLP) approaches to supplement manual outcome validation, specifically to validate pneumonia cases from chest radiograph reports.

Methods

We trained one NLP system, ONYX, using radiograph reports from children and adults that were previously manually reviewed. We then assessed its validity on a test set of 5000 reports. We aimed to substantially decrease manual review, not replace it entirely, and so, we classified reports as follows: (1) consistent with pneumonia; (2) inconsistent with pneumonia; or (3) requiring manual review because of complex features. We developed processes tailored either to optimize accuracy or to minimize manual review. Using logistic regression, we jointly modeled sensitivity and specificity of ONYX in relation to patient age, comorbidity, and care setting. We estimated positive and negative predictive value (PPV and NPV) assuming pneumonia prevalence in the source data.

Results

Tailored for accuracy, ONYX identified 25% of reports as requiring manual review (34% of true pneumonias and 18% of non‐pneumonias). For the remainder, ONYX's sensitivity was 92% (95% CI 90–93%), specificity 87% (86–88%), PPV 74% (72–76%), and NPV 96% (96–97%). Tailored to minimize manual review, ONYX classified 12% as needing manual review. For the remainder, ONYX had sensitivity 75% (72–77%), specificity 95% (94–96%), PPV 86% (83–88%), and NPV 91% (90–91%).

Conclusions

For pneumonia validation, ONYX can replace almost 90% of manual review while maintaining low to moderate misclassification rates. It can be tailored for different outcomes and study needs and thus warrants exploration in other settings. Copyright © 2013 John Wiley & Sons, Ltd.
Study of the morphology and rheological behavior of polymer‐modified asphalt blends prepared with poly(styrene‐b‐butadiene‐b‐styrene) and poly(styrene‐b[(butadiene)1—x‐(Ethylene‐co‐Butylene) x]‐b‐Styrene) of Star‐Like Molecular Architecture
Authors: Aguirre Paola González , Torres Luís Medina , Fonteix Christian , Pla Fernand , Nájera Rafael Herrera
Published: April 2013

Asphalt‐modification was studied using two different types of triblock copolymers both with star‐like molecular architecture: poly(styrene‐b‐butadiene‐b‐styrene), SBS, and poly(styrene‐b[(butadiene)1−x‐(ethylene‐co‐butylene)x]‐b‐styrene), SBEBS, to elucidate the effect of the molecular characteristics of the polymer and the polymer‐content on the morphology and rheological behavior of polymer‐modified asphalt, P‐MA. The P‐MAs were prepared using a hot mixing process and characterized using fluorescence microscopy and oscillatory shear flow measurements under linear viscoelastic conditions. Results revealed that the morphology of the polymer‐rich phase and rheological behavior of the P‐MA are dependent on the type and concentration of polymer: (i) P‐MAs prepared with SBEBS exhibited higher dispersion in the asphalt matrix and were more elastic and less responsive toward frequency changes; (ii) P‐MAs prepared with the polymer (SBS or SBEBS) of the larger molecular weight displayed higher elasticity; and (iii) the increase in the polymer concentration from 3 to 10 wt% resulted in the creation of P‐MAs with higher elastic response. These results substantiate the importance of the molecular characteristics of the polymer in determining the properties of P‐MAs, in particular composition of the elastomeric‐b and molecular weight of these polymers, and the results are explained considering the molecular characteristics of these polymers and the polymer/asphalt interaction. POLYM. ENG. SCI., 53:2454–2464, 2013. © 2013 Society of Plastics Engineers
Power rating of photovoltaic modules including validation of procedures to implement IEC 61853‐1 on solar simulators and under natural sunlight
Authors: Kenny Robert P. , Viganó Davide , Salis Elena , Bardizza Giorgio , Norton Matthew , Müllejans Harald , Zaaiman Willem
Published: April 2013

This paper describes the measurement of photovoltaic module performance over a range of temperatures and irradiances according to the international standard IEC 61853 Part 1. The purpose of this work is to assess the reproducibility of power matrix measurements obtained using two methods specified in the standard: under natural sunlight with a tracker, and with a solar simulator. A comparison of results using the third principal method (under natural sunlight without tracker) is also summarised for completeness. The same measurement techniques have been employed to measure four modules of different technologies, namely mono and poly crystalline Si, CdTe and CIS. The method used to vary the irradiance in the natural sunlight with tracker and solar simulator approaches is based on un‐calibrated mesh filters. The uniformity and effect on spectrum of the mesh filters have been studied, and the impact of these on the measurements estimated. Measurements from all methods are compared over as much of the ranges as possible. The results show that for all modules, the reproducibility is within the estimated measurement uncertainty. The suitability of the different methods is discussed in light of the results and the limitations of the various methods as applied to different modules technologies. On the basis of the results, parts of IEC 61853 Part 1 will be introduced into the ISO 17025 laboratory accreditation at the European Solar Test Installation (ESTI). Copyright © 2013 John Wiley & Sons, Ltd.
On the mechanical strength of monocrystalline, multicrystalline and quasi‐monocrystalline silicon wafers: a four‐line bending test study
Authors: Barredo Josu , Parra Vicente , Guerrero Ismael , Fraile Alberto , Hermanns Lutz
Published: April 2013

Quasi‐monocrystalline silicon wafers have appeared as a critical innovation in the PV industry, joining the most favorable characteristics of the conventional substrates: the higher solar cell efficiencies of monocrystalline Czochralski‐Si (Cz‐Si) wafers and the lower cost and the full square‐shape of the multicrystalline ones. However, the quasi‐monocrystalline ingot growth can lead to a different defect structure than the typical Cz‐Si process. Thus, the properties of the brand new quasi‐monocrystalline wafers, based on low and high crystal defect densities, have been for the first time studied from a mechanical point of view, comparing their strength with that of both Cz‐Si monocrystalline and typical multicrystalline materials. The study has been carried out employing the four line bending test and simulating them by means of FE models. For the analysis, failure stresses were fitted to a three‐parameter Weibull distribution. High mechanical strength was found in all the cases. However, the quasi‐monocrystalline wafers characterized by large density of bulk defects, due to the noticeable density of extended defects, showed lower fracture tensions. Copyright © 2013 John Wiley & Sons, Ltd.
Multiplex epitope detection: A new method overcomes limitations of antibody arrays
Authors: Cen Hui , Windler Sarah L. , Rice Lyle S. , Zhang Amy , Zhou Hua
Published: April 2013

Antibody arrays have been used as an effective method for simultaneously detecting multiple proteins such as cytokines. However, their use in quantifying a large number of cellular proteins has the following limitations: (i) unsuitable for simultaneously detecting proteins that may form complexes with each other; (ii) incapable of quantitatively detecting more than one epitope of each protein such as phospho‐ and nonphospho‐epitopes; and (iii) incapable of simultaneously detecting multiple biomarkers on solid surfaces such as formalin‐fixed tissue sections. Using a novel multiple epitope detection (MED) technique, we have overcome these limitations and have improved upon currently available antibody‐based protein detection technologies. The MED technique employs primary antibody detection of epitopes within fixed cells or tissue, followed by elution of bound antibodies, and subsequent quantification of the eluted antibodies by an epitope array. Using the MED method, we demonstrate accurate detection of individual proteins even in complex with each other, simultaneous quantitative detection of phospho‐ and nonphospho‐epitopes on a protein, and sensitive detection of multiple biomarkers on formalin‐fixed tissue sections.
Synthesis and photovoltaic properties of amorphous polymers based on dithienylbenzothiadiazole‐triphenylamine with hexyl side chains on different positions of thienyl groups
Authors: Yasuda Takeshi , Shinohara Yuki , Matsuda Takaaki , Han Liyuan , Ishi‐i Tsutomu
Published: April 2013

We synthesized and characterized three new amorphous dithienylbenzothiadiazole (TBT)‐triphenylamine (TPA) polymers for application in bulk‐heterojunction (BHJ) organic photovoltaic (OPV) cells. Poly(3HTBT‐TPA) has hexyl side chains on the thienyl groups (pointing toward the benzothiadiazole (BTD) unit), and poly(4HTBT‐TPA) has hexyl side chains on the thienyl groups (pointing outward from the BTD unit). The incident photon to current conversion efficiencies (IPCEs) in the region from 550 to 650 nm for the OPV cells prepared using poly(4HTBT‐TPA) were higher than those for the OPV cells prepared using poly(3HTBT‐TPA) because the absorption spectrum for the poly(4HTBT‐TPA) has a slightly red‐shifted absorption edge. We also demonstrated that the poly(4HTBT‐TPA)‐based OPV performance is independent of the fabrication process, so using an amorphous film to fabricate BHJ OPV cells offers great advantages over using a polycrystalline film in terms of the high reproducibility of the OPV performance. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2536–2544
Improved phase separation in polymer solar cells by solvent blending
Authors: Kästner Christian , Muhsin Burhan , Wild Andreas , Egbe Daniel A. M. , Rathgeber Silke , Hoppe Harald
Published: April 2013

The effect of solvent blending on the performance of an anthracene‐containing poly(p‐phenylene‐ethynylene)‐alt‐poly(p‐phenylene‐vinylene) backbone‐based donor polymer with asymmetrically substituted branched 2‐ethylhexyloxy and methyloxy side‐chains in bulk heterojunction solar cells is reported. This copolymer yields relatively high open‐circuit voltages with fullerene‐based electron acceptors. We systematically studied the thin‐film blend morphology and solar cell performance as a function of solvent composition (chlorobenzene to chloroform ratio) and polymer to [6,6]‐phenyl C61‐butyric acid methylester (PCBM) ratio. We combined photophysical investigations with atomic force microscopy and grazing incidence wide‐angle X‐ray scattering to elucidate the solid‐state morphology in thin films. In the investigated polymer system, the blend morphology becomes independent of the supporting solvent for high PCBM concentrations. Deposition from solvent blends rather than from pure chlorobenzene facilitates the beneficial phase separation between polymer and PCBM, leading to improved charge transport properties (short‐circuit currents) at lower PCBM concentrations. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013, 51, 868–874
Post‐traumatic growth among an ethnically diverse sample of adolescent and young adult cancer survivors
Authors: Arpawong T. Em , Oland Alyssa , Milam Joel E. , Ruccione Kathleen , Meeske Kathleen A.
Published: April 2013

Objective

Although some survivors of childhood cancer report significant psychosocial distress, many also report having derived benefits, or post‐traumatic growth (PTG), from their cancer experience. This study examines PTG and its correlates among an ethnically diverse sample of adolescent/young adult (AYA) cancer survivors who have recently completed treatment.

Methods

Survivors of childhood cancer (n = 94; 47% Hispanic), ages 11–21 and within 6 months of completing cancer therapy, were recruited from three pediatric cancer centers. Participants completed a structured interview that assessed demographics, PTG, post‐traumatic stress symptoms, health‐related quality of life, optimism, and depressive symptoms. Diagnosis/treatment information was collected from each patient's medical record. Multiple regression analyses were used to identify significant correlates of PTG.

Results

The majority of survivors reported positive growth. PTG was positively associated with psychosocial functioning and post‐traumatic stress symptoms and inversely associated with physical functioning and depressive symptoms. PTG was significantly lower among survivors of bone tumors (vs. survivors of other cancers) and Hispanic survivors who primarily spoke English at home (vs. Hispanics who primarily spoke Spanish at home and non‐Hispanics). PTG was not significantly related to age, sex, optimism, cancer treatment modality, duration of treatment, or treatment intensity.

Conclusions

The AYA survivors commonly reported PTG in the immediate aftermath of cancer treatment. Findings regarding PTG among more acculturated Hispanic and bone tumor AYA survivors may help to inform risk‐adapted clinical interventions, among those transitioning from active treatment to post‐treatment surveillance, to mitigate negative long‐term sequelae and enhance positive psychosocial adaptation from the cancer diagnosis and treatment. Copyright © 2013 John Wiley & Sons, Ltd.
Dispersion theory of nucleon Compton scattering and polarizabilities
Authors: Schumacher M. , Scadron M.D.
Published: April 2013

A status report on the topic nucleon Compton scattering and polarizabilities is presented with emphasis on the scalar t‐channel as entering into dispersion theory. Precise values for the polarizabilities are obtained leading to αp = 12.0 ± 0.6 (12.0), βp= 1.9∓ 0.6 (1.9), αn= 12.5 ± 1.7 (13.4), βn= 2.7 ∓ 1.8 (1.8) in units of 10−4 fm3 and γ(p)π= −36.4 ± 1.5 (−36.6), γ(n)π= 58.6 ± 4.0 (58.3), (γ(p)0 = −0.58 ± 0.20), (γ(n)0 = +0.38 ± 0.22) in units of 10−4 fm4, for the proton (p) and neutron (n), respectively. The data given with an error are recommended experimental values with updates compared to [1] where necessary, the data in parentheses are predicted values. These predicted values are not contained in [1], but are the result of a newly developed analysis which is the main topic of the present paper. The most important recent discovery is that the largest part of the electric polarizability and the total diamagnetic polarizability of the nucleon are properties of the σ meson as part of the constituent‐quark structure, as expected from the mechanism of chiral symmetry breaking. This view is supported by an experiment on Compton scattering by the proton carried out in the second resonance region, where a large contribution from the σ meson enters into the scattering amplitudes. This experiment led to a determination of the mass of the σ meson of mσ= 600± 70 MeV. From the experimental αp and predicted differences (αn‐αp) neutron polarizabilities in the range αn = 12.0 – 13.4 are predicted, where the uncertainties are related to the f0(980) and a0(980) scalar mesons.
Layer transfer process assisted by laser scribing for thin film solar cells based on epitaxial foils
Authors: Matte Eric , van Nieuwenhuysen Kris , Depauw Valerie , Govaerts Jonathan , Gordon Ivan
Published: April 2013

The lift‐off step of a layer transfer process for the production of thin‐film solar cells using a double porous layer is studied in detail. The goal is to locally weaken the thin film to improve the detachment. A UV nanosecond pulse laser is used to induce the weakening by scribing trenches. A relation between the pulse fluence, the number of pulses per point and the ablated area is found and used to predict the ablation depth. The grooving step is applied at different points in the process chain. The most suitable grooves are obtained when the scribing process is done after front‐side processing of the attached thin film and before the bonding step. A yield of around 80% is obtained for samples that went through the process chain up to the detachment step, by using the optimized process conditions.

magnified image

SEM of the mother substrate (right) and the remaining of the thin film (left) after detachment of the useful foil area. The white points on the substrate are the leftover of the pillars from the weak layer.
Comparative analysis of mechanical properties of Si substrates processed by different routes
Authors: Gouttebroze Sylvain , Lange Hans Ivar , Ma Xiang , Gløckner Ronny , Emamifard Behnaz , Syvertsen Martin , Vardavoulias Michalis , Ulyashin Alexander
Published: April 2013

The purpose of this work is to check the potential of innovative processes for the Si wafers production toward the solar cell industry. Studies have been focused on a comparative analysis of mechanical properties of such wafers, since: (i) reduced wafer strength leads to a high breakage rate during subsequent handling and solar cell processing steps, (ii) cracking of solar cells has become one of the major sources of solar module failure and rejection. Therefore while developing new types of wafer materials and processing, it is essential to assess the mechanical strength of the wafers. Mechanical properties of several innovative Si based substrates are estimated. The bending strength measurements of the silicon wafer are performed using the ring‐on‐ring set‐up coupled with a numerical model to obtain estimate of the fracture stress and the Weibull parameters of the fracture distribution. Results are presented for five different materials: sintered Si powder, standard multi‐crystalline Si, Czochralski monocrystalline Si, and two types of thermal sprayed Si wafers.
Effects of pressure on photo‐induced formation of Se and Te clusters in II–VI compounds
Authors: Lindberg G. P. , Tallman R. E. , Lauck R. , Cardona M. , Liu X. , Furdyna J. K. , Weinstein B. A.
Published: April 2013

The tendency for clusters of crystalline Se or Te to form in the zincblende (ZB) phases of ZnSe, ZnTe, and CdSe is investigated as a function of applied pressure and under exposure to laser light. We find that nanoclusters of these elements in the trigonal phase form at pressures of >4.8 GPa for ZnSe and 0–0.9 GPa for ZnTe under exposure to moderate fluxes of sub‐bandgap light ∼102 W mm−2. The appearance of the A1 Raman peaks of Se or Te, clearly identified by their negative pressure shifts, provide definitive evidence of the cluster formation. Several mis‐assignments of these peaks in the literature are noted. For CdSe, the phase transition at 2.5 GPa leads to ambiguity in our results. Some mechanisms for the formation of Se (Te) clusters in II–VI solids are briefly considered.
Magnetotransport in Zn1−xMnxSe:Cl under hydrostatic pressure
Authors: Petznick Steve , Hetterich Michael , Klar Peter J.
Published: April 2013

Pressure dependent magnetotransport measurements have been carried out on a chlorine‐doped Zn0.98Mn0.02Se epilayer with a carrier concentration below the critical concentration of the metal‐insulator transition (MIT). The large positive magnetoresistance at low temperatures can qualitatively be related to the giant Zeeman splitting of the donor states. The increase of the resistivity and the magnetoresistance effects under hydrostatic pressure is mainly related to the increase of the electron effective mass in the conduction band. This increase of the effective mass is the reason for an increase of the donor depth and a corresponding shrinkage of the donor wavefunction, which in turn leads to a narrowing of the impurity band (IB). The splitting of this narrow IB, which results from an applied pressure, is the main reason for the enhancement of the large positive magnetoresistance effects under pressure.
Pressure tuning of high‐power laser diodes in the 720–1540 nm range
Authors: Dybala Filip , Bercha Artem , Klimczak Mariusz , Piechal Bernard , Ivonyak Yurii , Trzeciakowski Witold A.
Published: April 2013

Laser diodes with output powers of 1–2 W and emission wavelengths of 808, 860, 975, 1060, 1120, 1210, and 1540 nm have been tuned with pressure up to 2 GPa. Pressure tuning might become a practical method for tuning near‐infrared lasers in spectroscopic applications, such as photoluminescence excitation, photoreflectance, and resonant Raman scattering, as well as in applications as optical pumps at unique wavelengths.
Use of dynamic compression to probe semiconductor response at large strains
Authors: Grivickas P. , McCluskey M. D. , Gupta Y. M.
Published: April 2013

Large strains in semiconductors are expected to be more common in future electronic devices utilizing nanostructure components. Hydrostatic pressure (HP) and uniaxial stress (US) loading have inherent limitations for probing the desired strain conditions. Uniaxial strain loading, achieved in dynamic compression experiments, is particularly attractive for attaining well‐defined, large strains and to complement HP and US loading. Recent dynamic compression studies on III–V semiconductors (GaN, GaP, and GaAs) are summarized to review notable findings ranging from improved deformation potentials to free carrier properties. These findings demonstrate the benefits of dynamic compression experiments for semiconductor research.
Origin of the visible light absorption of Co2+ and NH4+ co‐doped hydrogen titanate nanotube thin films
Authors: An Yongliang , Li Zhonghua , Wang Dongjun , Shen Jun
Published: April 2013

Hydrogen titanate nanotube (HTNT) thin films were synthesized by hydrothermal method and then Co2+ and NH4+ co‐doped hydrogen titanate nanotube (Co, N‐HTNT) thin films were prepared by ion‐exchange method. The Co, N‐HTNT thin films exhibit strong absorption in the visible light range compared with the HTNT and NH4+ doped hydrogen titanate nanotube (N‐HTNT) thin films. The first‐principles calculations reveal that NH4+ doping has no effect on the visible light absorption of HTNTs. The red shift of Co, N‐HTNTs is only due to the mixture of the Co 3d and O 2p states in the top of the valence band, which results in the band gap narrowing. Relative to HTNTs and N‐HTNTs, both the valence band maximum (VBM) and conduction band minimum (CBM) of Co, N‐HTNTs shift to lower potential based on the valence band XPS spectra. Furthermore, the up‐shift of the VBM is much larger than that of the conduction band, which can result in band gap reduction explaining the origin of the visible light absorption of Co, N‐HTNTs.
Rigorous analysis of axisymmetric transformation optics lenses embedded in layered media illuminated by obliquely incident plane waves
Authors: Wang Xiande , Wu Qi , Turpin Jeremiah P. , Werner Douglas H.
Published: April 2013

A body of revolution, finite‐difference time‐domain (BOR‐FDTD) method is developed for rigorous analysis of axisymmetric transformation optics (TO) lens devices. For normal incidence, a one dimensional (1‐D) FDTD method based on the total‐field scattered‐field (TFSF) technique was proposed to model the propagation of a plane wave launched from the top of a layered medium in cylindrical coordinates. The 1‐D FDTD solutions were employed to efficiently inject normally incident plane waves into the BOR‐FDTD method. For oblique incidence, analytical formulations were derived and presented by expanding the plane wave into a series of cylindrical modes via Fourier series expansion of the ϕ‐dependent variables, which were then used to introduce obliquely incident plane waves into the TFSF formulas associated with the BOR‐FDTD method. These procedures allowed for accurate simulations of BOR TO lenses embedded in layered media illuminated by obliquely incident waves. The accuracy and efficiency of the proposed method were verified by comparing numerical results with either analytical solutions or a commercial software (COMSOL) package. Thereafter, the developed BOR‐FDTD code was utilized to study the imaging properties of (a) radial gradient‐index (GRIN) lenses with a parabolic index profile, (b) a flat TO GRIN lens, (c) a spherical Luneburg lens, and (d) a cylindrical TO Luneburg lens both in free space and on top of a substrate. Here the TO GRIN lenses were designed by using the quasi‐conformal transformation optics (QCTO) technique. It was found that the flat TO lens was able to provide identical focusing properties as a cemented doublet in both free space and over a dielectric substrate. Moreover, the numerical results demonstrated that the flattened TO Luneburg lens possessed the desired imaging properties under different illuminations for both polarizations.
The use of propensity scores and observational data to estimate randomized controlled trial generalizability bias
Authors: Pressler Taylor R. , Kaizar Eloise E.
Published: April 2013

Although randomized controlled trials are considered the ‘gold standard’ for clinical studies, the use of exclusion criteria may impact the external validity of the results. It is unknown whether estimators of effect size are biased by excluding a portion of the target population from enrollment. We propose to use observational data to estimate the bias due to enrollment restrictions, which we term generalizability bias. In this paper, we introduce a class of estimators for the generalizability bias and use simulation to study its properties in the presence of non‐constant treatment effects. We find the surprising result that our estimators can be unbiased for the true generalizability bias even when all potentially confounding variables are not measured. In addition, our proposed doubly robust estimator performs well even for mis‐specified models. Copyright © 2013 John Wiley & Sons, Ltd.
Tragverhalten der Seilklemmen der Dachkonstruktion des Lehrter Bahnhofs
Authors: Bechtold M. , Saal H.
Published: April 2013

Die Untersuchung des Tragverhaltens der Binderseilklemmen und der Netzseilklemmen im Rahmen der Zustimmung im Einzelfall erforderte Bauteilversuche, deren Ziel die Festlegung der notwendigen Klemmkräfte zur Übertragung der erforderlichen Grenzgleitkräfte war. Dabei wurde der Unterschied der Seilkräfte beim Auftreten der maximalen Differenzkraft zu denen beim Vorspannen der Schrauben berücksichtigt und der zeitliche Klemmkraftabfall bestimmt.
Nachweis für Sonderlagerungen beim Lehrter Bahnhof
Authors: Gerber A. , Wiedemeyer J.
Published: April 2013

Die fortschrittliche bauliche Gesamtkonzeption für den Lehrter Bahnhof machte in einigen Bereichen die Realisierung neuartiger Lagerungskonzepte unter Verwendung sowohl konstruktiv als auch werkstofflich neuer Lösungen erforderlich. Es mußten deshalb umfangreiche Grundlagen erarbeitet bzw. Prüfungen vorgenommen werden, um die Brauchbarkeit solcher Lagerungen für die Eisenbahnbrücken und für die Dachkonstruktion nachzuweisen bzw. deren ordnungsgemäße Ausführung sicherzustellen. In interdisziplinärer Kooperation zwischen Auftraggeber, Ingenieurbüros, Lagerhersteller, Bauüberwachung und Prüfstellen sowie durch iterative Verbesserung der Konzeptionen im Zuge der Arbeiten ist es gelungen, für den speziellen Fall optimierte Bauprodukte in der Regel termingerecht bereitzustellen. Auf Basis der kollektiv mit anderen Stellen erarbeiteten Erkenntnisse wurde die Zustimmung für den Einbau der neuartigen Lager erteilt. Im Zuge des Verfahrens wurde die Perspektive für künftige Projekte erweitert und im Einzelfall ein neues Bauprodukt allgemein bauaufsichtlich zugelassen, d. h., die Erkenntnisse aus dem Projekt Lehrter Bahnhof auf dem Sektor Lager im Bauwesen wirken sich sicherlich auch nutzbringend für weitere Bauvorhaben aus.
Statisches Verhalten von X‐, T‐ und Y‐Knoten aus dünnwandigen Rechteckhohlprofilen unter Axial‐ und Biegebelastung der Strebe
Authors: Puthli R. S. , Herion St. , Veselcic M.
Published: April 2013

Der Beitrag legt die Ergebnisse einer Untersuchung an dünnwandigen kaltgeformten und an warmgewalzten Rechteckhohlprofilen mit t > 4 mm dar. Gegenwärtige Bemessungsrichtlinien und Fachliteratur liefern nur sehr wenige Informationen über das Verhalten solch dünnwandiger Verbindungen. Daher wurden Versuche unter statischer Belastung durchgeführt, um zu überprüfen, ob die gegenwärtigen Regeln für Verbindungen mit t > 4 mm auch auf dünnwandige Profile angewandt werden können. Die Ergebnisse werden mit Eurocode 3 und anderen zur Verfügung stehenden Bemessungsempfehlungen verglichen.
Zum Einsatz hochfester Materialien bei Verbundträgern unter positiver Momentenbeanspruchung
Authors: Hegger J. , Goralski C. , Döinghaus P.
Published: April 2013

Der Einsatz hochfester Werkstoffe im Verbundbau führt zu deutlich höheren Querschnittstragfähigkeiten. Die Spannungs‐Dehnungs‐Charakteristik von hochfesten Baustoffen und der Last‐Schlupfverlauf von Kopfbolzendübeln in hochfestem Beton erfordern eine Anpassung der Bemessungsregeln in Eurocode 4 (Draft No. 3, March 2001). Dieser Aufsatz beschreibt Vorschläge zum wirtschaftlichen und sicheren Einsatz hochfester Baustoffe in Verbundträgern. Die Bemessungsregeln des aktuellen Entwurfs von Eurocode 4 (EC 4) werden vorgestellt und durch Vorschläge für den Einsatz von hochfestem Beton C 70/85 in Kombination mit Stahl S 460 ergänzt. Anhand von Bemessungsbeispielen wird die Anwendung der Bemessungsvorschläge erläutert. In [2] wurde hierzu bereits die Bemessung des Betongurtes für Verbundträger aus hochfestem Beton und hochfestem Stahl im negativen Momentenbereich diskutiert.
Optimierung von profilierten Sandwichbalken
Authors: Timár I. , Borbély T. , Horváth P.
Published: April 2013

Bei der Optimierung symmetrischer, gelenkig gelagerter Sandwichbalken sind die Dicke der Zwischenschicht aus Polyurethan‐Hartschaum und die geometrischen Abmessungen der I‐Träger (aus Stahl) unbekannt. Zu bestimmen sind das Minimum der Zielfunktion und die Dicke der Schichten bei nichtlinearen Restriktionen. Die Zielfunktion enthält die Fertigungs‐ und Materialkosten. Dabei werden die Begrenzung der Spannungen aus Biegung bzw. Schub, die Begrenzung der maximalen Durchsenkung, Vorschriften für Schwingungsdämpfung bzw. Eigenfrequenzen und die geometrischen Abmessungen berücksichtigt. Die Berechnungen werden mittels eines nichtlinearen Optimierungsprogramms durchgeführt.
Die Reichenbachtalbrücke der Thüringer Waldautobahn A 71
Authors: Peter J. , Wetzel R. , Bach Th.
Published: April 2013

Für die Reichenbachtalbrücke der Autobahn A 71 wird der Entwurf und die Herstellung der Brücke beschrieben. Aus mehreren Entwurfsvarianten wurde für die Ausführung ein Stahlverbundüberbau gewählt, bestehend aus einem einzelligen Hohlkasten mit seitlichen Streben zur Unterstützung der weit auskragenden Fahrbahnplatte. Auf wesentliche architektonische Kriterien und technische Detailpunkte der Brücke wird hingewiesen.
Experimentelle Untersuchungen an vorgespannten Ringflanschstößen mit Imperfektionen
Authors: Jakubowski A. , Schmidt H.
Published: April 2013

In vorgespannten geschraubten Ringflanschverbindungen, die als Montagestöße in turmartigen Stahlbauten (z. B. Rohrtürmen von Windenergieanlagen) eingesetzt werden, ist der Nachweis gegen Ermüdung der Schrauben oft bemessungsbestimmend. Die Ermüdungsbeanspruchung der Schrauben wird von Flanschimperfektionen (Klaffungen zwischen den Kontaktflächen vor dem Vorspannen) sehr stark beeinflußt. Zur experimentellen Klärung dieser Einflüsse wurden Biegeversuche an großmaßstäblichen Stahlrohrversuchskörpern mit integrierten L‐ und T‐Flanschstößen, die zum Teil planmäßig imperfekt hergestellt worden waren, durchgeführt. Umfangreiche Dehnungsmessungen an Schrauben und Rohrmänteln erlauben eine detaillierte Analyse der Einflüsse von Imperfektionen und wiederholten Belastungen auf das ermüdungsrelevante innere Kräftespiel der Ringflanschstöße.
Schwingfestigkeitsanalyse eines geschweißten Winkelknotens auf der Basis von lokalen Konzepten
Authors: Schliebner R. , Vormwald M.
Published: April 2013

Am Beispiel eines geschweißten Winkelanschlusses werden die Schwingfestigkeitsergebnisse unterschiedlicher Berechnungskonzepte und Modellierungsvarianten vorgestellt und mit den in einer vorangegangenen Untersuchung der Universitäten Karlsruhe und Aachen experimentell ermittelten verglichen. Die Berechnungsergebnisse aus Strukturspannungskonzept und Konzept der örtlich elastischen Spannungen zeigen beim Vergleich untereinander eine relativ gute Übereinstimmung. Die Abweichungen zwischen experimentellen und berechneten Lebensdauern sind jedoch sehr groß.
Traglasten von torsionsbeanspruchten dünnwandigen Stäben
Authors: Weber M.
Published: April 2013

Ein Berechnungsverfahren für die Ermittlung der Traglast von torsionsbeanspruchten dünnwandigen Stäben wird vorgestellt. Die mit diesem Verfahren ermittelten Torsionstraglasten liegen erheblich über entsprechenden elastischen Grenzlasten. Der Grundgedanke des Verfahrens besteht darin, Laststeigerungsfaktoren für die St. Venantsche‐ und Wölbkrafttorsion zu ermitteln und diese zu addieren, wobei die gegenseitige Beeinflussung der beiden Torsionsmechanismen durch eine Interaktionsbeziehung berücksichtigt wird. Versagensmechanismen für verschiedene Lagerungs‐ und Belastungsfälle und die Ermittlung der zugehörigen Laststeigerungsfaktoren werden erläutert, eine Interaktionsbeziehung für I‐Profile wird angegeben. Die Berechnung nach diesem Verfahren ist im allgemeinen einfacher als die aufwendige elastische Wölbkrafttorsionsrechnung. Die Anwendung des Verfahrens wird an zwei Rechenbeispielen demonstriert.
Verbesserte Computerprogramme für die Bemessung von räumlichen Stahlbrückenkonstruktionen und deren Anwendung
Authors: Kitada T. , Kano M. , Yamano T. , Okada J. , Tanaka K.
Published: April 2013

In diesem Beitrag werden fünf Computerprogramme vorgestellt, EPASS, USSP, EPASS Plus, USSP‐D und J‐F‐C‐P. EPASS ist ein FEM‐Programm für das elasto‐plastische und finite Verformungsverhalten von räumlichen Stahlrahmenbrücken, bestehend aus Bauteilen und Kabeln, ohne Berücksichtigung des lokalen Beulens. USSP ist ein FEM‐Programm, das sich zur Ermittlung des elasto‐plastischen und finiten Verformungsverhaltens von dünnwandigen Bauteilen eignet, mit Berücksichtigung des lokalen Beulens. In dem Programm EPASS Plus sind die Programme USSP und EPASS kombiniert. USSP‐D, eine Kombination von USSP mit einem FDM‐Programm für die Untersuchung der dynamischen Reaktion, wurde zur Berechnung des dynamischen, elasto‐plastischen und finiten Verformungsverhaltens von Stahlbrückenpylonen, die starken Einwirkungen aus Erdbeben ausgesetzt sind, entwickelt. J‐F‐C‐P ist geeignet für die Ermittlung der elasto‐plastischen und finiten Verformung von vorgespannten Betonkastenträgerbrücken mit Trapezblechstegen. Es kann als USSP‐Programm mit zusätzlichen 3D‐Elementen und Stäben zur Erfassung der Nichtlinearität des Betons und der Bewehrung, aufgefaßt werden.
Ermüdungslasten für stählerne Autobahnbrücken in Japan
Authors: Mori T. , Tamakoshi T. , Nishikawa K.
Published: April 2013

Die japanischen Bemessungsvorschriften für Autobahnbrücken wurden überarbeitet und im März 2002 veröffentlicht. Sie enthalten nun auch Vorschriften für die Ermüdung. Bemessungsvorschriften für die Ermüdung bei Betonbauten sind ebenfalls in den "Bemessungsnormen für Ermüdung bei Stahlbrücken" enthalten, die ebenfalls im März 2002 veröffentlicht wurden. In diesem Beitrag werden Hintergrundinformationen über die Bestimmung der Ermüdungslast gegeben.
Konstruktion der Yumemai‐Brücke ‐ schwimmende Bogenbrücke in Osaka
Authors: Watanabe E. , Ueda S. , Maruyama T. , Takeda S.
Published: April 2013

Die erste drehbare, schwimmfähige Bogenbrücke wurde im März 2001 in der Nähe des Hafens von Osaka fertiggestellt. Die Brücke verbindet die zwei künstlichen Inseln Yumeshima und Maishima, die auch der Namensgeber der Brücke sind (Bild 1). Die Brücke mit sechs Fahrbahnen hat eine Gesamtlänge von 410 m. Das statische System ist eine räumliche Bogenbrücke. Die Brücke wird vertikal von zwei stählernen Pontons gestützt. Die horizontale Übertragung von Kräften aus Wind, Wellen und Gezeiten wird von Dalben und Gummipuffern übernommen. Nachdem die Übergangsbereiche zwischen Vorlandbrücke und Haupttragwerk abgesenkt worden sind, kann die Brücke um einen Drehpunkt, der am Ende der Brücke liegt, geschwenkt werden. In diesem Beitrag werden die wesentlichen Schritte der Konstruktion der Yumemai‐Brücke vorgestellt.
Untersuchung der Seilklemmen des Messeturms Neue Messe München
Authors: Peil U. , Einsiedler O.
Published: April 2013

Es wird über theoretische und experimentelle Untersuchungen an ungewöhnlichen Seilklemmen des Messeturms München berichtet. Diese Klemmen sind integraler Bestandteil eines Druckringes, sie müssen neben ihrer Funktion als Seilklemme auch Beanspruchungen infolge zweiachsiger Biegung und Normalkraft des Druckrings abtragen. Diese doppelte Funktion der Seilklemmen machte eine völlig neuartige Konstruktion erforderlich. Die Untersuchungen zeigen, daß auch das komplexe Tragverhalten dieser Seilklemme mit Hilfe der FE‐Methode gut beschrieben werden kann, wie der Vergleich der theoretisch ermittelten Ergebnisse mit denen von durchgeführten Versuchen zeigt.
Reiner Sauls Brücken
Authors: Svensson H.
Published: April 2013

Es werden die bedeutendsten Brücken beschrieben, an denen Reiner Saul in seiner 40jährigen Berufszeit maßgeblich beteiligt war. Dabei handelt es sich in erster Linie um Schrägkabelbrücken und weitgespannte Stahl‐ und Verbundbalkenbrücken, bei deren Bearbeitung seine besonderen theoretischen und praktischen Kenntnisse im Entwurf, der Ausführungs‐ und Montageplanung und der Bauleitung erfolgreiche Anwendung fanden.
Die neue Leinetalbrücke bei Heiligenstadt
Authors: Roesler H. , Schmidt D.
Published: April 2013

Beim Neubau der Leinetalbrücke im Zuge der Ortsumfahrung Heilbad Heiligenstadt in Thüringen wird die stark befahrene Bahnstrecke Göttingen‐Halle überquert. Durch die Planung des Überbaus als Verbundkonstruktion unter Verwendung von Fertigteilen können Konfliktpunkte mit der Bahnstrecke auf ein Minimum begrenzt werden. Durch sorgfältige Detailplanung bei der Gestaltung fügt sich das Bauwerk gut in den Erweiterungsbereich des Kurparks ein.
Das Parkhaus für die Neue Landesmesse Baden‐Württemberg: Verkehrspolitische Innovation durch verkehrstechnische Integration
Authors: Andelfinger J. , Angelmaier V. , Herrmann J. , Sandner D.
Published: April 2013

Die Planung der in unmittelbarer Nähe zum Stuttgarter Flughafen liegenden Neuen Landesmesse Baden‐Württemberg sieht u. a. eine Überbauung der Autobahn und der Neubaustrecke Stuttgart‐Ulm der Deutschen Bahn AG mit einem Parkhaus vor. Mit der verkehrstechnischen Integration der 350 m langen und 90 m breiten, sechsgeschossigen Parkhauskonstruktion innerhalb eines vollwertigen Autobahnanschlusses werden neue Wege bei der Verkehrserschließung beschritten.
Querkrafttragfähigkeit zugbeanspruchter Betonfahrbahnplatten von Verbundbrücken
Authors: Kuhlmann U. , Ehmann J.
Published: April 2013

Im Verbundbau aus Stahl und Beton werden im Unterschied zum Massivbau große Zugnormalkräfte in der Betonplatte nicht durch Vorspannung überdrückt, sondern das Reißen des Betons wird zugelassen und der Beton entsprechend für die Mitwirkung zwischen den Rissen bewehrt. Die Fahrbahnplatten von Verbundbrücken sind daher u. U. auch schon im Gebrauchszustand fast vollständig gerissen. Über diese Risse hinweg müssen Querlasten wie beispielsweise die Radlasten des über die Fahrbahnplatte rollenden Verkehrs abgetragen werden.

Am Institut für Konstruktion und Entwurf, Universität Stuttgart, wurden Versuche zur Bestimmung der Querkrafttragfähigkeit infolge Zugbeanspruchung gerissener Verbundplatten durchgeführt. Ein numerisches Modell auf der Grundlage der Methode der Finiten Elemente wurde durch Versuchsergebnisse verifiziert und zur Untersuchung verschiedener Einflußparameter auf die Querkrafttragfähigkeit verwendet. Ein mechanisches Modell wurde entwickelt, das den Versagensmechanismus des Querkraftversagens bei gleichzeitiger Normalkraftbeanspruchung beschreibt. Die Ergebnisse dieser Untersuchungen münden in einen Bemessungsansatz, der die Querkrafttragfähigkeit von Platten unter Längszug wirklichkeitsnah erfaßt.
Mischbauweise Stahl/Holz am Beispiel einer Parkdeckerweiterung
Authors: Demetz S. , Frajo‐Apor K. , Schaur Ch.
Published: April 2013

Am Beispiel einer dreigeschossigen Parkdeckerweiterung im Bereich eines bestehenden Einkaufszentrums wird über die Lösungsfindung innerhalb komplexer Rahmenbedingungen, die konstruktive Umsetzung, aber auch über die besonderen Montageanforderungen berichtet. Detailliert wird auf die Kombination Stahl/Holz eingegangen und die Erfahrungen in schwingungstechnischer Hinsicht zusammengefaßt.
Anmerkungen zur Fließgelenk‐Rotation in Stabtragwerken
Authors: Scheer J. , Nölke H.
Published: April 2013

Die Begriffe Rotation, Rotationskapazität = Rotationsvermögen = Rotationsfähigkeit und Rotationsanforderung werden nicht eindeutig verwendet. In der Vornorm zum Eurocode 3 wird für Bauwerke, die nicht Hochbauten zuzuordnen sind, ein Rotationssicherheitsnachweis gefordert. Angaben für das Vorgehen werden nicht gemacht. Daher wird auf einige offene Fragen eingegangen.