bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further results on error estimators for local refinement with first‐order system least squares (FOSLS)
Authors: Manteuffel Thomas , McCormick Steven , Nolting Joshua , Ruge John , Sanders Geoff 
Published: January 2010

AbstractAdaptive local refinement (ALR) can substantially improve the performance of simulations that involve numerical solution of partial differential equations. In fact, local refinement capabilities are one of the attributes of first‐order system least squares (FOSLS) in that it provides an inexpensive but effective a posteriori local error bound that accurately identifies regions that require further refinement. Previous theory on FOSLS established the effectiveness of its local error estimator, but only under the assumption that the local region is not too ‘thin’. This paper extends this theory to the case of a rectangular domain by showing that the estimator's effectiveness holds even for certain ‘thin’ local regions. Further, we prove that when the approximation satisfies a local saturation property, convergence of a FOSLS ALR scheme is guaranteed. Copyright © 2010 John Wiley & Sons, Ltd.
Thermally conductive and electrically insulative nanocomposites based on hyperbranched epoxy and nano‐Al2O3 particles modified epoxy resin
Authors: Fu Ji‐Fang , Shi Li‐Yi , Zhong Qing‐Dong , Chen Yi , Chen Li‐Ya 
Published: January 2010

AbstractNovel epoxy nanocomposites based on a diglycidyl ether of bisphenol A (DGEBA) epoxy, an epoxy functionalized hyperbranched polymer (HTTE) and nano‐Al2O3 were synthesized with the aim of determining the effect of the nano‐Al2O3 particles and HTTE on the structure and properties of epoxy nanocomposites. The mechanical properties, thermal conductivity, bulk resistivity, and thermal stability of the nano‐Al2O3/HTTE/DGEBA ternary composites were evaluated and compared with the corresponding matrix. The improvement in impact properties of these nanocomposites was explained in terms of fracture surface analysis by SEM. The results indicate that the incorporation of nanoparticles and hyperbranched epoxy effectively improved the toughness of epoxy composites without sacrificing thermal conductivity and bulk resistivity compared to the neat epoxy and Al2O3/DGEBA, obtaining a well dispersion of nanoparticles in epoxy matrix and solving the drawbacks for single fillers filled epoxy nanocomposite. Copyright © 2010 John Wiley & Sons, Ltd.
CS‐Fe(II,III) complex as precursor for magnetite nanocrystal
Authors: Wang Yongliang , Li Baoqiang , Zhou Yu , Jia Dechang , Song Yang 
Published: January 2010

AbstractChitosan‐iron ions complex (CS‐Fe(II,III) complex) was used as precursor to synthesize magnetite nanocrystals and the mechanism was discussed. The magnetite nanocrystals have diameters of about 10 nm and clusters were formed due to slight aggregation of several magnetite nanocrystals. FT‐IR and X‐ray photoelectron spectrometer (XPS) investigations indicated that the Fe(II) and Fe(III) were chelated by NH2 and OH groups of chitosan in CS‐Fe(II,III) complex, and the molar ratio of NH2/Fe(II,III) was approximately 2. This chelation effect destroyed the hydrogen bonds of chitosan. In the following alkali treatment process, the chelated Fe(II) and Fe(III) provided nucleation site and formed the magnetite nanocrystals. After alkali treatment, the chelation effect between iron ions and NH2 groups disappeared and some kind of weak interaction formed between magnetite and NH2 groups. Moreover, the OH groups of chitosan have an interaction with the synthesized magnetite nanocrystals. Copyright © 2010 John Wiley & Sons, Ltd.
Network parameters of poly(N‐isopropylacrylamide)/montmorillonite hydrogels: effects of accelerator and clay content
Authors: Erbil C. , Topuz D. , Gökçeören A. T. , Şenkal B. F. 
Published: January 2010

AbstractThe results of network parameters of poly(N‐isopropylacrylamide)/montmorillonite (PNIPAAm/MMT) hydrogels prepared with two different types and concentrations of accelerators (tetramethylethylenediamine, TEMED and quaternary TEMED containing decyl bromide, QTEMED) using three different clay contents (1.0, 3.0, and 5.0 wt% of total monomer concentration) at two different polymerization temperatures (10 and 32°C) were presented and discussed. It was observed that when the reaction temperature of PNIPAAm crosslinked with MMT was chosen as 10°C both volume swelling ratios (i.e., thermodynamic interaction) and shear moduli, G increased. In hydrogels, thermodynamic interaction is reflected by polymer–water interaction parameter (χ). The lower is the value of χ, the stronger is the interaction between polymer and water, and the lower is the interaction between hydrophobic groups or between polymer chains. In addition, increase in MMT content was slightly affected on these intermolecular interactions. Therefore, this effect that combines high‐shear modulus with lower value of χ in the same molecular structure was defined as clay content‐independent diffusion behavior. On the other hand, in the case of the hydrogels synthesized with the higher concentration of TEMED and MMT, the values of χ and G decreased. These facts were interpreted that increase in both accelerator concentration and clay content, for fixed NIPAAm concentration made the number of effective crosslinks between MMT layers smaller. Copyright © 2010 John Wiley & Sons, Ltd.
Magnetic particles as powerful purification tool for high sensitive mass spectrometric screening procedures
Authors: Peter Jochen F. , Otto Angela M. 
Published: January 2010

AbstractThe effective isolation and purification of proteins from biological fluids is the most crucial step for a successful protein analysis when only minute amounts are available. While conventional purification methods such as dialysis, ultrafiltration or protein precipitation often lead to a marked loss of protein, SPE with small‐sized particles is a powerful alternative. The implementation of particles with superparamagnetic cores facilitates the handling of those particles and allows the application of particles in the nanometer to low micrometer range. Due to the small diameters, magnetic particles are advantageous for increasing sensitivity when using subsequent MS analysis or gel electrophoresis. In the last years, different types of magnetic particles were developed for specific protein purification purposes followed by analysis or screening procedures using MS or SDS gel electrophoresis. In this review, the use of magnetic particles for different applications, such as, the extraction and analysis of DNA/RNA, peptides and proteins, is described.
Synthesis of well‐defined rod‐coil block copolymers containing trifluoromethylated poly(phenylene oxide)s by chain‐growth condensation polymerization and atom transfer radical polymerization
Authors: Kim Yun Jun , Seo Myungeun , Kim Sang Youl 
Published: January 2010

AbstractWell‐defined trifluoromethylated poly(phenylene oxide)s were synthesized via nucleophilic aromatic substitution (SNAr) reaction by a chain‐growth polymerization manner. Polymerization of potassium 4‐fluoro‐3‐(trifluoromethyl)phenolate in the presence of an appropriate initiator yielded polymers with molecular weights of ∼4000 and polydispersity indices of <1.2, which were characterized by 1H nuclear magnetic resonance spectroscopy and gel permeation chromatography. Initiating sites for atom transfer radical polymerization (ATRP) were introduced at the either side of chain ends of the poly(phenylene oxide), and used for ATRP of styrene and methyl methacrylate, yielding well‐defined rod‐coil block copolymers. Differential scanning calorimetry study indicated that the well‐defined trifluoromethylated poly(phenylene oxide)s showed high crystallinity and were immiscible with polystyrene. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1049–1057, 2010
Novel diblock copolymer‐grafted multiwalled carbon nanotubes via a combination of living and controlled/living surface polymerizations
Authors: Priftis Dimitrios , Sakellariou Georgios , Mays Jimmy W. , Hadjichristidis Nikos 
Published: January 2010

AbstractDiels–Alder cycloaddition reactions were used to functionalize multiwalled carbon nanotubes (MWNTs) with 1‐benzocylcobutene‐1′‐phenylethylene (BCB‐PE) or 4‐hydroxyethylbenzocyclobutene (BCB‐EO). The covalent functionalization of the nanotubes with these initiator precursors was verified by FTIR and thermogravimetric analysis (TGA). After appropriate transformations/additions, the functionalized MWNTs were used for surface initiated anionic and ring opening polymerizations of ethylene oxide and ε‐caprolactone (ε‐CL), respectively. The OH‐end groups were transformed to isopropylbromide groups by reaction with 2‐bromoisobutyryl bromide, for subsequent atom transfer radical polymerization of styrene or 2‐dimethylaminoethyl methacrylate to afford the final diblock copolymers. 1H NMR, differential scanning calorimetry (DSC), TGA, and transmission electron microscopy (TEM) were used for the characterization of the nanocomposite materials. TEM images showed the presence of a polymer layer around the MWNTs as well as the dissociation of MWNT bundles. Consequently, this general methodology, employing combinations of different polymerization techniques, increases the diversity of diblocks that can be grafted from MWNTs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1104–1112, 2010
Epoxy‐based networks combining chemical and supramolecular hydrogen‐bonding crosslinks
Authors: Montarnal Damien , Tournilhac François , Hidalgo Manuel , Leibler Ludwik 
Published: January 2010

AbstractWe combine the supramolecular chemistry of heterocyclic ureas with the chemistry of epoxides to synthesize new crosslinked materials incorporating both chemical and supramolecular hydrogen‐bonded links. A two‐step facile and solvent‐free procedure is used to obtain chemically and thermally stable networks from widely available ingredients: epoxy resins and fatty acids. The density of both chemical and physical crosslinks is controlled by the stoichiometry of the reactants and the use of a proper catalyst to limit side reactions. Depending on the stoichiometry, a wide range of thermomechanical properties can be attained. The method can be used to produce elastomeric objects of complex shapes. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1133–1141, 2010
Thermosensitive behavior of poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) double hydrophilic block copolymers
Authors: Dong Anjie , Zhai Yinglei , Xiao Li , Qi Haiying , Tian Qi , Deng Liandong , Guo Ruiwei 
Published: January 2010

AbstractThe poly(ethylene glycol)/poly(2‐(N,N‐dimethylamino)ethyl methacrylate) (PEG/PDMAEMA) double hydrophilic block copolymers were synthesized by atom transfer radical polymerization using mPEG‐Br or Br‐PEG‐Br as macroinitiators. The narrow molecular weight distribution of PEG/PDMAEMA block copolymers was identified by gel permeation chromatography results. The thermosensitivity of PEG/PDMAEMA block copolymers in aqueous solution was revealed to depend significantly on pH, ionic strength, chain structure, and concentration of the block copolymers. By optimizing these factors, the cloud point temperature of PEG/PDMAEMA block copolymers can be limited within body temperature range (30–37 °C), which suggests that PEG/PDMAEMA block copolymers could be a good candidate for drug delivery systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 503–508, 2010
Synergistic effects of PEG and MWCNTs on crystallization behavior of PLLA
Authors: Li Yanli , Wu Haiyan , Wang Yong , Liu Li , Han Liang , Wu Jun , Xiang Fangming 
Published: January 2010

AbstractThis work reported the crystallization behaviors of poly(L‐lactide) (PLLA) with the presence of polyethylene glycol (PEG) and/or functionalized multiwalled carbon nanotubes (FMWCNTs). The crystallization behaviors occurred in the different conditions, including nonisothermal, isothermal and during the annealing process, were analyzed comparatively using differential scanning calorimetry, wide angle X‐ray diffraction, and polarized optical microscope. The results show that PEG as an efficient plasticizer of PLLA enhances the mobility of PLLA chain segments, which leads to the decrease of glass transition temperature and the enhancement of crystallization ability of PLLA. FMWCNTs as a nucleating agent of PLLA crystallization promote the crystallization of PLLA apparently. With the presence of PEG and FMWCNTs, the crystallization of PLLA is well improved in all conditions, indicating the synergistic effects of PEG and FMWCNTs on PLLA crystallization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 520–528, 2010
Quantum modeling of semiconductor gain materials and vertical‐external‐cavity surface‐emitting laser systems
Authors: Bückers Christina , Kühn Eckhard , Schlichenmaier Christoph , Imhof Sebastian , Thränhardt Angela , Hader Jörg , Moloney Jerome V. , Rubel Oleg , Zhang Wei , Ackemann Thorsten , Koch Stephan W. 
Published: January 2010

AbstractThis article gives an overview of the microscopic theory used to quantitatively model a wide range of semiconductor laser gain materials. As a snapshot of the current state of research, applications to a variety of actual quantum‐well systems are presented. Detailed theory–experiment comparisons are shown and it is analyzed how the theory can be used to extract poorly known material parameters. The intrinsic laser loss processes due to radiative and nonradiative Auger recombination are evaluated microscopically. The results are used for realistic simulations of vertical‐external‐cavity surface‐emitting laser systems. To account for nonequilibrium effects, a simplified model is presented using pre‐computed microscopic scattering and dephasing rates. Prominent deviations from quasi‐equilibrium carrier distributions are obtained under strong in‐well pumping conditions.
Angular distributions of electrons emitted from free and deposited Na8 clusters
Authors: Bär Matthias , Dinh Phuong Mai , Moskaleva Lyudmila V. , Reinhard Paul‐Gerhard , Rösch Notker , Suraud Eric 
Published: January 2010

AbstractWe explore from a theoretical perspective angular distributions of electrons emitted from a Na8 cluster after excitation by a short laser pulse. The tool of the study is time‐dependent density‐functional theory (TDDFT) at the level of the local‐density approximation (LDA) augmented by a self‐interaction correction (SIC) to put emission properties in order. We consider free Na8 and Na8 deposited on the surfaces MgO(001) or Ar(001). For the case of free Na8, we distinguish between a hypothetical situation of known cluster orientation and a more realistic ensemble of orientations. We also consider the angular distributions for emission from separate single‐electron levels.
Kinetic roughening and mound surface growth in microcrystalline silicon thin films
Authors: Liu Fengzhen , Li Chaowei , Zhu Meifang , Gu Jinhua , Zhou Yuqin 
Published: January 2010

AbstractThe roughening evolution of the hydrogenated microcrys‐talline silicon (μc‐Si:H) film by plasma enhanced chemical vapor deposition (PECVD) and hot wire chemical vapor deposition (HWCVD) were investigated using atomic force microscopy (AFM). It is found that the kinetic roughening of the μc‐Si:H film surface can not be described by the traditional dynamic scaling approach. The appearance of characteristic peaks in the power spectral density (PSD) curves, calculated from the AFM images, indicates the mounded growth characteristic of μc‐Si:H film. The correlation between the mounded surface growth of μc‐Si:H thin films and the shadowing effect has been studied. It is found that high hydrogen dilution ratio in the early growth stage retards the formation of the mound structure (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties of diamond‐like carbon films modified by silver nanoclusters
Authors: Sarsembinov Sh. Sh. , Prikhodko O. Yu. , Ryaguzov A. P. , Maksimova S. Ya. , Daineko Ye. A. , Mahmoud F. A. 
Published: January 2010

AbstractThe results of electronic properties and microstructure investigations in amorphous diamond like carbon films (a‐C:H) containing different concentrations of silver impurity are presented. The films were prepared by the combined graphite‐silver target sputtering in the atmosphere of argon‐hydrogen plasma. By the method of transmission electron microscopy it was established that Ag was embedded in the matrix of a‐C:H as isolated spherical shape nanoclusters. The average size of the nanoclusters was grown from 2 to 8 nm when silver concentration was ranged from 1 to 20 at.%, respectively. The resonance optical absorption at ∼ 420 nm was revealed in the films. The dependence of films conductivity on Ag content is typical of percolation systems (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural and defect changes of hydrogenated SiGe films due to annealing up to 600°C
Authors: Sládek Petr , Buršíková Vilma , St'ahel Pavel 
Published: January 2010

AbstractIn order to better understand the effects of the hydrogen incorporation on the defects and the disorder in the undoped nano/microcrystalline SiGe:H, we performed a comparative study on samples deposited under different plasma conditions. With variation of the pressure, we were able to change the structure of SiGe:H films. We have used the combination of the infrared spectroscopy, CPM, PDS and thermal desorption measurements to study the thermal dependence of defect density, disorder, as well as hydrogen concentration. The film mechanical properties were tested by depth sensing indentation technique. The results showing a different hydrogen bonding with the change of deposition conditions are interpreted as a whole by terms of the specific local hydrogen bonding environment, related to different growth mechanism. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
CuxSnSx+1 (x = 2, 3) thin films grown by sulfurization of metallic precursors deposited by dc magnetron sputtering
Authors: Fernandes P. A. , Salomé P. M. P. , da Cunha A. F. 
Published: January 2010

AbstractWe report the results of the growth of Cu‐Sn‐S ternary chalcogenide compounds by sulfurization of dc magnetron sputtered metallic precursors. Tetragonal Cu2SnS3 forms for a maximum sulfurization temperature of 350 °C. Cubic Cu2SnS3 is obtained at sulfurization temperatures above 400 °C. These results are supported by XRD analysis and Raman spectroscopy measurements. The latter analysis shows peaks at 336 cm‐1, 351 cm‐1 for tetragonal Cu2SnS3, and 303 cm‐1, 355 cm‐1 for cubic Cu2SnS3. Optical analysis shows that this phase change lowers the band gap from 1.35 eV to 0.98 eV. At higher sulfurization temperatures increased loss of Sn is expected in the sulphide form. As a consequence, higher Cu content ternary compounds like Cu3SnS4 grow. In these conditions, XRD and Raman analysis only detected orthorhombic (Pmn21) phase (petrukite). This compound has Raman peaks at 318 cm‐1, 348 cm‐1 and 295 cm‐1. For a sulfurization temperature of 450 °C the samples present a multi‐phase structure mainly composed by cubic Cu2SnS3 and orthorhombic (Pmn21) Cu3SnS4. For higher temperatures, the samples are single phase and constituted by orthorhombic (Pmn21) Cu3SnS4. Transmittance and reflectance measurements were used to estimate a band gap of 1.60 eV. For comparison we also include the results for Cu2ZnSnS4 obtained using similar growth conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of principal photoinduced effects in amorphous chalcogenides: In‐situ simultaneous measurements of photodarkening, volume changes, and defect creation
Authors: Nakagawa N. , Shimakawa K. , Itoh T. , Ikeda Y. 
Published: January 2010

AbstractTo understand the direct relation among photodarkening (PD), photoinduced volume change (PVC), and photoinduced defect creation (PDC), we perform in‐situ simultaneous measurements of all three phenomena, i.e. optical absorption coefficient (for PD), surface height (for PVC), and photocurrent which monitors PDC, in amorphous As2Se3 films. The time evolution of PDC during light excitation is empirically described by a stretched exponential function: 1 ‐ exp[‐(t /τ)β], where τ is the effective response time and β (< 1.0) the dispersion parameter, while we have found that the PVC and PD were essentially given by a simple exponential function (β = 1). The value of τ for the PDC is very much smaller than those for the PVC and PD. As the time evolutions for all three phenomena are independent of each others, there may be no direct relationship among them. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vertical modeling: A pattern mixture approach for competing risks modeling
Authors: Nicolaie, M. A. , van Houwelingen Hans C. , Putter H. 
Published: January 2010

AbstractWe study an alternative approach for estimation in the competing risks framework, called vertical modeling. It is motivated by a decomposition of the joint distribution of time and cause of failure. The two elements of this decomposition are (1) the time of failure and (2) the cause of failure condition on time of failure. Both elements of the model are based on observable quantities, namely the total hazard and the relative cause‐specific hazards. The model can be implemented using the standard software. The relative cause‐specific hazards are flexibly estimated using multinomial logistic regression and smoothing splines. We show estimates of cumulative incidences from vertical modeling to be more efficient statistically than those obtained from the standard nonparametric model. We illustrate our methods using data of 8966 leukemia patients from the European Group for Blood and Marrow Transplantation. Copyright © 2010 John Wiley & Sons, Ltd.
Peer ratings of chronic stress: can spouses and friends provide reliable and valid assessments of a target person's level of chronic stress?
Authors: Kromm Walter , Gadinger Michael C. , Schneider Sven 
Published: January 2010

AbstractThe aim of this study was to determine whether spouses and friends could provide reliable ratings and discriminate between different sources of chronic stress as experienced by a target person. Further, this study assessed the convergence of self‐ and observer ratings of chronic stress. The target persons were 384 executives from Germany, Austria and Switzerland. Observer ratings were obtained from 275 spouses and 127 friends of the executives. The results imply that both spouses and friends can provide reliable ratings of different sources of chronic stress, which are equivalent to the reliabilities observed in the executives' self‐reports. Two independent factor analyses suggested that the spouses and friends were able to discriminate between the eight distinct sources of chronic stress proposed by the Trier Inventory of Chronic Stress. Convergent validities within the pairs executive–friend (range: 0.30–0.57) and executive–spouse (0.30–0.54) were all significant and indicate good self‐observer agreement in ratings of chronic stress. Generally, stress scales capturing work‐related chronic stress were found to yield higher convergent validities than scales assessing chronic stress due to social events. The results of this study imply that chronic stress can be validly assessed by well‐acquainted peers and spouses. Copyright © 2009 John Wiley & Sons, Ltd.