bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and properties of novel polyimides from sulfonated binaphthalene dianhydride for proton exchange membranes
Authors: Li Nanwen , Cui Zhiming , Zhang Suobo , Li Shenghai 
Published: March 2008

AbstractA sulfonated dianhydride monomer, 6,6′‐disulfonic‐4,4′‐binaphthyl‐1,1′,8,8′‐tetracarboxylic dianhydride (SBTDA), was successfully synthesized by direct sulfonation of the parent dianhydride, 4,4′‐binaphthyl‐1,1′,8,8′‐tetracarboxylic dianhydride (BTDA), using fuming sulfuric acid as the sulfonating reagent. A series of sulfonated homopolyimides were prepared from SBTDA and various common nonsulfonated diamines. The resulting polymer electrolytes, which contain ion conductivity sites on the deactivated positions of the aryl backbone rings, displayed high proton conductivities of 0.25–0.31 S cm−1 at 80 °C. The oxidative stability test indicated that the attachment of the SO3H groups onto the dianhydride units did not deteriorate the oxidative stability of the SPI membranes. The better membranes were achieved by the copolymerization of nonsulfonated diamine, SBTDA, and BTDA. Copolymer membrane synthesized from hexane‐1,6‐diamine, SBTDA, and BTDA displayed excellent water stability of more than 1000 h at 90 °C, while its proton conductivity was still at a high level (comparable to that of Nafion 117). Furthermore, the novel block copolymer (II‐b) displayed higher proton conductivity compared with the random one (II‐r) obviously, probably due to the slightly higher water uptake and better microphase separated morphology. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2820–2832, 2008
Characterization of the micellar ring opening metathesis polymerization in water of a norbornene derivative initiated by Hoveyda‐Grubbs' catalyst
Authors: Mingotaud Anne‐Françoise , Mingotaud Christophe , Moussa Wissam 
Published: March 2008

AbstractSolubilization of the hydrophobic Hoveyda‐Grubbs' catalyst in micellar aqueous phase has been achieved using dodecyl and cetyl ammonium chloride as surfactants. The domain of solubilization has been estimated before carrying out ring‐opening metathesis polymerization in these micellar solutions with a hydrophilic monomer. Kinetics orders have been determined relative to monomer, initiator, and surfactant. A good control of the molecular weight has been obtained for ratios [micelles]/[initiator] over 1. The better control of the polymerization obtained in micellar solution has been explained by a difference of reactivity leading to a more efficient initiation step in the presence of the micelles. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2833–2844, 2008
Raman spectroscopic study of CO2 sorption process in poly methyl methacrylate
Authors: Ikeda‐Fukazawa Tomoko , Kita Daisuke , Nagashima Kazushige 
Published: March 2008

AbstractRaman spectra of poly methyl methacrylate (PMMA) in contact with compressed CO2 were measured, to investigate effects of CO2 sorption on structure of the PMMA chain. The solubility and diffusivity of CO2 in PMMA were estimated from temporal variations of intensities of CO2 peaks. The PMMA structure was analyzed from temporal variations of vibrational energies of PMMA peaks. The results show that the vibration energies of CH stretching modes of PMMA increase with CO2 sorption, whereas those for skeletal vibration modes decrease. These energy shifts are attributed to elongational deformation of PMMA. The PMMA structure is deformed with stretching of the chains as a bundle. From energy shifts of the CO2 peaks, the size of the CO2 accommodated space between the bundles is estimated to be 1.6–1.9 nm. Furthermore, it was observed that the vibrational energies of the PMMA modes in foamed glassy PMMA differ from the values in glassy PMMA without foams. This result suggests that the local structure of the PMMA chain changes with the process of the CO2 sorption and/or foaming. The local structure of the PMMA chain might be one of the dominant factors governing the properties of cellular materials. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 831–842, 2008
Solid Propellant Burning Rate From Strand Burner Pressure Measurement
Authors: Yilmaz Nadir , Donaldson Burl , Gill Walter , Erikson William 
Published: March 2008

AbstractStrand burner pressure–time data are analyzed to determine if the propellant burning rate can be extracted. This approach is based on strand burner pressure–time history that is related to the temperature change due to exothermic reaction heating of chamber gases and gas addition to the chamber by propellant combustion products. In support of this method, chemical equilibrium calculations were made to project product composition, internal energy, and other needed properties. A mathematical model was formulated and solved numerically and the calculated burning rates were compared with the experimental wire‐break time results provided simultaneously and with the propellant manufacturer's results, when available. The comparisons reveal that the approach has merit and that more accurate pressure determination coupled with additional thermochemical information and strand burner gas temperature measurements has the potential to make this approach a viable technique and one that can be applied in conjunction with other burning rate measurements. The proposed method is similar to a well‐developed technique which is commonly applied to ballistic powders but with adjustments for the differences in geometry, pressure, and time of event.
Crystal structure of native O‐acetyl‐serine sulfhydrylase from Entamoeba histolytica and its complex with cysteine: Structural evidence for cysteine binding and lack of interactions with serine acetyl transferase
Authors: Chinthalapudi Krishna , Kumar Manish , Kumar Shivesh , Jain Shaifali , Alam Neelima , Gourinath S. 
Published: March 2008

AbstractCysteine plays a major role in the antioxidative defense mechanisms of the human parasite Entameoba histolytica. The major route of cysteine biosynthesis in this parasite is the condensation of O‐acetylserine with sulfide by the de novo cysteine biosynthetic pathway involving two key enzymes O‐acetyl‐L‐serine sulfhydrylase (OASS) and serine acetyl transferase (SAT). The crystal structure of native OASS from Entameoba histolytica (EhOASS) has been determined at 1.86 Å resolution and in complex with its product cysteine at 2.4 Å resolution. In comparison with other known OASS structures, insertion in the N‐terminal region and C‐terminal helix reveal critical differences, which may influence the protein‐protein interactions. In spite of lacking chloride binding site at the dimeric interface, the N‐terminal extension compared with other known cysteine synthases, participates in dimeric interactions in an interesting domain swapping manner, enabling it to form a stronger dimer. Sulfate is bound in the active site of the native structure, which is replaced by cysteine in the cysteine bound form causing reorientation of the small N‐terminal domain and thus closure of the active site. Ligand binding constants of OAS, Cys, and Met with EhOASS are comparable with other known OASS indicating similar active site arrangement and dynamics. The cysteine complexed structure represents the snapshot of the enzyme just before releasing the final product with a closed active site. The C‐terminal helix positioning in the EhOASS may effect its interactions with EhSAT and thus influencing the formation of the cysteine synthase complex in this organism. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Crystal growth and optical performance of Nd:Sr3Ga2Ge4O14 crystals
Authors: Wu Anhua , Ding Jiaxuan , Xu Jiayue , Shen Hui , Ogawa Takayo , Wada Satoshi 
Published: March 2008

AbstractNd:Sr3Ga2Ge4O14 (Nd:SGG) single crystals up to ∅︁25 mm × 50 mm were grown by the modified Bridgman method. Absorption and fluorescence spectra of Nd:SGG crystals were measured at room temperature. Compared with Nd:YAG crystals, the absorption of Nd:SGG single crystals presented broad absorption bands of Nd3+ ions. The fluorescence inten‐ sity increased with Nd concentration while the fluorescence lifetime of the 4F3/2–4I11/2 transition excited by a diode laser at room temperature showed a slight decrease when the Nd concentration increased to 8 at%. The results indicated that the quenching effect might occur in Nd:SGG crystals doped with higher Nd concentrations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quasiparticle density of states in a half metal in the presence of odd‐frequency Cooper pairs
Authors: Asano Yasuhiro , Yokoyama Takehito , Tanaka Yukio , Golubov Alexander A. 
Published: March 2008

AbstractWe study the local density of states in a half metal sandwiched by the two superconductors. The spin‐flip scattering at the junction interface opens the Josephson channels of the odd‐frequency spin‐triplet s‐wave Cooper pairs. The penetration of the odd‐frequency pairs enhances the quasiparticle density of states near the Fermi energy in a half metal, which is responsible for the unusual nonmonotonic temperature dependence of the Josephson current. On the basis of calculated results, we propose experiments to confirm the odd‐frequency Cooper pairs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical constants and critical‐point parameters of GaAs1–xSbx alloy films grown on GaAs
Authors: Ben Sedrine N. , Gharbi T. , Harmand J. C. , Chtourou R. 
Published: March 2008

AbstractSpectroscopic Ellipsometry (SE) is used in this work to investigate the optical properties of the GaAs1–x Sbx alloys. The present study is based on a set of GaAs1–x Sbx layers (x = 0.0%, 6.7% and 10.8%) grown on GaAs substrate by molecular beam epitaxy (MBE). The SE measurements were carried out in the energy range of 1.4 – 5.5 eV at room temperature for 70° and 75° incident angles, before and after chemical etching. The optical constants of GaAs1–x Sbx alloys were extracted using the Newton–Raphson method based on the four‐phase model (ambient – GaAs native oxide overlayer – GaAs1–x Sbx film – GaAs substrate). Analytic line shapes fitted to numerically calculated second derivatives of the dielectric functions determined the critical‐points parameters above the GaAs1–x Sbx bandgap E0. The best fit parameters and the experimental extracted data show in particular a red‐shift and a broadening increase of E1, E1 + Δ1, E ′0 and E2 transitions by increasing Sb content. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stiffening and hydrophilisation of SOG low‐k material studied by ellipsometric porosimetry, UV ellipsometry and laser‐induced surface acoustic waves
Authors: Urbanowicz A. M. , Meshman B. , Schneider D. , Baklanov M. R. 
Published: March 2008

AbstractIn this paper we evaluate the correlation between UV light absorption of SOG (spin‐on glass) low dielectric constant (low‐k) films and chemical changes induced by an excimer UV source at several wavelengths: 172 nm, 222 nm, and 308 nm. Low‐k absorption in the UV range was measured by nitrogen purged UV ellipsometry. It is shown that im‐ provement of mechanical properties is accompanied by degradation (hydrophilisation) of low‐k films. Changes in hydrophobic properties were evaluated by water‐source ellipsometric porosimetry (WEP). The Young's moduli of the films were measured by laser‐induced surface acoustic waves (LAwaves). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Changes in optical properties of MnAs thin films on GaAs(001) induced by α‐ to β‐phase transition
Authors: Gallas B. , Rivory J. , Arwin H. , Vidal F. , Etgens V. H. 
Published: March 2008

AbstractMnAs layers with 45 nm thickness were grown epitaxially on GaAs(001) substrates. Ellipsometry measurements were made in the spectral range 0.045 eV to 6 eV as a function of temperature (between –10 °C and 50 °C) at 70° of incidence. In this way the transition from the hexagonal α‐phase to the orthorhombic β‐phase could be monitored. Non‐zero off‐diagonal elements of the Jones matrix for an azimuth of 38° off the [1$ \bar 1 $0] axis of the substrate indicate that the optical functions of MnAs are anisotropic in both phases. The optical conductivity exhibits low‐energy interband transitions around 0.3 eV, more clearly seen in the α‐phase than in the β‐phase. Extrapolation of the optical conductivity to zero frequency confirms that the α‐phase is about two times more conducting than the β‐phase. A broad structure is observed in the visible range around 3 eV. The α‐phase is characterised by an anisotropy induced energy difference of this structure with a maximum at 2.8 eV for the extraordinary index and at 3.15 eV for the ordinary index. This difference vanishes in the β‐phase in which anisotropy mainly induces changes in amplitude of the 3 eV structure. The assignment of the structures will be discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monitoring the α‐ to β‐phase transition in MnAs/GaAs(001) thin films as function of temperature
Authors: Gallas B. , Rivory J. , Arwin H. , Vidal F. , Stchakovsky M. 
Published: March 2008

AbstractMnAs layers with a 5 nm thick amorphous GaAs capping layer were grown epitaxially on GaAs(001). Generalized ellipsometric measurements were made on a 45 nm thick layer in the spectral range 1.5–4 eV at temperatures between –10 °C and 50 °C in steps of 5 °C. By using both the diagonal and off‐diagonal elements of the Jones matrix, the in‐plane unixial anisotropy of MnAs was determined in terms of the ordinary and extraordinary complex dielectric functions. The measurements at each temperature could be well reproduced by modeling using the optical properties of the two limiting phases α‐MnAs and β‐MnAs determined at –10 °C and 50 °C, respectively. The best sensitivity to the volume fractions of the two phases was obtained near 2.2 eV by monitoring the generalized ellipsometric parameter Δp for which the variations reached 30°. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Precise phase‐modulation generalized ellipsometry of anisotropic samples
Authors: Halagacˇka L. , Postava K. , Foldyna M. , Pištora J. 
Published: March 2008

AbstractA procedure for the measurement of the generalized ellipsometric angles using a phase‐modulation spectroscopic ellipsometer is described. Generalized phase‐modulation ellipsometry combined with zone averaging enables precise characterization of samples with generalized anisotropy including anisotropic thin films with general axis orientation, liquid crystals, gratings, and anisotropic nanostructures. We employed a UVISEL Jobin Yvon spectroscopic ellipsometer with a photoelastic modulator (PEM). The Jones matrix formalism is applied to nondepolarizing samples and ellipsometer components description. The zone averaging proposed enables elimination of azimuth‐angle error and component imperfection. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact of a proprietary concentrate of Sambucus nigra L. on urinary pH
Authors: Walz Brigitte , Chrubasik Sigrun 
Published: March 2008

AbstractA proprietary concentrate from Sambucus nigra L. – in its diluted preparation as part of a hypocaloric diet available in Switzerland – had no impact on urinary pH, urinary hydrogen ion concentrations or 24 h excretion and thus did not influence the solubility of stone‐inducing ions. Copyright © 2008 John Wiley & Sons, Ltd.
Antimycobacterial polyacetylenes from Levisticum officinale
Authors: Schinkovitz Andreas , Stavri Michael , Gibbons Simon , Bucar Franz 
Published: March 2008

AbstractNo conflicts of interest concerning financial matters or personal relationships exist between the authors and those who might bias this work. The present work is in part included the PhD thesis of A. Schinkovitz (University of Graz) but has not been published elsewhere previously.The dichloromethane extract of the roots of Levisticum officinale L. (Apiaceae) exhibited significant antimycobacterial activity against Mycobacterium fortuitum and Mycobacterium aurum in a microtiter plate dilution assay and was further analysed following a bioassay‐guided fractionation strategy. 3(R)‐Falcarinol (3(R)‐(‐)‐1,9‐heptadecadien‐4,6‐diin‐3‐ol] and 3(R)‐8(S)‐falcarindiol [3(R)‐8(S)‐(+)‐1,9‐heptadecadien‐4,6‐diin‐3,8‐diol] could be identified as the active components in this extract. The minimal inhibitory concentration (MIC) of 3(R)‐falcarinol against M. fortuitum and M. aurum was 16.4 µm while that of 3(R)‐8(S)‐falcarindiol was 30.7 µm against M. fortuitum and 61.4 µm against M. aurum, respectively. Previously, 3(R),8(R)‐dehydrofalcarindiol was isolated from Artemisia monosperma and surprisingly this polyacetylene exhibited no antimycobacterial activity at 128 µg/mL. This indicates that the terminal methyl group is vital for retention of antimycobacterial activity. Reference antibiotics ethambutol and isoniazid exhibited an activity of 115.5 µm and 14.6 µm against M. fortuitum, and 3.4 µm and 29.2 µm against M. aurum, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
In vitro antileukaemic activity of extracts from chokeberry (Aronia melanocarpa [Michx] Elliott) and mulberry (Morus alba L.) leaves against sensitive and multidrug resistant HL60 cells
Authors: Skupień Katarzyna , Kostrzewa‐Nowak Dorota , Oszmiański Jan , Tarasiuk Jolanta 
Published: March 2008

AbstractThe aim of the present study was to determine in vitro antileukaemic activities of extracts obtained from chokeberry (Aronia melanocarpa [Michx] Elliot) and mulberry (Morus alba L.) leaves against promyelocytic HL60 cell line and its multidrug resistant sublines exhibiting two different MDR phenotypes: HL60/VINC (overexpressing P‐glycoprotein) and HL60/DOX (overexpressing MRP1 protein). It was found that the extracts from chokeberry and mulberry leaves were active against the sensitive leukaemic cell line HL60 and retained the in vitro activity against multidrug resistant sublines (HL60/VINC and HL60/DOX). The values of resistance factor (RF) found for these extracts were very low lying in the range 1.2–1.6. Copyright © 2008 John Wiley & Sons, Ltd.
Performance optimisation of a new‐generation orthogonal‐acceleration quadrupole‐time‐of‐flight mass spectrometer
Authors: Bristow Tony , Constantine Jill , Harrison Mark , Cavoit Fabien 
Published: March 2008

AbstractOrthogonal‐acceleration quadrupole time‐of‐flight (oa‐QTOF) mass spectrometers, employed for accurate mass measurement, have been commercially available for well over a decade. A limitation of the early instruments of this type was the narrow ion abundance range over which accurate mass measurements could be made with a high degree of certainty. Recently, a new generation of oa‐QTOF mass spectrometers has been developed and these allow accurate mass measurements to be recorded over a much greater range of ion abundances. This development has resulted from new ion detection technology and improved electronic stability or by accurate control of the number of ions reaching the detector. In this report we describe the results from experiments performed to evaluate the mass measurement performance of the Bruker micrOTOF‐Q™, a member of the new‐generation oa‐QTOFs. The relationship between mass accuracy and ion abundance has been extensively evaluated and mass measurement accuracy remained stable (±1.5 m m/z units) over approximately 3–4 orders of magnitude of ion abundance. The second feature of the Bruker micrOTOF‐Q™ that was evaluated was the SigmaFit™ function of the software. This isotope pattern‐matching algorithm provides an exact numerical comparison of the theoretical and measured isotope patterns as an additional identification tool to accurate mass measurement. The smaller the value, the closer the match between theoretical and measured isotope patterns. This information is then employed to reduce the number of potential elemental formulae produced from the mass measurements. A relationship between the SigmaFit™ value and ion abundance has been established. The results from the study for both mass accuracy and SigmaFit™ were employed to define the performance criteria for the micrOTOF‐Q™. This provided increased confidence in the selection of elemental formulae resulting from accurate mass measurements. Copyright © 2008 John Wiley & Sons, Ltd.
Front and backstages of the diminished routinization of innovations: what innovation research makes public and organizational research finds behind the scenes
Authors: Bartunek Jean M. , Trullen Jordi , Immediato Sherry , Schneider Frank 
Published: March 2008

AbstractResearch on innovation routinization emphasizes public aspects of this process. The issues such research addresses are important, but do not fully describe routinization processes or account for all the characteristics that generate them. Based on a study of an innovative course, we explore organizational factors that affect the diminished routinization of innovations, the loss of core components of the innovation while it is being routinized. We develop a model of how organizational structure and intergroup dynamics affect the diminished routinization of innovations by impacting knowledge sharing and links between the innovation and its core organizational purpose. Copyright © 2008 Strategic Management Society.
Cross‐boundary disruptors: powerful interindustry entrepreneurial change agents
Authors: Burgelman Robert A. , Grove Andrew S. 
Published: March 2008

AbstractBased on comparative case studies of Apple Computer's strategic actions in the music and cellular telephony industries, we develop the concept of cross‐boundary disruptor as a new type of entrepreneurial actor in interindustry strategic dynamics. We document how the confluence of forces that drove the convergence of the music and computing industries gave rise to Apple becoming a defining example of a cross‐boundary disruptor to the music industry, and examine Apple's chances to do the same in the cellular telephony industry. Using our preliminary conceptual framework, we further examine what kind of company could become a cross‐boundary disruptor in the U.S. health care industry to help overcome its long‐standing stasis. We summarize our case study‐based findings into a preliminary substantive theory of the cross‐boundary disruption phenomenon, and discuss several implications for further strategic entrepreneurship research and strategic leadership practice. Copyright © 2008 Strategic Management Society.
Comparing alliance network structure across industries: observations and explanations
Authors: Rosenkopf Lori , Schilling Melissa A. 
Published: March 2008

AbstractMuch research in strategic entrepreneurship has focused on the consequences of network structure for firm performance. Despite this emphasis, little is known about variation in network structure across industries, or about the antecedents of this variation. In a comparative study of alliance networks in 32 industries, we demonstrate substantial variety in network structure, and develop a typology of network structures. We then endeavor to explain this variation by focusing on dimensions of the products and technologies that characterize these industries—such as technological uncertainty and dynamism, product modularity, and architectural control—and associating them with underlying characteristics of network structure. We conclude with a discussion of implications of our findings for research in strategic entrepreneurship. Copyright © 2008 Strategic Management Society.