bluuebunny/crossref_metadata_2025 huggingface dataset:
Children speak about neighborhoods: using mixed methods to measure the construct neighborhood
Authors: Nicotera Nicole
Published: March 2008

This study contributes to the knowledge base of community practice and research by examining the construct neighborhood from qualitative and quantitative perspectives. Mixed methodology was employed to explore the associations and discrepancies between a census measure of neighborhood based in social disorganization theory and a qualitative measure based on the voices of children (N=59). Qualitative results indicate nine dimensions of the construct neighborhood that are not found in census‐based measures of the construct. Mixed methods results demonstrate that children in both higher and lower socially disorganized neighborhoods express the presence of neighborhood resources and neighborly affiliations as well as negative neighborhood experiences. Expressions of fear, needs for safety, and qualities of unsavory characters distinguish the two types of neighborhoods. © 2008 Wiley Periodicals, Inc.
Determination of triptonide by cloud point extraction combined with MEKC
Authors: Wu Yi‐Wei , Jiang Yin‐Yan , Xiao Tang‐Xin , Zhang Hai‐Li
Published: March 2008

A method has been developed for the determination of triptonide in the traditional Chinese herb Tripterygium wilfordii Hook F. by micellar electrokinetic capillary chromatography combined with cloud point extraction. The analyte was extracted at pH 3.0 by micelles of the nonionic surfactant polyoxyethylene 7,5‐octylphenyl ether (Triton X‐114). A 250‐μL aliquot from the extracted surfactant‐rich phase was diluted to 400 μL with ethanol to reduce its viscosity before separation by MEKC. Under optimum conditions, an enrichment factor of 25 is obtained and the determination limit of triptonide is found to be 3.15×10–7 mol/L. The proposed method has been successfully applied to the determination of triptonide in T. wilfordii tablet and spiked urine matrix, demonstrating the feasibility and reliability of the proposed method.
Utility of separation science in metabolomic studies
Authors: Issaq Haleem J. , Abbott Eric , Veenstra Timothy D.
Published: March 2008

Metabolomics, or alternately metabonomics, an emerging field of biochemical research, is a complementary technique to genomics, transcriptomics, and proteomics. Direct quantitative measurements of metabolite expressions in urine, serum, plasma, and tissue are essential for the study of biological processes in normal and disease states. Since the number of metabolites in a biological sample is large separation science plays an important role in metabolomic research. This review describes the role of GC, HPLC, CE, and supercritical fluid chromatography in metabolomic research. The application of each technique is discussed and its advantages and limitations are discussed with selective illustrative examples.
Chemical Conjugation of Linear and Cyclic RGD Moieties to a Recombinant Elastin‐Mimetic Polypeptide ‐ A Versatile Approach towards Bioactive Protein Hydrogels
Authors: Kaufmann Doris , Fiedler Anne , Junger Andreas , Auernheimer Jörg , Kessler Horst , Weberskirch Ralf
Published: March 2008

An elastin‐mimetic polypeptide, (EMM)7, with the amino‐acid sequence GRDPSS [VPGVG VPGKG VPGVG VPGVG VPGEG VPGIG]7 was used for chemical conjugation of various integrin ligands (RGD peptides) to prepare bioactive hydrogels. The chemical approach involved (1) chemical protection of lysine residues with Fmoc or Boc groups, (2) chemical ligation of a protected linear or cyclic RGD ligand, with or without a hexanoic‐acid spacer to the glutamic acid residue, (3) deprotection of the lysine functionalities and the RGD moieties and (4) cross‐linking to form a bioactive hydrogel. 1H NMR spectroscopy was used to quantify the multiple steps in the reaction. The chemical protection was found to be between 65 and 93% for Fmoc and Boc, respectively. The ligands studied included linear RGD cell‐binding [HFGRGDSOH (1‐l‐RGD), HAhxFGRGDSOH (2‐AhxFGRGDS) and a cyclic H2N(CH2)6COHNcyclo(RGDfK) (HAhxc(RGDfK)) peptide also with a hexanoic‐acid spacer. Cell adhesion with mouse osteoblast cells was dependent on the ligand type, ligand density and the use of a spacer.

magnified image
Open‐Pore Biodegradable Foams Prepared via Gas Foaming and Microparticulate Templating
Authors: Salerno Aurelio , Iannace Salvatore , Netti Paolo A.
Published: March 2008

Open‐pore biodegradable foams with controlled porous architectures were prepared by combining gas foaming and microparticulate templating. Microparticulate composites of poly(ε‐caprolactone) (PCL) and micrometric sodium chloride particles (NaCl), in concentrations ranging from 70/30 to 20/80 wt.‐% of PCL/NaCl were melt‐mixed and gas‐foamed using carbon dioxide as physical blowing agent. The effects of microparticle concentration, foaming temperature, and pressure drop rate on foam microstructure were surveyed and related to the viscoelastic properties of the polymer/microparticle composite melt. Results showed that foams with open‐pore networks can be obtained and that porosity, pore size, and interconnectivity may be finely modulated by optimizing the processing parameters. Furthermore, the ability to obtain a spatial gradient of porosity embossed within the three‐dimensional polymer structure was exploited by using a heterogeneous microparticle filling. Results indicated that by foaming composites with microparticle concentration gradients, it was also possible to control the porosity and pore‐size spatial distribution of the open‐pore PCL foams.

magnified image
A Non‐Covalent Method to Functionalize Multi‐Walled Carbon Nanotubes Using Six‐Armed Star Poly(L‐lactic acid) with a Triphenylene Core
Authors: Yang Li‐Ping , Pan Cai‐Yuan
Published: March 2008

Well‐defined six‐armed star poly(L‐lactic acid) (PLLA) with a triphenylene core has been prepared by ring‐opening polymerization of L‐lactide. As a result of strong π–π interactions between the triphenylene core and the multi‐walled carbon nanotubes (MWCNTs), the polymer was conveniently immobilized on the surface of the as‐received MWCNTs by a simple ultrasonic process while the intrinsic graphitic structure of the pristine MWCNTs is retained. The non‐covalent interaction between the carbon nanotubes and the polymer has been proven by the UV‐vis absorption spectra, the fluorescence spectra, the Raman spectra, and the X‐ray photoelectron spectra.

magnified image
Elongational Rheology of Polymer/Clay Dispersions: Determination of Orientational Extent in Elongational Flow Processes
Authors: Stefanescu Eduard A. , Petrovan Simioan , Daly William H. , Negulescu Ioan I.
Published: March 2008

The purpose of the present contribution is to provide an efficient method that would help to quantify the orientational levels occurring in polymer/clay dispersions subjected to elongational flow. The extent of internal orientation developed in salt containing montmorillonite/poly(ethylene oxide) gels is investigated, combining shear and elongational rheology methods. Entropic changes indicate that the strength of the transient network present in each gel affects the orientational ability of clay particles and polymer chains. We found that an increased Hencky strain of the hyperbolic die leads to a higher variation of the calculated entropy of the material.

magnified image
Novel Electrospun Nanofibers Composed of Polyelectrolyte Complexes
Authors: Penchev Hristo , Paneva Dilyana , Manolova Nevena , Rashkov Iliya
Published: March 2008

A simple method to obtain novel nanofibers composed of polyelectrolyte complexes (PECs) has been proposed. It consists of the electrospinning of a mixed homogeneous solution of polyelectrolyte partners, and the formation of PEC during the electrospinning. This was achieved by careful choice of the composition of the spinning solutions. Chitosan was the polycationic partner, with either a weak polyacid [poly(acrylic acid), PAA] as a counterpart or a strong one [poly(2‐acrylamido‐2‐methylpropanesulfonic acid), PAMPS]. The fibrous mats were composed of nanofibers with mean diameters of ca. 100 nm. They retained their integrity over the pH range which is typical of the corresponding PEC.

magnified image
Influence of surface residual stresses on gigacycle fatigue response of high chromium cold work tool steel
Authors: Sohar C. R. , Betzwar‐Kotas A. , Gierl C. , Weiss B. , Danninger H.
Published: March 2008

The effect of surface compressive residual stresses (RS) induced by surface grinding and polishing on the gigacycle fatigue behavior of medium‐carbon high‐chromium alloy cold work tool steel was evaluated. Two test series were performed: Specimens of series I revealed high compressive RS of about ‐800 MPa at the surface, resulting from grinding with fine emery paper, which treatment had definitely a beneficial influence on the fatigue endurance strength. The existence of surface RS was also revealed to be responsible for the location of the fatigue crack initiation. High compressive RS favored internal crack origins. In this case crack nucleation sites were primary carbide clusters in the interior of the specimen, forming so‐called fish‐eyes at the fracture surface. In contrast, specimens of test series II had only very low RS, which enabled crack initiation near/at the surface at primary carbides/clusters. Furthermore, it has been shown that the high initial RS are prone to partial relaxation through cyclic loading for which the mechanisms are currently unknown. In this case near‐surface induced failure was obtained. It was possible to confirm the experimentally obtained data by the use of the concept of local fatigue strength as function of effective RS. The relaxation of high initial RS was experimentally confirmed through RS measurements at runout specimens (1010 cycles without failure).
Erratum: MRI monitoring of focal cerebral ischemia in peroxisome proliferator‐activated receptor (PPAR)‐deficient mice
Authors: Pialat Jean‐Baptiste , Cho Tae‐Hee , Beuf Olivier , Joye Elisabeth , Moucharaffie Samir , Langlois Jean‐Baptiste , Nemoz Chantal , Janier Marc , Berthezene Yves , Nighoghossian Norbert , Desvergne Béatrice , Wiart Marlène
Published: March 2008

NMR In Biomedicine: MRI monitoring of focal cerebral ischemia in peroxisome proliferator‐activated receptor (PPAR)‐deficient mice. Jean‐Baptiste Pialat, Tae‐Hee Chao, Olivier Beuf, Elisabeth Joye, Samir Moucharaffie, Jean‐Baptiste Langlois, Chantal Nemoz, Marc Janier, Yves Berthezene, Norbert Nighoghossian, Béatrice Desvergnre and Marlene Wiart. Published online April 24 2007, Issue 20:3, pp. 335–342; DOI: 10.1002/nbm.1157.

Following publication it has been noted that an author's name was misspelt. As above, the author was spelt as “Samir Moucharaffie”. It should have been spelt as “Samir Moucharrafie”.
Efficiency of mixed hybrid finite element and multipoint flux approximation methods on quadrangular grids and highly anisotropic media
Authors: Younes Anis , Fontaine Vincent
Published: March 2008

The mixed hybrid finite element (MHFE) and the multipoint flux approximation (MPFA) methods are well suited for anisotropic heterogeneous domains since both are locally conservative and can handle general irregular grids. In this work, behaviours and performances of MHFE and MPFA methods are studied numerically for different heterogeneities and anisotropy factors on parallelograms and then on a more general quadrilateral grid.

The superiority of MPFA in terms of accuracy and efficiency is clearly demonstrated for parallelogram grids. In the case of more general quadrilateral grids, MPFA becomes more central processing unit time consuming than MHFE. For high anisotropy factors, both methods give results with significant non‐physical oscillations. Copyright © 2008 John Wiley & Sons, Ltd.
Iterative solution schemes for quadratic DRM‐MD
Authors: Portapila M. , Power H.
Published: March 2008

The aim of this work is to find the most suitable iterative technique to solve linear systems of equations arising from the dual reciprocity method in multidomains (DRM‐MD). In this article, the surface variables of the governing equations and the shape functions of the boundary elements are quadratic functions, and for the dual reciprocity approximation the radial basis function (RBF) used is the augmented thin plate spline. A series of tests are carried out studying efficiency and accuracy of different Krylov iterative solvers, every one assessed with several preconditioners. The results are related to intrinsic properties of the linear systems such as condition numbers, sparsity patterns, singular values, and eigenvalues. Besides, the performance of the selected iterative solvers is studied in relation with the subdivision of the domain, taking into account total number of nodes of the whole mesh, number of internal nodes per subdomain, as well as different aspect ratios of the mesh grids. As a result, performances of different refining schemes are considered. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2008
Mortar element methods for parabolic problems
Authors: Patel Ajit , Pani Amiya K. , Nataraj Neela
Published: March 2008

In this article a standard mortar finite element method and a mortar element method with Lagrange multiplier are used for spatial discretization of a class of parabolic initial‐boundary value problems. Optimal error estimates in L∞(L2) and L∞(H1)‐norms for semidiscrete methods for both the cases are established. The key feature that we have adopted here is to introduce a modified elliptic projection. In the standard mortar element method, a completely discrete scheme using backward Euler scheme is discussed and optimal error estimates are derived. The results of numerical experiments support the theoretical results obtained in this article. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2008
Null‐field approach for Laplace problems with circular boundaries using degenerate kernels
Authors: Chen Jeng‐Tzong , Shen Wen‐Cheng
Published: March 2008

In this article, a semi‐analytical method for solving the Laplace problems with circular boundaries using the null‐field integral equation is proposed. The main gain of using the degenerate kernels is to avoid calculating the principal values. To fully utilize the geometry of circular boundary, degenerate kernels for the fundamental solution and Fourier series for boundary densities are incorporated into the null‐field integral equation. An adaptive observer system is considered to fully employ the property of degenerate kernels in the polar coordinates. A linear algebraic system is obtained without boundary discretization. By matching the boundary condition, the unknown coefficients can be determined. The present method can be seen as one kind of semianalytical approaches since error only attributes to the truncated Fourier series. For the eccentric case, vector decomposition technique for the normal and tangential directions is carefully considered in implementing the hypersingular equation in mathematical essence although we transform it to summability to divergent series. The five advantages, well‐posed linear algebraic system, principal value free, elimination of boundary‐layer effect, exponential convergence, and mesh free, are achieved. Several examples involving infinite, half‐plane, and bounded domains with circular boundaries are given to demonstrate the validity of the proposed method. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Features of mechanism of free radical initiation in polymers under exposure to nitrogen oxides
Authors: Davydov E. Y. , Gaponova I. S. , Pokholok T. V. , Vorotnikov A. P. , Pariiskii G. B. , Zaikov G. E.
Published: March 2008

The mechanism of interactions of NO, NO2, NO3 as well as dimers of NO2 with functional groups of organic molecules and polymers is considered. It is shown that nitrogen oxides are active initiators of radical reactions as a result of which various molecular products of nitration and stable nitrogen‐containing radicals are formed. Features of the initiation mechanism determining the composition of molecular and radical products of conversions of the compounds on exposure to nitrogen oxides have been revealed. Copyright © 2008 John Wiley & Sons, Ltd.
Mechanical properties of injection molded long fiber polypropylene composites, Part 2: Impact and fracture toughness
Authors: Senthil Kumar K. , Bhatnagar Naresh , Ghosh Anup K.
Published: March 2008

This study describes the effect of fiber length and compatibilizer content on notched izod impact and fracture toughness properties. Long fiber polypropylene (LFPP) pellets of different sizes were prepared by extrusion process using a new radial impregnation die, and subsequently, pellets were injection molded as described in previous publication 1. The content of glass fiber reinforcement was maintained same for all compositions. Maleic‐anhydride grafted polypropylene (MA‐g‐PP) was chosen as a compatibilizer to increase the adhesion between glass fiber and PP matrix and its content was maintained at 2 wt%. Notched izod impact property was studied for LFPP composites prepared with and without compatibilizer for different pellet sizes. Failure mechanism due to sudden impact was analyzed with scanning electron micrographs and was correlated with impact property of LFPP composites. Fracture and failure behavior of injection molded LFPP composite were studied and relationship between fracture toughness and microstructure of LFPP composite was analyzed. The microstructure of the composites was characterized by the dimensionless reinforcing effectiveness parameter, which accounts for the influence of fiber layer structure, fiber alignment, fiber volume fraction, fiber length distribution, and aspect ratio. Matrix stress condition factor and energy absorption ratio were determined for LFPP composites prepared with and without compatibilizer. Failure mechanism of both the matrix and fiber, revealed with SEM images, were discussed. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
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

A 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

Solubilization 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

Raman 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

Strand 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

Cysteine 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

Nd: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

We 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

Spectroscopic 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

In 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

MnAs 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

MnAs 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

A 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

A 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

No 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

The 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

Orthogonal‐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

Research 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

Based 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

Much 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.
The process of creative construction: knowledge spillovers, entrepreneurship, and economic growth
Authors: Agarwal Rajshree , Audretsch David , Sarkar M. B.
Published: March 2008

Questioning the underlying assumptions of the process of creative destruction, we conceptualize an alternative process of creative construction that may characterize the dynamics between entrants and incumbents. We discuss the underlying mechanism of knowledge spillover strategic entrepreneurship whereby knowledge investments by existing organizations, when coupled with entrepreneurial action by individuals embedded in their context, results in new venture creation, heterogeneity in performance, and subsequent growth in industries, regions, and economies. The framework has implications for future research in entrepreneurship, strategy, and economic growth. Copyright © 2008 Strategic Management Society.
Association of different obesity indices with blood pressure and blood lipids in children and adolescents
Authors: Plachta-Danielzik Sandra , Landsberg Beate , Johannsen Maike , Lange Dominique , Müller Manfred James
Published: March 2008

The aim of the present study was to compare individual associations of BMI, triceps skinfold (TSF), waist circumference (WC) and percentage fat mass (%FM) with blood pressure (BP) and blood lipids in children and adolescents. Cross-sectional data on BMI, TSF, WC, %FM as well as on BP, TAG and HDL were analysed in 4220 (BP) and 729 (lipids) 9–11-year-old children and 3174 (BP) and 536 (lipids) 13–16-year-old adolescents as part of the Kiel Obesity Prevention Study. All obesity indices were similarly associated with BP and blood lipids. In girls, WC had closer correlations to BP than BMI (systolic BP: 0·27 and 0·24 for BMI, 0·34 and 0·28 for WC in 9–11- and 13–16-year-olds). Subjects with an obesity index ≥ 90th percentile had higher prevalences of elevated BP and blood lipids than subjects with a normal index. In children with normal BMI or WC, an additionally elevated second obesity index was associated with a 2·5–7·4-fold higher prevalence of high BP when compared with children with normal indices. In adolescents, an elevated WC plus an elevated second obesity index was associated with a 2·6–8·2-fold higher prevalence of high BP when compared with adolescents with an elevated WC plus a normal second index. We conclude that (i) both BMI and WC are appropriate to estimate CVD risk, (ii) the use of a second obesity index is recommended in children with normal BMI or normal WC as well as in adolescents with elevated WC and (iii) all obesity indices seemed to be appropriate for risk assessment.
Validity and reliability of body composition analysers in children and adults
Authors: Jensky-Squires Nicole E. , Dieli-Conwright Christina M. , Rossuello Amerigo , Erceg David N. , McCauley Scott , Schroeder E. Todd
Published: March 2008

We tested the validity and reliability of the BioSpace InBody 320, Omron and Bod-eComm body composition devices in men and women (n 254; 21–80 years) and boys and girls (n 117; 10–17 years). We analysed percentage body fat (%BF) and compared the results with dual-energy X-ray absorptiometry (DEXA) in adults and compared the results of the InBody with underwater weighing (UW) in children. All body composition devices were correlated (r 0·54–0·97; P ≤ 0·010) to DEXA except the Bod-eComm in women aged 71–80 years (r 0·54; P = 0·106). In girls, the InBody %BF was correlated with UW (r 0·79; P ≤ 0·010); however, a more moderate correlation (r 0·69; P ≤ 0·010) existed in boys. Bland–Altman plots indicated that all body composition devices underestimated %BF in adults (1·0–4·8 %) and overestimated %BF in children (0·3–2·3 %). Lastly, independent t tests revealed that the mean %BF assessed by the Bod-eComm in women (aged 51–60 and 71–80 years) and in the Omron (age 18–35 years) were significantly different compared with DEXA (P ≤ 0·010). In men, the Omron (aged 18–35 years), and the InBody (aged 36–50 years) were significantly different compared with DEXA (P = 0·025; P = 0·040 respectively). In addition, independent t tests indicated that the InBody mean %BF in girls aged 10–17 years was significantly different from UW (P = 0·001). Pearson's correlation analyses demonstrated that the Bod-eComm (men and women) and Omron (women) had significant mean differences compared with the reference criterion; therefore, the %BF output from these two devices should be interpreted with caution. The repeatability of each body composition device was supported by small CV ( < 3·0 %).
MODERNIZATION OR CULTURAL MAINTENANCE: THE PRACTICE OF CONSANGUINEOUS MARRIAGE IN IRAN
Authors: JALAL ABBASI-SHAVAZI MOHAMMAD , MCDONALD PETER , HOSSEINI-CHAVOSHI MEIMANAT
Published: March 2008

Consanguineous marriage has been the culturally preferred form of marriage in Iran. This paper examines the extent to which education, urbanization and changes in modes of economic production have affected the incidence of consanguineous marriage and attitudes towards consanguineous marriages. The 2002 Iran Fertility Transition Survey conducted in the four provinces of Gilan, Sistan and Baluchistan, Yazd and West Azarbaijan provides information on the degree of relationship of marriage partners from around 6550 ever-married women aged 15–49. Attitudinal data were also obtained. Overall, the level of marriage to biological relatives ranged from 23% in Gilan to 78% in Sistan and Baluchistan. The paper finds that the practice of marriage to biological relatives has remained surprisingly resilient in the face of modernizing influences and that ethnicity, province and area of residence remain important determinants. On the other hand, attitudes have shifted towards marriage with a non-relative. Anthropological research would illuminate the processes of consanguineous marriage in Iran.
Gravity-driven reacting flows in a confined porous aquifer
Authors: VERDON JAMES , WOODS ANDREW W.
Published: March 2008

We develop a model for the dynamics of a reactive gravity-driven flow in a porous layer of finite depth, accounting for the change in permeability and density across the dissolution front. We identify that the two controlling parameters are the mobility ratio across the reaction front and the ratio of the buoyancy-driven flow to the fluid injection rate. We present some numerical solutions for the evolution of a two-dimensional dissolution front, and develop an approximate analytic solution for the limit of large injection rate compared to the buoyancy-driven flow. The model predictions are compared with some new analogue laboratory experiments in which fresh water displaces a saturated aqueous solution initially confined within a two-dimensional reactive permeable matrix composed of salt powder and glass ballotini. We also present self-similar solutions for an axisymmetric gravity-driven reactive current moving through a porous layer of finite depth. The solutions illustrate how the reaction front becomes progressively wider as the ratio of the buoyancy-driven flow to the injection rate increases, and also as the mobility contrast across the front increases.