bluuebunny/crossref_metadata_2025_split huggingface dataset:
Poly(methyl methacrylate)‐modified vinyl ester thermosets: Morphology, volume shrinkage, and mechanical properties
Authors: Schroeder Walter F. , Borrajo Julio , Aranguren Mirta I. 
Published: September 2007

AbstractThermoset materials obtained from styrene/vinyl ester resins of different molecular weights modified with poly(methyl methacrylate) (PMMA) were prepared and studied. Scanning electron microscopy and transmission electron microscopy micrographs of the fracture surfaces allowed the determination of a two‐phase morphology of the modified networks. Depending on the molecular weight of the vinyl ester oligomer, the initial content of the PMMA additive, and the selected curing temperature, different morphologies were obtained, including the dispersion of thermoplastic‐rich particles in a thermoset‐rich matrix, cocontinuous structures, and the dispersion of thermoset‐rich particles in a thermoplastic‐rich matrix (phase‐inverted structure). Density measurements were performed to determine the effect of the PMMA‐modifier concentration and curing temperature on the volume shrinkage of the final materials. The development of cocontinuous or thermoplastic‐rich matrices was not too effective in controlling the volume shrinkage of the studied vinyl ester systems. The evaluation of the dynamic mechanical behavior, flexural modulus, compressive yield stress, and fracture toughness showed that the addition of PMMA increased the fracture resistance without significantly compromising the thermal or mechanical properties of the vinyl ester networks. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Impacts of impregnation with Timbercare Aqua on the red and yellow color tone of some woods and varnishes
Authors: Keskin Hakan , Atar Musa 
Published: September 2007

AbstractThis study has been performed for determining the effects of impregnation with Timbercare Aqua (Tc) on the red and yellow color tone of some woods and varnishes. For this purpose, the test samples prepared from Oriental beech, European oak, Scotch pine, Oriental spruce, and Uludag fir woods, which met the requirements of ASTM D 358, was impregnated with Tc according to ASTM D 1413 and producer's definition. After impregnation, wood surfaces have been coated by Sayerlack parquet varnish (Sp), Sayerlack interior varnish (Si), and Sayerlack exterior varnish (Se) varnishes in accordance with the ASTM D 3023 standards. According to ASTM D 2244, the red and yellow color tone of samples after varnishing process was determined. As a result, the value of red color tone was the highest in Oriental beech (15.21) and the lowest in Uludag fir (5.38). For the wood material, impregnation material, and varnish interaction, the red color tone value was the highest in Oriental beech + Tc + Sp (18.43) and the lowest in Uludag fir + Tc + Si (3.92). The value of the yellow color tone was the highest in pine (34.45) and the lowest in Oriental beech (26.50). For the wood material, impregnation material, and varnish interaction, the yellow color tone value was the highest in Oriental spruce + Tc + Sp (42.12) and the lowest in Oriental beech + Tc + Si (21.47). This effect may be due to the impacts of impregnation chemical on wood extractives and color pigments in varnish. Accordingly, it should be taken into care for applications where the red and yellow color tone value is important. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Pervaporation performance of polystyrene membrane surface with perfluoroalkyl groups
Authors: Ni HuaGang , Zhang Hao , Wang XiaoBin , Wang XinPing 
Published: September 2007

AbstractResearch on the effect of various chemical groups on the pervaporation performance of membranes was very important for understanding the separation phenomenon. In this article, a polystyrene membrane with CF3 groups on its surface was prepared by casting normal polystyrene (PS‐H) solution with small‐molecular‐weight α,ω‐fluoroalkyl‐terminated polystyrene (S‐PS‐(CF3)2) on a glass plate. The amount of CF3 groups on the surface was adjusted by changing S‐PS‐(CF3)2 content, which was documented by X‐ray photoelectron spectroscopy analysis, surface energy, and contact angle measurements. The effect of S‐PS‐(CF3)2 content on separation performance of S‐PS‐(CF3)2/PS‐H blend membranes for ethanol/water mixture was investigated. The results showed that water concentration in the permeate decreased with increasing S‐PS‐(CF3)2 content; however, the permeation rate did not change until the S‐PS‐(CF3)2 content was increased to 1 wt %. The reason for this was attributed to the fact that a small amount of S‐PS‐(CF3)2 enables a simple surface modification of the membrane keeping its inner structure relatively unchanged. This was confirmed by swelling degree measurements and other experiments. Comparison with our previous work showed that the CF3 groups on the surface lowers the water permselectivity of the polystyrene membranes, whereas the COOH groups enhance the water permselectivity. However, neither hydrophobic CF3 nor hydrophilic groups on the membrane surface appeared to have any influence on flux. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Analysis of polyolefins and olefin copolymers using Crystaf technique: Resolution of Crystaf curves
Authors: Kissin Yury V. , Fruitwala Hitesh A. 
Published: September 2007

AbstractAn experimental technique, crystallization analysis fractionation (Crystaf), is used to analyze compositional uniformity of ethylene/α‐olefin copolymers and isotactic polypropylene. A computerized method for quantifying Crystaf data is developed based on resolution of Crystaf curves into their elemental components, with each component representing a fraction of the polymer with the same degree of chain imperfection. This analysis of Crystaf curves gives three parameters characterizing crystallizable polymer material: (a) the number of compositionally uniform components, (b) properties of each compositionally uniform component (in the case of ethylene/α‐olefin copolymers, the comonomer content), and (c) the quantity of each component. Crystaf analysis of several ethylene/1‐hexene copolymers produced with supported Ti‐based Ziegler‐Natta catalysts shows the existence of two groups of copolymer components. The first group includes components with low comonomer content, in the Crystaf analysis they precipitate at high temperatures as several relatively sharp peaks. The second group includes components with high comonomer contents; they precipitate at much lower temperatures, as a broad overlapping group of peaks. The peak resolution technique was applied to analysis of ethylene/α‐olefin copolymers prepared with a supported catalyst at different temperatures, a copolymer produced with a pseudo‐homogenous Ziegler‐Natta catalyst, and to isotactic polypropylene. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Visualizing the marrow of science
Authors: Moya‐Anegón SCImago Group: Félix de , Vargas‐Quesada Benjamín , Chinchilla‐Rodríguez Zaida , Corera‐Álvarez Elena , Munoz‐Fernández Francisco J. , Herrero‐Solana Victor 
Published: September 2007

AbstractThis study proposes a new methodology that allows for the generation of scientograms of major scientific domains, constructed on the basis of cocitation of Institute of Scientific Information categories, and pruned using PathfinderNetwork, with a layout determined by algorithms of the spring‐embedder type (Kamada–Kawai), then corroborated structurally by factor analysis. We present the complete scientogram of the world for the Year 2002. It integrates the natural sciences, the social sciences, and arts and humanities. Its basic structure and the essential relationships therein are revealed, allowing us to simultaneously analyze the macrostructure, microstructure, and marrow of worldwide scientific output.
Silver(I) Double and Multiple Salts Containing the 1,3‐Butadiynediide Dianion: Coordination Diversity and Assembly with the Supramolecular Synthon Ag4⊂CCCC⊃Ag4
Authors: Zhao Liang , Du Miao , Mak Thomas C. W. 
Published: September 2007

AbstractA series of 13 silver(I) double and multiple salts containing 1,3‐butadiynediide, C42−, were synthesized by dissolving the silver carbide Ag2C4 in a concentrated aqueous solution of one or more of the silver salts AgNO3, AgCF3CO2, AgC2F5CO2, AgF, AgBF4, and AgPF6. The 1,3‐butadiynediide anion invariably adopts a μ4,μ4 coordination mode in these compounds, which indicates that the Ag4⊂CCCC⊃Ag4 moiety can be used as a new type of metalloligand supramolecular synthon for the construction of coordination networks. Fine‐tuning with various ancillary anionic ligands caused the Ag4 aggregate at each ethynide terminus to adopt a butterfly‐shaped, planar, or barblike configuration, within which the silver–ethynide interactions can be classified into three types: σ, π, and mixed (σ,π). The effect of coexisting nitrile ligands and quaternary ammonium salts on supramolecular assembly with the above synthon was also explored. The hydrolysis of PF6− and BF4− led to the formation of the quadruple salt Ag2C4⋅4 AgNO3⋅AgPF2O2⋅Ag3PO4 and a novel (F)2(H2O)18 hydrogen‐bonded tape in the triple salt Ag2C4⋅2 AgF⋅ 10 AgC2F5CO2⋅CH3CN⋅12 H2O, respectively. The largest silver–ethynide cluster aggregate described to date, (C4)3@Ag18, occurs in 3 Ag2C4⋅ 12 AgC2F5CO2⋅5[(BnMe3N)C2F5CO2]⋅ 4 H2O (Bn=benzyl).
Empfehlungen des Arbeitskreises 6.1 “Geotechnik der Deponiebauwerke” der Deutschen Gesellschaft für Geotechnik e., V. (DGGT)
Authors: Witt Karl Josef , Ramke Hans‐Günter 
Published: September 2007

AbstractDer Arbeitskreis Geotechnik der Deponiebauwerke hat in den Empfehlungsgruppen E1 bis E5 bisher 76 Empfehlungen veröffentlicht. Die jährliche Publikation wird fortgesetzt durch eine grundlegend überarbeitete Fassung der zuletzt im Jahre 2001 erschienenen Empfehlung E2‐36 “Oberflächenabdichtungssysteme mit Tondichtungsbahnen”. In die Überarbeitung sind die jüngsten Forschungsergebnisse, Erfahrungen mit der Planung, dem Bau und der messtechnischen Überwachung von Maßnahmen eingeflossen.
Ermittlung der Einbindetiefe von Stützwänden mit dem Verfahren nach Blum unter Nutzung des Teilsicherheitskonzepts
Authors: Winkler Andreas 
Published: September 2007

AbstractDas Verfahren nach Blum hat sich in den letzten Jahrzehnten zur Ermittlung der Einbindetiefe bei Baugrubenwänden etabliert. Mit Einführung des Teilsicherheitskonzepts auf Grundlage der DIN 1054 kann bei getrennter Betrachtung des Widerstandes sowie der ständigen und veränderlichen Einwirkungen das Verfahren nicht mehr in seiner bisherigen Form eingesetzt werden. Durch entsprechende Modifizierungen ist der Einsatz des Verfahrens nach Blum als einfache, per Hand durchführbare Berechnungsmethode weiterhin möglich. Im Fall, dass keine veränderlichen Einwirkungen vorhanden sind, kann weiterhin die Einbindetiefe direkt ermittelt werden (Verfahren I). Andernfalls kann durch Variation der Einbindetiefe gezielt ein vorgebbarer Ausnutzungsgrad des Erdwiderlagers für den Nachweis im Grenzzustand GZ 1B erreicht werden (Verfahren II). Die leicht handhabbaren Berechnungsalgorithmen werden für beide Verfahren jeweils für die eingespannte ungestützte Wand, die einfach gestützte frei aufgelagerte Wand und die einfach gestützte eingespannte Wand vorgestellt.
Berücksichtigung des Frischbetondrucks bei der FE‐Simulation der Schlitzwandherstellung
Authors: Loreck Christoph , Triantafyllidis Theodor 
Published: September 2007

AbstractBaugrundverformungen im Umfeld einer Schlitzwandbaugrube entstehen sowohl aus dem Baugrubenaushub als auch aus der Herstellung der Baugrubenwand selbst. Für die numerische Simulation der Schlitzwandherstellung sind die Berücksichtigung der Herstellungsreihenfolge sowie der im Boden induzierten Spannungszustände aus Suspensions‐ und Frischbetondruck in einem 3D‐Modell erforderlich. Zur Frage der Frischbetondruckentwicklung in Schlitzwandlamellen wurden Zentrifugenmodellversuche und Elementversuche durchgeführt und ein Berechnungsmodell abgeleitet, das die verfügbaren Baustellenmessungen gut wiedergibt und eine differenzierte Berücksichtigung des Frischbetondrucks in FE‐Simulationen ermöglicht.
Assessment of magnetic fields surrounding electronic article surveillance systems in Sweden
Authors: Trulsson Jimmy , Anger Gert , Estenberg Ulrika 
Published: September 2007

AbstractMagnetic fields surrounding 11 EAS systems in Swedish shops and libraries were measured, in real‐life conditions, according to the CENELEC standard. For each system, the arithmetic mean of 45 measurement points was compared to ICNIRP's reference level. Six of eleven measured systems exceeded the reference levels. Bioelectromagnetics 28:664–666, 2007. © 2007 Wiley‐Liss, Inc.
Direct current electrical fields induce apoptosis in oral mucosa cancer cells by NADPH oxidase‐derived reactive oxygen species
Authors: Wartenberg Maria , Wirtz Nina , Grob Alexander , Niedermeier Wilhelm , Hescheler Jürgen , Peters Saskia C. , Sauer Heinrich 
Published: September 2007

AbstractThe presence of more than one dental alloy in the oral cavity often causes pathological galvanic currents and voltage resulting in superficial erosions of the oral mucosa and eventually in the emergence of oral cancer. In the present study the mechanisms of apoptosis of oral mucosa cancer cells in response to electromagnetic fields was investigated. Direct current (DC) electrical fields with field strengths between 2 and 16 V/m, applied for 24 h to UM‐SCC‐14‐C oral mucosa cancer cells, dose‐dependently resulted in decreased cell proliferation as evaluated by Ki‐67 immunohistochemistry and upregulation of the cyclin‐dependent kinase (CDK) inhibitors p21cip1/waf1 and p27kip1, which are associated with cell cycle arrest. Electrical field treatment (4 V/m, 24 h) increased apoptosis as evaluated by immunohistochemical analysis of cleaved caspase‐3 and poly‐(ADP‐ribose)‐polymerase‐1 (PARP‐1). Furthermore, robust reactive oxygen species (ROS) generation, increased expression of NADPH oxidase subunits as well as Hsp70 was observed. Electrical field treatment (4 V/m, 24 h) resulted in increased expression of Cu/Zn superoxide dismutase and decreased intracellular concentration of reduced glutathione (GSH), whereas the expression of catalase remained unchanged. Pre‐treatment with the free radical scavenger N‐acetyl cysteine (NAC) and the superoxide dismutase mimetic EUK‐8 abolished caspase‐3 and PARP‐1 induction, suggesting that apoptosis in oral mucosa cancer cells is initated by ROS generation in response to DC electrical field treatment. Bioelectromagnetics 29:47–54, 2008. © 2007 Wiley‐Liss, Inc.
Optimization of oxygen mass transfer in a multiphase bioreactor with perfluorodecalin as a second liquid phase
Authors: Amaral Priscilla F.F. , Freire Mara G. , Rocha‐Leão Maria Helena M. , Marrucho Isabel M. , Coutinho João A.P. , Coelho Maria Alice Z. 
Published: September 2007

AbstractOxygenation is an important parameter involved in the design and operation of mixing–sparging bioreactors and it can be analyzed by means of the oxygen mass transfer coefficient (kLa). The operational conditions of a stirred, submerged aerated 2‐L bioreactor have been optimized by studying the influence of a second liquid phase with higher oxygen affinity (perfluorodecalin or olive oil) in the kLa. Using kLa measurements, the influence of the following parameters on the oxygen transfer rate was evaluated: the volume of working medium, the type of impellers and their position, the organic phase concentration, the aqueous phase composition, and the concentration of inactive biomass. This study shows that the best experimental conditions were achieved with a perfluorodecalin volume fraction of 0.20, mixing using two Rushton turbines with six vertical blades and in the presence of YPD medium as the aqueous phase, with a kLa value of 64.6 h−1. The addition of 20% of perfluorodecalin in these conditions provided a kLa enhancement of 25% when pure water was the aqueous phase and a 230% enhancement when YPD medium was used in comparison to their respective controls (no perfluorodecalin). Furthermore it is shown that the presence of olive oil as a second liquid phase is not beneficial to the oxygen transfer rate enhancement, leading to a decrease in the kLa values for all the concentrations studied. It was also observed that the magnitude of the enhancement of the kLa values by perfluorodecalin depends on the biomass concentration present. Biotechnol. Bioeng. 2008;99: 588–598. © 2007 Wiley Periodicals, Inc.
Engineering poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) copolymer composition in E. coli
Authors: Wong Matthew S. , Causey Thomas B. , Mantzaris Nikos , Bennett George N. , San Ka‐Yiu 
Published: September 2007

AbstractA strain of Escherichia coli was metabolically engineered to produce poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) of specified composition between 5% and 18% HV. A gene encoding propionyl‐CoA synthetase (prpE from S. enterica) was placed under the control of the IPTG‐inducible tac promoter (PtaclacUV5) while the polyhydroxyalkanoate synthesis operon (phaBCA) from R. eutropha was expressed constitutively. A strain of E. coli harboring both plasmids was grown in defined medium and PHBV was produced with specified hydroxyvalerate (HV) molar content between 5% and 18%. The molecular weight of the copolymer was ∼700,000 across various HV contents, and average polydispersity was ∼ 1.3. The majority of the PHBV production occurred during the late exponential/stationary phase. The HV content of the copolymer generally peaked early in the incubation before falling to its final value. We found that the time profiles of PrpE activity, propionyl‐CoA, and acetyl‐CoA were well correlated to the HV content time profile. Despite an abundance of propionyl‐CoA, incorporation of HV into the copolymer was inefficient. Therefore, both the PHA operon and conditions affecting the availability of propionyl‐CoA must be chosen carefully to achieve the desired HV content. The ability to engineer copolymer composition control into an E. coli strain would be useful in cases where the feedstock composition is not adjustable. Biotechnol. Bioeng. 2008;99: 919–928. © 2007 Wiley Periodicals, Inc.
Protein engineering of nitrilase for chemoenzymatic production of glycolic acid
Authors: Wu Shijun , Fogiel Arthur J. , Petrillo Kelly L. , Jackson Raymond E. , Parker Kimberley N. , DiCosimo Robert , Ben‐Bassat Arie , O'Keefe Daniel P. , Payne Mark S. 
Published: September 2007

AbstractA key step in a chemoenzymatic process for the production of high‐purity glycolic acid (GLA) is the enzymatic conversion of glycolonitrile (GLN) to ammonium glycolate using a nitrilase derived from Acidovorax facilis 72W. Protein engineering and over‐expression of this nitrilase, combined with optimized fermentation of an E. coli transformant were used to increase the enzyme‐specific activity up to 15‐fold and the biocatalyst‐specific activity up to 125‐fold. These improvements enabled achievement of the desired volumetric productivity and biocatalyst productivity for the conversion of GLN to ammonium glycolate. Biotechnol. Bioeng. 2008;99: 717–720. © 2007 Wiley Periodicals, Inc.
Combining classification and regression approaches for the quantification of highly overlapping capillary electrophoresis peaks by using evolutionary sigmoidal and product unit neural networks
Authors: Hervás Cesar , Gutierrez Pedro Antonio , Silva Manuel , Serrano Juan Manuel 
Published: September 2007

AbstractThis is a study of the potential of neural networks built by using different transfer functions (sigmoidal, product and sigmoidal–product units) designed by an evolutionary algorithm to quantify highly overlapping electrophoretic peaks. To test this approach, two aminoglycoside antibiotics, amikacin and paramomycin, were quantified from samples containing either only one component or mixtures of them though capillary zone electrophoresis (CZE) with laser‐induced fluorescence (LIF) detection. The three models assayed used as input data the four‐parameter Weibull curve associated with the profile of the electrophoretic peak and in some cases the class label for each sample estimated by cluster analysis. The combination of classification and regression approaches allowed the establishment of straightforward network topologies enabling the analytes to be quantified with great accuracy and precision. The best models for mixture samples were provided by product unit neural networks (PUNNs), 4:4:1 (14 weights) for both analytes, after discrimination by cluster analysis, allowing the analytes to be quantified with great accuracy: 8.2% for amikacin and 5.6% for paromomycin within the standard error of prediction for the generalization test, SEPG. For comparison, partial least square regression was also used for the resolution of these mixtures; it provided a minor accuracy: SEPG 11.8 and 15.7% for amikacin and paramomycin, respectively. The reduced dimensions of the neural networks models selected enabled the derivation of simple quantification equations to transform the input variables into the output variable. These equations can be more easily interpreted from a chemical point of view than those provided by other ANN models. Copyright © 2007 John Wiley & Sons, Ltd.
A randomization test for PLS component selection
Authors: Wiklund Susanne , Nilsson David , Eriksson Lennart , Sjöström Michael , Wold Svante , Faber Klaas 
Published: September 2007

AbstractDuring the last two decades, a number of methods have been developed and evaluated for selecting the optimal number of components in a PLS model. In this paper, a new method is introduced that is based on a randomization test. The advantage of using a randomization test is that in contrast to cross validation (CV), it requires no exclusion of data, thus avoiding problems related to data exclusion, for example in designed experiments. The method is tested using simulated data sets for which the true dimensionality is clearly defined and also compared to regularly used methods for 10 real data sets. The randomization test works as a good statistical selection tool in combination with other selection rules. It also works as an indicator when the data require a pre‐treatment. Copyright © 2007 John Wiley & Sons, Ltd.
Evidence for Significant Through‐Space and Through‐Bond Electronic Coupling in the 1,4‐Diphenylcyclohexane‐1,4‐diyl Radical Cation Gained by Absorption Spectroscopy and DFT Calculations
Authors: Ikeda Hiroshi , Hoshi Yosuke , Namai Hayato , Tanaka Futoshi , Goodman Joshua L. , Mizuno Kazuhiko 
Published: September 2007

AbstractPhotoinduced single‐electron‐transfer promoted oxidation of 2,5‐diphenyl‐1,5‐hexadiene by using N‐methylquinolinium tetrafluoroborate/biphenyl co‐sensitization takes place with the formation of an intense electronic absorption band at 476 nm, which is attributed to the 1,4‐diphenylcyclohexane‐1,4‐diyl radical cation. The absorption maximum (λob) of this transient occurs at a longer wavelength than is expected for either the cumyl radical or the cumyl cation components. Substitution at the para positions of the phenyl groups in this radical cation by CH3O, CH3, F, Cl, and Br leads to an increasingly larger redshift of λob. A comparison of the ρ value, which was obtained from a Hammett plot of the electronic transition energies of the radical cations versus σ+, with that for the cumyl cation shows that the substituent effects on the transition energies for the 1,4‐diarylcyclohexane‐1,4‐diyl radical cations are approximately one half of the substituent effects on the transition energies of the cumyl cation. The observed substituent‐induced redshifts of λob and the reduced sensitivity of λob to substituent changes are in accordance with the proposal that significant through‐space and ‐bond electronic interactions exist between the cumyl radical and the cumyl cation moieties of the 1,4‐diphenylcyclohexane‐1,4‐diyl radical cation. This proposal gains strong support from the results of density functional theory (DFT) calculations. Moreover, the results of time‐dependent DFT calculations indicate that the absorption band at 476 nm for the 1,4‐diphenylcyclohexane‐1,4‐diyl radical cation corresponds to a SOMO‐3→SOMO transition.