bluuebunny/crossref_metadata_2025_split huggingface dataset:
Degradation and in situ reaction of polyolefin elastomers in the melt state induced by ultrasonic irradiation
Authors: Chen Jinyao , Li Huilin , Lai Shih‐Yaw , Jow Jinder 
Published: June 2007

AbstractThe degradation and in situ reaction with polystyrene (PS) of polyolefin elastomers in the melt state induced through high intensity ultrasonic wave were investigated. The effects of initial molecular weight of polyolefin elastomers, irradiation time, ultrasonic intensity, as well as reaction temperature on the ultrasonic degradation of polyolefin elastomers melt were studied using a “static” ultrasonic vibration system. The results show that the degradation occurs mostly at the tip of the ultrasonic probe, and little or no degradation was observed at the distance of 5 mm or greater from the tip of the probe. The intrinsic viscosity [η] of polyolefin elastomers near the tip of ultrasound probe significantly decreases with irradiation time in the first 100 s and tends toward a limiting value for all samples. The degradation rates increased with an increase in ultrasonic intensity and decrease in reaction temperature. The ultrasonic degradation kinetics of polyolefin elastomers in melt state follows the equation: [η]t = [η]∞ + Ae−kt. The fitting results by this equation accord well with the experimental data. The feasible ultrasonic degradation mechanism is proposed based on the viscoelastic characteristic of polymer melt. FTIR analysis confirms that the copolymer forms under ultrasonic irradiation for PS/POE mixtures and in situ reaction of polymer in melt state can be induced by ultrasonic irradiation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Structure and properties of collagen‐konjac glucomannan‐sodium alginate blend films
Authors: Wang Bi , Jia Dong‐Ying , Ruan Shang‐Quan , Qin Song 
Published: June 2007

AbstractA new kind of blend film was made by mixing the solutions of collagen, konjac glucommnnan (KGM), and sodium alginate. The structure of the blend film was characterized by FTIR, XRD, atomic absorption spectrophotometer, and SEM, respectively. The effects of weight ratio between the polymers on light transmittance, tensile strength, elongation at break, water permeability, and water absorption of the film were studied. The results showed that there were strong interactions and good compatibility between collagen, KGM, and sodium alginate in the film. The film possesses good mechanical properties. Therefore, it can be applied in biomedicine as a new type of biomaterial. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
PVDF‐PZT‐5H composites prepared by hot press and tape casting techniques
Authors: Seema A. , Dayas K. R. , Varghese Justin M. 
Published: June 2007

AbstractPiezoelectric polymer–ceramic composites are promising materials for transducer applications, and they are widely used in underwater hydrophones, biomedical imaging with ultrasound, and nondestructive testing applications. The critical factor in the 0–3 composite is to ensure homogeneous distribution of the filler in the matrix. To ensure this objective, PVDF‐PZT composite was prepared by two different routes: hot press and tape casting techniques. Loss on ignition and scanning electron microscopy studies were conducted to find out the uniformity of the composites prepared. It is found that hot press technique gives better uniformity compared to tape casting technique. PZT concentration was varied from 20 to 60 vol %. Physical and dielectric properties were studied. FT‐IR, DSC, and XRD characterization studies of PVDF were also recorded. Density of the composites was 2.74 to 5.13 g/cm3 as PZT concentration increased from 20 to 60 volume fractions. The dielectric constant of composites at 1 MHz varied from 16.74 to 98.48 as PZT concentration increased from 20 to 60 volume fractions. Hot press technique that combines solution and melt processing was found to be the better method for the preparation of 0–3 composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Flame retardancy and thermomechanical properties of the poly‐(glycidyloxypropyl) phenyl silsesquioxane/layered titanate nanocomposites
Authors: Harada Miyuki , Minamigawa Shuichi , Tachibana Kumiko , Ochi Mitsukazu 
Published: June 2007

AbstractPoly‐(glycidyloxypropyl) phenyl silsesquioxane (PGPSQ) was combined with an organo‐layered titanate filler. The phase structure of the obtained composite was evaluated by XRD and TEM observations. Moreover, a burning test was carried out according to the UL‐94 test method. The extinguishing time of the nanocomposites was classified V‐0 even for the 1 wt % layered titanate content. Based on the results, it was clarified that the frame retardancy of the PGPSQ/organo‐layered titanate system was superior to the poly‐(glycidyloxypropyl) silsesquioxane (PGSQ)/organo‐layered titanate system, which was reported in a previous paper. In addition, the layered titanate as a filler also improved the ductility of the PGPSQ. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Styrene maleic anhydride copolymer mediated dispersion of single wall carbon nanotubes in polyamide 12: Crystallization behavior and morphology
Authors: Bhattacharyya Arup R. , Bose Suryasarathi , Kulkarni Ajit R. , Pötschke Petra , Häuβler Liane , Fischer Dieter , Jehnichen Dieter 
Published: June 2007

AbstractMelt mixed composites based on polyamide 12 (PA12) were prepared using single wall carbon nanotubes (SWNT), which were encapsulated by styrene maleic anhydride copolymer (SMA). The aim was to achieve a reactive coupling between the maleic anhydride functionality of SMA at the surface of the SWNT and the amine end groups of PA12 during the melt mixing. The reaction could be proven by infrared spectroscopy. The modified nanocomposites exhibited a better SWNT dispersion. An enhanced interfacial adhesion between PA12 and SWNT was detected from SEM investigations of tensile fractured surfaces of the SMA encapsulated PA12/SWNT composites. Electrical conductivity measurements revealed the formation of “network‐like” structure formation at 6 wt % SWNT content in PA12/SWNT composites, however, PA12/SWNT + SMA composites showed insulating behavior due to encapsulating SMA layer on SWNT surface. Studies on crystallization behavior indicated the nucleating action of unmodified and SMA encapsulated SWNT in the respective composites as found in the increase of crystallization temperature and the change in the crystalline morphology of PA12 as observed from DSC, WAXD, and SAXS. However, the degree of crystallinity of PA12 increased only marginally on incorporation of either unmodified or SMA encapsulated SWNT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
A comparative study of fracture behavior between carbon black/poly(ethylene terephthalate) and multiwalled carbon nanotube/poly(ethylene terephthalate) composite films
Authors: Kobayashi Haruki , Shioya Masatoshi , Tanaka Tomoya , Irisawa Toshihira , Sakurai Shinichi , Yamamoto Katsuhiro 
Published: June 2007

AbstractFracture behavior of amorphous poly(ethylene terephthalate) (PET) films added multiwalled carbon nanotube (MWCNT) has been compared with that of the PET films added with carbon black (CB) to elucidate the effects of the large aspect ratio of MWCNT. Fracture toughness has been evaluated using the essential work of fracture tests. Evolution of the crazes has been analyzed by conducting time‐resolved small‐angle X‐ray scattering measurements during tensile deformation of the films at room temperature using synchrotron radiation. CB and MWCNT increased the fracture toughness of the PET film by increasing the plastic work of fracture. This resulted from the effects of the fillers to prevent the localization of deformation upon the crazes formed at earlier stages of tensile deformation and to retard the growth of the fibrils in the crazes to a critical length. The CB particles provided a number of sites where the crazes were preferably formed due to stress concentration. In the case of MWCNT, on the other hand, the widening of the crazes formed at earlier stages was suppressed due to the bridging effect arising from the large aspect ratio of MWCNT. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Investigations of the initial state polymerization of propylene with Ziegler–Natta catalysts in slurry
Authors: Heuvelsland Albert , Wichmann Silke , Schellenberg Jürgen 
Published: June 2007

AbstractThe initial state polymerization of propylene with Ziegler–Natta catalysts has been investigated and discussed at very low polymerization yields under adiabatic industrial prepolymerization conditions in diluted slurry regarding the effects of significant process parameters like monomer pressure, aluminum alkyl, and donor kind and concentration including the morphology of the catalyst/polymer particles formed. A sharp temperature increase in the first minutes of the initial state polymerization is followed by a temperature maximum and a slow decrease. With cocatalyst triethyl aluminum (TEAL), high prepolymerization yields were already achieved at a molar ratio TEAL/Ti of 3.0, remaining about constant until ratios of at least 300. The external donor dicyclopentyl dimethoxy silane leads to higher polymerization yields than the donor cyclohexyl dimethoxymethyl silane in the initial state polymerization too; however, both show a remarkable decreasing effect on polymerization yield above a specific molar ratio donor/Ti obviously correlated with the bulkiness of the alkyl groups. The particle size of the catalyst and the catalyst/prepolymer particles is increasing with polymerization yield until about 22 g PP/g Cat with particles almost perfectly spherical. The particle size distribution is rather broad at lower prepolymerization stages but unifying with lower polymerization rates at higher polymerization times. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Synthesis and characterization of poly(L‐lactic acid)‐b‐poly(ethylene terephthalate‐co‐sebacate)‐b‐poly(L‐lactic acid) copolyesters
Authors: Hui Zhao Yun , Zhao Yun , Yuan Xu‐Bo , Sheng Jing 
Published: June 2007

AbstractRandom copolyester namely, poly(ethylene terephthalate‐co‐sebacate) (PETS), with relatively lower molecular weight was first synthesized, and then it was used as a macromonomer to initiate ring‐opening polymerization of l‐lactide. 1H NMR quantified composition and structure of triblock copolyesters [poly(l‐lactic acid)‐b‐poly(ethylene terephthalate‐co‐sebacate)‐b‐poly(l‐lactic acid)] (PLLA‐PETS‐PLLA). Molecular weights of copolyesters were also estimated from NMR spectra, and confirmed by GPC. Copolyesters exhibited different solubilities according to the actual content of PLLA units in the main chain. Copolymerization effected melting behaviors significantly because of the incorporation of PETS and PLLA blocks. Crystalline morphology showed a special pattern for specimen with certain composition. It was obvious that copolyesters with more content of aromatic units of PET exhibited increased values in both of stress and modulus in tensile test. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Removal of Cd(II), Hg(II), and Pb(II) ions from aqueous solution using p(HEMA/chitosan) membranes
Authors: Bayramoglu Gulay , Yakup Arica M. , Bektas Sema 
Published: June 2007

AbstractAn interpenetration network (IPN) was synthesized from 2‐hydroxyethyl methacrylate (HEMA) and chitosan, p(HEMA/chitosan) via UV‐initiated photo‐polymerization. The selectivity to different heavy metal ions viz Cd(II), Pb(II), and Hg(II) to the IPN membrane has been investigated from aqueous solution using bare pHEMA membrane as a control system. Removal efficiency of metal ions from aqueous solution using the IPN membranes increased with increasing chitosan content and initial metal ions concentrations, and the equilibrium time was reached within 60 min. Adsorption of all the tested heavy metal ions on the IPN membranes was found to be pH dependent and maximum adsorption was obtained at pH 5.0. The maximum adsorption capacities of the IPN membrane for Cd(II), Pb(II), and Hg(II) were 0.063, 0.179, and 0.197 mmol/g membrane, respectively. The adsorption of the Cd(II), Hg(II), and Pb(II) metal ions on the bare pHEMA membrane was not significant. When the heavy metal ions were in competition, the amounts of adsorbed metal ions were found to be 0.035 mmol/g for Cd(II), 0.074 mmol/g for Hg(II), and 0.153 mmol/g for Pb(II), the IPN membrane is significantly selective for Pb(II) ions. The stability constants of IPN membrane–metal ions complexes were calculated by the method of Ruzic. The results obtained from the kinetics and isotherm studies showed that the experimental data for the removal of heavy metal ions were well described with the second‐order kinetic equations and the Langmuir isotherm model. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Simultaneous Inference for Ratios of Linear Combinations of General Linear Model Parameters
Authors: Hare David R. , Spurrier John D. 
Published: June 2007

AbstractConsider a general linear model with p ‐dimensional parameter vector β and i.i.d. normal errors. Let K1, …, Kk , and L be linearly independent vectors of constants such that LT β ≠ 0. We describe exact simultaneous tests for hypotheses that K$ _i ^T $β/LT β equal specified constants using one‐sided and two‐sided alternatives, and describe exact simultaneous confidence intervals for these ratios. In the case where the confidence set is a single bounded contiguous set, we describe what we claim are the best possible conservative simultaneous confidence intervals for these ratios – best in that they form the minimum k ‐dimensional hypercube enclosing the exact simultaneous confidence set. We show that in the case of k = 2, this “box” is defined by the minimum and maximum values for the two ratios in the simultaneous confidence set and that these values are obtained via one of two sources: either from the solutions to each of four systems of equations or at points along the boundary of the simultaneous confidence set where the correlation between two t variables is zero. We then verify that these intervals are narrower than those previously presented in the literature. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Residual Analysis for Linear Mixed Models
Authors: Santos Nobre Juvêncio , da Motta Singer Julio 
Published: June 2007

AbstractResiduals are frequently used to evaluate the validity of the assumptions of statistical models and may also be employed as tools for model selection. For standard (normal) linear models, for example, residuals are used to verify homoscedasticity, linearity of effects, presence of outliers, normality and independence of the errors. Similar uses may be envisaged for three types of residuals that emerge from the fitting of linear mixed models. We review some of the residual analysis techniques that have been used in this context and propose a standardization of the conditional residual useful to identify outlying observations and clusters. We illustrate the procedures with a practical example. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Random Time Interval Approach for Analysing the Impact of a Possible Intermediate Event on a Terminal Event
Authors: Beyersmann Jan 
Published: June 2007

AbstractWe consider the impact of a possible intermediate event on a terminal event in an illness‐death model with states ‘initial’, ‘intermediate’ and ‘terminal’. One aim is to unambiguously describe the occurrence of the intermediate event in terms of the observable data, the problem being that the intermediate event may not occur. We propose to consider a random time interval, whose length is the time spent in the intermediate state. We derive an estimator of the joint distribution of the left and right limit of the random time interval from the Aalen‐Johansen estimator of the matrix of transition probabilities and study its asymptotic properties. We apply our approach to hospital infection data. Estimating the distribution of the random time interval will usually be only a first step of an analysis. We illustrate this by analysing change in length of hospital stay following an infection and derive the large sample properties of the respective estimator. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
REML Estimation of Variance Parameters in Nonlinear Mixed Effects Models Using the SAEM Algorithm
Authors: Meza Cristian , Jaffrézic Florence , Foulley Jean‐Louis 
Published: June 2007

AbstractNonlinear mixed effects models are now widely used in biometrical studies, especially in pharmacokinetic research or for the analysis of growth traits for agricultural and laboratory species. Most of these studies, however, are often based on ML estimation procedures, which are known to be biased downwards. A few REML extensions have been proposed, but only for approximated methods. The aim of this paper is to present a REML implementation for nonlinear mixed effects models within an exact estimation scheme, based on an integration of the fixed effects and a stochastic estimation procedure. This method was implemented via a stochastic EM, namely the SAEM algorithm. The simulation study showed that the proposed REML estimation procedure considerably reduced the bias observed with the ML estimation, as well as the residual mean squared error of the variance parameter estimations, especially in the unbalanced cases. ML and REML based estimators of fixed effects were also compared via simulation. Although the two kinds of estimates were very close in terms of bias and mean square error, predictions of individual profiles were clearly improved when using REML vs. ML. An application of this estimation procedure is presented for the modelling of growth in lines of chicken. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional fibrous PLGA/HAp composite scaffold for BMP‐2 delivery
Authors: Nie Hemin , Soh Beng Wee , Fu Yin‐Chih , Wang Chi‐Hwa 
Published: June 2007

AbstractA protein loaded three‐dimensional scaffold can be used for protein delivery and bone tissue regeneration. The main objective of this project was to develop recombinant human bone morphogenetic protein‐2 (rhBMP‐2) loaded poly(D,L‐lactide‐co‐glycolide)/hydroxylapatite (PLGA/HAp) composite fibrous scaffolds through a promising fabrication technique, electrospinning. In vitro release of BMP‐2 from these scaffolds, and the attachment ability and viability of marrow derived messenchymal stem cells (MSCs) in the presence of the scaffolds were investigated. The PLGA/HAp composite scaffolds developed in this study exhibit good morphology and it was observed that HAp nanoparticles were homogeneously dispersed inside PLGA matrix within the scaffold. The composite scaffolds allowed sustained (2–8 weeks) release of BMP‐2 whose release rate was accelerated with increasing HAp content. It was also shown that BMP‐2 protein successfully maintained its integrity and natural conformations after undergoing the process of electrospinning. Cell culture experiments showed that the encapsulation of HAp could enhance cell attachment to scaffolds and lower cytotoxicity. Biotechnol. Bioeng. 2008;99: 223–234. © 2007 Wiley Periodicals, Inc.
Structures of ionic liquids dictate the conversion and selectivity of enzymatic glycerolysis: Theoretical characterization by COSMO‐RS
Authors: Chen Biqiang , Guo Zheng , Tan Tianwei , Xu Xuebing 
Published: June 2007

AbstractLipase‐catalyzed glycerolysis of triolein has been examined using a group of tetraammonium‐based ionic liquids (ILs) as media, specifically with functional groups in cation part. The results demonstrated that the reaction evolution and profile specificity of respective IL system could be quantitatively associated with the structural characteristics of the IL by means of quantum chemical and COSMO‐RS calculation. Misfit interaction, Van der Waals interaction and chemical potential, etc. derived from COSMO‐RS calculation are shown to be effective measures to delineate multiple interactions of ILs and then can be used to understand the effects of ILs on reactions. The hydrophobic substituents in the cation are found to contribute to the increase of triolein solubility and enhancement of initial reaction rate; while strong polar anion and polyethoxyl and free hydroxyl groups in the cation part dictate improved product selectivity through reducing activity coefficients of monoglycerides. Integration of these structures into the same molecule constitutes a promising group of ILs that could produce over 90% monoglyceride with almost 100% triglyceride conversion, as well as bulky productivity, of particular potential for industrial applications. Overall, this work has presented a first attempt to characterize the IL structure‐dependency of reaction specificity by associating structural variations of ILs with thermodynamic property changes of resided compounds and subsequent effects on reaction specificity. This might be of general value to help to understand the multiple solvation interaction among IL reaction systems at molecular level and promote the application of IL‐mediated reactions to practical interests. Biotechnol. Bioeng. 2008;99: 18–29. © 2007 Wiley Periodicals, Inc.
Use of a whole‐cell biosensor to assess the bioavailability enhancement of aromatic hydrocarbon compounds by nonionic surfactants
Authors: Keane Angela , Lau Peter C.K. , Ghoshal Subhasis 
Published: June 2007

AbstractThe whole‐cell bioluminescent biosensor Pseudomonas putida F1G4 (PpF1G4), which contains a chromosomally‐based sep‐lux transcriptional fusion, was used as a tool for direct measurement of the bioavailability of hydrophobic organic compounds (HOCs) partitioned into surfactant micelles. The increased bioluminescent response of PpF1G4 in micellar solutions (up to 10 times the critical micellar concentration) of Triton X‐100 and Brij 35 indicated higher intracellular concentrations of the test compounds, toluene, naphthalene, and phenanthrene, compared to control systems with no surfactants present. In contrast, Brij 30 caused a decrease in the bioluminescent response to the test compounds in single‐solute systems, without adversely affecting cell growth. The decrease in bioluminescent response in the presence of Brij 30 did not occur in the presence of multiple HOCs extracted into the surfactant solutions from crude oil and creosote. The effect of the micellar solutions on the toluene biodegradation rate was consistent with the bioluminescent response in single‐solute systems. None of the surfactants were toxic to PpF1G4 at the doses employed in this study, and PpF1G4 did not produce a bioluminescent response to the surfactants nor utilize them as growth substrates. TEM images suggest that the surfactants did not rupture the cell membranes. The results demonstrate that for Pseudomonas putida F1, nonionic surfactants such as Triton X‐100 and Brij 35, at doses between 2 and 10 CMC, may increase the bioavailability and direct uptake of micellar phase HOCs that are common pollutants at contaminated sites. Biotechnol. Bioeng. 2008;99: 86–98. © 2007 Wiley Periodicals, Inc.