bluuebunny/crossref_metadata_2025 huggingface dataset:
A multi‐scale spectral stochastic method for homogenization of multi‐phase periodic composites with random material properties
Authors: Tootkaboni M. , Graham‐Brady L.
Published: February 2010

In this work a spectral stochastic computational scheme is proposed that links the global properties of multi‐phase periodic composites to the geometry and random material properties of their microstructural components. To propagate the uncertainties associated with the material properties to the microstructural response the scheme benefits from a combination of homogenization theory built into a finite element framework and the spectral representation of uncertainty based on Hermite Chaos where a probabilistic characterization of the solutions to a set of local problems defined on the period cell is first sought. A full stochastic description of the global (effective) properties is then obtained by averaging the solutions to the forgoing set of local problems over the unit cell. A representative subset of results is compared with the results obtained using Monte Carlo simulation to demonstrate the accuracy of the proposed procedure. Copyright © 2010 John Wiley & Sons, Ltd.
Eigensolution of augmented graph products using shifted inverse iteration method
Authors: Kaveh A. , Fazli H.
Published: February 2010

Two important matrices associated with graphs are adjacency and Laplacian matrices. In this paper efficient methods are presented for eigensolution of graph products augmented by other graphs. For augmentations that do not destroy the symmetry of the graph products, a method is proposed for decomposition of matrices resulting in considerable simplification of their eigensolution. For graphs composed of two non‐overlapping graph products joined through a small number of link members, a method based on shifted inverse iteration is proposed which utilizes all eigenvalues and eigenvectors of each individual graph products. Owing to the availability of fast methods for eigensolution of graph products, this method simplifies the eigensolution of a variety of graph models and proves to be very efficient in determining the few smallest eigenpairs of these models with high levels of accuracy. Copyright © 2010 John Wiley & Sons, Ltd.
Synthesis of bipolar charge transporting block copolymers and characterization for organic light‐emitting diode
Authors: Tsuchiya Kousuke , Kasuga Hidemasa , Kawakami Akira , Taka Hideo , Kita Hiroshi , Ogino Kenji
Published: February 2010

A series of hole and electron transporting random and block copolymers consisting of triphenylamine moiety as a hole transporting unit and oxadiazole moiety as an electron transporting unit have been prepared via a nitroxide mediated radical polymerization. Oxadiazole monomers with t‐butyl or trifluoromethyl groups, 2 and 7, respectively, were used for copolymerization. Photoluminescent measurements of polymers revealed that the formation of the exciplex between triphenylamine and oxadiazole units tends to occur in the order of random copolymers, block copolymers, and polymer blends, implying phase‐separated morphologies in block or blend systems. The polymers were applied for OLED devices, and we found that the morphology in the polymer layer critically affected device performance. The block copolymer comprising hole and electron transporting units with the composition of 14/86 showed the highest external quantum efficiency over 10%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1461–1468, 2010
Electrochromic material containing unsymmetrical substituted N,N,N′,N′‐tetraaryl‐1,4‐phenylenediamine: Synthesis and their optical, electrochemical, and electrochromic properties
Authors: Wu Han‐Yu , Wang Kun‐Li , Liaw Der‐Jang , Lee Kueir‐Rarn , Lai Juin‐Yih
Published: February 2010

A novel dibromo compound containing unsymmetrical substituted bi‐triarylamine was synthesized. A conjugated polymer was prepared via the Suzuki coupling from the newly prepared dibromo compound and 9,9‐dioctylfluorene‐2,7‐bis(trimethyleneboronate). The glass transition temperature (Tg) of the conjugated polymer was 140 °C, 10% weight‐loss temperatures (Td10) in nitrogen was 458 °C, and char yield at 800 °C in nitrogen higher than 64%. Cyclic voltammogram of the polymer film cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited two reversible oxidation redox couples at 0.70 and 1.10 V versus Ag/Ag+ in acetonitrile solution. The polymer films revealed excellent stability of electrochromic characteristics, with a color change from yellow green of the neutral form to the dark green and blue of oxidized forms at applied potentials ranging from 0 to 1.3 V. The color switching time and bleaching time were 4.25 and 7.22 s for 860 nm and 5.51 s and 6.48 s for 560 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1469–1476, 2010
Synthesis of MWCNTs‐core/thiophene polymer‐sheath composite nanocables by a cationic surfactant‐assisted chemical oxidative polymerization and their structural properties
Authors: Reddy Kakarla Raghava , Jeong Han Mo , Lee Youngil , Raghu Anjanapura Venkataramanaiah
Published: February 2010

Multi‐walled carbon nanotubes (MWCNTs)‐core/thiophene polymer‐sheath composite nanocables were synthesized by chemical oxidative polymerization of 3,4‐ethylenedioxythiophene (EDOT) with oxidant (FeCl3) in the presence of cationic surfactant, deceyltrimethyl ammonium bromide (DTAB). In the polymerization process, DTAB surfactant molecules were adsorbed on the surface of MWCNTs and forms MWCNTs‐DTAB soft template. Upon the addition of EDOT and oxidant, the polymerization take place on the surface of MWCNTs and PEDOT is gradually deposited on the surface of MWCNTs. The resulting MWCNTs‐PEDOT nanocomposites have the nanocable structure. Nanocomposites were characterized by HRTEM, FE‐SEM, XRD, XPS, TGA, FTIR and PL, respectively. The π‐π interactions between PEDOT and MWCNTs enhancing the thermal and electrical properties of the nanocomposites with loading of MWCNTs. The temperature dependence conductivity measurements show that the conductivity of the nanocomposite decrease with a decrease of temperature, and conductivity‐temperature relationship is well fit by the quasi‐one dimensional variable range hopping mode. The mechanism for the formation of composite nanocables was explained on the basis of self‐ assembly of micelles. The reported self‐assembly strategy for the synthesis of PEDOT‐coated MWCNTs in micellar medium is a rapid, versatile, potentially scalable, stable, and making it useful for further exploitation in a varies types of applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1477–1484, 2010
A new strategy for the synthesis of methacrylate end‐functionalized macromonomers by ATRP
Authors: Piogé Sandie , Fontaine Laurent , Soutif Jean‐Claude , Nicol Erwan , Pascual Sagrario
Published: February 2010

The influence of the polymerization temperature, the [CuBr]0/[PMDETA]0 ratio, and the monomer conversion on the chain‐end functionality of poly(ethyl acrylate)s (PEAs) was studied during the atom transfer radical polymerization (ATRP) of ethyl acrylate (EA) using CuBr/N,N,N′,N′,N″‐pentamethyldiethylenetriamine (PMDETA) as a catalyst system and ethyl‐2‐bromo‐2‐methylpropionate (EBiB) as an initiator. The presence of bromine chain‐end of PEA was checked by MALDI‐TOF spectrometry and by chain‐extension reaction. It was shown that ATRP of EA performed with [EA]0/[EBiB]0/[CuBr]0/[PMDETA]0 ratios of 25/1/0.5/0.5 in toluene at 50 °C allows to obtain a quantitative functionality of halide end‐groups of PEA up to 66% monomer conversion. Well‐defined poly(ethylene oxide)‐b‐poly(ethyl acrylate) PEO‐b‐PEA bearing bromide chain‐ends were obtained by the ATRP of EA using PEO‐Br as a macroinitiator under previous experimental conditions. A more detailed study of PEO‐b‐PEA block copolymers synthesis was previously published (Piogé et al., Macromolecules 2009, 42, 4262–4272). These end‐groups were transformed into methacrylate end‐groups by a two‐step pathway. An original approach to generate hydroxyl end‐groups was based on the nucleophilic substitution of the halogen end‐groups using different mercaptoalcohols. Using 6‐mercaptohexan‐1‐ol, a quantitative functionalization was observed. In a second step, hydroxyl groups were esterified quantitatively with methacryloyl chloride, and the resulting methacrylate end‐functionalized PEO‐b‐PEA macromonomers have well‐defined molecular weights and low polydispersities. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1526–1537, 2010
The nature of Cu(II) species in ATRP: New insights via EPR
Authors: Caretti Ignacio , Dervaux Bart , Du Prez Filip E. , Van Doorslaer Sabine
Published: February 2010

Identification of the paramagnetic species present in the Cu(I)Br‐catalyzed atom transfer radical polymerization (ATRP) of a model monomer (isobornyl acrylate) has been carried out by electron paramagnetic resonance (EPR) in the continuous wave mode at 90 K. Up to five different species—four copper‐based species and one organic radical—were detected with this technique. The EPR parameters of the copper‐based species are found to differ strongly, and originate from diverse isolated Cu(II) complexes, as well as dipolarly interacting and even exchange‐coupled Cu(II) species. The work highlights the complexity of the copper‐based EPR signal observed in copper‐mediated ATRP reactions. Analysis of the time evolution of the individual EPR contributions reveals the disadvantages of quantitative kinetics studies based on the summed EPR intensity of all copper‐based species, as is commonly used in literature for this type of reactions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1493–1501, 2010
A novel mesogen‐jacketed liquid crystalline electroluminescent polymer with both thiophene and oxadiazole in conjugated side chain
Authors: Yang Qian , Xu Yiding , Jin Hao , Shen Zhihao , Chen Xiaofang , Zou Dechun , Fan Xinghe , Zhou Qifeng
Published: February 2010

Mesogen‐jacketed liquid crystalline polymers (MJLCPs) with both electron‐transport oxadiazole and hole‐transport thiophene in the side chain were reported for their promising electroluminescent property. Monomers of 2,5‐bis{5‐[(4‐alkoxyphenyl)‐1,3,4‐oxadiazole]thiophen‐2‐yl}styrene (M‐Cm, m is the number of the carbons in the alkoxy groups, m = 8,10) were synthesized and confirmed by 1H‐NMR, mass spectrometry, and elemental analysis. The corresponding polymers were successfully obtained and characterized by thermal analysis, optical spectroscopy, cyclic voltammetry, electroluminescent analysis, polarized light microscopy (PLM), and wide‐angle X‐ray diffraction (WAXD). The polymers exhibited high decomposition temperatures reaching 382 °C and high Tg's reaching 184 °C. The absorption spectra indicated that both the monomers and polymers had little aggregation in film than that in solution, and the absorption spectra of the polymers showed an obvious blue‐shift compared with those of the monomers. Both the monomers and the polymers had blue‐green emission, and the photoluminescence spectra of the polymers in film suggested the formation of excimer or exciplex. The polymers showed lower HOMO energy levels and LUMO energy levels than those of the MJLCPs containing oxadiazole unit reported before. Electroluminescence study with the device configuration of ITO/PEDOT/PVK/polymer/TPBI/Ca/Ag showed maximum brightness and current efficiency of 541 cd/m2 and 0.10 cd/A, which proved that the introduction of directly connected electron‐ and hole‐transport units could greatly improve the EL property of side‐chain conjugated polymers. The phase structures of the polymers were confirmed to be smectic A phase through the results of PLM and WAXD. The annealed samples emitted polarized photoluminescence at room temperature, which indicated potential utility for practical applications in display. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1502–1515, 2010
Polymerized pickering HIPEs: Effects of synthesis parameters on porous structure
Authors: Gurevitch Inna , Silverstein Michael S.
Published: February 2010

A polyHIPE is a highly porous polymer synthesized from monomers within the external phase of a high internal phase emulsion (HIPE). The large amount of difficult to remove surfactant needed for HIPE stabilization can affect the properties of the resulting polymer. A Pickering emulsion is a surfactant‐free emulsion stabilized by solid particles that preferentially migrate to the interface. In this article, the synthesis of crosslinked polyacrylate polyHIPEs based on Pickering HIPEs stabilized using silane‐modified silica nanoparticles is described and the effects of the synthesis parameters on the porous structure are discussed. The silane chemistry, silane content, and nanoparticle content had significant effects on the size of the polyhedral, relatively closed‐cell polyHIPE voids that resulted from aqueous‐phase initiation. Increasing the mixing intensity reduced the wall thickness and produced a more open‐cell structure. The locus of initiation had a significant effect on polyHIPE morphology. Organic‐phase initiation yielded larger, more spherical voids from the more extensive coalescence before the structure could be “locked‐in” at the gel point. Most significantly, the nanoparticles were located within the polymer walls rather than at the interface, as might be expected. The void walls were shown to be an assembly of nanoparticle agglomerate shells that become embedded within the polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1516–1525, 2010
Tailored composite polymer–metal nanoparticles by miniemulsion polymerization and thiol‐ene functionalization
Authors: van Berkel Kim Y. , Hawker Craig J.
Published: February 2010

A simple and modular synthetic approach, based on miniemulsion polymerization, has been developed for the fabrication of composite polymer–metal nanoparticle materials. The procedure produces well‐defined composite structures consisting of gold, silver, or MnFe2O4 nanoparticles (∼10 nm in diameter) encapsulated within larger spherical nanoparticles of poly(divinylbenzene) (∼100 nm in diameter). This methodology readily permits the incorporation of multiple metal domains into a single polymeric particle, while still preserving the useful optical and magnetic properties of the metal nanoparticles. The morphology of the composite particles is retained upon increasing the inorganic content and also upon redispersion in organic solvents. Finally, the ability to tailor the surface chemistry of the composite nanoparticles and incorporate steric stabilizing groups using simple thiol‐ene chemistry is demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1594–1606, 2010
Photoresponsive poly(methyl methacrylate)‐b‐azodendron block copolymers prepared by ATRP and click chemistry
Authors: del Barrio Jesús , Oriol Luis , Alcalá Rafael , Sánchez Carlos
Published: February 2010

A range of block copolymers (BCs) consisting of a linear poly(methyl methacrylate) (PMMA) block linked to an aliphatic polyester dendron functionalized with azobenzene moieties have been synthesized by sequential atom transfer radical polymerization (ATRP) and Click Chemistry. Two alkyne‐functionalized PMMA homopolymers with different molecular weights were obtained by ATRP and coupled to generations 2 to 4 of azodendrons bearing an azide group at the focal points. In the case of the azodendron with the highest generation number, the length of the flexible spacer attaching the cyanoazobenzene units to the dendron has also been modified. The coupling of both blocks and purity of BCs were checked by gel permeation chromatography, nuclear magnetic resonance, and infrared spectroscopy. The thermal transitions and liquid crystalline behavior of the BCs were investigated by differential scanning calorimetry and polarized‐light optical microscopy. A morphological study was carried out by transmission electron microscopy, using samples annealed at 115 °C. Photo‐induced anisotropy was induced in thin films of these materials after annealed at 115 °C. The highest stable birefringence values were obtained for the BCs bearing 8 and 16 azobenzene units in the dendritic block. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1538–1550, 2010
Colorimetric naked‐eye recognizable anion sensors synthesized via RAFT polymerization
Authors: Jiang Jianbing , Xiao Xiao , Zhao Ping , Tian He
Published: February 2010

A polymeric sensor (PTH) containing naphthalimide signal moiety and thiourea recognition moiety for the detection of anions was synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization, which can guarantee controllable molecular weight, narrow molecular weight distribution, and precise polymer structure. Both PTH and its corresponding monomer (TH) showed naked‐eye recognizable yellow‐to‐orange changes upon addition of fluoride (F−), acetate (AcO−), and dihydrogen phosphate (H2PO) of low concentration. However, only F− can result in orange‐to‐purple change when the aforementioned anions were added at high concentrations, which was attributed to the deprotonation of the thiourea NH groups and the mechanism was supported by the UV‐Vis absorption spectra and 1H NMR titration. The effect of these anions on thin PTH films was also investigated, and the addition of F− led to obvious spectra change. It was found that other halide anions (Cl−, Br−, and I−) could hardly induce any variation of absorption spectra. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1551–1556, 2010
Nanoparticles consisting of optically active helical polymers: Preparation via aqueous catalytic miniemulsion polymerization and the effects of particles size on their optical activity
Authors: Luo Xiaofeng , Kang Naiwen , Li Lei , Deng Jianping , Yang Wantai
Published: February 2010

This article reports a class of nanoscale materials, that is, optically active nanoparticles consisting of helical‐substituted polyacetylenes. Such nanoparticles were prepared via aqueous catalytic miniemulsion polymerization, by which nanoparticles with a wide range of size (diameter: 60–400 nm) can be easily prepared. The nanoparticles could be obtained in quantitative monomer conversions. Large specific rotations and intense circular dichroism effects demonstrated that the nanoparticles possessed large optical activities; moreover, the optical activities were found to increase with a decrease in particle size. From the obtained polymer nanoparticles and with poly(vinyl alcohol) (PVA) as supporting material, composite films were further prepared and also exhibited considerable optical activities. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1661–1668, 2010
Multiarm star triblock terpolymers via sequential double click reactions
Authors: Durmaz Hakan , Dag Aydan , Gursoy Duygu , Demirel A. Levent , Hizal Gurkan , Tunca Umit
Published: February 2010

Multiarm star triblock terpolymers were obtained by using two different click reactions sequentially: Cu(I) catalyzed azide–alkyne and Diels–Alder. The synthetic strategy is described as follows: (poly(methyl methacrylate))n‐(polystyrene)m‐poly(divinyl benzene)) ((PMMA)n‐(PS)m‐polyDVB) multiarm star diblock copolymer was first obtained from an azide–alkyne click reaction of (alkyne‐PS)m‐polyDVB multiarm star polymer with α‐anthracene‐ω‐azide PMMA (anth‐PMMA‐N3), followed by a Diels–Alder click reaction of the anthracene groups at the star periphery with α‐maleimide poly (tert‐butyl acrylate) (PtBA‐MI) or α‐maleimide poly(ethylene glycol) (PEG‐MI) leading to target (PtBA)k‐(PMMA)n‐(PS)m‐polyDVB and (PEG)p‐(PMMA)n‐(PS)m‐polyDVB multiarm star triblock terpolymers. The hydrodynamic diameter of individual multiarm star triblock terpolymers were measured by dynamic light scattering (DLS) to be ∼24–27 nm in consistent with the atomic force microscopy (AFM) images on silicon substrates. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1557–1564, 2010
Synthesis and characterization of a narrow‐bandgap polymer containing alternating cyclopentadithiophene and diketo‐pyrrolo‐pyrrole units for solar cell applications
Authors: Chen Guan‐Yu , Chiang Chien‐Ming , Kekuda Dhananjay , Lan Shang‐Che , Chu Chih‐Wei , Wei Kung‐Hwa
Published: February 2010

We have synthesized a narrow‐bandgap conjugated polymer (PCTDPP) containing alternating cyclopentadithiophene (CT) and diketo‐pyrrolo‐pyrrole (DPP) units by Suzuki coupling. This PCTDPP exhibits a low band gap of 1.31 eV and a broad absorption band from 350 to 1000 nm, which allows it to absorb more available photons from sunlight. A bulk heterojunction polymer solar cell incorporating PCTDPP and C70 at a blend ratio of 1:3 exhibited a high short‐circuit current of 10.87 mA/cm2 and a power conversion efficiency of 2.27%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1669–1675, 2010
The AFM observation of linear chain and crystalline conformations of ultrahigh molecular weight polyethylene molecules on mica and graphite
Authors: Prokhorov V. V. , Nitta K.
Published: February 2010

Atomic force microscopy (AFM) has been applied to visualize expanded linear chain and compact crystalline conformations of ultrahigh molecular weight polyethylene (PE) molecules deposited on mica and graphite from diluted solutions at elevated temperatures. Isolated PE chains are visualized on mica with the apparent negative AFM height and the contour length much shorter than the molecular length. The chain conformations have both the kinked random‐coil sites and the sites of the unexpectedly large two‐dimensional expansion. The crystalline conformations on mica are small single‐molecule rod‐like nanocrystallites and the isolated block‐type “edge‐on” nanolamellae comprising several PE molecules. Noticeable fluctuations of the fold length in the range of approximately 10–20 nm around the averaged value of about 15 nm are observed for nanocrystallites and on tips of some nanolamellae. The explanation of the experimentally observed features of chain surface conformations on mica is proposed. It implies the immobilization of PE molecules in the nm‐thickness salt layer formed on mica surface at ambient conditions after PE deposition and the presence along the chain of multiple expanded chain folds. Only isolated lamellae and lamellar domains of a monolayer height are observed on graphite samples. The substrate/polymer epitaxial incommensurability important for the observation of the PE linear chain surface conformations is discussed from the comparison of the results obtained for mica and graphite, the coil‐to‐crystal intramolecular transformation is assumed to be inhibited on mica surface. The slow disintegration of the original gel structure of PE stock‐solution used for the high‐temperature depositions was found to result in the characteristic large‐scale morphological heterogeneity of the samples. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 766–777, 2010
Hydrogen bonding interactions, crystallization, and surface hydrophobicity in nanostructured epoxy/block copolymer blends
Authors: Hameed Nishar , Guo Qipeng , Hanley Tracey , Mai Yiu‐Wing
Published: February 2010

Hydrogen bonding interactions, phase behavior, crystallization, and surface hydrophobicity in nanostructured blend of bisphenol A‐type epoxy resin (ER), for example, diglycidyl ether of bisphenol A (DGEBA) and poly(ε‐caprolactone)‐block‐poly(dimethyl siloxane)‐block‐poly(ε‐caprolactone) (PCL–PDMS–PCL) triblock copolymer were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, transmission electron microscopy, small‐angle X‐ray scattering, and contact angle measurements. The PCL–PDMS–PCL triblock copolymer consisted of two epoxy‐miscible PCL blocks and an epoxy‐immiscible PDMS block. The cured ER/PCL–PDMS–PCL blends showed composition‐dependent nanostructures from spherical and worm‐like microdomains to lamellar morphology. FTIR study revealed the existence of hydrogen bonding interactions between the PCL blocks and the cured epoxy, which was responsible for their miscibility. The overall crystallization rate of the PCL blocks in the blend decreased remarkably with increasing ER content, whereas the melting point was slightly depressed in the blends. The surface hydrophobicity of the cured ER increased upon addition of the block copolymer, whereas the surface free energy (γs) values decreased with increasing block copolymer concentration. The hydrophilicity of the epoxy could be reduced through blending with the PCL–PDMS–PCL block copolymer that contained a hydrophobic PDMS block. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 790–800, 2010
Viscoelastic interfacial properties of compatibilized poly(ε‐caprolactone)/polylactide blend
Authors: Wu Defeng , Zhang Yisheng , Yuan Lijuan , Zhang Ming , Zhou Weidong
Published: February 2010

Poly(ε‐caprolactone)/polylactide blend (PCL/PLA) is an interesting biomaterial because the two component polymers show good complementarity in their physical properties. However, PCL and PLA are incompatible thermodynamically and hence the interfacial properties act as the important roles controlling the final properties of their blends. Thus, in this work, the PCL/PLA blends were prepared by melt mixing using the block copolymers as compatibilizer for the studies of interfacial properties. Several rheological methods and viscoelastic models were used to establish the relations between improved phase morphologies and interfacial properties. The results show that the interfacial behaviors of the PCL/PLA blends highly depend on the interface‐located copolymers. The presence of copolymers reduces the interfacial tension and emulsified the phase interface, leading to stabilization of the interface and retarding both the shape relaxation and the elastic interface relaxation. As a result, besides the relaxation of matrices (τm) and the shape relaxation of the dispersed PLA phase (τF), a new relaxation behavior (τβ), which is attribute to the relaxation of Marangoni stresses tangential to the interface between dispersed PLA phase and matrix PCL, is observed on the compatibilized blends. In contrast to that of the diblock copolymers, the triblock copolymers show higher emulsifying level. However, both can improve the overall interfacial properties and enhance the mechanical strength of the PCL/PLA blends as a result. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 756–765, 2010
Rheological properties of crystallizing polylactide: Detection of induction time and modeling the evolving structure and properties
Authors: Yuryev Yury , Wood‐Adams Paula
Published: February 2010

Linear viscoelastic properties of polymer melts are highly sensitive to any structural changes, including molecular weight changes and the formation and growth of crystallites. Here, we make use of this sensitivity to study the homogeneous crystallization of polylactide. As this polymer is rather quickly susceptible to thermal degradation even at moderate temperatures, it is essentially impossible to study homogeneous crystallization in the absence of degradation. Thus, the evolution of complex viscosity of a polylactide due to thermal degradation in the absence of crystallization was studied. A simple empirical model is used to characterize the variation of complex viscosity due to thermal degradation and to determine the induction time of homogeneous crystallization at wide range of degrees of supercooling. Next, the evolution of complex viscosity due to crystallization was measured at several temperatures. Based on the results, a phenomenological model describing the viscosity evolution during homogeneous crystallization is proposed and validated. Finally, the linear viscoselastic data in the early stages of crystallization are shown to be consistent with gelation due to the formation of a network of tie molecules between spherulites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 812–822, 2010
Upregulation of L‐type Cav1 channels in the development of psychological dependence
Authors: Shibasaki Masahiro , Kurokawa Kazuhiro , Ohkuma Seitaro
Published: February 2010

Although L‐type voltage‐dependent Ca2+channels regulate activity‐dependent processes including synaptic plasticity and synapse formation, there are few data on the changes of Cav1 channel expression in psychological dependence. This study investigated the role of L‐type Cav1 channel expression in the brain of mouse that was psychologically dependent on methamphetamine (2 mg/kg, subcutaneous injection [s.c.]), cocaine (10 mg/kg, s.c.), and morphine (5 mg/kg, s.c.) with the conditioned place preference paradigm. Intracerebroventricular administration of nifedipine (3, 10, and 30 nmol/mouse) dose‐dependently reduced the development of methamphetamine‐, cocaine‐, and morphine‐induced rewarding effect. Under such conditions, protein levels of both Cav1.2 and Cav1.3 in the frontal cortex and the limbic forebrain were significantly increased on methamphetamine‐, cocaine‐, and morphine‐induced psychologically dependent mice. These findings suggest that the upregulation of Cav1.2 and Cav1.3 participated in the development of psychological dependence. Synapse 64:440–444, 2010. © 2010 Wiley‐Liss, Inc.
Prenatal and postnatal exposure to bisphenol a induces anxiolytic behaviors and cognitive deficits in mice
Authors: Tian Yu‐Hua , Baek Joung‐Hee , Lee Seok‐Yong , Jang Choon‐Gon
Published: February 2010

Bisphenol A (BPA), an environmental endocrine‐disrupting chemical, has been extensively evaluated for reproductive toxicity and carcinogenicity. However, little is known about the behavioral and neurochemical effects of BPA exposure. This study examined whether chronic daily exposure to an environmental endocrine‐disrupting chemical, bisphenol A [(BPA); 100 μg/kg/day or 500 μg/kg/day, p.o.], from prenatal Day 7 to postnatal Day 36 would lead to changes in anxiety and memory in mice. First, we observed the behavioral alterations of BPA‐treated mice using two anxiety‐related models, the open field test and elevated plus maze (EPM) test. In the open field test, BPA treatment (100 μg/kg/day) increased movement in the central zone. BPA treatment (500 μg/kg/day) also increased the time spent in the open arms in the EPM test. Second, we measured cognitive ability in the Y‐maze test and novel object test. BPA‐treated mice showed decreased alternation behavior in the Y‐maze at both of doses, indicating working memory impairment. BPA‐treated mice (100 μg/kg/day) also showed decreased novel object recognition as expressed by central locomotion and frequency in the central zone, showing recognition memory impairment. Finally, to measure changes in the dopaminergic and NMDAergic systems in the brain, we performed autoradiographic receptor binding assays for dopamine D1 and D2 receptors, the NMDA receptor, and the dopamine transporter. BPA treatment increased D2 receptor binding in the caudate putamen (CPu) but decreased DAT binding. BPA treatment also decreased NMDA receptor binding in the frontal cortex and CA1, CA3, and DG of the hippocampus. Taken together, our results suggest that long‐term BPA exposure in mice can induce anxiolytic behaviors, cognitive deficits and changes in the dopaminergic and NMDAergic systems. Synapse 64:432–439, 2010. © 2010 Wiley‐Liss, Inc.
Scientific reasoning and epistemological commitments: Coordination of theory and evidence among college science students
Authors: Zeineddin Ava , Abd‐El‐Khalick Fouad
Published: February 2010

Reasoning skills are major contributors to academic and everyday life success. Epistemological commitments (ECs) are believed to underlie reasoning processes and, when considered, could do much in delineating the complex nature of scientific reasoning. This study examined the relationship between ECs and scientific reasoning among college science students. Prior knowledge (PK) was factored in as an intervening variable. Participants were 139 college students enrolled in two physics courses in a large Midwestern university. They completed an online questionnaire, which assessed their PK regarding buoyancy in liquids and EC to the consistency of theory with evidence. Responses to the online questionnaire were used to select 40 participants with varying levels of PK and EC. These participants were divided into four groups, each with 10 students, representing four conditions: High PK–High EC, High PK–Low EC, Low PK–High EC, and Low PK–Low EC. These groups allowed using a 2 × 2 factorial quasi‐experimental design to examine the relationship between participants' reasoning and ECs, accounting for their PK. The quality of participants' reasoning was assessed during individual interviews, which presented them with four problem‐solving tasks involving objects immersed in water. Two‐way analysis of variance (ANOVA) indicated the absence of interaction between PK and EC. The results showed that the higher the ECs were, the higher the quality of reasoning was for comparable levels of PK. Additionally, it was found that PK impacted reasoning more strongly when ECs were weaker. © 2010 Wiley Periodicals, Inc. J Res Sci Teach 47: 1064–1093, 2010
Junior high school physics: Using a qualitative strategy for successful problem solving
Authors: Mualem Roni , Eylon Bat Sheva
Published: February 2010

Students at the junior high school (JHS) level often cannot use their knowledge of physics for explaining and predicting phenomena. We claim that this difficulty stems from the fact that explanations are multi‐step reasoning tasks, and students often lack the qualitative problem‐solving strategies needed to guide them. This article describes a new instructional approach for teaching mechanics at the JHS level that explicitly teaches such a strategy. The strategy involves easy to use visual representations and leads from characterizing the system in terms of interactions to the design of free‐body force diagrams. These diagrams are used for explaining and predicting phenomena based on Newton's laws. The findings show that 9th grade students who studied by the approach advanced significantly from pretests to post‐tests on items of the Force Concept Inventory—FCI and on other items examining specific basic and complex understanding performances. These items focused on the major learning goals of the program. In the post‐tests the JHS students performed on the FCI items better than advanced high‐school and college students. In addition, interviews conducted before, during, and after instruction indicated that the students had an improved ability to explain and predict phenomena using physics ideas and that they showed retention after 6 months. © 2010 Wiley Periodicals, Inc. J Res Sci Teach 47: 1094–1115, 2010
Immigrant entrepreneurship: Scrutinizing a promising type of business venture
Authors: Chrysostome Elie , Lin Xiaohua
Published: February 2010

Immigrant entrepreneurship is an important socioeconomic phenomenon today. In major destination countries for immigrants such as the United States, Canada, the United Kingdom, and Australia, immigrant entrepreneurship plays a critical role in economic development. The economic impact of immigrant entrepreneurship in the host country is well known, but the influence of immigrant entrepreneurship in the host country is not limited to its economic aspects. It includes important noneconomic effects such as the development of vibrant ethnic communities, social integration and recognition of immigrants, a nurturing entrepreneurial spirit, and providing role models for immigrants. From the management perspective, there are many aspects of immigrant entrepreneurship that are still unknown and need to be addressed. The purpose of this special issue is to shed light on some of those aspects. The articles selected to be published in this issue offer an excellent analysis of various important aspects of the topic, including the success factors of immigrant entrepreneurship, the influence of family networks, and the noneconomic effects of immigrant entrepreneurship. We believe the issue breaks new ground and offers excellent information on the topic. © 2010 Wiley Periodicals, Inc.
Noneconomic effects of ethnic entrepreneurship: A focused look at the Chinese and Korean enclave economies in Los Angeles
Authors: Zhou Min , Cho Myungduk
Published: February 2010

In this article, we aim to develop a conceptual framework from a community perspective to examine the noneconomic effects of ethnic entrepreneurship, paying close attention to the linkage between entrepreneurship and community building. We base our analysis on ethnographic data from our comparative case studies of the Chinese and Korean enclave economies in Los Angeles. We argue that it is the social embeddedness of entrepreneurship, rather than individual entrepreneurs per se, that creates a unique social environment conducive to upward social mobility. This study suggests that ethnic entrepreneurship plays a pivotal role in immigrant adaptation beyond observable economic gains. Policy implications are discussed. © 2010 Wiley Periodicals, Inc.
Immigrant business enterprises: A classification framework conceptualization and test
Authors: Curci Roberto , Mackoy Robert
Published: February 2010

This article proposes the Immigrant Business Enterprises Classification Framework to organize immigrant‐owned businesses into categories associated with different levels of business integration into a host country's mainstream business community. The article applies the framework and reports the findings of structured face‐to‐face interviews with 199 Hispanic business enterprises (HBEs) in Indianapolis. The authors find Hispanic‐owned businesses hold different characteristics depending upon the integration category in which they are classified; the findings suggest that to support immigrant entrepreneurship, governments, business development organizations, and researchers should address category‐specific challenges, opportunities, and needs. © 2010 Wiley Periodicals, Inc.
The diaspora solution to innovation capacity development: Immigrant entrepreneurs in the contemporary world
Authors: Lin Xiaohua
Published: February 2010

The international migration of highly skilled labor was formerly a threat to the underdeveloped world with regard to indigenous innovation capacity. However, certain countries have successfully turned “brain drain” into “brain gain” by effective engagement with a skilled diaspora who have returned to set up business ventures in the homeland. This article advocates an entrepreneurial approach to the development of national innovation capacity through contemporary diasporic entrepreneurship (CDE). Drawing evidence mostly from China, the article argues that (1) CDE offers an alternative to conventional indigenously and internationally oriented approaches toward innovation capacity development; (2) compared to other ways of diaspora homeland engagement, CDE is most beneficial to capacity development; and (3) besides participating in philanthropic and scientific projects, a skilled diaspora returning as private business owners represents an often more productive way of contributing to national capacity development. © 2010 Wiley Periodicals, Inc.
Relativistic invariance of dispersion‐relations and their associated wave‐operators and Green‐functions
Authors: Censor D.
Published: February 2010

Identifying invariance properties helps in simplifying calculations and consolidating concepts. Presently the Special Relativistic invariance of dispersion relations and their associated scalar wave operators is investigated for general dispersive homogeneous linear media. Invariance properties of the four‐dimensional Fourier‐transform integrals is demonstrated, from which the invariance of the scalar Green‐function is inferred. Dispersion relations and the associated group velocities feature in Hamiltonian ray tracing theory. The derivation of group velocities for moving media from the dispersion relation for these media at rest is discussed. It is verified that the group velocity concept satisfies the relativistic velocity‐addition formula. In this respect it is considered to be ‘real’, i.e., substantial, physically measurable, and not merely a mathematical artifact. Conversely, if we assume the group velocity to be substantial, it follows that the dispersion relation must be a relativistic invariant.
On the existence of solution in the linear elasticity with surface stresses
Authors: Altenbach H. , Eremeyev V.A. , Lebedev L.P.
Published: February 2010

The mathematical investigation of the initial‐boundary and boundary value problems in the linear elasticity considering surface stresses is presented. Weak setup of the problems based on mechanical variational principles is studied. Theorems of uniqueness and existence of the weak solution in energy spaces of static and dynamic problems are formulated and proved. Some properties of the spectrum of the problems under consideration are established. The studies are performed applying the functional analysis techniques. Finally, the Rayleigh principle for eigenfrequencies is constructed.
La réflexion benthamienne sur les mathématiques
Authors: Cléro Jean-Pierre
Published: February 2010

En 1814, Jeremy Bentham entreprend la rédaction de Chrestomathia, qui expose le savoir qu'il est utile d'apprendre. Mais ce texte est plus généralement une organisation entière du savoir de son temps à partir d'une «théorie des fictions », qui est à la fois une réflexion sur les concepts et une critique des nomenclatures. L'article qui suit s'intéresse particulièrement à la cinquantaine de pages consacrées aux mathématiques dans un ouvrage qui porte sur toutes les sciences du début du XIXe siècle et critique l' Encyclopédie de Diderot et D'Alembert. L'une des idées les plus originales développées par l'auteur et dont on trouvera un écho lointain chez Gaston Bachelard est celle d'un conflit entre les concepts et la façon dont ils sont désignés par les mots. Signifiés, signifiants et concepts dérivent les uns par rapport aux autres en des sens que nul ne peut contrôler, pas même les savants; ce qui rend l'éducation durablement difficile.
La publication du Treatise on electricity and magnetism de James Clerk Maxwell
Authors: Achard Franck
Published: February 2010

Cet article vise à éclairer le contexte universitaire et éditorial qui favorisa la publication du Treatise on electricity and magnetism de James Clerk Maxwell afin de mieux cerner la nature de cette entreprise scientifique. Le projet fut formé en 1867 à l'occasion d'une réforme introduisant l'étude de l'électricité et du magnétisme dans l'enseignement délivré à Cambridge et s'inscrivait dans un mouvement plus vaste qui développait l'enseignement de ces disciplines dans les universités britanniques. L'étude des relations entre le projet de Maxwell et d'autres ouvrages contemporains indique que le Treatise était en situation de devenir un ouvrage de référence en Grande-Bretagne. Ainsi, le livre de Maxwell était-il l'instrument d'une très ambitieuse tentative de transformation de l'électromagnétisme, indissociable de son contexte et conforme à sa fonction pédagogique.
Questions ethnographiques et mathématiques de la préhistoire
Authors: Keller Olivier
Published: February 2010

L'étude des mathématiques de la préhistoire ne peut être fondée uniquement sur les documents archéologiques bruts, sous peine de stérilité ; elle a tout intérêt à les mettre en situation grâce au comparatisme ethnographique, selon lequel les sociétés primitives actuelles ou récemment disparues nous renseignent sur nos ancêtres de la préhistoire. D'abord utilisée spontanément par quelques historiens des mathématiques, cette méthode est de nos jours rejetée en principe par le courant récent des ethnomathématiciens. Il s'agit de montrer par quelques exemples que la méthode est pourtant féconde, d'une part parce qu'elle ruine les constructions fantastiques dont raffolent certains mathématiciens, et d'autre part parce qu'elle ouvre un vaste champ de recherches pratiquement inexploré.
Structural comparison and consumer choice
Authors: Markman Arthur B. , Loewenstein Jeffrey
Published: February 2010

Psychological research has demonstrated important parallels between the structural alignment process involved in judgments of similarity and the processes that are involved in analogical reasoning. Gradually, this work on comparisons was applied to consumer choice. In this paper, we review the influence of structural alignment on choices among a set of options. Then, we discuss extensions of this work to comparative advertising and to the role of analogy in marketing communication. Finally, we discuss important extensions to structural alignment suggested by this work such as the key role that affect plays in comparisons made during the choice process.
A Brief Review on the Mechanisms of miRNA Regulation
Authors: Cai Yimei , Yu Xiaomin , Hu Songnian , Yu Jun
Published: February 2010

MicroRNAs (miRNAs) are a class of short, endogenously-initiated non-coding RNAs that post-transcriptionally control gene expression via either translational repression or mRNA degradation. It is becoming evident that miRNAs are playing significant roles in regulatory mechanisms operating in various organisms, including developmental timing and host-pathogen interactions as well as cell differentiation, proliferation, apoptosis and tumorigenesis. Likewise, as a regulatory element, miRNA itself is coordinatively modulated by multifarious effectors when carrying out basic functions, such as SNP, miRNA editing, methylation and circadian clock. This mini-review summarized the current understanding of interactions between miRNAs and their targets, including recent advancements in deciphering the regulatory mechanisms that control the biogenesis and functionality of miRNAs in various cellular processes.
New fossils of Sirenia from the Middle Eocene of Navarre (Western Pyrenees): the oldest West European sea cow record
Authors: ASTIBIA H. , BARDET N. , PEREDA-SUBERBIOLA X. , PAYROS A. , DE BUFFRÉNIL V. , ELORZA J. , TOSQUELLA J. , BERRETEAGA A. , BADIOLA A.
Published: February 2010

Postcranial remains of Sirenia from the early Middle Eocene (late Lutetian) Urbasa-Andia Formation of Navarre (Western Pyrenees) are described. The material consists of two partial atlas vertebrae, one humerus and several dorsal ribs (from Arrasate, Urbasa plateau), and partial dorsal ribs (from Lezaun, Andia plateau). The morphology of the fossils is consistent with referral to Dugongidae, the only sirenian clade known so far in the Middle Eocene of Europe. Moreover, the histological study of the ribs shows that the pachyosteosclerosis of extant Sirenia was definitively present by the early Middle Eocene. The oldest sirenian remains reported to date in the Pyrenean Realm were assigned to the Biarritzian, a regional stage that is currently ascribed either to the middle or to the lower–middle Bartonian. Therefore, the sirenian remains of Lezaun, reliably dated as late Lutetian (SBZ16 zone) in age, are definitively the earliest sirenian fossils known in Western Europe and are among the oldest sea cow records of Europe.