bluuebunny/crossref_metadata_2025_split huggingface dataset:
Context-aware recommender for mobile learners
Authors: Benlamri Rachid , Zhang Xiaoyun 
Published: August 2014

AbstractAs mobile technologies become widespread, new challenges are facing the research community to develop lightweight learning services adapted to the learner’s profile, context, and task at hand. This paper attempts to solve some of these challenges by proposing a knowledge-driven recommender for mobile learning on the Semantic Web. The contribution of this work is an approach for context integration and aggregation using an upper ontology space and a unified reasoning mechanism to adapt the learning sequence and the learning content based on the learner’s activity, background, used technology, and surrounding environment. Whenever context change occurs, the system identifies the new contextual features and translates them into new adaptation constraints in the operating environment. The proposed system has been implemented and tested on various mobile devices. The experimental results show many learning scenarios to demonstrate the usefulness of the system in practice.
Synthesis and characterization of macrocyclic poly(.-methylstyrene)
Authors: Dong Dahai , Hogen-Esch Thieo E. 
Published: August 2014

AbstractThe synthesis is described of macrocyclic poly(α-methylstyrene) (PAMS) by the lithium naphthalide initiated polymerization of AMS followed by high dilution end to end coupling with 1,4-bis(bromomethyl)benzene (DBX). The cyclization is carried out by simultaneous addition of tetrahydrofuran solutions of the PAMS dianion and DBX at about -100ºC. A sample of the matching linear PAMS is obtained by protonation of the PAMS dianion. The purified cycles are obtained by fractional precipitation that is monitored by size exclusion chromatograhy. A careful study of the coupling reactions carried out at high concentrations indicates that coupling is efficient and this is borne out by the ratios (<G>) of apparent molecular weights (MW’s) of cycles and matching linear polymers. The <G> values of the cycles tend to vary with MW in the same manner as was demonstrated for polystyrene and other vinyl polymers and increase from around 0.74 at MW of about 30000 to values of around 0.82 at MW of about 2500. A higher apparent <G> value was observed for a very low MW PAMS but this sample could not be purified and analyzed adequately. As was also observed for other macrocyclic vinylpolymers, the glass transition temperatures of the cycles are MW independent above MW of about 5000 but decrease sharply at lower MW’s.
Polyzwitterionic aqueous solutions – a new class of electrorheological fluids
Authors: Georgiev George S. , Tzoneva Anna A. , Spassov Velin A. 
Published: August 2014

AbstractIt has been established that the electroviscosity effect of polyzwitterionic (PZI) aqueous solutions is more considerable than and acts in a direction opposite to that of aqueous polyelectrolyte solutions. Temperature and electric field strength influence the electroviscosity of PZI aqueous solutions in parallel, though the reasons for these effects are quite different. The unusual electroviscosity behaviour of PZI solutions is explained by a ‘core-shell’ model for the structural organization of PZI macromolecules, suggesting that cluster formation is due to intensive dipoledipole interactions between monomer units of the same or of different macromolecules.
Photoluminescence and electroluminescence of mono- and dialkyl-substituted soluble polythiophenes
Authors: Angiolini Luigi , Salatelli Elisabetta , Bolognesi Alberto , Botta Chiara 
Published: August 2014

AbstractWe report a comparison between optical properties (photoluminescence and UV-Vis absorption) and electroluminescence in a series of soluble polyalkylthiophenes with the aim of better understanding the role of different structural parameters, viz. length of side chains and introduction of unsubstituted thiophenes and their position in the backbone, on the electro-optical properties. The potential of these polymers as material for an active film in a single layer light emitting diode is evaluated.
Towards polymer-inorganic hybrid molecular composites: calorimetric studies of the polymer-inorganic particles interaction
Authors: Penczek Stanislaw , Kaluzynski Krzysztof , Pretula Julia , Bartczak Zbigniew , Zielenkiewicz Wojciech , Kaminski Miron 
Published: August 2014

AbstractInorganic particles of 3 CaO ⋅ SiO2 were reacted in water dispersion with dihydrophilic ionic-nonionic block copolymers, and the heat effect of interaction was measured by calorimetry. The ionic block was constituted of monoesters of phosphoric acid or alkyl phosphonic acid, both built on the polyglycidol block, attached to the poly(ethylene oxide) block. The heat evolved during the interaction is a function of the degree of phosphorylation (phosphonylation). The higher the degree of -OH substitution the stronger the interaction, the latter being stronger for phosphates than for phosphonates.
Chain expansion and chain localisation in the homogenous regime of blends of liquid low molar mass polysiloxanes as revealed by neutron scattering investigations
Authors: Götz Heide , Ewen Bernd , Maschke Ulrich , Monkenbusch Michael , Meier Gerd 
Published: August 2014

Abstract Using small angle neutron scattering and neutron spin echo spectroscopy, two isotopic blends of low molar mass polydimethylsiloxane (PDMS) and polyethylmethylsiloxane (PEMS), and the corresponding binary blends d-PDMS/ p-PEMS and p-PDMS/d-PEMS (d: deuterated, p: protonated) were studied at the critical composition in the homogeneous regime. From the scattering data it becomes evident that coil dimensions and collective dynamics of these both blend systems behave significantly different. Compared to the isotopic mixtures, which exhibit the expected unperturbed chain dimensions and the typical Rouse relaxation, in the binary blends, which differ by a large shift with respect to the critical temperature, considerable coil expansion and spatially restricted Rouse relaxation occur. Both these structural and dynamic effects are in agreement with the model of droplet formation and chain localization, resulting from the existence of microscopic heterogeneities within the spinodal boundaries of the phase diagram. In addition, the observation of Rouse relaxation, spatially restricted to microscopic length scales, provides a new access to the molecular understanding of the critical slowing down of the mutual diffusion process, observed by photon correlation spectroscopy.
31P NMR measurement of the homolysis rate constant of the C-ON bond of β-phosphorylated alkoxyamines
Authors: Bertin Denis , Gigmes Didier , Marque Sylvain , Tordo Paul 
Published: August 2014

Abstract In the presence of an excess of various alkyl radical scavengers or nitroxide reductants (TEMPO, phenylhydrazine and thiophenol), 31P NMR monitoring was used to determine the homolysis rate constant (kd) of β-phosphorylated alkoxyamines. The kd values for a mixture of diastereoisomeric alkoxyamines can be obtained in a single experiment and the formation of reaction products can be followed. The measured values were in good agreement with those obtained with other approaches involving chromatography or electron paramagnetic resonance (EPR).
Novel photosensitive polyurethanes based on photochromic dithienylethene monomers: synthesis, characterization and photophysical properties of a new film-building material for photonic applications
Authors: Bens Arthur Thomas , Comanici Radu , Gabel Bianca , Kryschi Carola , Martin Hans-Dieter , Ritter Helmut 
Published: August 2014

Abstract The synthesis of a novel photochromic dithienylethene-based polyurethane and its characterization by optical spectroscopy and scanning tunneling microscopy are presented. This linear polyurethane builds up perfect free-standing films suited for photonic applications. Moreover it may be extruded to long mechanically stable fibers. The photochromic reactions of the polyurethane, as being the electrocyclic ring-closure and ring-opening reactions of the dithienylethene unit in the polymer backbone, occur in a completely reversible and highly efficient fashion.
Impact modification of polyamide-12 through blending with liquid polybutadiene, 3 a Properties of compatibilized blends of PA12 and liquid polybutadiene
Authors: Talon Olivier , Couvercelle Jean-Pierre , Bunel Claude 
Published: August 2014

Abstract Blends of polyamide 12 (PA12) and liquid polybutadiene (HTPB) compatibilized with pyromellitic anhydride (APy) were prepared by melt blending. 10%, 12% and 20% HTPB blends were prepared, with various amounts of APy. The influence of the amount of APy on the morphology of the blends was studied for a wide composition range in the 12% series. Injection moulded tensile and Charpy testing bars were prepared from 10% and 20% binary and compatibilized blends. The deformations of the matrix under room temperature impact and the morphology of the blends were investigated with scanning electron microscopy. Partial miscibilization of HTPB with PA12 due to the addition of APy was postulated to explain the disappearance of polybutadiene in some cases. The mechanical properties of the blends were correlated with morphological parameters. A strong correlation between impact fracture toughness and the amount of non-miscible HTPB was found.
Approach to observe folded chains of syndiotactic polystyrene on solution-grown crystals by atomic force microscopy
Authors: Suto Nobuyuki , Fujimori Atsuhiro , Masuko Toru 
Published: August 2014

Abstract Folded chains of syndiotactic polystyrene located on the surface of its solution-grown crystals (SGCs) have been observed on nano scale by use of atomic force microscopy (AFM). Transmission electron micrographs of the SGCs on the mesoscopic scale exhibited truncated-lozenge platelets accompanied by a sharp electron diffraction pattern of the β”-form. AFM images of selected areas on the SGC surface indicated folded chains existing periodically on the surface with c. 1.3 to 1.4 nm spacing, suggesting that the polymer chains are aligned in parallel with the {230} growth faces of SGC.
Atom transfer radical polymerization of styrene initiated by the novel initiator N-bromosuccinimide
Authors: Zhang Wei , Zhu Xiulin , Zhu Jian 
Published: August 2014

Abstract Heterogeneous atom transfer radical polymerization of styrene initiated by N-bromosuccinimide in bulk was successfully carried out with CuBr/2,2’-bipyridine as the catalyst. The kinetics follow first order in monomer and molecular weights (polydispersities Mw/Mn = 1.23 - 1.66) increase linearly with monomer conversion, indicating the ‘living’/controlled nature of the polymerization. However, the number-average molecular weights were usually higher than the theoretical ones. That demonstrates the relatively low efficiency of the initiator, the causes of which are discussed. The obtained polystyrenes functionalized with α-α-pyrrolidine- 2,5-dionyl and ω-Br as the end groups were characterized by 1H NMR spectroscopy. They can be used as macroinitiators for chain extension reaction. A polymerization mechanism for this novel initiation system is proposed.
Macromolecular design of the network structure of copolymers of ethylene glycol dimethacrylate with methyl methacrylate using the catalytic chain transfer reaction
Authors: Kurmaz Svetlana V. , Bubnova Maria L. , Perepelitsina Evgenia O. , Estrina Genrietta A. 
Published: August 2014

Abstract It has been shown that catalytic chain transfer reaction is an effective instrument for the macromolecular design of the network structure of copolymers of ethylene glycol dimethacrylate with methyl methacrylate. Copolymers of various macromolecular architectures - from networks to soluble branched low-molecularweight oligomers - have been produced using cobalt porphyrin as catalytic chain transfer agent. The influence of cobalt porphyrin on the kinetics of copolymerization, structure and properties of final copolymers has been studied.
A study of aging in dental composites using IR and Raman spectroscopy
Authors: Pallikari Fotini , Iosifidou Soultana 
Published: August 2014

Abstract The application of dental restorative composites has opened wide possibilities in modern dentistry. The dental pastes studied in this work consist of a dimethacrylate-based matrix to which silica or ceramic fillers are added to improve their mechanical properties, colour stability and aesthetic appearance. The pastes were cured through free-radical polymerisation with visible light and were subjected to accelerated aging in the laboratory. The degree of monomer conversion with photo-curing, studied with FTIR and FT-Raman spectroscopy, was 42 ± 2% on average, which further advanced after aging to 56 ± 4%. The samples exhibited fluorescence at various intensities, which declined by the curing and aging procedures by a maximum of c. 20%, depending on the type of fillers present.
Microwave dielectric properties of glass-reinforced polymers
Authors: Costa Luís Cadillon , Devesa Susana , André Paulo 
Published: August 2014

AbstractThe well-balanced combination of properties of some polymers makes them good materials for industrial microwave applications, such as telecommunications or microwave ovens. Particular electrical properties are usually needed and can be controlled by additives. In this work, we present the results of complex dielectric permittivity measurements, ε* = ε’ - iε’’, in the microwave frequency region (2.7 and 12.8 GHz), at constant temperature 300 K, on different glass-reinforced and pigmented plastics (poly(butylene terephthalate), polypropylene and acrylonitrile- butadiene-styrene), using the resonant cavity method. We measured the shift in the resonant frequency of the cavity, Δf, caused by the insertion of the sample, which can be related to the real part of complex permittivity, ε’, while the change in the inverse of the quality factor of the cavity, Δ(1/Q), gives the imaginary part, ε’’.
Kinetic investigation of styrene emulsion polymerization with surface-active polyelectrolytes as emulsifier, 1 Kinetic study
Authors: Kato Satoshi , Suzuki Kiyoshi , Nomura Mamoru 
Published: August 2014

AbstractA copolymer of methyl methacrylate and methacrylic acid to be used as a polymeric surfactant was synthesized by emulsifier-free semi-batch emulsion copolymerization. Emulsion polymerization of styrene was carried out at 50°C utilizing the ammonium salt of the copolymer as the polymeric emulsifier and potassium persulfate as the initiator, respectively. Both the number of polymer particles produced and the rate of polymerization were proportional to the 0.6 power of the initial emulsifier concentration, to the 0.4 power of the initial initiator concentration, and independent of the initial monomer concentration, respectively. These relationships are almost the same as those observed in the emulsion polymerization of styrene conducted using conventional surfactants like sodium dodecyl sulfate as the emulsifier and potassium persulfate as the initiator.
A facile method to prepare methylcellulose from annual plants and wood using iodomethane
Authors: Ye Daiyong , Farriol Xavier 
Published: August 2014

AbstractA novel facile method was developed to prepare methylcellulose from miscanthus, cardoon and eucalyptus. Pulps were obtained by the impregnation rapid steam pulping process (IRSP). A total-chlorine-free (TCF) method was used to bleach the pulps with hydrogen peroxide. Bleached pulps were mercerized in 40% NaOH solution for one hour at ambient temperature. Mercerized cellulose reacted with iodomethane in 2-propanol slurry at 60°C for 22 h. Mercerization and methylation were repeated. Intrinsic viscosities of methylcellulose were measured in 4% NaOH solution. Super-molecular substitution patterns of methylcellulose were determined by 13C NMR. Molecular weights of methylcellulose were measured in dimethyl sulfoxide by gel permeation chromatography. Pulping severity is a key factor influencing the properties of the methylcellulose prepared.
Coagulation kinetics and the stability of surfactant-free emulsion-polymerised latexes
Authors: Sadiku E. Rotimi , Sanderson Ron D. 
Published: August 2014

AbstractThe stability factor of styrene/sulfopropyl methacrylate (styrene/SPM) and styrene/3-[N,N-dimethyl-N-(methacryloxyethyl)ammonium]propane sulfate (styrene/ SPE) latexes was studied using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and the critical coagulation concentration, CCC, was deduced for the latexes. Photon correlation spectroscopy was used to study ionic stabilities. The stability factor was determined as the ratio of the rate constant for rapid coagulation to that of slow coagulation, obtained from the coagulation kinetics data. The log-log plot of the stability factor, W, as a function of NaCl electrolyte concentration shows an asymptotic decrease in W of both latexes. DLVO theory was successfully employed, whereby the characteristic properties of the diffuse electric double layers or the Stern layers around latex particles in terms of their Hamaker constants and diffuse potentials were determined. The electric double layer thickness decreases with increasing NaCl concentration. Stability curves revealed a higher CCC value for the styrene/SPM latex than for the styrene/SPE latex, which is in accordance with the higher surface charge density and an indication of a better stability.
Extraction and characterization of polysaccharides from Mesembryanthemum crystallinum
Authors: M’sakni Nour H. , Zayane Hamouda , Majdoub Hatem , Morvan Claudine , Roudesli Sadok , Deratani André 
Published: August 2014

AbstractWater-soluble polysaccharides were isolated from Mesembryanthemumcrystallinum. Two methods were applied, based (i) on the extraction in hot water (for fresh and dry plants, FP and DP) and (ii) on freeze-thawing of fresh plants (FT). Each fraction was purified by precipitation in ethanol followed by ultrafiltration of recovered solids dissolved in water through a membrane with a molecular weight cut off of 100 000. Elemental analysis demonstrated that the extracted products were polysaccharides exempt from proteins. The yield relative to the corresponding dry matter varied from 1.6 to 3% depending on the starting sample and the extraction process. Obtained products were characterised by their structural (sugar composition, degree of methylation (DM) and acetylation, molar mass of acid equivalent unit) and macromolecular characteristics (molar mass and intrinsic viscosity). A galacturonic-acid content larger than 65% and a DM value of c. 40% showed that the isolated polysaccharides belong to the fairly methylated pectin class. FP and FT structures consisted of the two blocks homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) with relative proportions of 62 - 68% and 29 - 34%, respectively. They showed very similar physicochemical behaviour. On the other hand, DP exhibited significant differences in the chemical structure (50% HG and 46% RG-I blocks) and physical properties, indicating that partial degradation of HG moieties occurred during plant drying.
Morphology of nanocomposites from ethylene-acrylic acid copolymers
Authors: Magagnini Pierluigi , Filippi Sara , Marazzato Cristina , La Mantia Francesco P. , Minkova Liliya I. 
Published: August 2014

AbstractNew nanocomposites have been prepared by melt-compounding from commercial ethylene-acrylic acid copolymers (EAA) of different molar mass, molecular structure (branched or linear) and AA concentration, and a Zn-ionomer, with three commercial clays containing different proportions of the same organic modifier (dimethyldi(hydrogenated tallow)ammonium ion). Their morphology has been preliminarily investigated by X-ray scattering and transmission electron microscopy. The nanocomposites showed disordered intercalated morphology, with an expansion of the average gallery height, which appears to depend quite strongly on the molecular architecture of the EAA, whereas the other investigated variables, including the excess of surfactant used to organically modify the silicate, have negligible effect.
Annealing effects on the electrical conductivity of polymerized liquid crystalline 3,4-ethylenedioxythiophene derivatives
Authors: Wrubbel Noelle , Ritter Helmut , Reuter Knud , Karbach Alexander , Drechsler Doris 
Published: August 2014

Abstract3,4-Ethylenedioxythiophene derivatives with aromatic, in most cases mesogenic, side groups were synthesized and their liquid crystal behaviour was characterized. These monomers were polymerized oxidatively to charged, electrically conductive polythiophenes. X-ray and atomic force microscopy studies were performed. Films of theses polythiophenes achieved via in situ polymerization were prone to a significant increase of the conductivity by annealing.
Emulsion copolymerization of hydrophobic and hydrophilic monomers: an experimental study with styrene and 2- hydroxyethyl methacrylate
Authors: Ahmad Hasan , Islam A.H.M. T. , Hossain M. Amran , Miah M.A. Jalil , Tauer Klaus 
Published: August 2014

AbstractAb initio emulsion copolymerization of styrene with 2-hydroxyethyl methacrylate (HEMA) at weight ratios of the hydrophilic monomer of 1 and greater was investigated at various temperatures in dependence on the concentration of sodium dodecylsulfate (SDS) and potassium peroxodisulfate as emulsifier and initiator, respectively. Both the course of the polymerization and the latex properties are strongly influenced by the hydrophilic monomer. For instance, transparent or highly translucent latexes are obtained resembling the appearance of microemulsion latexes with polymer contents as high as 10 weight-% but at much lower surfactant concentration. Moreover, polymerization rate, average particle size, and particle morphology depend on the surfactant and initiator concentration, monomer feed composition, and polymerization temperature.
Use of new hydroxytelechelic cis-1,4-polyisoprene (HTPI) in the synthesis of polyurethanes (PUs): Influence of isocyanate and chain extender nature and their equivalent ratios on the mechanical and thermal properties of PUs
Authors: Kébir Nasreddine , Campistron Irène , Laguerre Albert , Pilard Jean-François , Bunel Claude , Couvercelle Jean-Pierre 
Published: August 2014

AbstractNew segmented polyurethanes (thermoplastic-elastomers) based on previously described hydroxytelechelic cis-1,4-polyisoprene (HTPI), miscellaneous isocyanates and chain extenders at various equivalent ratios were prepared by the classical one-shot method. The influence of the nature of isocyanate and chain extender, as well as their equivalent ratios, on the mechanical and thermal materials behavior was investigated. Thus, a comparative assessment of material properties was performed. Microphase separation of hard and soft segments was observed by DMTA, DSC and AFM. Moreover, according to Thermogravimetric Analysis (TGA), linear relationships depending on the isocyanate and chain extender nature were found between the weight loss (%) and the percentages of hard segments. A classification of thermal stability in terms of weight loss was established. With the aim of a thermo-mechanical comparative study, polyurethane elastomers based on HTPI and isocyanates without chain extender, were also synthesized.
Development and Characterization of Bismaleimides Containing Aliphatic Chain for Microelectronics Application
Authors: Feng J. L. , Yue C. Y. , Chian K. S. 
Published: August 2014

AbstractA series of bismaleimide systems containing aliphatic backbone chain have been synthesized and investigated. Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Thermomechanical analysis (TMA), rheometry and tensile test were used to characterize the thermal and mechanical properties. It was noted that backbone chain length and odd-even effect affected properties. As the chain length increases, the curing peak temperature, gel temperature of BMI all increase, but the melting point, glass transition and moisture absorption decrease. The melting points of BMI-3,5,7 reduced most significantly. The tensile properties were affected by odd even effect significantly. BMI-3,5,7 with odd number of carbons have less stress and strain than those of even ones.