bluuebunny/crossref_metadata_2025_split huggingface dataset:
Properties of Polyimide/Silica Nanohybrids from Silicic Acid Oligomer
Authors: Wang Haitao , Zhong Wei , Xu Peng , Du Qiangguo 
Published: August 2004

AbstractSummary: A new method to synthesize polyimide (PI)/silica nanohybrids has been presented. It uses silicic acid oligomer as the silica precursor, which was obtained by extracting with tetrahydrofuran (THF) from PH‐adjusted water glass. The films of PI/silica nanohybrids remained transparent even at high silica content due to the formation of nanometer‐scaled SiO2 particles at the addition of γ‐aminopropyltriethoxysilane (APTES). In comparison with pure PI, PI/silica hybrids showed improved thermal stability and mechanical properties, and lower linear coefficients of thermal expansion (CTEs). The glass transition temperatures of the hybrids were increased with increasing content of silica or APTES as a result of the increasing limitation to the movements of the PI backbone.SEM photograph of PI 20/4.magnified imageSEM photograph of PI 20/4.
Formaldehyde Resins Bearing Diaminodiphenylmethane Groups: Synthesis, Characterization and Properties
Authors: Mustata Fanica , Bicu Ioan 
Published: August 2004

AbstractSummary: Novel formaldehyde resins bearing diaminodiphenylmethane groups were synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), cyclohexanone (CHx) and o‐cresol (o‐Cz) with formaldehyde (FA) in the presence of an acid catalyst (HCl). The resins obtained were characterized by spectral, elemental and thermal analysis and used as a hardener for epoxy resins. The curing and temperature behavior of these epoxy resin/formaldehyde systems were investigated using differential scanning calorimetry and thermogravimetry techniques. The resins had good thermal stability and the activation energies of degradation reactions had values between 70–98 kJ · mol−1.The curing reaction of epoxy resins with the DDM/CHx/o‐Cz/formaldehyde resins.magnified imageThe curing reaction of epoxy resins with the DDM/CHx/o‐Cz/formaldehyde resins.
Micromechanical Processes in PET/PC Multilayered Tapes: High Voltage Electron Microscopy Investigations
Authors: Ivan'kova Elena M. , Michler Goerg H. , Hiltner Anne , Baer Eric 
Published: August 2004

AbstractSummary: A totally new kind of multilayered tape consisting of two macroscopically ductile polymers (PET and PC) was studied using high voltage electron microscopy (HVEM). Both components were co‐extruded as uniform laminates with thousands of alternating layers. The multilayered PET/PC samples were annealed at high temperature. Investigation of the multilayered PET/PC tapes with various compositions clearly demonstrated a transition of the microdeformation mechanism which was dependent on the thickness of the individual layers. The annealing of the tapes led to a significant change in the deformation behavior. However, no lamellae formation was revealed in the PET phase after annealing, leading to the assumption of constrained crystallization in very thin PET layers.
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Heat Induced Structure Modifications in Polymer‐Layered Silicate Nanocomposites
Authors: Pastore Heloise O. , Frache Alberto , Boccaleri Enrico , Marchese Leonardo , Camino Giovanni 
Published: August 2004

AbstractSummary: The success of the use of layered silicates in polymer nanocomposites, to improve physical and chemical properties is strictly related to a deeper knowledge of the mechanistic aspects on which the final features are grounded. This work shows the temperature induced structural rearrangements of nanocomposites based on poly[ethylene‐co‐(vinyl acetate)] (EVA) intercalated‐organomodified clay (at 3–30 wt.‐% silicate addition) which occur in the range between 75 and 350 °C. In situ high temperature X‐ray diffraction (HT‐XRD) studies have been performed under both nitrogen and air to monitor the modifications of the nanocomposite structure at increasing temperatures under inert/oxidative atmosphere. Heating between 75 and 225 °C, under nitrogen or air, causes the layered silicate to migrate towards the nanocomposite surface and to increase its interlayer distance. The degradation of both the clay organomodifier and the VA units of the EVA polymer seems to play a key role in driving the evolution of the silicate phase in the low temperature range. The structural modifications of the nanocomposites in the high temperature range (250–350 °C), depended on the atmosphere, either inert or oxidizing, in which the samples were heated. Heating under nitrogen led to deintercalation and thus a decrease of the silicate interlayer space, whereas exfoliation was the main process under air leading to an increase of the silicate interlayer space.Heat induced structural modification of EVA‐clay nanocomposite under nitrogen and air.magnified imageHeat induced structural modification of EVA‐clay nanocomposite under nitrogen and air.
Modulated Crosslinking of Polyolefins through Radical Processes in the Melt
Authors: Passaglia Elisa , Coiai Serena , Giordani Guido , Taburoni Elisa , Fambri Luca , Pagani Valerio , Penco Maurizio 
Published: August 2004

AbstractSummary: The possibility to submit a semi‐crystalline polyolefin (or a mixture of different polyolefins) to a phase selective crosslinking process, in order to produce a material with unchanged crystallinity but a partially crosslinked amorphous fraction, has been investigated. The crosslinking process has been performed in the melt in the presence of radical initiators. Three different polymer systems have been considered: a LLDPE sample (an ethylene‐1‐butene 91/9 w/w copolymer), two EVA samples (ethylene‐vinyl acetate copolymers containing a different amount (10 and 15 wt.‐%) of acetate monomer units), and mixtures of LLDPE with polybutadiene (BR) (90/10 w/w). All the reaction products have been characterized by selective solvent extractions to determine the gel content, by analysis with different spectroscopies (IR and NMR) and by viscosity measurements to evaluate changes of the structure and the molecular weight (MW) of the partially crosslinked samples. Finally DSC and DMTA analyses have been used to correlate the variations of the macromolecule structure to the thermo‐mechanical properties and, in the case of the mixtures, TEM analysis has been carried out to gather information about the morphology.TEM micrograph of the partially crosslinked polyethylene/polybutadiene blend 90/10 (w/w).magnified imageTEM micrograph of the partially crosslinked polyethylene/polybutadiene blend 90/10 (w/w).
Why sad people like shoes better: The influence of mood on the evaluative conditioning of consumer attitudes
Authors: Walther Eva , Grigoriadis Sofia 
Published: August 2004

AbstractAn experimental study investigated the influence of mood on the acquisition of affective consumer attitudes. Within an evaluative conditioning paradigm, participants in happy or sad mood were presented with evaluatively neutral products paired with affectively liked or disliked faces. Subsequent likability ratings revealed that the mere co‐occurrence of a product with the valenced face influenced the evaluation of the previously neutral targets. However, this effect of affective learning was significantly stronger in the sad‐mood condition. A subsequent awareness test indicated that contingency awareness plays a role in the acquisition of consumer attitudes. The implications for consumer research and attitude formation processes are discussed. © 2004 Wiley Periodicals, Inc.
Customer perceived value, satisfaction, and loyalty: The role of switching costs
Authors: Yang Zhilin , Peterson Robin T. 
Published: August 2004

AbstractIt is a marketplace reality that marketing managers sometimes inflict switching costs on their customers, to inhibit them from defecting to new suppliers. In a competitive setting, such as the Internet market, where competition may be only one click away, has the potential of switching costs as an exit barrier and a binding ingredient of customer loyalty become altered? To address that issue, this article examines the moderating effects of switching costs on customer loyalty through both satisfaction and perceived‐value measures. The results, evoked from a Web‐based survey of online service users, indicate that companies that strive for customer loyalty should focus primarily on satisfaction and perceived value. The moderating effects of switching costs on the association of customer loyalty and customer satisfaction and perceived value are significant only when the level of customer satisfaction or perceived value is above average. In light of the major findings, the article sets forth strategic implications for customer loyalty in the setting of electronic commerce. © 2004 Wiley Periodicals, Inc.
Caving, role playing, and staying home: Shopper coping strategies in a negotiated pricing environment
Authors: Trocchia Philip J. 
Published: August 2004

AbstractThis interpretive study reveals specific behaviors that shoppers enact in order to cope with the tensions they experience in an environment where negotiated pricing is the expected norm. Consumers experience inner conflict, or tension, when they feel that a pleasant shopping experience may only be attained at the risk of a poor financial outcome. These tensions, derived from 34 depth interviews with auto shoppers, include “truth versus deception,” “self‐presentation versus testing the limits,” and “reciprocation versus looking out for number one.” Some coping strategies emanating from these tensions include using analogies, role playing, and bringing one's own audience. Implications for academicians and retailers are discussed. © 2004 Wiley Periodicals, Inc.
Flow experiences and image making: An online chat‐room ethnography
Authors: Shoham Aviv 
Published: August 2004

AbstractChat rooms are a relatively new phenomenon. They provide a unique experiential locale, much like a community. They have become a popular replacement for oft‐diminishing communities of yore. Qualitatively building on three overarching themes, chat rooms are put at the nexus of three diverse theoretical themes: community, flow experiences, and image management—the latter two being explored in this article. Chat rooms provide flow‐like experiences to participants and allow chatters to manage and enhance their images. Given that chatters are highly involved and frequent visitors to their online community (specific chat rooms), they provide a unique opportunity to study this relatively new phenomenon, which has far‐reaching, multidisciplinary implications. © 2004 Wiley Periodicals, Inc.
Synthesis of Polymeric Topological Isomers through Electrostatic Self‐Assembly and Covalent Fixation with Star Telechelic Precursors
Authors: Tezuka Yasuyuki , Tsuchitani Akiko , Oike Hideaki 
Published: August 2004

AbstractSummary: A pair of macromolecular constitutional isomers having topologically distinctive, dicyclic constructions, that is, θ‐shaped and manacle‐shaped polymers, has been synthesized from a polymer self‐assembly, comprised of three‐armed star poly(tetrahydrofuran) [poly(THF)] having N‐phenylpyrrolidinium salt end groups carrying dicarboxylate counteranions (1S/2d). The presence of the two constitutional polymeric isomers was confirmed by means of a reversed‐phase liquid chromatography (RPC) technique. Moreover, size exclusion chromatography (SEC) showed that a major component possesses notably larger hydrodynamic volume than the others, and is assignable as a manacle‐shaped isomer while a minor component is assigned as a θ‐shaped isomer. The statistics of the covalent‐linking process of 1S/2d were consistent with the other experimental results.An “electrostatic self‐assembly and covalent fixation” process of a trifunctional star‐shaped precursor gives rise to θ‐shaped and manacle‐shaped polymers.imageAn “electrostatic self‐assembly and covalent fixation” process of a trifunctional star‐shaped precursor gives rise to θ‐shaped and manacle‐shaped polymers.
New Challenges in Combinatorial Polymer Research: 3rd DPI Workshop on Automated Synthesis and High‐Throughput Experimentation in Polymer and Materials Research at the Eindhoven University of Technology
Authors: Wiesbrock F. , Schubert U. S. 
Published: August 2004

AbstractConference Reports: This section contains reports on topical conferences. Reports are usually written at the request of the editorial office, but unsolicited contributions are also welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de.
Segregation of Coronal Chains in Micelles Formed by Supramolecular Interactions
Authors: Gohy Jean‐François , Khousakoun Eric , Willet Nicolas , Varshney Sunil K. , Jérôme Robert 
Published: August 2004

AbstractSummary: Spherical micelles have been formed by mixing, in DMF, a poly(styrene)‐block‐poly(2‐vinylpyridine)‐block‐poly(ethylene oxide) (PS‐block‐P2VP‐block‐PEO) triblock copolymer with either poly(acrylic acid) (PAA) or a tapered triblock copolymer consisting of a PAA central block and PEO macromonomer‐based outer blocks. Noncovalent interactions between PAA and P2VP result in the micellar core while the outer corona contains both PS and PEO chains. Segregation of the coronal chains is observed when the tapered copolymer is used.Inclusion of comb‐like chains with short PEO teeth in the corona triggers the nanophase segregation of PS and PEO as illustrated here (PS = polystyrene; PEO = poly(ethylene oxide)).imageInclusion of comb‐like chains with short PEO teeth in the corona triggers the nanophase segregation of PS and PEO as illustrated here (PS = polystyrene; PEO = poly(ethylene oxide)).
Predictions of Some Internal Microstructural Models for Polymer Melts and Solutions in Shear and Elongational Flows
Authors: Eslami Hassan , Ramazani S. A. Ahmad , Khonakdar Hossein Ali 
Published: August 2004

AbstractSummary: In this work, the behavior of some internal microstructural models with different mobility tensors has been studied for polymer melts and solutions under steady and transient simple shear and elongational flows. The time evolution equations for conformation and stress tensors in the models reviewed have their root in the Generalized Poisson bracket formalism. Two different families of conformational models have been selected for this study. The first family is based on the Modified Finitely Extensible Nonlinear Elastic (FENE‐P) energy while the second uses a Volume Preserving Conformational Rheological (VPCR) model based on the Hookean Helmholtz free energy function. Several expressions for the mobility tensor based on the previously mentioned energy functions are used to obtain the models. The sensitivity of both families of models to the choice of the mobility tensors on the prediction of material functions in the transient and steady flows is discussed. Also, effects of shear rate on the material functions in start‐up and relaxation shear flows for both models are studied. The predictions of both models are compared with experimental data taken from the literature for some polymer melts. These results show that the family of VPCR models is able to predict the steady shear and elongational flow material functions in an extended range of deformation rates whereas the family of FENE‐P models can predict the behavior of only some specified polymer melts.Experimental data and VPCR model predictions for steady and elongational viscosity for PS [data of H. Munstedt, 1980].imageExperimental data and VPCR model predictions for steady and elongational viscosity for PS [data of H. Munstedt, 1980].
Local solutions to a model of piezoelectric materials
Authors: Hamdache Kamel , Hamroun Djamila 
Published: August 2004

AbstractA local existence theorem is proved for a non‐linear coupled system modelling the electromechanical motion of a one‐dimensional piezoelectric body with domain switching. The system is composed by a heat equation describing the behaviour of the number of electric dipoles and by a wave equation governing the dynamic of the electric displacement. The main coupling in the system appears in the time‐dependent velocity of the waves depending on the number of electric dipoles. The proof of the result relies on a time decay estimate satisfied by the number of electric dipoles and an uniform estimate of the solution of the regularized wave equation. Copyright © 2004 John Wiley & Sons, Ltd.
The pig caecum model: A suitable tool to study the intestinal metabolism of flavonoids
Authors: Labib Samira , Erb Annette , Kraus Michael , Wickert Thomas , Richling Elke 
Published: August 2004

AbstractPig caecum was used under anaerobic conditions to metabolize flavonoids from several classes, i. e., chrysin 1, naringenin 2, quercetin 3, and hesperetin 4. Whereas chrysin 1 was not converted by the pig intestinal flora under the experimental conditions used, naringenin 2 was transformed to 3‐(4‐hydroxyphenyl)‐propionic acid and 3‐phenylpropionic acid. Quercetin 3 was metabolized to phloroglucinol, 3,4‐dihydroxyphenylacetic acid, and 3,4‐dihydroxytoluene. Hesperetin 4 was degraded via eriodictyol to 3‐(3‐hydroxyphenyl)‐propionic acid and phloroglucinol. Structural elucidation of the formed metabolites was performed by high‐performance liquid chromatography – diode array detection (HPLC–DAD) as well as HPLC‐electrospray ionization – mass spectrometry (ESI‐MS (MS)) and high resolution gas chromatography‐mass spectrometry (HRGC‐MS) analyses. The time course of microbial conversion of 2–4 was determined by HPLC‐DAD analysis, revealing slow degradation of 2 and rapid transformation of 3 and 4. The results lead to the conclusion that the pig caecum model is a suitable ex vivo model for studying the intestinal degradation of flavonoids.
Sensitive in vitro test systems to determine androgenic/antiandrogenic activity
Authors: Guth Sabine E. , Böhm Sonja , Mußler Bernd H. , Eisenbrand Gerhard 
Published: August 2004

AbstractWe report on the establishment of one transgenic and two endogenous reporter gene assays to determine androgenic/antiandrogenic activity. A transient transactivation assay was developed in COS‐7 African green monkey kidney cells. Three plasmids were co‐transfected by electroporation: the human androgen receptor expression vector pSG5AR, the reporter gene vector pMamneoLuc, expressing luciferase under the control of the mouse mammary tumor virus (MMTV) promotor containing 4 hormone responsive elements (HREs), and the control plasmid pSVβ . Transcriptional activation was measured by luciferase‐mediated chemoluminescence. In T47D human breast cancer cells two endogenous reporter gene systems were established: one based on the androgen‐induced expression of prostate‐specific antigen (PSA), the other based on the androgen‐repressed expression of testosterone repressed message 2 (TRPM‐2). PSA protein was measured by enzyme‐linked immunosorbent assay (ELISA), TRPM‐2 m‐RNA by reverse transcriptase polymerase chain reaction (RT‐PCR). All three test systems were validated using the physiological androgen dihydrotestosterone (DHT) as agonist and the established antiandrogens hydroxyflutamide and p,p′‐dichlorodiphenylethene (p,p′‐DDE) as antagonists. The PSA assay was the most sensitive test system with an EC50 of 0.7 nM for DHT‐induced response. The transient transactivation assay in COS‐7 cells was less sensitive with an EC50 of 9.7 nM DHT. In the PSA assay hydroxyflutamide was a more potent antagonist (IC30 = 0.02 μM) than p,p′‐DDE (IC30 = 0.9 μM). Similar results were obtained in the TRPM‐2 assay. In the transient transactivation assay in COS‐7 cells, both compounds elicited about 30% of the agonistic response induced by 100 nM DHT, thus showing partial agonistic properties. In summary, three highly sensitive and complementary in vitro test systems, together achieving enhanced specificity for detection and assessment of androgenic/antiandrogenic activity have been established and validated.
Heterocyclic amines in some Swedish cooked foods industrially prepared or from fast food outlets and restaurants
Authors: Borgen Eva , Skog Kerstin 
Published: August 2004

AbstractAccurate assessment of human intake of mutagenic/carcinogenic heterocyclic amines (HAs) is necessary for epidemiological studies and future risk assessment. Using questionnaires, the frequency of consumption of specific dishes can be obtained at an individual level and linked to analyzed concentrations of different compounds in corresponding dishes. Some typical Swedish cooked meat dishes, hamburgers and kebab, industrially prepared or from fast food outlets and restaurants, were analyzed regarding their content of 11 different HAs. The amount of each of these compounds was below 0.1 ng/g cooked weight in most of the industrially prepared products. The total amount of HAs was highest in the kebab samples. The intake of HAs from 200 g of the dishes was estimated to range from not detectable levels to 0.6 μg. The results of the present study indicate that the content of HAs in a specific dish may vary with origin, and that the concentrations of HAs in commercial fried meat products are generally low, although some of these food items may contain elevated amounts.
Levels of mycotoxins and sample cytotoxicity of selected organic and conventional grain‐based products purchased from Finnish and Italian markets
Authors: Jestoi Marika , Somma Maria Carmela , Kouva Merja , Veijalainen Pirjo , Rizzo Aldo , Ritieni Alberto , Peltonen Kimmo 
Published: August 2004

AbstractThe contamination levels of 16 different Fusarium‐ and Aspergillus‐mycotoxins were chemically determined from randomly selected organic and conventional grain‐based products purchased from Finnish and Italian markets. The cytotoxicity of the samples was analyzed with an in vitro test using feline fetal lung cells. Overall, the concentrations of the mycotoxins studied were low in all of the samples. Enniatins B and B1 as well as deoxynivalenol were the most predominant mycotoxins in the samples, being present in 97%, 97%, and 90% of the samples, respectively. The geographical origin or the agricultural practice had no influence on the mycotoxin concentrations of the samples. The babyfoods included in the samples had significantly lower concentrations of mycotoxins than the other products with a mean total mycotoxin content of 47 μg/kg compared with 99 μg/kg for the other kinds of food. All the samples evoked toxicity in the in vitro test, but no correlation between cytotoxicity and the mycotoxin concentrations was observed.
A three‐dimensional computational procedure for reproducing meshless methods and the finite element method
Authors: Schembri Philip , Crane David L. , Reddy J. N. 
Published: August 2004

AbstractA flexible computational procedure for solving 3D linear elastic structural mechanics problems is presented that currently uses three forms of approximation function (natural neighbour, moving least squares—using a new nearest neighbour weight function—and Lagrange polynomial) and three types of integration grids to reproduce the natural element method and the finite element method. The addition of more approximation functions, which is not difficult given the structure of the code, will allow reproduction of other popular meshless methods. Results are presented that demonstrate the ability of the first‐order meshless approximations to capture solutions more accurately than first‐order finite elements. Also, the quality of integration for the three types of integration grids is compared. The concept of a region is introduced, which allows the splitting of a domain into different sections, each with its own type of approximation function and spatial integration scheme. Copyright © 2004 John Wiley & Sons, Ltd.