bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical conductivity and electromagnetic interference shielding effectiveness of polyaniline–ethylene vinyl acetate composites
Authors: Das Narayan Chandra , Yamazaki Shinichi , Hikosaka Masamichi , Chaki Tapan Kumar , Khastgir Dipak , Chakraborty Ajay 
Published: December 2004

AbstractElectrical conductivity and electromagnetic interference (EMI) shielding effectiveness at microwave (200–2000 MHz) and X‐band (8–12 GHz) frequency range of polyaniline (PAni) composites were studied. It has been observed that EMI shielding of conductive polyaniline (PAni)–ethylene vinyl acetate composites increases with the increase in the loading levels of the conductive polymer doped with dodecylbenzene sulfonic acid. The result indicates that the composites having higher PAni loading (>23%) can be used for EMI shielding materials and those with lower PAni loading can be used for the dissipation of electrostatic charge. Copyright © 2004 Society of Chemical Industry
Mechanical properties of esterified tapioca starch–LDPE blends using LDPE‐co‐glycidyl methacrylate as compatibilizer
Authors: Sailaja RRN 
Published: December 2004

AbstractStudies on the mechanical properties of acetylated and phthalated starch blends with low density polyethylene (LDPE) were performed with and without LDPE‐co‐glycidyl methacrylate copolymer as compatibilizer. Impact and tensile properties of the blend specimens were measured following standard ASTM methods. Thermogravimetric analysis of esterified starches and of the blends were also conducted. Scanning electron microscopy was used to analyze the fractured and unfractured blends. Results indicate a significant improvement in the mechanical properties by starch esterification, which is further enhanced by the addition of the compatibilizer. Copyright © 2004 Society of Chemical Industry
Compatibility of reactively compatibilized polyamide 11 (nylon 11)/polyethylene (PE) alloys
Authors: Hu Guosheng , Wang Biaobing , Zhou Xiumiao 
Published: December 2004

AbstractThe compatibility of nylon 11/polyethylene (PE) alloys on addition of reactive maleated ethylene‐propylene‐diene copolymer (EPDM‐graft‐MAH) was investigated by differential scanning calorimetry, morphological observations and rheology. The decrease in the differential volume of the melting temperature of nylon 11 and PE with increasing compatibilizer suggests that the addition of EPDM‐graft‐MAH affects the crystalline behavior of nylon 11 and PE. The decreased particle size of the dispersed phase also confirmed the improvement in the compatibility. The rheological behavior revealed that the addition of the compatibilizer enhanced the apparent viscosity of the melting blends, which resulted from the increasing interaction between the chains due to the improvement in compatibility of nylon 11 and PE. Copyright © 2004 Society of Chemical Industry
Synthesis and properties of novel aromatic poly(ester–amide)s derived from 1,5‐bis(3‐aminobenzoyloxy)naphthalene and aromatic dicarboxylic acids
Authors: Hsiao Sheng‐Huei , Leu Wen‐Tsuen 
Published: December 2004

AbstractA new naphthalene‐ring‐containing bis(ester–amine), 1,5‐bis(3‐aminobenzoyloxy)naphthalene, was prepared from the condensation of 1,5‐dihydroxynaphthalene with 3‐nitrobenzoyl chloride followed by catalytic hydrogenation. A series of novel naphthalene‐containing poly(ester–amide)s was synthesized by direct phosphorylation polyamidation from this bis(ester–amine) with various aromatic dicarboxylic acids. The polymers were produced in high yields and had moderate inherent viscosities of 0.47–0.81 dL g−1. The poly(ester–amide) derived from terephthalic acid was semicrystalline and showed less solubility. Other polymers derived from less rigid and symmetrical diacids were amorphous and readily soluble in most polar organic solvents and could be solution‐cast into transparent, flexible and tough films with good mechanical properties. The amorphous poly(ester–amide)s displayed well‐defined glass transition temperatures of between 179 and 225 °C from differential scanning calorimetry and softening temperatures of between 178 and 211 °C from thermomechanical analysis. These poly(ester–amide)s did not show significant decomposition below 400 °C in nitrogen or air. Copyright © 2004 Society of Chemical Industry
Copolymers of N‐isopropylacrylamide, HEMA‐lactate and acrylic acid with time‐dependent lower critical solution temperature as a bioresorbable carrier
Authors: Lee Bae Hoon , Vernon Brent 
Published: December 2004

AbstractCopolymers of N‐isopropylacrylamide (NIPAAm), 2‐hydroxyethyl methacryl lactate (HEMA‐lactate) and acrylic acid (AAc) were prepared, with varying mole ratios of monomers, to develop a bioresorbable in‐situ‐gelling material with a time‐dependent lower critical solution temperature (LCST). The synthesized copolymers were characterized by nuclear magnetic resonance, gel permeation chromatography and differential scanning calorimetry. In 0.1 M phosphate‐buffered saline solution of pH 7.4, these copolymers had an LCST below body temperature. The LCST decreased as the HEMA‐lactate content of the copolymers was increased. Furthermore, in these conditions, the LCST of the copolymers exhibited time‐dependent properties, due to hydrolysis of the HEMA‐lactate. As the HEMA‐lactate hydrolyzed, the copolymers became more hydrophilic, thereby leading to an increase in LCST. This hydrophilicity caused copolymers of approximately 6 mol% of AAc to exhibit an LCST above body temperature after hydrolysis. In neutral solution, copolymers with varying mol% of AAc saw their LCST rise above 37 °C within one to ten days, depending upon the HEMA‐lactate/NIPAAm ratio, due to the complete hydrolysis of the HEMA‐lactate. The above properties indicate that these copolymers would be useful for drug delivery because their variable LCST makes them bioresorbable. Copyright © 2004 Society of Chemical Industry
Morphology, thermal and mechanical properties of nylon 12/organoclay nanocomposites prepared by melt compounding
Authors: Phang In Yee , Liu Tianxi , Mohamed Ashiq , Pramoda Kumari Pallathadka , Chen Ling , Shen Lu , Chow Shue Yin , He Chaobin , Lu Xuehong , Hu Xiao 
Published: December 2004

AbstractNylon 12 (PA12) nanocomposites with different organoclay loadings were successfully prepared by melt compounding. X‐ray diffraction indicated the dominance of the exfoliated clay morphology throughout the matrix after mixing in a Brabender twin‐screw extruder, in accordance with transmission electron microscopy observations. Thermogravimetric analysis showed that the thermal stability of the PA12 matrix was improved by about 20 °C on incorporation of only 5 wt% clay. Tensile and nanoindentation tests indicated that the elastic modulus and the hardness steadily increased by about 52 % and 67 %, respectively, with a clay concentration up to 5 wt%, while improvements in tensile strength were limited. Impact strength decreased linearly by about 25 % as the clay loading increased (up to 5 wt%), indicating an embrittlement due to clay addition, as evidenced by SEM observation on the fracture surfaces. The embrittling effect may be due to the weak interfacial adhesion between the clay platelets and the polymer matrix. Copyright © 2004 Society of Chemical Industry
Gas barrier properties of poly(ε‐caprolactone)/clay nanocomposites: Influence of the morphology and polymer/clay interactions
Authors: Gain O. , Espuche E. , Pollet E. , Alexandre M. , Dubois Ph. 
Published: December 2004

AbstractPoly(ε‐caprolactone)/montmorillonite nanocomposites were prepared maintaining a constant inorganic content with three means: melt blending of poly(ε‐caprolactone) with natural or organomodified clays, in situ polymerization of ε‐caprolactone in the presence of organomodified clays, and initiation of ε‐caprolactone polymerization from the silicate layer with appropriate organomodified montmorillonites and activator. In this last case, the polymer chains were grafted to the silicate layers and it was possible to tune up the grafting density. The presence of clays did not modify the polymer crystallinity. It was shown that the in situ polymerization process from the clay surface improved the clay dispersion. The gas barrier properties of the different composite systems were discussed both as a function of the clay dispersion and of the matrix/clay interactions. The highest barrier properties were obtained for an exfoliated morphology and the highest grafting density. Similar evolution of the permeability and the diffusion coefficients was observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 205–214, 2005
Effect of cooling rate and plastic deformation under heat treatment on the structure of Sn–5wt% Bi alloy samples
Authors: Khalifa B. A. , Nagy M. R. , Afify R. 
Published: December 2004

AbstractThe effect of plastic deformation on the microstructure of heat treated superplastic alloy samples (Sn–5wt% Bi) prepared at two different rates of cooling 1.77 × 10–3 K/s and 18.4 K/s, named as slowly cooled and quenched in liquid nitrogen samples, have been studied as a function of temperature in the range of 308–388 K. The work hardening parameters for the two alloy samples were found to be dependent on both temperature and cooling rate. These parameters indicate the transition temperature at 328 K. The slowly cooled samples are much harder than those quenched in liquid nitrogen. This is explained by precipitation of Bi‐atoms which segregate to form a non‐coherent cubic α‐phase in the slowly cooled samples. The activation energy for fracture of the Sn–5wt% Bi alloy is divided into three stages with values of 19.2 ± 1.6, 18.7 ± 1.4 and 10.9 ± 0.81 kJ/mol and 15.6 ± 1.9, 14.6 ± 1.8 and 7.9 ± 1.1 kJ/mol for the slowly cooled and quenched alloy samples, respectively. The lattice parameters (a, c), the ratio (c/a) and the residual lattice strains (Δa/a, Δc/c) are found to be dependent on the test temperature and the rate of cooling with either maximum or minimum values at the transition temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of NH+: An ab initio study
Authors: Amero José M. , Vázquez Gabriel J. 
Published: December 2004

AbstractWe report ab initio self‐consistent field MRSD‐CI electronic structure calculations of the NH+ cation. A basis set of DZ + POL quality augmented with Rydberg and bond functions was employed together with an extensive treatment of electron correlation. More than 50 electronic states of NH+ are reported, including doublets, quartets, and sextets. Leading configurations, vertical ionization energies of NH, vertical excitation energies of NH+, and potential energy curves are reported. Spectroscopic properties calculated for the known bound electronic states of NH+ are found in good agreement with experiment. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Comparative study of kinetics and reactivity indices of free radical polymerization reactions
Authors: Van Cauter K. , Hemelsoet K. , Van Speybroeck V. , Reyniers M. F. , Waroquier M. 
Published: December 2004

AbstractDensity functional theory calculations are used to determine the kinetics and reactivity indices of the first propagation steps of the polyethylene and poly(vinyl chloride) polymerization. Transition state theory is applied to evaluate the rate coefficient from the microscopically determined energies and partition functions. A comparison with the experimental Arrhenius plots validates the level of theory. The ability of reactivity indices to predict certain aspects of the studied propagation reactions is tested. Global softnesses of the reactants give an indication of the relative energy barriers of subsequent monomer additions. The correlation between energy and hardness profiles along the reaction path confirm the principle of maximum hardness. Local indices predict the regioselectivity of the attack of the growing radical to vinyl chloride. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Ab initio EPR study of S and Se defects in alkali halides
Authors: Stevens F. , Vrielinck H. , Callens F. , Pauwels E. , Van Speybroeck V. , Waroquier M. 
Published: December 2004

AbstractCalculations using density functional theory are performed to study the electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) properties of S and Se impurities in alkali halide lattices. Cluster in vacuo models are used to describe the defect and the lattice surroundings. The trivacancy defect model proposed in the literature is able to reproduce both the experimental principal values and directions of the g tensor for S and Se defects doped in alkali halides. The alternative monovacancy model gives rise to important discrepancies with experiment and can be discarded. For the KCl lattice, the hyperfine tensors of the S and Se molecular ions also agree well with the available experimental data, giving further evidence to the trivacancy model. In addition, for NaCl:S and KCl:S computational results for the 23Na and 35Cl superhyperfine and quadrupole tensors are compared with experimental ENDOR parameters. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
The analysis of high explosives by liquid chromatography/electrospray ionization mass spectrometry: multiplexed detection of negative ion adducts
Authors: Mathis John A. , McCord Bruce R. 
Published: December 2004

AbstractThe negative ion electrospray ionization mass spectrometric (ESI‐MS) detection of adducts of high explosives with chloride, formate, acetate, and nitrate was used to demonstrate the gas‐phase interaction of neutral explosives with these anions. The relative intensities of the adduct species were determined to compare the competitive formation of the selected high explosives and anions. The relative stability of the adduct species varies, yielding preferential formation of certain anionic adducts with different high explosives. To exploit this effect, an isocratic high‐performance liquid chromatography (HPLC)/ESI‐MS method was developed and used for the simultaneous analysis of high explosives using two different techniques for the addition of the anionic additives; pre‐ and post‐column. The results show that the pre‐column approach provides similar results with improved selectivity for specific explosives. By detecting characteristic adduct species for each explosive, this method provides a qualitative and quantitative approach for the analysis and identification of high explosives. Copyright © 2004 John Wiley & Sons, Ltd.
Application of DNA pooling to large studies of disease
Authors: Law Graham R. , Rollinson Sara , Feltbower Richard , Allan James M. , Morgan Gareth J. , Roman Eve 
Published: December 2004

AbstractLarge collections of individuals are required to investigate the association of commonly occurring genetic variation with disease. The laboratory assessment of one form of variation, single nucleotide polymorphisms, is costly in time and DNA. Robust statistical approaches are developed to allow the successful implementation of a recently described laboratory method for rapidly estimating allele frequency using pools of DNA. A substantial reduction in Type I error is demonstrated using simulation, through the incorporation of measurement error into confidence limits for a case–control study, illustrated on a case–control study of acute leukaemia in adults. A method for creating multiple sub‐pools is described which will allow large studies, such as the proposed U.K. Biobank, to take advantage of this method. Furthermore, a set‐based logistic regression is presented which allows the investigation of joint effects and interactions with other genes or environmental factors. Copyright © 2004 John Wiley & Sons, Ltd.
The graft‐versus‐leukaemia effect after allogeneic bone‐marrow transplantation: assessment through competing risks approaches
Authors: Katsahian Sandrine , Porcher Raphaël , Mary Jean‐Yves , Chevret Sylvie 
Published: December 2004

AbstractIn failure time studies involving a chronic disease such as cancer, data often focus on one or more non‐fatal events, in addition to survival, to describe the course of the disease. In the example of allogeneic bone marrow transplantation in leukaemic patients, acute graft‐versus host disease (aGvHD), relapse and death were taken as the reported events, and we focused on testing the existence of graft‐versus‐leukaemia (GvL) effect, i.e. that the occurrence of aGvHD modifies the probability of relapse. One of the weaknesses of the standard competing risks models is their inability to model secondary relapses. We thus derived, from two competing risks models, two estimators of cumulative incidence functions of primary and secondary relapses, as well as statistics to test the GvL effect. The approach is illustrated by application to a data set from a cohort of 442 children with acute leukaemia who received an unrelated transplant. Copyright © 2004 John Wiley & Sons, Ltd.
A comparison of goodness of fit tests for the logistic GEE model
Authors: Evans Scott , Li Lingling 
Published: December 2004

AbstractGeneralized estimating equations have become a popular regression method for analysing clustered binary data. Methods to assess the goodness of fit of the fitted models have recently been developed. However, evaluations and comparisons of these methods are limited. We discuss these methods and develop two additional statistics to evaluate goodness of fit. We evaluate the performance of each of the statistics with respect to type I error rates and power in a simulation study. Guidance is provided regarding appropriate use of the statistics under various scenarios. Copyright © 2004 John Wiley & Sons, Ltd.
Choice of time‐scale in Cox's model analysis of epidemiologic cohort data: a simulation study
Authors: Thiébaut Anne C. M. , Bénichou Jacques 
Published: December 2004

AbstractCox's regression model is widely used for assessing associations between potential risk factors and disease occurrence in epidemiologic cohort studies. Although age is often a strong determinant of disease risk, authors have frequently used time‐on‐study instead of age as the time‐scale, as for clinical trials. Unless the baseline hazard is an exponential function of age, this approach can yield different estimates of relative hazards than using age as the time‐scale, even when age is adjusted for. We performed a simulation study in order to investigate the existence and magnitude of bias for different degrees of association between age and the covariate of interest. Age to disease onset was generated from exponential, Weibull or piecewise Weibull distributions, and both fixed and time‐dependent dichotomous covariates were considered. We observed no bias upon using age as the time‐scale. Upon using time‐on‐study, we verified the absence of bias for exponentially distributed age to disease onset. For non‐exponential distributions, we found that bias could occur even when the covariate of interest was independent from age. It could be severe in case of substantial association with age, especially with time‐dependent covariates. These findings were illustrated on data from a cohort of 84329 French women followed prospectively for breast cancer occurrence. In view of our results, we strongly recommend not using time‐on‐study as the time‐scale for analysing epidemiologic cohort data. Copyright © 2004 John Wiley & Sons, Ltd.
Construct validity of the Maslach Burnout Inventory‐General Survey
Authors: Kitaoka‐Higashiguchi Kazuyo , Nakagawa Hideaki , Morikawa Yuko , Ishizaki Masao , Miura Katsuyuki , Naruse Yuchi , Kido Teruhiko , Higashiyama Masako 
Published: December 2004

AbstractThe construct validity of the Maslach Burnout Inventory (MBI) has been a major point of focus for many studies. The validity of the MBI‐General Survey (MBI‐GS), a newly developed instrument intended for use outside the human services has not been sufficiently investigated. The aim of this present study is to investigate the validity of the MBI‐GS. The Japanese language version of the MBI‐GS was prepared for this research and it was administered to a sample of intermediate managers (n = 696) working for a manufacturing company in Japan. The total of 691 effective data were obtained. The exploratory factor analysis replicated the same three‐factor structure (Exhaustion, Cynicism, and Professional Efficacy) as the original whereas inter‐factor correlation between Exhaustion and Cynicism was moderate. Cronbach's alpha coefficients for all three subscales were above 0.80. The confirmatory factor analysis supported a three‐factor model whereas Exhaustion and Cynicism were moderately related. To investigate the construct validity, three subscales of the MBI‐GS were then related to selected work characteristics. Based on conservation of resources theory, differential patterns of effects were predicted among the correlates and the burnout subscales. A path analysis revealed that the expectations were largely supported, suggesting that the meaning of the three subscales is quite different with a path from Exhaustion to Cynicism. The study found support for the construct validity of the MBI‐GS. Copyright © 2004 John Wiley & Sons, Ltd.
Plastic changes of leaf mass per area and leaf nitrogen content in response to canopy openings in saplings of eight deciduous broad‐leaved tree species
Authors: Takahashi Koichi , Seino Tatsuyuki , Kohyama Takashi 
Published: December 2004

AbstractLeaf nitrogen content per area (Narea) is a good indicator of assimilative capacity of leaves of deciduous broad‐leaved trees. This study examined the degrees of increase in Narea in response to canopy openings as leaf mass per area (LMA) and leaf nitrogen content per mass (Nmass) in saplings of eight deciduous broad‐leaved tree species in Hokkaido, northern Japan. Five of the species were well‐branched species with a large number of small leaves (lateral‐growth type), and the other three species were less‐branched species with a small number of large leaves (vertical‐growth type). The degrees of increase in Narea were compared between the two crown types. In closed‐canopy conditions, leaves of the vertical‐growth species tended to have a lower LMA and higher Nmass than those of the lateral‐growth species, which resulted in similar Narea for both. LMA increased in canopy openings in the eight species, and the degrees of increase were not largely different between the lateral‐ and vertical‐growth species. On the contrary, Nmass was unchanged in canopy openings in the eight species. As a result, Narea of each species increased in canopy openings in proportion to the increase in LMA, and the degrees of increase in Narea were similar in the lateral‐ and vertical‐growth species. Therefore, this study showed that the degrees of increase in Narea were not correlated with the crown architecture (i.e., the lateral‐ and vertical‐growth types).
Spatio‐temporal variation of colony structure and eusociality level of the Japanese sweat bee Lasioglossum (Evylaeus) duplex (Hymenoptera: Halictidae)
Authors: Hirata Masanori , Cronin Adam L. , Kidokoro Midori , Azuma Noriko 
Published: December 2004

AbstractColony structure and eusociality level of the sweat bee Lasioglossum (Evylaeus) duplex were studied in 2001 in Sapporo and Assabu, Hokkaido, northern Japan. Sakagami and his colleagues had also studied this species in Sapporo in 1957–1968. Brood size, sex ratio and queen–worker size dimorphism were geographically and temporally variable, indicating spatio‐temporal variation at the eusociality level. Inseminated workers constituted only 7.9% of the populations in 1957–1968 Sapporo but about 60% in 2001 in Sapporo and Assabu. A few of the inseminated workers were believed to leave natal nests for independent colony founding. Thus, partial bivoltinism is likely in this sweat bee species. The presence of workers with developed ovaries and/or corpora lutea suggests the occurrence of worker oviposition.