bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid and controlled deswelling of porous poly(N‐isopropylacrylamide) hydrogels prepared by the templating of interpenetrated nanoporous silica particles
Authors: Serizawa Takeshi , Uemura Masami , Kaneko Tatsuo , Akashi Mitsuru 
Published: October 2002

AbstractFree radical polymerization of N‐isopropylacrylamide (NIPAAm) and crosslinker solutions, which were fulfilled in silica particles with an interpenetrated and nanometer‐sized porous structure (a diameter of 3 mm and mean pore sizes of 15, 30, and 50 nm), fabricated hybrids of organic hydrogels and inorganic silica. Differential scanning calorimetric analyses of the hybrids revealed that silica components affected the thermoresponsive properties of polyNIPAAm hydrogels. Porous polyNIPAAm hydrogels were prepared by the subsequent acid treatment of the hybrids to remove silica. Transmission Fourier transformed infrared spectra indicated the selective extraction of silica. Scanning electron microscopic observation of the hydrogels confirmed the porous structure. The deswelling rate of porous hydrogels was 7 times larger than that of conventional hydrogels and increased with increasing the pore size of silica used. However, the swelling was not affected by the pore formation. The thermoresponsiveness of porous polyNIPAAm hydrogels could be regulated by the pore size. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3542–3547, 2002
Poly(aryl ether ketone)s with (3‐methyl)phenyl and (3‐trifluoromethyl)phenyl side groups
Authors: Liu Baijun , Wang Guibin , Hu Wei , Jin Yuhui , Chen Chunhai , Jiang Zhenhua , Zhang Wanjin , Wu Zhongwen , Wei Yen 
Published: October 2002

AbstractNew bisphenol monomers, (3‐methyl)phenylhydroquinone and (3‐trifluoromethyl)phenylhydroquinone, were prepared in a two‐step synthesis. A series of poly(aryl ether ketone)s were derived from these bisphenols via a nucleophilic aromatic substitution polycondensation with various bisfluoro compounds. The polycondensation proceeded quantitatively in tetramethylene sulfone in the presence of anhydrous potassium carbonate and afforded the polymers with inherent viscosities of 0.63–0.91 dL/g. The fluorinated polymers showed lower glass‐transition temperatures and higher thermal‐decomposition temperatures than the corresponding nonfluorinated polymers. The solubility of the polymers was improved by the introduction of bulky pendant groups. All the polymers formed transparent, strong, and flexible films, with tensile strengths of 86.4–102.0 MPa, Young's moduli of 2.28–3.03 GPa, and elongations at break of 14–42%. All the polymers had low dielectric constants of 2.70–2.83 at 1 MHz. Compared with the methylated polymers, the trifluoromethylated polymers exhibited lower water sorption, which was attributed to the stronger hydrophobicity of the fluorine‐containing groups. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3392–3398, 2002
Bimodal molecular weight distribution formed in the emulsion polymerization of ethylene
Authors: Tobita Hidetaka 
Published: October 2002

AbstractIt is known that the molecular weight distribution (MWD) formed in an emulsion polymerization of ethylene can be bimodal. However, the origin of the bimodality has not been elucidated. In this article, a Monte Carlo simulation is conducted, mostly with parameters reported in the literature. The simulated MWDs are bimodal because of the limited volume effect; that is, the high molecular weight profiles are distorted by the small particle size, which is comparable to the size of the largest branched polymer molecule in a particle. The simulated MWDs agree reasonably well with the experimentally obtained MWDs. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3426–3433, 2002
Synthesis of comb‐shaped poly(methyl methacrylate)‐b‐poly(polytetrahydrofuran acrylate) under 60Co γ‐ray irradiation
Authors: He Tao , Zou Ying‐Fang , Pan Cai‐Yuan 
Published: October 2002

AbstractComb‐shaped graft copolymers with poly(methyl methacrylate) as a handle were synthesized by the macromonomer technique in two steps. First, polytetrahydrofuran acrylate (A‐PTHF), prepared by the living cationic ring‐opening polymerization of tetrahydrofuran, underwent homopolymerization with 1‐(ethoxycarbonyl)prop‐1‐yl dithiobenzoate as an initiator under 60Co γ irradiation at room temperature; Second, the handle of the comb‐shaped copolymers was prepared by the block copolymerization of methyl methacrylate with P(A‐PTHF) as a macroinitiator under 60Co γ irradiation. The two‐step polymerizations were proved to be controlled with the following evidence: the straight line of ln[M]0/[M] versus the polymerization time, the linear increase in the number‐average molecular weight with the conversion, and the relatively narrow molecular weight distribution. The structures of the P(A‐PTHF) and final comb‐shaped copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3367–3378, 2002
Synthesis and characterization of soluble copoly(ether ketone)s containing double bonds
Authors: Gao Yan , Jian Xigao , Xuan Yingnan , Xiang Sheng , Liang Ping , Guiver Michael D. 
Published: October 2002

AbstractA series of copoly(ether ketone)s containing double bonds along the polymer chains were synthesized from the condensation polymerization of hydroquinone with 4,4′‐difluorobenzophenone and 4,5‐bis(4‐fluorobenzoyl)‐1‐methylcyclohexene in sulfolane containing anhydrous potassium carbonate. The presence of methylcyclohexene in the polymer chains resulted in an improvement in the solubility of poly(ether ketone)s in organic solvents such as chloroform, chlorobenzene, and sulfolane. As a result, the conditions for synthesizing these polymers were much milder than those for poly(ether ether ketone). The new copoly(ether ketone)s also showed good tensile properties and reasonable thermal stability. New polyethers containing pyrazine unites were obtained from the cyclization reaction of these copoly(ether ketone)s with hydrazine. The hydrazine cycloderivatives led to an increase in the glass‐transition temperatures and a decrease in solubility in organic solvents. © 2002 Government of Canada. Exclusive world‐wide publication rights in the article have been transferred to Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3449–3454, 2002
Reactions and structural changes during thermal annealing in a semicrystalline, aromatic diacetylene‐containing polyester
Authors: Hu Xiao , Li Xiqiang 
Published: October 2002

AbstractThermally induced solid‐state reactions and microstructure changes in a high molar mass, semicrystalline, aromatic diacetylene‐containing polyester, poly[2,4‐hexadiyn‐1,6‐ylene terephthalate], were investigated with a combination of laser Raman spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction analysis. The study has provided some new insights into the rather complex solid‐state reactions in the semicrystalline diacetylene‐containing polyester. Results suggest that, in addition to the usual desired solid‐state topochemical crosspolymerization in the crystalline region, a certain degree of random crosslinking reaction occurs in the amorphous region, especially when the annealing is carried out above the glass transition. After prolonged annealing or annealing at a higher temperature, a further reaction involving the formed polydiacetylene chains may occur, as evident from the reduction in crystallinity and even complete loss of crystallinity. An attempt has been made to separate the contribution of the topochemical reaction from the overlapping exothermic activities in the differential scanning calorimetry curves via subtraction. This allows the monitoring of the crystalline‐phase solid‐state topochemical crosspolymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2354–2363, 2002
Molecular motions and conformational changes of HPPK
Authors: Keskin O. , Ji X. , Blaszcyk J. , Covell D.G. 
Published: October 2002

Abstract6‐Hydroxymethyl‐7,8‐dihydropterin pyrophosphokinase (HPPK) belongs to a class of catalytic enzymes involved in phosphoryl transfer and is a new target for the development of novel antimicrobial agents. In the present study, the fundamental consideration is to view the overall structure of HPPK as a network of interacting residues and to extract the most cooperative collective motions that define its global dynamics. A coarse‐grained model, harmonically constrained according to HPPK's crystal structure is used. Four crystal structures of HPPK (one apo and three holo forms with different nucleotide and pterin analogs) are studied with the goal of providing insights about the function‐dynamic correlation and ligand induced conformational changes. The dynamic differences are examined between HPPK's apo‐ and holo‐forms, because they are involved in the catalytic reaction steps. Our results indicate that the palm‐like structure of HPPK is nearly rigid, whereas the two flexible loops: L2 (residues 43–53) and L3 (residues 82–92) exhibit the most concerted motions for ligand recognition and presumably, catalysis. These two flexible loops are involved in the recognition of HPPKs nucleotide and pterin ligands, whereas the rigid palm region is associated with binding of these cognate ligands. Six domains of collective motions are identified, comprised of structurally close but not necessarily sequential residues. Two of these domains correspond to the flexible loops (L2 and L3), whereas the remaining domains correspond to the rigid part of the molecule. Proteins 2002;49:191–205. Published 2002 Wiley‐Liss, Inc.
Evaluating CASP4 predictions with physical energy functions
Authors: Feig Michael , Brooks Charles L. 
Published: October 2002

AbstractPhysical energy scoring functions based on implicit solvation models are tested by evaluating predictions from the most recent CASP4 competition. The best performing scoring functions are identified along with the best protocol for preparing structures before energies are evaluated. Ranking of structures with the best scoring functions is compared across CASP4 targets to establish when physical scoring functions can be expected to reliably distinguish structures that are most similar to the native fold in a set of misfolded or unfolded protein conformations. The results are used to interpret previous studies where scoring functions were tested on the standard decoy sets by Park, Levitt, and Baker. We show that the best physical scoring functions can be applied successfully in automated consensus scoring applications where a single best conformation has to be selected from a set of structures from different sources. Finally, the potential for better protein structure scoring functions is discussed with a suggestion for an empirically parameterized linear combination of energy components. Proteins 2002;49:232–245. © 2002 Wiley‐Liss, Inc.
Susceptibility of field‐collected populations of the Southwestern corn borer, Diatraea grandiosella, to Bacillus thuringiensis
Authors: Trisyono Y Andi , Chippendale G Michael 
Published: October 2002

AbstractThe susceptibility of newly hatched larvae of laboratory‐adapted and field‐collected populations of the Southwestern corn borer, Diatraea grandiosella (Dyar) (Lepidoptera: Crambidae), to a Bacillus thuringiensis protein (Cry1Ab) was examined using a larval feeding bioassay. D grandiosella populations were collected from five states: Missouri, Kansas, Texas, Tennessee and Kentucky. Using larval mortality as the end‐point of the bioassay, the magnitude of differences in the susceptibility of the laboratory‐adapted and the field‐collected populations to Cry1Ab protein varied from one to 46 times depending on the time of observation and the standard of comparison (LC50 or LC95). However, significant differences in susceptibility to Cry1Ab protein among these populations were not detected when the comparisons were based on growth inhibition (EC50 or EC95); the magnitude of differences was less than fourfold. Either using larval mortality or larval growth inhibition, the results indicated that the field‐collected populations of D grandiosella were susceptible to Cry1Ac, and differences in susceptibility may reflect natural variation among populations. The bioassay using larval growth inhibition offers advantages over that using larval mortality, including giving more accurate representation of the toxicological effects of the toxin.© 2002 Society of Chemical Industry
Experimental and numerical study of sorption/diffusion of esters into polypropylene packaging films
Authors: Safa Laurent , Abbes Boussad 
Published: October 2002

AbstractThe sorption and diffusion of four esters into polypropylene packaging films immersed in four different solutions have been studied by the FTIR method at 45°C. Kinetic curves have been generated for these systems to compute diffusion coefficients. The calculated results are discussed in terms of size and shape of diffusing molecules into a polymer film. Isovalues and profiles of liquid concentrations have been calculated by solving Fick's diffusion equation using a numerical method based on a two‐dimensional finite element method. Copyright © 2002 John Wiley & Sons, Ltd.
Statistical modelling of predicted non‐stationary vehicle vibrations
Authors: Rouillard V. , Sek M. A. 
Published: October 2002

AbstractThis paper describes a method to predict the vertical vibrations of road vehicles from measured pavement profiles. It discusses the limitations of current methods used for analysing and simulating vehicle vibrations and shows that more accurate characterization and simulation of the transport environment must take into account the non‐stationary nature of road vehicle vibrations. Vertical vibrations for typical transport vehicles under various operating conditions and pavement profiles are predicted using a computer model of the vehicle characteristics and analysed to produce the spectral and statistical characteristics. The paper also presents an improved method to compute the vibration intensity by using a dynamic segmentation data reduction technique. The effectiveness of the procedure to characterize the non‐stationarity of random vehicle vibrations is demonstrated. Finally, the paper deals with the statistical distribution of the vibration intensity and demonstrates how it can be adapted to a technique for the simulation the non‐stationary nature of random vehicle vibrations. Copyright © 2002 John Wiley & Sons, Ltd.
Mechanistic investigation of the interaction between bisquaternary antimicrobial agents and phospholipids by liquid secondary ion mass spectrometry and differential scanning calorimetry
Authors: Pashynskaya V. A. , Kosevich M. V. , Gömöry A. , Vashchenko O. V. , Lisetski L. N. 
Published: October 2002

AbstractMechanisms of interaction between the antimicrobial drugs decamethoxinum and aethonium, which are based on bisquaternary ammonium compounds, and a phospholipid component of biological membranes, dipalmitoylphosphatidylcholine, were studied by means of liquid secondary ion mass spectrometry (LSIMS) and differential scanning calorimetry (DSC). Supramolecular complexes of the drugs with this phospholipid were recorded under secondary ion mass spectrometric conditions. The dependence of the structures of these complexes on structural parameters of the dications of the bisquaternary ammonium compounds was demonstrated. Tandem mass spectrometric investigations of the metastable decay of doubly charged ions of decamethoxinum and aethonium complexes with dipalmitoylphosphatidylcholine allowed estimation of structural parameters of these complexes in the gas phase. Interactions of decamethoxinum and aethonium with model membrane assemblies built from hydrated dipalmitoylphosphatidylcholine were studied using DSC. It was shown that while both drugs can interact with model membranes, the mechanisms of such interactions for decamethoxinum and aethonium differ. The correlation between the nature of these interactions and structural and electronic parameters of the dications of the two bisquaternary agents is discussed. Interpretation of combined mass spectrometric and calorimetric experimental data led to proposals that the molecular mechanisms of antimicrobial action of bisquaternary ammonium compounds are related to their effect on the membrane phospholipid components of microbial cells. Copyright © 2002 John Wiley & Sons, Ltd.
Goodness‐of‐fit processes for logistic regression: simulation results
Authors: Hosmer David W. , Hjort Nils Lid 
Published: October 2002

AbstractIn this paper we use simulations to compare the performance of new goodness‐of‐fit tests based on weighted statistical processes to three currently available tests: the Hosmer–Lemeshow decile‐of‐risk test; the Pearson chi‐square, and the unweighted sum‐of‐squares tests. The simulations demonstrate that all tests have the correct size. The power for all tests to detect lack‐of‐fit due to an omitted quadratic term with a sample of size 100 is close to or exceeds 50 per cent to detect moderate departures from linearity and is over 90 per cent for these same alternatives for sample size 500. All tests have low power with sample size 100 to detect lack‐of‐fit due to an omitted interaction between a dichotomous and continuous covariate, while the power exceeds 80 per cent to detect extreme interaction with a sample size of 500. The power is low to detect any alternative link function with sample size 100 and for most alternative links for sample size 500. Only in the case of sample size 500 and an extremely asymmetric link function is the power over 80 per cent. The results from these simulations show that no single test, new or current, performs best in detecting lack‐of‐fit due to an omitted covariate or incorrect link function. However, one of the new weighted tests has power comparable to other tests in all settings simulated and had the highest power in the difficult case of an omitted interaction term. We illustrate the tests within the context of a model for factors associated with abstinence from drug use in a randomized trial of residential treatment programmes. We conclude the paper with a summary and specific recommendations for practice. Copyright © 2002 John Wiley & Sons, Ltd.
Value creation through enriched marketing–operations interfaces: an empirical study in the printed circuit board industry
Authors: Sawhney Rajeev , Piper Chris 
Published: October 2002

AbstractThe paper examines the short‐term capacity interface between marketing and operations, i.e. marketing–operations interface (MOI) in relation to customer value. A field study involving 10 firms in the printed circuit board (PCB) manufacturing industry was used to develop a conceptual framework and measures of the constructs. Subsequently, a 180‐plant PCB industry survey was used to test the model, finding support for the proposed relationship between MOI effectiveness and customer value.
On the support of solutions to the generalized KdV equation
Authors: Vega Luis , Kenig Carlos E. , Ponce Gustavo 
Published: October 2002

It is shown that if

u

is a solution of the initial value problem for the generalized Korteweg–de Vries equation such that there exists

b \in ℝ

with

\text{supp}u\left(.,t_{j}\right) \subseteq \left(b,\infty \right)

(or

(−∞,b)

), for

j*=1,2

(

t_1≠t_2), then

u≡0$.

Résumé

On montre que si

u

est une solution du problème de Cauchy pour l'équation généralise de Korteweg–de Vries et

b \in ℝ

tel que

\text{supp}u\left(.,t_{j}\right) \subseteq \left(b,\infty \right)

(ou

(−∞,b)

), pour

j=1,2

(

t_1≠t_2

), alors

u

est nulle.
A functional analysis approach to Arnold diffusion
Authors: Berti Massimiliano , Bolle Philippe 
Published: October 2002

We discuss in the context of nearly integrable Hamiltonian systems a functional analysis approach to the “splitting of separatrices” and to the “shadowing problem”. As an application we apply our method to the problem of Arnold Diffusion for nearly integrable partially isochronous systems improving known results.

Résumé
Nous discutons dans le contexte des systèmes hamiltoniens presque intégrables une approche basée sur l'analyse fonctionnelle des problèmes de “splitting” des séparatrices et de “shadowing”. Nous appliquons notre méthode au problème de la diffusion d'Arnold pour des systèmes presque intégrables partiellement isochrones, améliorant des résultats connus.
Correctors and error estimates in the homogenization of a Mullins–Sekerka problem
Authors: Garroni Adriana , Niethammer Barbara 
Published: October 2002

We study the homogenization of a Mullins–Sekerka free boundary problem which serves as a model for coarsening of nuclei in a first order phase transformation. We consider a regime where the volume fraction of the nuclei is small but screening effects are not negligible. The limit equation was recently derived in [12]. We improve this convergence result by constructing correctors and providing error estimates in terms of the volume fraction. This yields in particular an asymptotic expansion for the growth rate of the nuclei.

Résumé
On étudie l'homogénéisation d'un problème de frontiere libre de Mullins–Sekerka, qui sert de modèle pour le “coarsening” des noyaux dans une transformation de phase du premièr ordre. On considére un régime où la fraction de volume des noyaux est petite mais où les effets de criblage ne sont pas négligeables. L'équation limite a récemment été dérivée dans [12]. Nous améliorons ce résultat de convergence en construisant des correcteurs et fournissant des evaluations d'erreur en termes de la fraction de volume. Ceci conduit en particulier á une expansion asymptotique pour le taux de croissance des noyaux.
5-HT2A gene promoter polymorphism as a modifying rather than a vulnerability factor in anorexia nervosa
Authors: Kipman A. , Bruins-Slot L. , Boni C. , Hanoun N. , Adès J. , Blot P. , Hamon M. , Mouren-Siméoni M.-C. , Gorwood P. 
Published: October 2002

SummaryThe A allele of the 5-HT2A gene (–1438A/G polymorphism) has been associated with anorexia nervosa in four studies, but not in three others. One possibility to explain such a discrepancy is that the A allele acts as a modifying rather than a vulnerability allele. To test this hypothesis, we increased our initial sample of 102 trios [Mol. Psychiatry 7 (2002) 90] with 43 new patients with anorexia nervosa and 98 healthy controls. In addition to confirming the absence of association on the global sample of 145 patients, we found that patients with the A allele had a significantly later age at onset of the disease (P = 0.032). Furthermore, the A allele was also transmitted with an older age at onset (P = 0.023) using a quantitative-trait TDT approach. The A allele may thus act as a modifying factor (delaying onset), potentially explaining variations of allele frequency across samples, in which differences in average age at onset are not only possible, but also expected. Taking into account vulnerability genes, but also genes modifying the expression of the disorder, will help to disentangle the complexity of the etiological factors involved in anorexia nervosa.
Efficacy of lithium treatment in Kleine–Levin syndrome
Authors: Muratori F. , Bertini N. , Masi G. 
Published: October 2002

SummaryThe Kleine–Levin syndrome (KLS) is characterized by periodic, sudden-onset episodes of hypersomnia, compulsive hyperphagia, and behavioral–emotional symptoms, lasting from a few days to a few weeks, with complete remission in the intercritical periods. We report on efficacy of lithium treatment in a highly recurring form of the disorder in a 17-year-old male adolescent. The decreasing severity of the disorder paralleled the progressive increase of lithium dosage, up to 0.9 mEq l–1. Implications regarding the pharmacological treatment of this neglected disorder are discussed.