bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three‐component, negative‐type, alkaline‐developable, thermally stable, and photosensitive polymer based on poly(2,6‐dihydroxy‐1,5‐naphthalene), a crosslinker, and a photoacid generator
Authors: Tsuchiya Kousuke , Shibasaki Yuji , Suzuki Masato , Ueda Mitsuru 
Published: March 2004

AbstractA negative working and chemically amplified photosensitive polymer has been developed, which is based on poly(2,6‐dihydroxy‐1,5‐naphthalene) (PDHN), the crosslinker 4,4′‐methylenebis[2,6‐bis(hydroxymethyl)]phenol, and the photoacid generator (5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐(2‐methylphenyl)acetonitrile. PDHN, with a number‐average molecular weight of 25,000, was prepared by the oxidative coupling polymerization of 2,6‐dihydroxynaphthalene with di‐μ‐hydroxo‐bis[(N,N,N′,N′‐tetramethylethylenediamine)copper(II)] chloride in 2‐methoxyethanol at room temperature. The resulting PDHN showed a 5% weight loss temperature of 440 °C in nitrogen and a low dielectric constant of 2.82. The resist showed a sensitivity of 8.3 mJ cm−2 and a contrast of 11 when it was exposed to 436‐nm light, followed by postexposure baking at 100 °C for 5 min and development with a 2.38 wt % aqueous tetramethylammonium hydroxide solution at 25 °C. A fine negative image featuring 10‐μm line‐and‐space patterns was obtained on a film 3 μm thick exposed to 10 mJ cm−2 of ultraviolet light at 436 nm in the contact‐printed mode. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2235–2240, 2004
Rheological properties of multisticker associative polyelectrolytes in semidilute aqueous solutions
Authors: Kujawa Piotr , Audibert‐Hayet Annie , Selb Joseph , Candau Françoise 
Published: March 2004

AbstractMultisticker associative polyelectrolytes of acrylamide (≈86 mol %) and sodium 2‐acrylamido‐2‐methylpropanesulfonate (≈12 mol %), hydrophobically modified with N,N‐dihexylacrylamide groups (≈2 mol %), were prepared with a micellar radical polymerization technique. This process led to multiblock polymers in which the length of the hydrophobic blocks could be controlled through variations in the surfactant‐to‐hydrophobe molar ratio, that is, the number of hydrophobes per micelle (NH). The rheological behavior of aqueous solutions of polymers with the same molecular weight and the same composition but with two different hydrophobic block lengths (NH = 7 or 3 monomer units per block) was investigated as a function of the polymer concentration with steady‐flow, creep, and oscillatory experiments. The critical concentration at the onset of the viscosity enhancement decreased as the length of the hydrophobic segments in the polymers increased. Also, an increase in the NH value significantly enhanced the thickening ability of the polymers and affected the structure of the transient network. In the semidilute unentangled regime, the behavior of the polymer with long hydrophobic segments (NH = 7) was studied in detail. The results were well explained by the sticky Rouse theory of associative polymer dynamics. Finally, the viscosity decreased with an increase in the temperature, mainly because of a lowering of the sample relaxation time. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1640–1655, 2004
Fourth‐order hydrodynamic contribution to the polymer self‐diffusion coefficient
Authors: Merriam S. C. , Phillies George D. J. 
Published: March 2004

AbstractA hydrodynamic scattering treatment of interacting polymer chains is extended to obtain the five‐point chain–chain–chain–chain–chain hydrodynamic interaction tensor. The tensor is used to calculate the second‐order concentration correction to the self‐diffusion coefficient of a polymer in solution. The self‐similarity assumption of the hydrodynamic scaling model of polymer dynamics is tested against these calculations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1663–1670, 2004
Toughness mechanism in polypropylene composites: Polypropylene toughened with elastomer and calcium carbonate
Authors: Zhang Ling , Li Chunzhong , Huang Rui 
Published: March 2004

AbstractPolypropylene (PP) was modified with elastomer or CaCO3 particles of two different sizes (1 μm and 50 nm) in various volume fractions. The dispersion morphology and mechanical properties of the two systems were investigated as functions of the particle size and volume fraction of the modifier. The brittle‐to‐tough transition occurred when the matrix ligament thickness was less than the critical ligament thickness, which was about 0.1 μm for the PP used here, being independent of the type of modifier. At the same matrix ligament thickness, the improvement of the toughness was obviously higher with the elastomer rather than with CaCO3, but adding CaCO3 increased the modulus of PP. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1656–1662, 2004
Preparation and properties of nanocomposites based on acrylonitrile–butadiene rubber, styrene–butadiene rubber, and polybutadiene rubber
Authors: Sadhu Susmita , Bhowmick Anil K. 
Published: March 2004

AbstractNanocomposites were prepared with different grades of nitrile rubber with acrylonitrile contents of 19, 34, and 50%, with styrene–butadiene rubber (23% styrene content), and with polybutadiene rubber with Na‐montmorillonite clay. The clay was modified with stearyl amine and was characterized by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies showed an increase in the gallery gap upon the modification of the filler by stearyl amine. The intercalation of the amine chains into the clay gallery gap was confirmed by the presence of some extra peaks (2928, 2846, and 1553 cm−1) in the FTIR spectra. The clay–rubber nanocomposites were characterized by TEM and XRD. The mechanical properties were studied for all the compositions. An improvement in the mechanical properties with the degree of filler loading up to a certain level was observed. The changes in the mechanical properties, with changes in the nature and polarity of the rubbers, were explained with the help of XRD and TEM results. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1573–1585, 2004
Mechanical properties of magnetically oriented epoxy
Authors: Al‐Haik M. S. , Garmestani H. , Li D. S. , Hussaini M. Y. , Sablin S. S. , Tannenbaum R. , Dahmen K. 
Published: March 2004

AbstractThe microstructure of an epoxy system oriented in high magnetic fields (15–25 T) has been observed to consist of highly oriented domains at the molecular level along the direction of the applied field. The changes in the microstructure have been characterized as a function of the magnetic‐field strength and have been investigated microscopically and with wide‐angle X‐ray diffraction. The mechanical properties of the epoxy have been examined in light of nanoindentation experiments at different load levels. The basic results of the experimental investigations for the effect of high magnetic fields on the structure and property of the epoxy are presented. Nanoindentation testing has revealed large differences in the nanomechanical behavior for thermomagnetically processed epoxy specimens. The differences can be ascribed to the microstructural changes (reorientation) of the polymer at the molecular level. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1586–1600, 2004
Exclusion effect of carbon dioxide on the crystallization of polypropylene
Authors: Oda Takafumi , Saito Hiromu 
Published: March 2004

AbstractWe investigated the crystallization growth of isotactic polypropylene under carbon dioxide (CO2) at various CO2 pressures and temperatures by in situ observation with a digital high‐fidelity microscope and a specially designed high‐pressure visualized cell. The fibrils within the spherulite were distorted and branched by crystallization under CO2 at pressures higher than 2 MPa, and this suggested the exclusion of CO2 from the growth front of the fibrils. The spherulite growth rate (G) at 140 °C increased with the CO2 pressure, attained a maximum value around 0.3 MPa, and then decreased. Above 6 MPa, it became slower than that under air at the ambient pressure. An analysis of the crystallization kinetics by the Hoffman–Lauritzen theory revealed that the pressure dependence of G could be ascribed to the change in the transportation rate of crystallizable molecules (βg) with pressure; that is, βg increased and then decreased with pressure. The increase in βg at a low pressure was caused by the plasticizing effect of CO2, whereas the decrease in βg at a high pressure was due to the exclusion of CO2 from the crystal growth front. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1565–1572, 2004
Investigation of glucose binding sites on insulin
Authors: Zoete Vincent , Meuwly Markus , Karplus Martin 
Published: April 2004

AbstractPossible insulin binding sites for D‐glucose have been investigated theoretically by docking and molecular dynamics (MD) simulations. Two different docking programs for small molecules were used; Multiple Copy Simultaneous Search (MCSS) and Solvation Energy for Exhaustive Docking (SEED) programs. The configurations resulting from the MCSS search were evaluated with a scoring function developed to estimate the binding free energy. SEED calculations were performed using various values for the dielectric constant of the solute. It is found that scores emphasizing non‐polar interactions gave a preferential binding site in agreement with that inferred from recent fluorescence and NMR NOESY experiments. The calculated binding affinity of −1.4 to −3.5 kcal/mol is within the measured range of −2.0 ± 0.5 kcal/mol. The validity of the binding site is suggested by the dynamical stability of the bound glucose when examined with MD simulations with explicit solvent. Alternative binding sites were found in the simulations and their relative stabilities were estimated. The motions of the bound glucose during molecular dynamics simulations are correlated with the motions of the insulin side chains that are in contact with it and with larger scale insulin motions. These results raise the question of whether glucose binding to insulin could play a role in its activity. The results establish the complementarity of molecular dynamics simulations and normal mode analyses with the search for binding sites proposed with small molecule docking programs. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Electron ionization mass spectral fragmentation of derivatized 4,5‐ and 5,6‐epoxysterols
Authors: Rontani J.‐F. , Aubert C. 
Published: March 2004

AbstractThe electron ionization (EI) mass spectral fragmentation of derivatized 4,5‐ and 5,6‐epoxysterols was investigated. Interesting fragmentation processes involving a transannular cleavage of the epoxide ring after transfer of the trimethylsilyl group are significant in the case of 4,5‐epoxysterol trimethylsilyl ethers (affording abundant fragment ions at m/z 403 and 404). Different pathways, which have been substantiated by deuterium labelling, are proposed in order to explain the formation of these ions. In contrast, this transfer is not significant in the case of 5,6‐epoxysterol trimethylsilyl ethers. The EI mass spectra of these latter compounds appear to be very complex and to differ slightly according to the stereochemistry of the epoxy group. Acetate and trifluoroacetate derivatives of 4,5‐epoxysterols display interesting EI mass spectra dominated by a fragment ion at m/z 332 resulting from cleavage of the steroid ring A. Copyright © 2004 John Wiley & Sons, Ltd.
Modelling risk when binary outcomes are subject to error
Authors: McInturff Pat , Johnson Wesley O , Cowling David , Gardner Ian A 
Published: March 2004

AbstractWe present methods for binomial regression when the outcome is determined using the results of a single diagnostic test with imperfect sensitivity and specificity. We present our model, illustrate it with the analysis of real data, and provide an example of WinBUGS program code for performing such an analysis. Conditional means priors are used in order to allow for inclusion of prior data and expert opinion in the estimation of odds ratios, probabilities, risk ratios, risk differences, and diagnostic test sensitivity and specificity. A simple method of obtaining Bayes factors for link selection is presented. Methods are illustrated and compared with Bayesian ordinary binary regression using data from a study of the effectiveness of a smoking cessation program among pregnant women. Regression coefficient estimates are shown to change noticeably when expert prior knowledge and imperfect sensitivity and specificity are incorporated into the model. Copyright © 2004 John Wiley & Sons, Ltd.
Interval‐censored survival time data: confidence intervals for the non‐parametric survivor function
Authors: Goodall Ruth L. , Dunn David T. , Babiker Abdel G. 
Published: March 2004

AbstractSurvival data are described as interval censored when the failure time is not measured exactly but is known only to have occurred within a defined interval. In this paper, we describe and assess three methods for calculating pointwise confidence intervals for the non‐parametric survivor function estimated from interval‐censored data: the first based on the full information matrix, the second a modification of this approach involving deletion of rows and columns of the information matrix corresponding to zero estimates prior to inversion and the third based on likelihood ratio inference. In a simulation study the likelihood ratio method gave the most accurate confidence intervals with coverage consistently close to the nominal level of 95 per cent. Copyright © 2004 John Wiley & Sons, Ltd.
Inflation of the type I error rate when a continuous confounding variable is categorized in logistic regression analyses
Authors: Austin Peter C. , Brunner Lawrence J. 
Published: March 2004

AbstractThis paper demonstrates an inflation of the type I error rate that occurs when testing the statistical significance of a continuous risk factor after adjusting for a correlated continuous confounding variable that has been divided into a categorical variable. We used Monte Carlo simulation methods to assess the inflation of the type I error rate when testing the statistical significance of a risk factor after adjusting for a continuous confounding variable that has been divided into categories. We found that the inflation of the type I error rate increases with increasing sample size, as the correlation between the risk factor and the confounding variable increases, and with a decrease in the number of categories into which the confounder is divided. Even when the confounder is divided in a five‐level categorical variable, the inflation of the type I error rate remained high when both the sample size and the correlation between the risk factor and the confounder were high. Copyright 2004 John Wiley & Sons, Ltd.
Increasing the sample size when the unblinded interim result is promising
Authors: Chen Y. H. Joshua , DeMets David L. , Gordon Lan K. K. 
Published: March 2004

AbstractIncreasing the sample size based on unblinded interim result may inflate the type I error rate and appropriate statistical adjustments may be needed to control the type I error rate at the nominal level. We briefly review the existing approaches which allow early stopping due to futility, or change the test statistic by using different weights, or adjust the critical value for final test, or enforce rules for sample size recalculation. The implication of early stopping due to futility and a simple modification to the weighted Z‐statistic approach are discussed. In this paper, we show that increasing the sample size when the unblinded interim result is promising will not inflate the type I error rate and therefore no statistical adjustment is necessary. The unblinded interim result is considered promising if the conditional power is greater than 50 per cent or equivalently, the sample size increment needed to achieve a desired power does not exceed an upper bound. The actual sample size increment may be determined by important factors such as budget, size of the eligible patient population and competition in the market. The 50 per cent‐conditional‐power approach is extended to a group sequential trial with one interim analysis where a decision may be made at the interim analysis to stop the trial early due to a convincing treatment benefit, or to increase the sample size if the interim result is not as good as expected. The type I error rate will not be inflated if the sample size may be increased only when the conditional power is greater than 50 per cent. If there are two or more interim analyses in a group sequential trial, our simulation study shows that the type I error rate is also well controlled. Copyright © 2004 John Wiley & Sons, Ltd.
Effects of Extruder Die Nozzle Dimensions on Expansion and Micrographic Characterization During Extrusion of Acetylated Starch
Authors: Ganjyal Girish M. , Hanna Milford A. 
Published: March 2004

AbstractStarch acetate (DS 2) with ethanol content of 16% (d. b.) was extruded in a twin‐screw extruder with nozzle length to diameter (L/D) ratios varying from 2.9 to 13.1, constant screw speed of 140 rpm and barrel temperature of 160°C. Effects of variation in L/D ratio and the individual effects of variations in L and D on expansion and micrographic properties were studied. With smaller D and larger L nozzles, back pressure developed in the die was immense, which resulted in high initial expansion and then collapse of extrudates, after a brief time, leading to smaller diameter extrudates. It was concluded that the pressure drop exerted tensile forces in the cell material in excess of its elastic limits. SEM results of the samples showed the effects. It is important to consider the elastic properties of the material in predicting ultimate radial expansion. The expansion phenomena have been explained in detail.
Analytical, Biochemical and Physicochemical Aspects of Starch Granule Size, with Emphasis on Small Granule Starches: A Review
Authors: Lindeboom Nienke , Chang Peter R. , Tyler Robert T. 
Published: March 2004

AbstractGranule size, size distribution and shape are among the most important morphologically distinguishing factors of starches from different origins. This article provides an overview of aspects related to starch granule size, including procedures for determining the size, the impact of granule size on the physicochemical characteristics of starch, and biosynthetic and environmental determinants of granule size. The focus is on small granule starches, including their isolation and current and potential utilization.
Study on the Synthesis and Application of Starch‐graft‐Poly(AM‐co‐DADMAC) by Using a Complex Initiation System of CS‐KPS
Authors: Lu Shaojie , Lin Songbai , Yao Kangde 
Published: March 2004

AbstractA graft copolymer was synthesized by graft copolymerization of starch with acrylamide (AM) and diallyldimethylammonium chloride (DADMAC). The copolymerization was carried out using a complex initiation system of cerium sulfate (CS) and potassium persulfate (KPS). The effects of reaction conditions on graft copolymerization and use of these copolymers as additives in papermaking was investigated. Experiments showed that a graft copolymer with higher grafting level, higher intrinsic viscosity and higher cationic degree could be obtained by changing the method of monomer addition and by controlling the ratio of DADMAC to AM. The graft copolymerization was more effective when the complex initiation system of CS‐KPS was used. When adding 0.05% of the grafted starch [S‐g‐P(AM‐co‐DADMAC)] to the papermaking system, a higher filler retention was obtained than with cationic starch and cationic polyacrylamide when the cationic degree of S‐g‐P(AM‐co‐DADMAC) was 22% and its intrinsic viscosity was 7.35.
Acylation of Starch with Vinyl Acetate in Water
Authors: Mormann Werner , Al‐Higari Mohamed 
Published: March 2004

AbstractAcetylation of different types of starch with vinyl acetate in water in the presence of a base is described. Maximum degree of substitution under these conditions is 1.1. Vinyl esters of higher homologous acids (vinyl laurate) react very slowly giving very low degrees of substitution after long reaction times. The reaction mixture is biphasic, because vinyl esters are not miscible with water. Formation of two layers reduces loss of acylating agent due to reaction with water – which is a major problem encountered for esterification with acid anhydrides or chlorides – to less than 5%. Unlike acylation of starch in DMSO with vinyl esters, the acetates of starch obtained by the method reported do not show regioselective distribution of acetyl groups within the anhydroglucose units.
Crystal engineering of photochromic diarylethene single crystals
Authors: Morimoto Masakazu , Kobatake Seiya , Irie Masahiro 
Published: March 2004

AbstractPhotochromic performance of diarylethene single crystals was controlled by crystal engineering using non‐covalent
aromatic‐aromatic interactions as the directional intermolecular force. A diarylethene derivative with two pentafluorophenyl
groups, 1,2‐bis(2‐methyl‐5‐pentafluorophenyl‐3‐thienyl)perfluorocyclopentene
(1a), formed stoichiometric co‐crystals with benzene (Bz) and naphthalene (Np)
by aryl‐perfluoroaryl interactions. Face‐to‐face π‐stacking interactions between the pentafluorophenyl
groups of 1a and the aromatic molecules are responsible for 2 : 1 and 1 : 1 stoichiometric compositions
in 1a/Bz and 1a/Np co‐crystals, respectively. The diarylethene underwent thermally stable and photoreversible
photochromic reactions in a homo‐crystal of 1a and co‐crystals 1a/Bz and 1a/Np. The absorption
spectra of the photogenerated closed‐ring isomers varied depending on the conformation of the diarylethene molecules packed in the
crystals. The diarylethene 1a also formed 1 : 1 stoichiometric co‐crystals with different kinds of diarylethenes,
1,2‐bis(2‐ethyl‐5‐phenyl‐3‐thienyl)perfluorocyclopentene (2a) and
1,2‐bis[2‐methyl‐5‐(1‐naphthyl)‐3‐thienyl]perfluorocyclopentene
(3a). Both co‐crystals 1a/2a and 1a/3a showed photochromism. Although 1a, 2a,
and 3a underwent efficient photocyclization reactions in their homo‐crystals, highly selective photocyclization reactions
of 2a or 3a were observed in the co‐crystals. The selective reactions were confirmed by HPLC and X‐ray
crystallography. Excited energy transfers from 1a to 2a and from 1a to 3a are considered to occur and cause
the selective reactions. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 23–38; 2004: Published
online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.10078
The stepwise supramolecular organisation of guanosine derivatives
Authors: Gottarelli Giovanni , Spada Gian Piero 
Published: March 2004

AbstractSeveral supramolecular architectures generated by guanosine derivatives are described. The research
started from the fortuitous observation of a lyotropic behavior exhibited by a guanylic nucleotide in water.
This observation stimulated extensive research on several natural and lipophilic guanosine derivatives which
self‐assemble in different architectures (discs, ribbons, helices . . .),
according to their structure and environment. These ordered structures can be used as scaffolds for photo‐
or electro‐active moieties and for the fabrication of molecular electronic devices. © 2004 The
Japan Chemical Journal Forum and John Wiley & Sons, Inc. Chem Rec 4: 39–49; 2004: Published online in
Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20005