bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel latent initiator for cationic polymerizations of epoxides: Composite catalysts containing aluminum complexes phase‐separated in epoxides
Authors: Murai S. , Fujieda S. , Hayase S. 
Published: August 2002

AbstractA novel latent initiator for cationic polymerizations of epoxides heterogeneous aluminum complex/phenol initiator (HAP) is reported. Phase transitions are newly employed for realizing the latent property. The initiator consists of 4,4′‐dihydroxydiphenylsulfone and aluminum tris(alkyl acetoacetate), with the alkyl group containing more than 18 carbons. The composite initiator is phase‐separated and dispersed uniformly in epoxy resins at room temperature. When the mixture is heated to a temperature greater than 70°C, the composite initiator makes clear mixtures with epoxy resins because of the phase change in the aluminum complexes. Homogeneous epoxy resins containing these composite initiators are ready for various types of processing, including impregnation and injection. Gelation occurs rapidly at temperatures greater than 100°C. The phase change in the initiator makes it possible for the epoxy compounds to have a long storage stability at room temperature and a high curing speed at greater than 100°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1046–1053, 2002
Yielding of polymers filled with large‐diameter particles
Authors: Metzner Arthur P. 
Published: August 2002

AbstractThe yield stress of a polymer filled with rigid filler particles much larger than 5 μm is affected by the single‐particle debonding stress at large volume fractions of filler. This relationship holds up to a limiting modulus based on the size of the polymer chains of the binder. An elastic yield energy, or resilience, is defined. Within the limits of the yield stress equation, this yield energy is constant over a wide range of strain rates and temperatures at high volume fractions of filler. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 455–466, 2002
Synthesis of branched polyethylene by ethylene homopolymerization with a novel (α‐diimine)nickel complex in the presence of methylaluminoxane
Authors: Zhu Fangming , Xu Wei , Liu Xinxing , Lin Shangan 
Published: August 2002

AbstractBranched polyethylene (PE) was prepared with a novel (α‐diimine)nickel(II) complex of 2,3‐bis(2,6‐dimethylphenyl)‐butanediimine nickel dichloride {[2,6‐(CH3)2C6H3NC(CH3)C(CH3)N2,6‐(CH3)2C6H3]NiCl2} activated by methylaluminoxane in the presence of a single ethylene monomer. The influences of various polymerization conditions, including the temperature, Al/Ni molar ratio, Ni catalyst concentration, and time, on the catalytic activity, molecular weight, degree of branching, and branch length of PE were investigated. According to gel permeation chromatography, the weight‐average molecular weights of the polymers obtained ranged from 1.7 × 105 to 6.0 × 105, with narrow molecular weight distributions of 2.0–3.5. The degree of branching in the polymers rapidly increased with the polymerization temperature increasing; this led to highly crystalline to totally amorphous polymers, but it was independent of the Al/Ni molar ratio and catalyst concentration. At polymerization temperatures greater than 20°C, the resultant PE was confirmed by 13C‐NMR to contain significant amounts of not only methyl but also ethyl, propyl, butyl, amyl, and long branches (longer than six carbons). The formation of the branches could be illustrated by the chain walking mechanism, which controlled their specific spacing and conformational arrangements with one another. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1123–1132, 2002; DOI 10.1002/app.10398
Synthesis and characterization of PMMA‐b‐PBMA block copolymers by atom transfer radical polymerization
Authors: Fernández‐García Marta , De La Fuente José Luis , Fernández‐Sanz Marina , Madruga Enrique López 
Published: August 2002

AbstractThe synthesis of diblock copolymers using atom transfer radical polymerization, ATRP, of n‐butyl methacrylate, BMA, and methyl methacrylate, MMA, is reported. These copolymers were prepared from 2‐bromoisobutyryl‐terminated macroinitiators of poly(MMA) and poly(BMA), using copper chloride, CuCl,/N,N,N′,N″,N″‐pentamethyldiethylenetretramine, PMDETA, as the catalyst system, at 100°C in bulk and in benzonitrile solution. The block copolymers were characterized by means of size‐exclusion chromatography, SEC, and 1H‐NMR spectroscopy. The SEC analysis of the synthesized diblock copolymers confirmed important differences in the molecular weight control depending on the reaction medium (solvent effect) and the chemical structure of the macroinitiator used. In addition, differential scanning calorimetry, (DSC) measurements were performed, showing for all the copolymers a phase separation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2683–2691, 2002
Novel polyureas having isobutenyl bis(aryl ether) moieties in the polymer main chain: Synthesis, tandem Claisen rearrangement, and thermal patterning on polymer film surface using microthermal analyzer
Authors: Yang Gang , Tokuhisa Hideo , Koyama Emiko , Matsuzono Shin‐Ichiro , Hiratani Kazuhisa 
Published: August 2002

AbstractTwo kinds of new polyureas 2a and 2b were synthesized by polyaddition of 1,4‐phenylene diisocyanate with 2‐{2‐[(2‐amino‐4‐methyl‐phenoxy)methyl]allyl}oxy‐5‐methyl‐aniline (diamine 1a) and 2‐{2‐[(2‐amino‐4‐tert‐butyl‐phenoxy)methyl]allyl}oxy‐5‐tert‐butyl‐aniline (diamine 1b), respectively. The isobutenyl bis(aryl ether) moiety, capable of yielding plural phenolic hydroxyls by means of tandem Claisen rearrangement (TCR), was successfully incorporated into the resulting polymer main chain. TCR at isobutenyl bis(aryl ether) moieties readily occurred by heating in the bulk state, affording phenolic hydroxy groups ortho to urea linkages. Subsequent intramolecular cyclization between the hydroxy groups and the urea groups gave the bis(2‐benzoxazolinone) derivatives, with loss of 1,4‐phenylenediamine, resulting in degradation of the polymers. At the same time, the thermal properties were investigated by TG/DTA. The degradation of these new polymers in the bulk state was shown to proceed smoothly by heating at 230°C. Using a microthermal analyzer (μTA), a preliminary study of thermal patterning on polyurea 2b film surface was carried out, and precise spot patterns were successfully processed with diameters of less than 1 μm. Two kinds of novel polyureas, containing isobutenyl bis(aryl ether) moieties ortho to the urea linkages were successfully synthesized. These results imply that these easily decomposable polymers might be used as patterning materials. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2287–2293, 2002
Short‐term effects of sea water on E‐glass/vinylester composites
Authors: Wu Lixin , Murphy Karen , Karbhari Vistasp M. , Zhang James S. 
Published: August 2002

AbstractThe use of ambient cured E‐glass/vinylester composites is increasingly being considered for infrastructure applications both along the shore and offshore, thereby exposing the composite to a marine aqueous environment. The use of ambient cure potentially results in incomplete polymerization and susceptibility for degradation early in life. This study characterizes the mechanical response of E‐glass/vinylester quadriaxial composites immersed in deionized water, sea water, and synthetic sea water. It is seen that there are substantial differences based on the solution type, with deionized water immersion causing the maximum drop in interlaminar shear performance and sea water causing the maximum reduction in tensile performance. The effect of cycling, simulating the tidal zone or the splash zone, is seen to be more pronounced in a resin‐dominated response. Drying of specimens, even over prolonged periods of time, is not seen to result in complete regain of performance degradation due to sorption processes. A clear competition is seen between the phenomena of moisture‐induced residual cure/postcure and physical (fiber‐matrix debonding, microcracking, plasticization) and chemical (hydrolysis) aging. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2760–2767, 2002
Effect of transesterification on the morphology and mechanical properties of a blend containing a liquid crystalline polymer
Authors: Radmard B. , Dadmun M. D. 
Published: August 2002

AbstractTransesterification of polymer blends containing polyesters is often utilized to improve the interfacial adhesion and mechanical properties of a phase‐separated blend. However, in some circumstances, the transesterification can also modify the morphology (crystallinity or liquid crystallinity) of the blend components due to the disruption of the structure of a regular polymer. This, in turn, can deteriorate the mechanical properties of the blend. We present, in this article, results that correlate the extent of transesterification between a liquid crystalline polyester and polycarbonate to the change in the mechanical properties of the blend and the liquid crystallinity of the liquid crystalline polymer (LCP). The results exemplify the need to understand the role of transesterification on the morphology and mechanical properties of the blend so that the optimum processing conditions may be found. The experimental protocol can also be used as a guide to determine these optimal processing conditions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2583–2592, 2001
Comparison of properties of segmented copolyetheresteramides containing uniform aramid segments with commercial segmented copolymers
Authors: Niesten M. C. E. J. , Gaymans R. J. 
Published: August 2002

AbstractThe thermal (using differential scanning calorimetry), dynamic mechanical (using a dynamic mechanical analyzer), and mechanical properties of segmented copolyetheresteramides with aramid units of uniform length (TΦT) and poly(tetramethylene oxide) (PTMO) segments were compared to those of commercial segmented copolyetheresters (PBT–PTMO) and thermoplastic polyurethanes. The hard segments in TΦT‐containing polymers were found to crystallize almost completely, unlike the hard segments of Arnitel and Desmopan. Consequently, the glass‐transition temperature of TΦT‐containing polymers is lower and the melting temperature higher than those of Arnitel and Desmopan. Furthermore, the rubbery plateau of the TΦT‐containing polymers is temperature independent, making the service temperature range wider. In TΦT‐containing polymers a lower concentration of hard segment is needed to obtain dimensionally stable polymers with a high melting temperature. No melt phasing occurs during polymerization and therefore long PTMO segments can be used, producing very soft and elastic materials. The polymers crystallize faster than do commercial materials. The elasticity of the TΦT‐containing polymers is comparable to the elasticity of Desmopan and better than that of Arnitel. TΦT–(PTMO1000/DMT) copolymers are transparent and the solvent resistance is high. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1372–1381, 2001
Cellulose furoate. II. Characterization
Authors: Hon David N.‐S. , Yan Hui 
Published: August 2002

AbstractThe chemical structure of furoate moiety in cellulose furoate was confirmed by FTIR, UV spectroscopy, and NMR and X‐ray spectroscopy. Thermal property was studied by TGA and DSC. TGA results showed cellulose furoate has a very similar thermal property to cellulose. Thermograms revealed its decomposition started at about 300°C, and had a maximum rate of weight loss at about 360°C. DSC studies revealed the glass transition temperatures for cellulose furoates ranged from 207 to 230°C, depending upon the DS. Myrothecium verrucaria, Cheatomium globosum, and Aspergillus terreus were used to determine the biodegradability of cellulose furoate. Biodegradation tests showed that each glucose unit in cellulose required as least one substitution to significantly improve the antibiodegradation property. Solubility tests revealed that cellulose furoates with DS ranged from 1.09 and 2.66, prepared from the homogeneous system, are dissolvable in dioxane, DMSO, DMF, and DMAc. Specimens prepared from the heterogeneous system; only those with DS ranging from 1.09 and 1.98 are dissolvable in DMSO. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 243–252, 2001
Natural protein fibers
Authors: Feughelman Max 
Published: August 2002

AbstractAlpha keratin fibers (hairs, wools, quills, and other mammalian appendages) together with fibroin fibers such as silks and spiders webs are all highly extensible fibrous proteins for which the mechanical properties are of primary importance both to the animal from which they originate and their ultimate application by man. Similarly, the collagens are highly inextensible fibrous proteins, which form the major component of mammalian skin and connecting structures such as tendons. All these fibrous proteins are biological polymers of polypeptide chains for which the mechanical and allied physical properties, such as water absorption, relate to both their macrostructure and their molecular and near‐molecular structure. Because of both their commercial application and their relatively complex structure at the molecular and near‐molecular level, interpretation of the physical properties of α‐keratin fibers represents the main component of this presentation. The mechanical properties of α‐keratin fibers are primarily related to the two components of the elongated cortical cells, the highly ordered intermediate filaments (microfibrils) which contain the α‐helices, and the matrix in which the intermediate filaments are embedded. The matrix consists of globular proteins plus water, the content of the latter being dependent on the fibers environment. The Extended Two‐Phase Model (ETPM) has been developed and results in a detailed coverage of the bulk mechanical properties of α‐helical fibers in terms of their known molecular and near‐molecular structure. The inextensible protein fibers, the collagens and fibroins, are also briefly discussed in terms of the relationship between mechanical properties and the structure of these fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 489–507, 2002
Transfer of marine organisms: a challenge to the conservation of coastal biocoenoses
Authors: Occhipinti Ambrogi A. 
Published: August 2002

Abstract1. The global transfer of species across the world's oceans is an increasing threat to the biodiversity of the sea and particularly of coastal areas: the magnitude of this peculiar aspect of global change and the significance of its effects on ecosystems are currently debated.2. The paper addresses, with reference to the Mediterranean situation, the main research needs in coastal ecosystem conservation, such as the availability of baseline assessment of native and non‐indigenous species (including biogeography, taxonomy and historical records). Studies on the transfer mechanisms and on the predictability of successful settlement by alien species are also important.3. Finally, management actions applicable to conservation issues are mentioned and discussed. Copyright © 2001 John Wiley & Sons, Ltd.
Neuromuscular compartments and fiber‐type regionalization in the human inferior pharyngeal constrictor muscle
Authors: Mu Liancai , Sanders Ira 
Published: August 2002

AbstractThe inferior pharyngeal constrictor (IPC) muscle functions during swallowing, respiration, and vocalization. The most‐caudal portion of the IPC is believed to be part of the functional upper esophageal sphincter (UES). We hypothesized that the caudal fibers of the human IPC may have enzyme‐histochemical characteristics similar to those of the cricopharyngeus muscle, a major component of the UES. In this study, human IPC muscles obtained from autopsy were studied using Sihler's stain to examine innervation patterns, and using myofibrillar ATPase, NADH tetrazolium reductase (NADH‐TR), and succinic dehydrogenase (SDH) techniques to investigate the distribution and oxidative capacity of the slow‐ (type I) and fast‐ (type II) twitch fibers in the muscle. The results showed that the human IPC consists of at least two neuromuscular compartments (NMCs): rostral and caudal. Each of the NMCs was innervated by a separate nerve branch derived from the pharyngeal branch of the vagus nerve. The rostral NMC is faster (39% type I, 61% type II) than the caudal NMC (70% type I, 30% type II). In addition, two histochemically‐delineated fiber layers were identified in the human IPC: a slow inner layer (SIL) with predominantly type I fibers (66%), and a fast outer layer (FOL) with predominantly type II fibers (62%) (P < 0.01). However, the dimensions of both fiber layers and proportions of the muscle fiber types varied with the NMCs. Specifically, the ratio of the thickness of the SIL to FOL was ∼2:1 for the caudal NMC and ∼1:2 for the rostral NMC, respectively. In the SIL the type I fibers accounted for 84% for the caudal NMC and 69% and 44% for the lower and upper portions of the rostral NMC. In contrast, the type II fibers in the FOL accounted for 46% for the caudal NMC and 67% and 74% for the lower and upper portions of the rostral NMC, respectively (P < 0.01). The caudal NMC of the IPC shared histochemical characteristics with the cricopharyngeus muscle, in that it contained predominantly slow oxidative fibers. Overall, the caudal NMC and the SIL in the IPC had high NADH‐TR and SDH activities. However, different patterns of oxidative enzyme activity were identified in both type I and type II fibers. This study provided histochemical evidence for the concept that the caudal NMC within the IPC contributes to the functional UES. In addition, the two histochemically‐defined fiber layers in the IPC may be a specialized adaptation in humans to enable different upper‐airway functions during respiration, swallowing, and speech. Anat Rec 264:367–377, 2001. © 2001 Wiley‐Liss, Inc.
Characterization of diethylstilbestrol‐induced hypospadias in female mice
Authors: Miyagawa Shinichi , Buchanan David L. , Sato Tomomi , Ohta Yasuhiko , Nishina Yukio , Iguchi Taisen 
Published: August 2002

AbstractThe urethral duct and vagina are formed from the urogenital sinus (UGS) during the early neonatal period in mice. Neonatal estrogen exposure results in hypospadias, or the malpositioning of vaginal and urethral openings, with wide cleft clitoris. We sought to characterize diethylstilbestrol (DES) influence on UGS morphogenesis and hypospadias formation. Newborn (day 0) and 1–4‐day‐old female mice (ICR/Jcl) were given (s.c.) oil or 3.0 μg DES. Animals were killed 24 hr later; then hypospadias formation and epithelial apoptosis and proliferation within the developing UGS were assessed. DES did not alter normal UGS morphogenesis by day 1, in comparison with controls. However, hypospadias formation was observed in DES‐treated mice by day 3. In these mice, the distal dorsal urethral duct appeared to fuse with and open into the lower vaginal solid cord region. Further, DES treatment produced a gradual significant increase in dorsal urethral epithelial apoptosis (P < 0.05) just prior to and during fusion and hypospadias formation. DES‐induced urethral epithelial and sinus cord proliferation appeared significantly increased (P < 0.05) and unchanged, respectively, just prior to fusion. By day 5, DES‐treated mice exhibited wide cleft clitoris. In addition, if DES was given on day 3 or 5, a gradual, distinct caudal shift in the vaginal‐urethral junction was observed compared to mice treated on days 0–2. Although hypospadias was not induced when neonates were given DES on day 7, these mice continued to display early vaginal opening. Dose‐response analysis indicated that 0.03 μg DES for 5 days is the lowest known critical dose for hypospadias induction. We have shown for the first time that DES‐induced hypospadias onset may primarily be the result of changes in developing dorsal urethral epithelial cell apoptotic and proliferative activity, and that the location of DES‐induced hypospadias formation is dependent on age at time of exposure. Anat Rec 266:43–50, 2002. © 2002 Wiley‐Liss, Inc.
Regional changes in the contralateral “healthy” hemisphere after ischemic lesions evaluated by quantitative T2 parametric maps
Authors: Sbarbati Andrea , Reggiani Angelo , Nicolato Elena , Arban Roberto , Lunati Ernesto , Osculati Francesco 
Published: August 2002

AbstractModifications in the contralateral “healthy” hemisphere in a population of rats bearing cortical infarction were studied in vivo by magnetic resonance imaging (MRI) with the aim to investigate whether cerebral areas not directly involved in the lesion react at the presence of an ischemic lesion. The study was performed in rats in which a transtemporal approach was adopted to occlude the right middle cerebral artery (MCA). For MRI, the animals were examined at 4.7 Tesla and quantitative T2 parametric images were obtained by a multiecho sequence. Healthy rats and sham‐operated animals were used as control groups. The quantitative T2 parametric images showed that in the first week after the ischemia a significant increase in the mean T2 was seen in the lesioned parietal cortex, compared to the corresponding region of healthy rats (106 msec vs. 68 msec, P < 0.001). The contralateral “healthy” hemisphere showed T2 mean values not significantly different from the corresponding hemisphere of healthy rats (71 msec vs. 70 msec). However, a statistically significant increase in the T2 values was evident in the hypothalamic region (74 msec vs. 66 msec, P < 0.001). In rats examined 1 month after the ischemia, the T2 values of the hypothalamus were lower than those observed one week after ischemia (69 msec) but remained higher than in controls. The present study demonstrates that after a cerebral ischemia areas of secondary involvement distant from the lesion are present and can be studied in vivo by quantitative MRI. Anat Rec 266:118–122, 2002. © 2002 Wiley‐Liss, Inc.
Maps of the Brain
Authors: Toga Arthur W. , Thompson Paul M. 
Published: August 2002

AbstractWe review recent developments in brain mapping and computational anatomy that have greatly expanded our ability to analyze brain structure and function. The enormous diversity of brain maps and imaging methods has spurred the development of population‐based digital brain atlases. These atlases store information on how the brain varies across age and gender, across time, in health and disease, and in large human populations. We describe how brain atlases, and the computational tools that align new datasets with them, facilitate comparison of brain data across experiments, laboratories, and from different imaging devices. The major methods are presented for the construction of probabilistic atlases, which store information on anatomic and functional variability in a population. Algorithms are reviewed that create composite brain maps and atlases based on multiple subjects. We show that group patterns of cortical organization, asymmetry, and disease‐specific trends can be resolved that may not be apparent in individual brain maps. Finally, we describe the creation of four‐dimensional (4D) maps that store information on the dynamics of brain change in development and disease. Digital atlases that correlate these maps show considerable promise in identifying general patterns of structural and functional variation in human populations, and how these features depend on demographic, genetic, cognitive, and clinical parameters. Anat Rec (New Anat) 265:37–53, 2001. © 2001 Wiley‐Liss, Inc.