bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐refractive‐index thin films prepared from aminoalkoxysilane‐capped pyromellitic dianhydride–titania hybrid materials
Authors: Chang Chao‐Ching , Chen Wen‐Chang 
Published: August 2002

AbstractHigh‐refractive‐index aminoalkoxysilane‐capped pyromellitic dianhydride (PMDA)–titania hybrid optical thin films (TP0–TP8) were synthesized and characterized in this study. They were prepared with PMDA, aminopropyltrimethoxysilane, and titanium(IV) isopropoxide via a sol–gel process followed by spin coating and multistep baking. Through adjustments in the concentration and reaction time, the inorganic content in the hybrid thin films could be as high as 59.1 wt %. The Fourier transform infrared results indicated successful bonding between the organic and inorganic moieties. However, residues of the chelating ligands were found in the hybrids with high titania contents, affecting their thermal and optical properties. Field emission scanning electron microscopy results suggested a nanosized domain of the titania segment in the hybrid materials TP0–TP8. An atomic force microscopy study suggested that the hybrid thin films had good planarization. The dispersions of the refractive index and extinction coefficient in the wavelength range 190–900 nm were studied. The refractive indices of the prepared hybrid thin films at 633 nm increased linearly from 1.567 to 1.780 with increasing titania content. However, the Abbe numbers of the hybrid thin films showed an opposite trend. Excellent optical transparence was obtained in the visible region for the prepared hybrid thin films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3419–3427, 2001
Crystallization studies of isotactic polypropylene containing nanostructured polyhedral oligomeric silsesquioxane molecules under quiescent and shear conditions
Authors: Fu Bruce X. , Yang Ling , Somani Rajesh H. , Zong Steven X. , Hsiao Benjamin S. , Phillips Shawn , Blanski Rusty , Ruth Patrick 
Published: August 2002

AbstractCrystallization studies at quiescent and shear states in isotactic polypropylene (iPP) containing nanostructured polyhedral oligomeric silsesquioxane (POSS) molecules were performed with in situ small‐angle X‐ray scattering (SAXS) and differential scanning calorimetry (DSC). DSC was used to characterize the quiescent crystallization behavior. It was observed that the addition of POSS molecules increased the crystallization rate of iPP under both isothermal and nonisothermal conditions, which suggests that POSS crystals act as nucleating agents. Furthermore, the crystallization rate was significantly reduced at a POSS concentration of 30 wt %, which suggests a retarded growth mechanism due to the molecular dispersion of POSS in the matrix. In situ SAXS was used to study the behavior of shear‐induced crystallization at temperatures of 140, 145, and 150 °C in samples with POSS concentrations of 10, 20, and 30 wt %. The SAXS patterns showed scattering maxima along the shear direction, which corresponded to a lamellar structure developed perpendicularly to the flow direction. The crystallization half‐time was calculated from the total scattered intensity of the SAXS image. The oriented fraction, defined as the fraction of scattered intensity from the oriented component to the total scattered intensity, was also calculated. The addition of POSS significantly increased the crystallization rate during shear compared with the rate for the neat polymer without POSS. We postulate that although POSS crystals have a limited role in shear‐induced crystallization, molecularly dispersed POSS molecules behave as weak crosslinkers in polymer melts and increase the relaxation time of iPP chains after shear. Therefore, the overall orientation of the polymer chains is improved and a faster crystallization rate is obtained with the addition of POSS. Moreover, higher POSS concentrations resulted in faster crystallization rates during shear. The addition of POSS decreased the average long‐period value of crystallized iPP after shear, which indicates that iPP nuclei are probably initiated in large numbers near molecularly dispersed POSS molecules. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2727–2739, 2001
Morphology and mechanical properties of blown films of a low‐density polyethylene/linear low‐density polyethylene blend
Authors: Lu Jianjun , Sue Hung‐Jue 
Published: August 2002

AbstractThe morphologies of films blown from a low‐density polyethylene (LDPE), a linear low‐density polyethylene (LLDPE), and their blend have been characterized and compared using transmission electron microscopy, small‐angle X‐ray scattering, infrared dichroism, and thermal shrinkage techniques. The blending has a significant effect on film morphology. Under similar processing conditions, the LLDPE film has a relatively random crystal orientation. The film made from the LDPE/LLDPE blend possesses the highest degree of crystal orientation. However, the LDPE film has the greatest amorphous phase orientation. A mechanism is proposed to account for this unusual phenomenon. Cocrystallization between LDPE and LLDPE occurs in the blowing process of the LDPE and LLDPE blend. The structure–property relationship is also discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 507–518, 2002; DOI 10.1002/polb.10115
Dislocation approach to the plastic deformation of semicrystalline polymers: Kinetic aspects for polyethylene and polypropylene*
Authors: Séguéla R. 
Published: August 2002

AbstractThe plasticity of semicrystalline polymers is analyzed in the framework of Young's dislocation model under the assumption of nucleation of screw dislocations from the lateral surface of the crystalline lamellae. It is proposed that the driving force for the nucleation and propagation across the crystal width of these screw dislocations relies on chain twist defects that migrate along the chains stems and allow a step‐by‐step translation of the stems through the crystal thickness. Such defects are identified as thermally activated conformational defects responsible for the so‐called crystalline relaxation. Dislocation kinetic equations are derived. Plastic flow rates attainable by dislocation motion in polyethylene and polypropylene are assessed with frequency–temperature data of the crystalline relaxation. Comparisons are made with experimental strain rates that enable homogeneous plastic deformation. In addition to temperature, the crystal lamellar thickness, which is a basic factor of the plastic flow stress in Young's dislocation model, is a major factor in dislocation kinetics through its influence on chain twist activation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 593–601, 2002; DOI 10.1002/polb.10118
Transport and mechanical properties of blends of poly(ϵ‐caprolactone) and a modified montmorillonite‐ poly(ϵ‐caprolactone) nanocomposite
Authors: Gorrasi Giuliana , Tortora Mariarosaria , Vittoria Vittoria , Galli Giancarlo , Chiellini Emo 
Published: August 2002

AbstractThe structural characterization and transport properties of blends of a commercial high molecular weight poly(ϵ‐caprolactone) with different amounts of a montmorillonite‐poly(ϵ‐caprolactone) nanocomposite containing 30 wt % clay were studied. Two different vapors were used for the sorption and diffusion analysis—water as a hydrophilic permeant and dichloromethane as anorganic permeant—in the range of vapor activity between 0.2 and 0.8. The blends showed improved mechanical properties in terms of flexibility and drawability as compared with the starting nanocomposites. The permeability (P), calculated as the product of the sorption (S) and the zero‐concentration diffusion coefficient (D0), showed a strong dependence on the clay content in the blends. It greatly decreased on increasing the montmorillonite content for both vapors. This behavior was largely dominated by the diffusion parameters. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1118–1124, 2002
Structural and mechanical behavior of polypropylene/ maleated styrene‐(ethylene‐co‐butylene)‐styrene/sisal fiber composites prepared by injection molding
Authors: Xie X. L. , Fung K. L. , Li R. K. Y. , Tjong S. C. , Mai Y.‐W. 
Published: August 2002

AbstractHybrid composites consisting of isotactic poly(propylene) (PP), sisal fiber (SF), and maleic anhydride grafted styrene‐(ethylene‐co‐butylene)‐styrene copolymer (MA‐SEBS) were prepared by melt compounding, followed by injection molding. The melt‐compounding torque behavior, thermal properties, morphology, crystal structure, and mechanical behavior of the PP/MA‐SEBS/SF composites were systematically investigated. The torque test, thermogravimetric analysis, differential scanning calorimetric, and scanning electron microscopic results all indicated that MA‐SEBS was an effective compatibilizer for the PP/SF composites, and there was a synergism between MA‐SEBS and PP/SF in the thermal stability of the PP/MA‐SEBS/SF composites. Wide‐angle X‐ray diffraction analysis indicated that the α form and β form of the PP crystals coexisted in the PP/MA‐SEBS/SF composites. With the incorporation of MA‐SEBS, the relative amount of β‐form PP crystals decreased significantly. Mechanical tests showed that the tensile strength and impact toughness of the PP/SF composites were generally improved by the incorporation of MA‐SEBS. The instrumented drop‐weight dart‐impact test was also used to examine the impact‐fracture behavior of these composites. The results revealed that the maximum impact force (Fmax), impact‐fracture energy (ET), total impact duration (tr), crack‐initiation time (tinit), and crack‐propagation time (tprop) of the composites all tended to increase with an increasing MA‐SEBS content. From these results, the incorporation of MA‐SEBS into PP/SF composites can retard both the crack initiation and propagation phases of the impact‐fracture process. These prolonged the crack initiation and propagation time and increased the energy consumption during impact fracture, thereby leading to toughening of PP/MA‐SEBS/SF composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1214–1222, 2002
A steady‐state mass balance model of the polycarbonate–CO2 system reveals a self‐regulating cell growth mechanism in the solid‐state microcellular process
Authors: Holl M. R. , Garbini J. L. , Murray W. R. , Kumar V. 
Published: August 2002

AbstractA simple mechanism regulating polymer mobility is demonstrated to determine initial and final growth states of solid‐state microcellular foams. This mechanism, governed by the extent of plasticization of the polymer by the dissolved gases, is examined with a mass balance model and results from foam growth experiments. Polycarbonate was exposed to CO2, which acted as both a plasticizing gas and a physical blowing agent driving foam growth. The polycarbonate specimens were saturated to the equilibrium gas concentration at 25 °C for CO2 pressures of 1–6 MPa in 1‐MPa increments. Equilibrated specimens were heated in a glycerin bath until thermal equilibrium was reached, and a steady foam structure was attained. Glycerin bath temperatures of 30–150 °C in 10 °C increments were examined. Using knowledge of gas solubility, the equation of state for CO2, the effective glass‐transition temperature as a function of gas concentration, and a model for mass balance within a solid‐state foam, we demonstrate that foam growth terminates when sufficient gas is driven from the polycarbonate matrix into the foam cells. The foam cell walls freeze at the elevated bath temperature because of gas transport from the polycarbonate matrix and the associated rise in the polymer glass‐transition temperature to that of the heated bath. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 868–880, 2001
Dynamic mechanical behavior of oriented semicrystalline polyethylene terephthalate
Authors: Xia Zhiyong , Sue Hung‐Jue , Hsieh Alex J. , Huang Joe W.‐L. 
Published: August 2002

AbstractThe dynamic mechanical behavior of molecularly oriented semicrystalline polyethylene terephthalate (PET) induced via the equal‐channel angular extrusion (ECAE) process was investigated. Dynamic mechanical analyses in both torsional mode and bending mode were utilized. The results indicate that the ECAE‐oriented PET has a higher dynamic storage modulus above the glass‐transition temperature than that of the reference (control sample). The combined effect of molecular orientation and crystallinity is responsible for the changes in the primary and secondary relaxations of PET. Further analyses show that the shifting and broadening of the primary and secondary peak positions in oriented PET are mainly due to the amorphous‐phase orientation because the crystallinity of PET decreases upon the ECAE processing. A good correlation was found between the structural anisotropy and the dynamic mechanical properties. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1394–1403, 2001
Onsager consistency checks for multicomponent diffusion models
Authors: Zielinski John M. , Alsoy Sacide 
Published: August 2002

AbstractThe Onsager reciprocity relations are applied to several recently proposed multicomponent diffusion models in an attempt to gauge their validity and ascertain their applicability. Each of these friction‐based diffusion models stems from the more general Bearman formalism through various assumptions regarding the individual friction coefficients. By assessing the compliance of the Bearman model with respect to the Onsager relations, we ascertain the validity of the simplifications introduced to each diffusion model and suggest which postulates lead to results consistent with the Onsager relations. Although some models are not consistent with the Onsager relations, each model predicts the multicomponent drying of polymer films reasonably well. The necessity for consistency with the Onsager development is, therefore, revisited. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1496–1504, 2001
Phase behavior and viscoelastic properties of entangled block copolymer gels
Authors: Vega Daniel A. , Sebastian John M. , Loo Yueh‐Lin , Register Richard A. 
Published: August 2002

AbstractTriblock copolymers in midblock‐selective solvents can form physical gels. However, at low triblock contents (near the percolation threshold), the bridging of chains between micelles can lead to macrophase separation. Adding a styrene–isoprene diblock to a styrene–isoprene–styrene triblock copolymer in squalane can eliminate macrophase separation, yielding a wide range of stable, single‐phase gels with a disordered arrangement of micelles. The plateau modulus of these triblock gels scales with the 2.2 power of polymer content, indicating the importance of entanglements in dictating the modulus. Comparing gels made from the midblock‐saturated derivative of the same polymer [styrene‐(ethylene‐alt‐propylene)‐styrene] in squalane reveals that the modulus differences in the gels are a direct consequence of the difference in the entanglement molecular weight of the midblock homopolymer in bulk. Finally, the broad relaxation spectrum of these triblocks is well‐described by a recent theory for the dynamics of entangled star polymers, with the breadth of the relaxation spectrum dictated by the number of entanglements per midblock in the gel. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2183–2197, 2001
Effects of composition drift on the effectiveness of random copolymer reinforcement at polymer–polymer interfaces
Authors: Benkoski J. J. , Fredrickson G. H. , Kramer E. J. 
Published: August 2002

AbstractRandom copolymer layers are surprisingly effective at reinforcing polymer–polymer interfaces. One hypothesis is that composition drift during synthesis can account for the higher than expected toughening. To test this hypothesis, we polymerized a series of poly(d‐styrene‐r‐2‐vinylpyridine) (dPSf‐r‐PVP1−f) copolymers with various fractions (f) of deuterated styrene to only 10% completion to avoid composition drift. The fracture energies (Gc) of polystyrene/dPS‐r‐PVP/poly(2‐vinylpyridine) interfaces with relatively thick layers of dPS‐r‐PVP were measured. Gc decreased relative to interfaces reinforced with composition‐drifted dPS‐r‐PVP. Conversely, Gc increased when two or more copolymers were blended together. In such samples, the copolymers form distinct layers with multiple interfaces characterized by the difference in f (Δf) between adjacent layers. We find that Gc is governed by Δfmax, the largest difference in adjacent compositions, and, therefore, by the width of the narrowest interface (wmin). Gc increases strongly as wmin increases from 3 to 5 nm. Remarkably, these wmin values are about half the entanglement spacing in bulk polystyrene. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2363–2377, 2001
Psychometric properties of the Impact of Event Scale amongst women at increased risk for hereditary breast cancer
Authors: Thewes Belinda , Meiser Bettina , Hickie Ian B. 
Published: August 2002

AbstractThe Impact of Event Scale (IES; Horowitz MJ, Wilner N, Alvarez W. 1979. Psychosom Med 41: 209–218) has been widely used in the psycho‐oncology literature as a measure of cancer‐related anxiety. More recently, the IES has been applied to the assessment of breast cancer‐related anxiety amongst women who are at increased risk of developing hereditary breast cancer. Despite its widespread use, no studies to date have described the validity of the IES amongst these women. The present study is a replication of reliability analyses and exploration of the factor structure and validity of the IES amongst a sample of 480 female hereditary breast cancer clinic patients. Results suggest good internal consistency (Cronbach's α=0.84–0.91), and satisfactory test‐retest reliability (IES‐Total r=0.80). The IES was found to have good face validity and be an acceptable instrument to women at increased risk of breast cancer. The two‐factor (intrusion and avoidance) structure originally reported (Horowitz et al. 1979; Zilberg NJ, Weiss DS, Horowitz MJ. 1982. J Consult Clin Psychol 50: 407–414) was replicated by factor analysis in the present study. Analysis of correlation coefficients between the IES, breast cancer‐related events and attitudes and other standardized measures of distress and general somatic concern, provide some preliminary support for the concurrent and discriminative validity of the IES amongst women at increased risk of developing hereditary breast cancer. Copyright © 2001 John Wiley & Sons, Ltd.
The radar signatures and age of periglacial slope deposits, Central Highlands of Germany
Authors: Völkel J. , Leopold M. , Roberts M. C. 
Published: August 2002

AbstractDetermining the age of periglacial slope deposits (head) in the Central Highlands (Mittelgebirge) of Germany is a research challenge because of the lack of dateable organics and the contentious role of the Laacher See Tephra (LST) as a dating indicator. Ground penetrating radar (GPR) and cores were used to establish the subsurface stratigraphic relationships between the peat deposits of two bogs (Totenauer Moor, Bayerischer Wald and Schwarzes Moor, Rhön) and underlying head deposits in order to provide minimum ages for the head. Radiocarbon dates were obtained from peat bogs overlying the head in the Bavarian Forest, while in the Rhön (Schwarzes Moor) LST was found bedded in the peat above the head indicating that the latter therefore, is older than Alleröd. Radar profiles show that the head is a stratigraphically continuous, not interbedded, unit beneath the peat. The lowest peat at Totenauer Moor, immediately above the Upper Head, was dated at 11,550 ± 260 yr BP thus establishing the minimum age of the Upper Head as being older than Bölling and perhaps even Older Dryas, but not Younger Dryas. The LST shards were not deposited contemporaneously with the head but were incorporated by bioturbation and mass movements. This study demonstrated the utility of GPR as a tool for imaging head deposits. Copyright © 2001 John Wiley & Sons, Ltd.
Effects of tobramycin solution for inhalation on global ratings of quality of life in patients with cystic fibrosis and Pseudomonas aeruginosa infection*†
Authors: Quittner Alexandra L. , Buu Anne 
Published: August 2002

AbstractIn a previously published placebo‐controlled trial, tobramycin solution for inhalation (TSI) was shown to improve lung function and other outcomes in patients with cystic fibrosis (CF). The objectives of the current study were to examine the effects of TSI on global ratings of health‐related quality of life (HRQOL) by patients (or their parents) and physicians blind to group assignment, and to determine whether any perceived benefits persisted over time. The global ratings of HRQOL in 520 patients with CF and chronic Pseudomonas aeruginosa infection were analyzed retrospectively. Patients were randomly assigned to receive 24 weeks of placebo or treatment with TSI 300 mg b.i.d., both administered in cycles of 28 days on drug (or placebo) followed by 28 days off, for a total of three cycles. After each on‐drug cycle, patients or parents, and physicians, were asked to rate whether the patient's condition was better, unchanged, or worse.There was strong agreement between the paired patient/parent and physician global HRQOL ratings across the three cycles. Regression analyses demonstrated that patients in the TSI group were significantly more likely to report improvements in HRQOL than were patients in the placebo group. This effect was found to be both immediate (end of on‐drug cycle 1) and delayed (end of subsequent on‐drug cycles 2 and 3) (P < 0.05). In addition, change in forced expired volume in 1 sec (FEV1) % predicted values was a significant predictor of improvement in HRQOL ratings by patients and parents. After controlling for change in FEV1 % predicted, physician ratings showed significant improvement only at the end of cycle 1. Finally, controlling for initial lung disease severity, longitudinal growth models revealed that patients on TSI and their physicians reported higher HRQOL ratings than did placebo patients and their physicians across the three cycles; however, the magnitude of this effect decreased over time.Results of this study provided consistent evidence that TSI was associated with improved global ratings of HRQOL completed by both patients or parents, and physicians. Although these results are promising, they are limited by the use of a single‐item rating of health. Future studies of the effects of TSI should utilize a well‐validated, disease‐specific measure of HRQOL. Pediatr Pulmonol. 2002; 33:269–276. © 2002 Wiley‐Liss, Inc.
Familial dysautonomia: A diagnostic dilemma. Chronic lung disease with signs of an autoimmune disease
Authors: van Egmond‐Fröhlich A.W.A. , Paul K. , Eggert W. , Gaedicke G. , Wahn U. , Bauer C.‐P. 
Published: August 2002

AbstractWe present an 11‐year‐old girl with sensory and autonomic neurological dysfunction, and respiratory insufficiency caused by recurrent aspiration. The diagnosis of familial dysautonomia (FD) was confirmed by a missing axonal flare to histamine, miosis in response to conjunctival methacholine and homozygous polymorphic linked markers DS58(18) and DS159(7) on chromosome 9. Ashkenazi Jewish descent could not be ascertained by history. A variety of positive tests for autoantibodies were initially interpreted as evidence for systemic lupus erythematosus vs. overlap syndrome with pulmonary, cerebral, skin, and ocular involvement. The diagnosis of FD was delayed because of the rarity of this disorder in Germany (second case reported). We discuss possible explanations for the misleading immunological findings, including interference by antibodies binding to milk proteins used as blocking reagents in enzyme‐linked immunoassays and circulating immune‐complexes due to chronic aspiration pneumonitis. Pediatr Pulmonol. 2001; 31:478–481. © 2001 Wiley‐Liss, Inc.