bluuebunny/crossref_metadata_2025_split huggingface dataset:
The synergistic effect of boron nitride particle and die on the capillary extrusion processability of mLDPE
Authors: Lee Sang Myung , Nam Gi Joon , Lee Jae Wook 
Published: March 2004

AbstractThe synergistic effects of boron nitride (BN) powder and die on the rheology and processability of metallocene‐catalyzed low density polyethylene (mLDPE) were investigated. The processability in the extrusion process is closely related to the interfacial properties between the polymer melts and the die wall. BN powder was added to mLDPE to reduce the friction coefficient and surface energy. Adding 0.5 wt% BN powder to mLDPE was very effective in improving the processability and the extrudate appearance. To study the effect of die surface property, three different dies were applied in capillary extrusion. One was conventional tungsten carbide (TC) die, and the others were hot‐pressed BN (hpBN) die and hot‐pressed BN composite (hpBNC) die. The applications of these BN dies were quite effective in delaying surface melt fracture (sharkskin) and postponing gross melt fracture to higher shear rate compared to the TC die. These improvements result from the fact that BN dies reduce the wall shear stress significantly and promote slip. The synergistic effect of processability could be obtained when both BN powder and hpBN die were used together.
Structure and properties of poly(ethylene‐co‐chlorotrifluoroethylene) and polyvinylidene fluoride exposed to water, hydrochloric acid, hydrobromic acid and tetrachloroethylene
Authors: Hedenqvist M. S. , Ritums J. E. , Condé‐Brana M. , Bergman G. 
Published: March 2004

AbstractThe transport of water, hydrochloric acid, hydrobromic acid and tetrachloroethylene in an poly(ethylene‐co‐chlorotrifluoroethylene) and polyvinylidene fluoride were studied at 70°C by the sorption/desorption technique. The effects on the structure and mechanical properties were studied using size‐exclusion chromatography, infrared spectroscopy, differential scanning calorimetry and tensile testing. Solute concentrations in the polymers indicated that both the water and HCl/HBr components diffused into the polymers on exposure to acid solutions. The calculated water contents of the diffusing acids generally differed from the water content in the solution. The ratio of water content in the diffusing acid to that in the surrounding acid solution was generally a function of the relative vapor activity of water and HCl/HBr. It was possible to describe the 35%HCl and 47%HBr desorption data using a two component model. It was here assumed that the water and HCl/HBr diffused separately, each having its own constant diffusion coefficient. The water diffusivity was obtained from the pure water system, and this allowed the HCl/HBr diffusivity to be calculated. It was found that the diffusivity decreased, in a non‐simple way, as a function of solute size. The exposure to solute did not lower the molar mass of the polyvinylidene fluoride. Differential scanning calorimetry indicated the development of low‐melting point polyvinylidene fluoride crystals during the exposure to all solutes. This seemed to be a consequence of the long‐term exposure (175 to 376 days) at 70°C. The long‐term exposure stiffened several of the polyvinylidene fluoride resins and occasionally made them less ductile. The poly(ethylene‐co‐chlorotrifluoroethylene) also became stiffer, but it was otherwise unaffected as far as observation by the other available techniques was concerned.
Peroxide crosslinking of Ziegler‐Natta thermoplastic polyolefins
Authors: Bacci Dino , Marchini Roberta , Scrivani Maria Teresa 
Published: March 2004

AbstractA range of reactor grade TPO alloys (PP/EPM alloys from Ziegler‐Natta catalysis) were studied in order to evaluate their dynamic cross‐linkability, using a peroxide system. The amount of ethylene content in EPM rubber ranged from 28 to 77 wt%, to investigate the competition between vis‐breaking and cross‐linking during the peroxide reaction. Processing temperature and different peroxide/coagent ratios were the parameters varied in the present work. Cross‐linking degree was evaluated with Compression Set measurements and Dynamic Mechanical Analysis. It was therefore possible to find a correlation between the two analytical techniques. Feasibility of TPV rubbers with Compression Set at about 50% (22 h, 70°C) was demonstrated.
Influence of untreated and novel electron beam modified surface coated silica filler on dynamic mechanical thermal properties of ethylene‐octene copolymer
Authors: Ray Sudip , Bhowmick Anil K. 
Published: March 2004

AbstractAn extensive study on dynamic mechanical thermal analysis has been carried out to investigate the effect of filler‐filler and polymer‐filler interaction in cured ethylene‐octene copolymer reinforced by unmodified and modified silica. The silica was treated with trimethylolpropane triacrylate (TMPTA) or triethoxyvinyl silane (TEVS), followed by electron beam irradiation at room temperature. Modification of the silica filler, especially via silanization, significantly reduces filler‐filler networking, as evidenced from the strain sweep tests, and thus helps reduce the Payne effect, particularly at high filler loadings. The effect of modification is quantified with the help of a new mathematical model correlating the storage modulus and the volume fraction of the filler. The enhancement in the storage modulus at high temperatures and changes in the loss tangent at the glass transition temperature suggest definite improvement in the polymer‐filler interaction in the case of these modified fillers. The results obtained from the master curves constructed based on the time‐temperature‐superposition principle further support the findings.
A rheokinetic study of bulk free radical polymerization performed with a helical barrel rheometer
Authors: Cioffi M. , Ganzeveld K. J. , Hoffmann A. C. , Janssen L. P. B. M. 
Published: March 2004

AbstractThe Trommsdorff effect is a non‐linear autoacceleration phenomenon in bulk free radical polymerizations. It is undesired in processes on industrial scale, as is causes hot spots and erratic behavior. In this paper a rheokinetic investigation of the Trommsdorff effect is performed with a helical barrel rheometer. This rheometer can be considered a small‐scale model of large reactors, particularly extruders. The rheokinetic measurements show that the Trommsdorff effect can be reduced when the polymerization is performed at a high rotational velocity of the screw. This confirms a previous study performed with a cone and plate rheometer and is encouraging with a view to designing better‐controlled bulk free radical polymerization processes on industrial scale.
Rheo‐optical studies of the effect of shear flow on the structure of elastomer blends
Authors: Xu Tao , Shaw Montgomery T. , Weiss R. A. 
Published: March 2004

AbstractThe effect of shear flow on the structure of a phase‐separated, near‐critical blend of 50/50 (w/w) poly(styrene‐ran‐butadiene) and polybutadiene was studied with two different custom‐built rheo‐optical instruments that combined polymer melt flow and small‐angle light scattering (SALS). The deformation of the phase domains during shear flow was nonaffine, and the SALS patterns evolved from a spinodal ring (SR) pattern to a squashed SR with two high‐intensity lobes, to an H‐pattern, to a butterfly pattern with a dark streak along the equator, and finally to a steady‐state, elliptical pattern. The SALS patterns were explained in terms of a network model, in which the strands of the network first orient in the flow direction, then extend in this direction, and finally break up into droplets aligned in the flow direction. According to this picture, the strands in the vorticity direction do not deform until relatively high strains, after which the periodicity of the network begins to disappear. Supporting this model was the observation that the transitions between the different SALS patterns corresponded to inflections and/or maxima in the shear stress or first normal stress difference. Increasing the shear rate changed the kinetics of the structure evolution and reduced the size of the phase‐separated droplets in the steady state. No evidence was obtained for flow‐induced miscibility. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1725–1738, 2004
Miscibility, melting, and crystallization of poly(butylene‐2,6‐naphthalate)/poly(ether imide) blends
Authors: Huang Jieh‐Ming 
Published: March 2004

AbstractWe prepared blends of poly(butylene‐2,6‐naphthalate) (PBN) and poly(ether imide) (PEI) by solution‐casting from dichloroacetic acid solutions. The miscibility, crystallization, and melting behavior of the blends were investigated with differential scanning calorimetry (DSC) and dynamic mechanical analysis. PBN was miscible with PEI over the entire range of compositions, as shown by the existence of single composition‐dependent glass‐transition temperatures. In addition, a negative polymer–polymer interaction parameter was calculated, with the Nishi–Wang equation, based on the melting depression of PBN. In nonisothermal crystallization investigations, the depression of the crystallization temperature of PBN depended on the composition of the blend and the cooling rate; the presence of PEI reduced the number of PBN segments migrating to the crystallite/melt interface. Melting, recrystallization, and remelting processes occurring during the DSC heating scan caused the occurrence of multiple melting endotherms for PBN. We explored the effects of various experimental conditions on the melting behavior of PBN/PEI blends. The extent of recrystallization of the PBN component during DSC heating scans decreased as the PEI content, the heating rate, the crystallization temperature, and the crystallization time increased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1694–1704, 2004
Effect of methyl substitution of the ethylene unit on the physical properties of poly(butylene succinate)
Authors: Chae Han Gi , Park Sun Ho , Kim Byoung Chul , Kim Dong Kook 
Published: March 2004

AbstractA series of poly(butylene succinate‐co‐butylene 2‐methyl succinate)s were prepared through variations in the molar fraction of succinic acid to 2‐methyl succinic acid, and the effects of methyl substitution on the shear‐induced crystallization, nonisothermal crystallization behavior, dynamic rheological properties, crystal morphology, and mechanical properties were investigated. Introducing 2‐methyl succinic units reduced the melting temperature and crystallization temperature; this indicated that the substituted units retarded crystallization of the polymer. The Avrami exponents, estimated by modified Avrami plots, ranged from 2.1 to 3.5 and were a little diminished by the substitution. The substitution also reduced the rate of crystallization under shear. However, the effect was diminished with an increasing shear rate because most polymer chains were more regularly arranged at higher shear rates. Dynamic experiments in the solid state revealed that the peak on a plot of the loss tangent against the temperature became sharper at higher contents of the substituted unit, and the peak temperature, the glass‐transition temperature, was reduced as the content of 2‐methyl succinic acid increased. Wide‐angle X‐ray diffraction patterns showed that there was little effect of the 2‐methyl succinic acid unit on the crystal morphology. The toughness of the polymer was abruptly increased up to 350% at the expense of the tensile modulus. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1759–1766, 2004
HP(2–9)‐magainin 2(1–12), a synthetic hybrid peptide, exerts its antifungal effect onCandida albicansby damaging the plasma membrane
Authors: Park Yoonkyung , Lee Dong Gun , Hahm Kyung‐Soo 
Published: March 2004

AbstractIn our previous study, HP(2–9)‐MA(1–12), HP‐MA for short, a hybrid peptide incorporating residues 2–9 ofHelicobacter pyloriribosomal protein L1 (HP) and residues 1–12 of magainin 2 (MA) was shown to have strong antibacterial activity. In this study the antifungal activity of HP‐MA was evaluated using various fungi, and it was shown that the activity was increased when compared with the parent peptides. In order to investigate the fungicidal mechanism(s) of HP‐MA its action against fungal cell membranes was examined by the potassium‐release test, which showed that HP‐MA caused an increase in the amount of K+released from the cells. Furthermore, HP‐MA induced significant morphological changes. These facts suggested that the fungicidal effect of HP‐MA involves damaging the fungal cell membranes. CD investigators suggested that the α‐helical structure of these peptides plays an important role in their antibiotic effect, but that α‐helicity is less directly correlated with the enhanced antibiotic activity of the hybrid. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
On‐resin head‐to‐tail cyclization of cyclotetrapeptides: optimization of crucial parameters
Authors: Alcaro Maria C. , Sabatino Giuseppina , Uziel Jacques , Chelli Mario , Ginanneschi Mauro , Rovero Paolo , Papini Anna M. 
Published: March 2004

AbstractCyclotetrapeptides are constrained cyclic peptides whose synthesis is considered a difficult task. A methodology based on on‐resin head‐to‐tail cyclization by anchoring the side chain of a trifunctional amino acid was investigated. A series of model cyclotetrapeptides containing the RGD sequence cyclo(Xaa‐Arg‐Gly‐Asp) (Xaa = Ala, Phe, Phg, D‐Ala, D‐Phe, D‐Phg) was synthesized with no cyclodimerization by‐products. An evaluation and optimization study of all of the parameters directly involved in the ring closure was performed. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
Characterizing bathocuproine self‐association and subsequent binding to Alzheimer's disease amyloid β‐peptide by NMR
Authors: Yao Shenggen , Cherny Robert A , Bush Ashley I. , Masters Colin L. , Barnham Kevin J. 
Published: March 2004

AbstractAggregated amyloid β‐peptide (Aβ) is the primary constituent of the extracellular plaques and perivascular amyloid deposits associated with Alzheimer's disease (AD). Deposition of the cerebral amyloid plaques is thought to be central to the disease progression. One such molecule that has previously been shown to ‘dissolve’ deposited amyloid in post‐mortem brain tissue is bathocuproine (BC). In this paper 1H NMR chemical shift analysis and pulsed field gradient NMR diffusion measurements were used to study BC self‐association and subsequent binding to Aβ. The results show that BC undergoes self‐association as its concentration increases. The association constant of BC dimerization, Ka, was estimated to be 0.64 mM−1 at 25°C from 1H chemical shift analysis. It was also found that dimerization of BC appeared to be essential for its binding to Aβ. From the self‐association constant of BC, Ka, the fraction of dimeric BC in the complex was obtained and the dissociation constant, Kd, of BC bound to Aβ40 peptide was then determined to be ∼1 mM. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
Photoaffinity scanning in the mapping of the peptide receptor interface of class II G protein—coupled receptors
Authors: Pham Vi , Sexton Patrick M. 
Published: March 2004

AbstractThe family of G protein‐coupled receptors constitutes about 50% of the therapeutic drug targets used in clinical medicine today, although the mechanisms of ligand binding, activation and signal transduction for G protein‐coupled receptors are not yet well defined. This review discusses ongoing research using the photoaffinity scanning method to map the bimolecular interface between class II G protein‐coupled receptors and their ligands. Furthermore the available computer model of class II peptide ligand docking into the receptor, based on the positional constraints imposed by the photoaffinity scanning analyses, will be discussed briefly. The ultimate goal of these efforts is to understand the molecular basis of receptor binding and therefore to generate a template for rational drug design. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.
Odd electrons and covalent bonding in fullerenes
Authors: Sheka Elena F. 
Published: March 2004

AbstractThe electronic structure of X60 molecules (XC, Si) is considered in terms of 60 odd electrons and the spin‐dependent interaction between them. The conditions for the electrons to be excluded from the covalent pairing are discussed. A computational spin‐polarized quantum‐chemical scheme is suggested to evaluate four parameters (energy of radicalization, exchange integral, atom spin density, and squared spin) to characterize the effect quantitatively. A polyradical character of the species, weak for C60 and strong for Si60, is established. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Phase diagram for the constrained integer partitioning problem
Authors: Borgs C. , Chayes J. T. , Mertens S. , Pittel B. 
Published: March 2004

AbstractWe consider the problem of partitioning n integers into two subsets of given cardinalities such that the discrepancy, the absolute value of the difference of their sums, is minimized. The integers are i.i.d. random variables chosen uniformly from the set {1,…,M}. We study how the typical behavior of the optimal partition depends on n, M, and the bias s, the difference between the cardinalities of the two subsets in the partition. In particular, we rigorously establish this typical behavior as a function of the two parameters κ :=n−1log2M and b := |s|/n by proving the existence of three distinct “phases” in the κb‐plane, characterized by the value of the discrepancy and the number of optimal solutions: a “perfect phase” with exponentially many optimal solutions with discrepancy 0 or 1; a “hard phase” with minimal discrepancy of order Me−Θ(n); and a “sorted phase” with an unique optimal partition with discrepancy of order Mn, obtained by putting the (s + n)/2 smallest integers in one subset. Our phase diagram covers all but a relatively small region in the κb‐plane. We also show that the three phases can be alternatively characterized by the number of basis solutions of the associated linear programming problem, and by the fraction of these basis solutions whose ±1‐valued components form optimal integer partitions of the subproblem with the corresponding weights. We show in particular that this fraction is one in the sorted phase, and exponentially small in both the perfect and hard phases, and strictly exponentially smaller in the hard phase than in the perfect phase. Open problems are discussed, and numerical experiments are presented. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Effects of downsizing practices on the performance of hospitals
Authors: Chadwick Clint , Hunter Larry W. , Walston Stephen L. 
Published: March 2004

AbstractResearch has found that downsizing is not generally followed by improved organizational performance. Using a sample of hospitals that recently downsized, we evaluate the effects on performance of the human resource management (HRM) practices used in layoffs. Strategic HRM theory suggests that practices can have an impact on performance outcomes. We find that showing consideration for employees' morale and welfare during downsizing is positively related both to perceived success of downsizing and to financial performance following layoffs. Advance notice of layoffs is positively related to subsequent financial performance, but the provision of extended insurance to laid‐off employees is negatively related to financial performance. Planned redesign of work structures is positively related to perceived success, but has neutral to negative effects on financial performance. Copyright © 2004 John Wiley & Sons, Ltd.
Technology search investments: evolutionary, option reasoning, and option pricing approaches
Authors: Miller Kent D. , Arikan Andaç T. 
Published: March 2004

AbstractHow do firms allocate limited search resources among substituting technologies with uncertain prospects? This paper contrasts three different approaches. The first follows evolutionary theorists' portrayals of decision‐making processes under bounded rationality. The second approach—real option reasoning—fosters flexibility by investing in more than one technology and postponing the decision to specialize. Following the third approach—real option pricing—firms base their search investments on forward‐looking calculations of technology option prices. We lay out the contrasting theoretical assumptions behind each of these three approaches and construct a simulation model to compare their implications. Copyright © 2004 John Wiley & Sons, Ltd.
Intrauterine versus transvaginal sonography for benign and malignant disorders of the female reproductive tract
Authors: Gruessner S. E. M. 
Published: March 2004

AbstractObjectiveTo determine the usefulness of high‐frequency intrauterine (IUS) vs. transvaginal (TVS) sonography in the evaluation of benign and malignant uterine and tubal abnormalities.MethodsFor IUS sonography, a high‐frequency (10–30 MHz) microtip probe with a maximum beam penetration depth of 126 mm was inserted intracervically; radial scanning (360°) was performed without cervical dilatation and without local or general anesthesia. For TVS, a 7.5‐MHz probe was used. The study population comprised 48 patients. Thirty‐three patients had gynecological diseases (cervical and endometrial cancer (n = 12), uterine leiomyomas (n = 10), sterility disorders (n = 11)); the remaining 15 patients served as a control group and had no gynecological diseases.ResultsIUS was accomplished in 45/48 (94%) patients. In contrast to TVS, preoperative staging by IUS—with assessment of depth of tumor invasion—concurred with the histopathological findings in all patients with cervical and endometrial cancer. The sonographic resolution of submucosal and intramural leiomyomas was superior with IUS vs. TVS. For patients with sterility disorders, intraluminal sonography of the Fallopian tubes was achieved in 64% of cases; endometrial nodules of the Fallopian tubes were depicted by intraluminal sonography (but not TVS).ConclusionsIUS is superior to TVS in the evaluation of uterine and tubal abnormalities. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
The association between isolated fetal echogenic cardiac foci on second‐trimester ultrasound scan and trisomy 21 in low‐risk unselected women
Authors: Lamont R. F. , Havutcu E. , Salgia S. , Adinkra P. , Nicholl R. 
Published: March 2004

AbstractObjectivesTo determine the prevalence of and the association between trisomy 21 and isolated fetal echogenic cardiac foci (FECF) identified in the second trimester in an unselected low‐risk population.MethodsAll cases with isolated FECF were collected by reviewing the antenatal ultrasound database for 3 consecutive years. In order to include all trisomy 21 cases for the same period, the regional cytogenetics database and pediatric databases were examined. A 2 × 2‐table analysis was performed to establish the sensitivity, specificity and positive and negative predictive values of isolated FECF as a screening test for trisomy 21 in a low‐risk unselected population.ResultsIn the 3‐year period of the study the total number of deliveries was 11 105, of which 10 769 (97%) had a routine detailed anomaly scan between 16 and 24 weeks' gestation. There were 311 cases (2.9%) of isolated FECF. Among these there was only one case (0.3%) of trisomy 21. In the same period, the total number of trisomy 21 cases was 14. Accordingly, the sensitivity of isolated FECF for detecting trisomy 21 was 7.1% and the specificity was 97.1%. Positive and negative predictive values of FECF were 0.3% and 99.9%, respectively.ConclusionIn an otherwise healthy pregnancy, the finding of isolated FECF on a routine second‐trimester anomaly scan is normal and should not be considered as a risk factor for trisomy 21 in an unselected low‐risk population. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.