bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of the tensile modulus of poly(p‐hydroxybenzoate)/poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) ternary polyester composite fibers
Authors: Lee Seung Goo , Kim Seong Hun 
Published: April 2003

AbstractLiquid crystalline polymer reinforced plastics were prepared by compounding (PHB/PEN/PET) blends. A fibrillar PHB structure was formed in situ in the PEN/PET matrix under a high elongational flow field during melt‐spinning of the composite fibers. The formation of PHB microfibrils in the composite fiber with different PHB contents and winding speeds was observed. The PHB microfibril reinforced PEN/PET composite fibers exhibited an unexpectedly low tensile modulus. We have evaluated the tensile modulus of the fibers using the non‐modified22 and a modified23 Halpin–Tsai model. From the analysis of both models, large differences were found between the theoretical and experimental values of the tensile modulus, and the low value of the tensile modulus of the composite fiber could not adequately be explained by either model. Thus, we analyzed the observed modulus values using the Takayanagi model,24 which describes the concept of mechanical discontinuities in semi‐crystalline polymers. Using the Takayanagi model, the effective fraction of continuous or discontinuous microfibrils was evaluated. Consequently, we could successfully explain the very low modulus of the PHB/PEN/PET composite fiber, having a large number of PHB microfibrils, using the Takayanagi model. Copyright © 2003 Society of Chemical Industry
Formation of monodisperse polyacrylamide particles by dispersion polymerization: particle size and size distribution
Authors: Ye Qiang , Zhang Zhicheng , Ge Xuewu 
Published: April 2003

AbstractHighly monodisperse polyacrylamide microparticles were directly prepared by dispersion polymerization in aqueous alcoholic media initiated by 2,2′‐azobisisobutyronitrile using poly(N‐vinylpyrrolidone) as a steric stabilizer. Monomer conversion was studied dilatometrically and polymer molecular weight was determined viscometrically. The hydrodynamic diameter of polymer particles and its distribution were measured with a dynamic laser light scattering spectrometer. The number of the nuclei produced in the early stage of the polymerization was found to be constant during the remainder of the polymerization. The influences of various polymerization parameters, such as initiator concentration, monomer concentration, stabilizer content, medium polarity, and polymerization temperature on the particle size and size distribution were systematically investigated. Copyright © 2003 Society of Chemical Industry
Copolymerization of N‐phenylmaleimide with 2‐hydroxyethyl and ethyl methacrylates
Authors: Şenel Serap , Rzaev Zakir M. O. , Pişkin Erhan 
Published: April 2003

AbstractRadical copolymerization of N‐phenylmaleimide (PhMI) with 2‐hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) was studied. Synthesis of copolymers was carried out in p‐dioxane at 65 °C with 2,2′‐azobisisobutyronitrile as the initiator. Copolymer compositions were calculated by the elemental analysis and 1H NMR spectroscopy methods. Monomer reactivity ratios for the studied monomer pairs were determined using Kelen–Tüdös and non‐linear regression methods. PhMI monomer was found to have substantially different copolymerization constants in the radical copolymerization of the two monomer systems. Poly(PhMI‐co‐HEMA) possessed higher values of intrinsic viscosity and higher thermal stability, as well as showing specific melting endo‐peaks in the DSC curves. These observations were explained by the effect of H‐bonding between hydroxyl and imide groups with the formation of complexed macromolecular structures. Copyright © 2003 Society of Chemical Industry
Photocrosslinking of a maleimide functionalized polymethacrylate
Authors: Decker Christian , Bianchi Catherine 
Published: April 2003

AbstractA polymethacrylate bearing pendent maleimide (MI) groups has been crosslinked by UV irradiation of the photoinitiator‐free functionalized polymer. The reaction was followed in situ by real‐time IR spectroscopy and shown to proceed with an initial quantum yield of two maleimide double bonds polymerized per photon absorbed, the value expected for a photocycloaddition mechanism. A twofold increase of the reaction rate was achieved by performing the UV irradiation in the presence of a thioxanthone photosensitizer (1 wt%). Insolubilization of the photoresist requires the reaction of at least 18 MI double bonds per polymer chain, thus implying the occurrence of an intramolecular coupling process between neighbouring MI groups located on the same polymer chain. In the presence of an electron donor monomer, like the divinylether of triethyleneglycol used, the cycloaddition reaction gives way to a radical‐induced copolymerization of maleimide and vinyl ether double bonds, which becomes the only crosslinking process in a stoichiometric mixture of the two components. Copyright © 2003 Society of Chemical Industry
Mechanical properties and morphology of LCP/ABS blends compatibilized with a styrene–maleic anhydride copolymer
Authors: Xie WB , Tam KC , Yue CY , Lam YC , Li L , Hu X 
Published: April 2003

AbstractA co‐polyester liquid crystalline polymer (LCP) was melt blended with an acrylonitrile–butadiene–styrene copolymer (ABS). LCP fibrils are formed and a distinct skin/core morphology is observed in the injection moulded samples. At higher LCP concentration (50 wt%), phase inversion occurs, where the dispersed LCP phase becomes a co‐continuous phase. While the tensile strength and Young's modulus remain unchanged with increasing LCP content up to 30 wt% LCP, a significant enhancement of the modulus at 50 wt% LCP is observed due to the formation of co‐continuous morphology. The blend modulus is lower than the values predicted by the rule of mixtures, suggesting a poor interface between the LCP droplets and ABS matrix. A copolymer of styrene and maleic anhydride (SMA) was added in the LCP/ABS blends during melt blending. It is observed that SMA has a compatibilizing effect on the blend system and an optimum SMA content exists for mechanical properties enhancement. SMA improves the interfacial adhesion, whereas excess of SMA reduces the LCP fibrillation. Copyright © 2003 Society of Chemical Industry
New aspects of unsaturated polyester resin synthesis. Part 2. Reactant sequence distribution and its effect on cure kinetics
Authors: Zetterlund Per B , Gosden Ray G , Weaver William , Johnson Anthony F 
Published: April 2003

AbstractThe distribution of unsaturations in the prepolymer of a typical unsaturated polyester (UP) resin (maleic anhydride, phthalic anhydride and 1,2‐propylene glycol) has been shown to influence the kinetics of the cure process with styrene monomer. Segments containing double bonds in close proximity appear to lower the reactivity of the resin due to steric hindrance, as indicated by the fact that the rate of cure and the final degree of cure, measured by differential scanning calorimetry (DSC), increase as the average sequence length (SL) of maleic units decreases. This implies that the reactivity of UP resins may be improved by synthesis of prepolymers with certain reactant sequence‐length distributions. The copolymer formed by the melt condensation process of maleic anhydride, phthalic anhydride and 1,2‐propylene glycol in the absence of a transesterification catalyst has a non‐random structure with a tendency towards blockiness. This was established using 1H NMR analysis in tandem with deterministic and Monte Carlo modelling techniques. Copyright © 2003 Society of Chemical Industry
Synthesis of superabsorbent copolymers as water manageable materials
Authors: Raju K Mohana , Raju M Padmanabha , Mohan Y Murali 
Published: April 2003

AbstractStrongly water‐absorbing polymers based on the monomers acrylamide, potassium acrylate and magnesium methacrylate were prepared by copolymerization using ammonium persulfate as initiator and N,N‐methylene‐bisacrylamide (MBA) as crosslinking agent. The copolymers are synthesized by varying monomer, crosslinker and initiator concentrations. The experimental results shows that superabsorbents (SAPs) have good absorbency both in water and NaCl solutions. The copolymers are characterized by IR spectroscopy. Water retention in soil is enhanced by use of these superabsorbents. The SAPs use for the growth of sunflower plants is also investigated. The water retention capacity of the SAPs was carried out at 60 °C and 100 °C. Copyright © 2003 Society of Chemical Industry
Adsorption of poly(4‐vinylpyridine) N‐alkyl quaternized at the chloroform/water interface
Authors: Urzúa Marcela D , Ríos Hernán E 
Published: April 2003

AbstractThe Du Noüy method has been employed to study the interfacial properties of poly(4‐vinylpyridine) N‐n‐alkyl quaternized with hexyl, octyl and decyl bromide, at the chloroform/water interface. The interfacial tension is highly dependent on the hydrophilic–hydrophobic balance between the pyridinium group and the length of the polyelectrolyte side aliphatic chain. The excess interfacial concentration, Γ, is determined according to the Gibbs–Szyszkowski equation. The areas covered by monomer unit at the interface, σ, are smaller than those reported for low molecular weight amphipathic molecules. The linear dependence of $\Delta G_{\rm{ads}}^{\rm{o}}$ with the number of carbon atoms on the side‐chain allows the determination of a contribution of just 0.13 kJ for each methylene lateral group and −36 kJ for the vinylpyridinium bromide contributions to $\Delta G_{\rm{ads}}^{\rm{o}}$. The dependence of the interfacial tension on temperature suggests that the entropy is the main factor determining the adsorption process. Copyright © 2003 Society of Chemical Industry
Eutectic‐forming binary system of poly(ethylene oxide) and p‐hydroxybenzaldehyde
Authors: Zhu Xinyuan , Xiao Yan , He Peng , Yan Deyue , Fang Yapeng 
Published: April 2003

AbstractThe binary system consisting of poly(ethylene oxide) (PEO) and p‐hydroxybenzaldehyde (PHD) was characterized with the aid of differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy and Fourier‐transform infrared spectroscopy. The phase diagram created from thermal analysis data provides clear evidence for the presence of a eutectic at 35.5 °C and PHD weight fraction of 42%. Microscopy studies show that, for the mixtures with a PHD weight fraction below 42%, the resulting morphology of the crystallized sample is coarse spherulitic texture. In the case of eutectic composition, the crystallization of the binary melt produces degenerated homogenous spherulites. For the hypoeutectic PEO–PHD mixtures, the PHD crystals become large and thick with decreasing the PEO fraction. Moreover, the infrared measurements indicate that hydrogen bonding in the PEO–PHD binary system has an important effect on the PEO helical conformation. With increase of the amount of PHD component, the PEO helical conformation in the PEO–PHD mixtures changes from the 72 helix to the 103 helix. Further increase of the PHD content leads to the destruction of the PEO helical conformation. Copyright © 2003 Society of Chemical Industry
Surface hydrophilicity and enzymatic hydrolyzability of biodegradable polyesters: 1. effects of alkaline treatment
Authors: Tsuji Hideto , Ishida Takuya , Fukuda Norio 
Published: April 2003

AbstractSurface treatment using alkaline solutions was attempted to enhance the surface hydrophilicity and enzymatic hydrolyzability of hydrophobic poly(L‐lactide) [ie poly(L‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL). The alkaline treatment was performed by immersing the PLLA and PCL films in 0.01 and 4 N NaOH solutions, respectively, for various periods of time. The effects of the alkaline treatment on the hydrophilicity of the films were monitored by dynamic contact angle measurements, while the enzymatic hydrolyzability of the PLLA and PCL films after the alkaline treatment were evaluated by weight losses in the presence of proteinase K and Rhizopus arrhizus lipase, respectively. With the alkaline treatment the hydrophilicity of the PLLA and PCL films was controllable in the advancing contact angle (θa) ranges of 84–108° and of 69–93°, respectively, by varying the alkaline treatment time. The enzymatic hydrolysis rates of the PLLA films became higher with decrease of the θa, irrespective of the crystallinity, strongly suggesting that the surface hydrophilicity or the surface molecular weight is crucial to determine their enzymatic hydrolyzability. In contrast, the enzymatic hydrolyzability of the PCL films remained unchanged even when the θa decreased from 93° to 73° by alkaline treatment for 4 h. However, prolonged alkaline treatment for periods of time exceeding 4 h, which insignificantly altered the θa but caused the formation of pores and cracks on the PCL film surface, accelerated the enzymatic hydrolysis of the PCL films. This indicates that the enzymatic hydrolyzability of the PCL film depends on the surface area per unit weight rather than the surface hydrophilicity. Copyright © 2003 Society of Chemical Industry
Treatment of plasticized PVC to reduce plasticizer/solvent migration: optimization with an experimental design
Authors: Fugit Jean‐Luc , Taverdet Jean‐Louis , Gauvrit Jean‐Yves , Lanteri Pierre 
Published: April 2003

AbstractThis work deals with mass transfers between liquid food and PVC packaging. A treatment which reduces the migration both of plasticizer toward a liquid food simulant and the liquid has been investigated. The treatment is a two step process: (1) soaking in a liquid and (2) drying at various temperatures. Some process parameters, such as time and temperature of soaking, temperature and time of drying, influence the treatment efficacy. The best values consider in from these factors were found due to experimental designs and the physical significance of the results is discussed.© 2003 Society of Chemical Industry
Ionization potential of excited states of Be‐like sequence in the concept of iso‐spectrum‐level series
Authors: Zheng Neng Wu , Wang Tao 
Published: April 2003

AbstractWith the introduction of the concept of the iso‐spectrum‐level series, a linear relationship is found between the first differences of the ionization potential of excited states and nuclear charge Z along an iso‐spectrum‐level series, and the ionization potential of excited states of Be‐like sequence are studied systematically on the basis of the weakest bound electron potential model theory. The expression of nonrelativistic ionization potential is derived from the weakest bound electron potential model theory, and relativistic effects are included by using a fourth‐order polynomial in Z. As a demonstration, the ionization potentials of [He]2s2p 3P, [He]2s3s 1S0, [He]2s3p 1P, [He]2s3d 1D2, and [He]2s4d 1D2 series for a range of Be‐like sequence from Z = 4–23 are calculated. The results are compared with the experimental data and the recent sophisticated ab initio results. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 344–350, 2003
Comment on “Computation of Two‐Center Coulomb Integrals over Slater‐Type Orbitals Using Elliptical Coordinates”
Authors: Harris Frank E. 
Published: April 2003

AbstractIn a recent article in this journal, Özmen, Karakas, Atav, and Yakar gave formulas for the evaluation of two‐center Coulomb integrals over Slater‐type orbitals (STOs) in ellipsoidal coordinates Int J Quantum Chem 2003, 91, 13–19. The relation of this work to the rich literature on STO integral evaluation is reviewed, with focus on the important issues of speed of computation and numerical stability. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 332–334, 2003
Tight‐binding molecular dynamics simulation of SiH bond dissociation in silicon clusters
Authors: Khakimov Z. M. , Umarova F. T. , Sulaymonov N. T. , Kiv A. E. , Levin A. A. 
Published: April 2003

AbstractNew model of SiH bond dissociation is proposed and tested in the cluster Si10H16 by the simulation approach that combines classic molecular dynamics method and the self‐consistent tight‐binding electronic and total energy calculation one. It is shown that the monohydride SiH bond is unstable with respect to silicon dangling bond and bend‐bridge SiHSi bond formation when this cluster traps the single positive charge and that hydrogen migrates through a path involving rather rotation around the SiSi bond than the center of this bond (the bond‐centered position). These results can be useful for understanding hydrogen‐related phenomena at surfaces, interfaces, and internal voids of various hydrogenated silicon systems: electronic devices, silicon solar cells, and nanocrystalline and porous silicon. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 351–359, 2003
Elimination of Protease Activity Restores Efficient Virion Production to a Human Immunodeficiency Virus Type 1 Nucleocapsid Deletion Mutant
Authors: Ott David E. , Coren Lori V. , Chertova Elena N. , Gagliardi Tracy D. , Nagashima Kunio , Sowder Raymond C. , Poon Dexter T. K. , Gorelick Robert J. 
Published: April 2003

ABSTRACT

The nucleocapsid (NC) region of human immunodeficiency virus type 1 (HIV-1) Gag is required for specific genomic RNA packaging. To determine if NC is absolutely required for virion formation, we deleted all but seven amino acids from NC in a full-length NL4-3 proviral clone. This construct, DelNC, produced approximately four- to sixfold fewer virions than did the wild type, and these virions were noninfectious (less than 10
−6
relative to the wild type) and severely genomic RNA deficient. Immunoblot and high-pressure liquid chromatography analyses showed that all of the mature Gag proteins except NC were present in the mutant virion preparations, although there was a modest decrease in Gag processing. DelNC virions had lower densities and were more heterogeneous than wild-type particles, consistent with a defect in the interaction assembly or I domain. Electron microscopy showed that the DelNC virions displayed a variety of aberrant morphological forms. Inactivating the protease activity of DelNC by mutation or protease inhibitor treatment restored virion production to wild-type levels. DelNC-protease mutants formed immature-appearing particles that were as dense as wild-type virions without incorporating genomic RNA. Therefore, protease activity combined with the absence of NC causes the defect in DelNC virion production, suggesting that premature processing of Gag during assembly causes this effect. These results show that HIV-1 can form particles efficiently without NC.
Sindbis Virus Vectors Designed To Express a Foreign Protein as a Cleavable Component of the Viral Structural Polyprotein
Authors: Thomas John M. , Klimstra William B. , Ryman Kate D. , Heidner Hans W. 
Published: April 2003

ABSTRACT
Alphavirus-based expression vectors commonly use a duplicated 26S promoter to drive expression of a foreign gene. Here we describe an expression strategy in which the foreign sequences are linked to the gene encoding the 2A protease of foot-and-mouth disease virus and then inserted in frame between the capsid and E3 genes of Sindbis virus. During replication, the 2A fusion protein is synthesized as a component of the viral structural polyprotein that is then released by intramolecular cleavages mediated by the capsid and 2A proteases. Recombinant Sindbis viruses that expressed fusion proteins composed of 2A linked to the green fluorescent protein (GFP) and to the VP7 protein of bluetongue virus were constructed. Viruses engineered to express GFP and VP7 from a duplicate 26S promoter were also constructed. All four viruses expressed the transgene and grew to similar titers in cultured cells. However, the GFP/2A- and VP7/2A-expressing viruses displayed greater expression stability and were less attenuated in newborn mice than the cognate double-subgenomic promoter-based viruses. By combining the two expression strategies, we constructed bivalent viruses that incorporated and expressed both transgenes. The bivalent viruses grew to lower titers in cultured cells and were essentially avirulent in newborn mice. Groups of mice were vaccinated with each VP7- and VP7/2A-expressing virus, and antibody responses to native VP7 were measured in an indirect enzyme-linked immunosorbent assay. Despite their genetic and phenotypic differences, all viruses induced similarly high titers of VP7-specific antibodies. These results demonstrate that 2A fusion protein-expressing alphaviruses may be particularly well suited for applications that require enduring expression of a single protein or coexpression of two alternative proteins.
Mutational Analysis of Open Reading Frames 62 and 71, Encoding the Varicella-Zoster Virus Immediate-Early Transactivating Protein, IE62, and Effects on Replication In Vitro and in Skin Xenografts in the SCID-hu Mouse In Vivo
Authors: Sato Bunji , Ito Hideki , Hinchliffe Stewart , Sommer Marvin H. , Zerboni Leigh , Arvin Ann M. 
Published: April 2003

ABSTRACT

The varicella-zoster virus (VZV) genome has unique long (U
L
) and unique short (U
S
) segments which are flanked by internal repeat (IR) and terminal repeat (TR) sequences. The immediate-early 62 (IE62) protein, encoded by open reading frame 62 (ORF62) and ORF71 in these repeats, is the major VZV transactivating protein. Mutational analyses were done with VZV cosmids generated from parent Oka (pOka), a low-passage clinical isolate, and repair experiments were done with ORF62 from pOka and vaccine Oka (vOka), which is derived from pOka. Transfections using VZV cosmids from which ORF62, ORF71, or the ORF62/71 gene pair was deleted showed that VZV replication required at least one copy of ORF62. The insertion of ORF62 from pOka or vOka into a nonnative site in U
S
allowed VZV replication in cell culture in vitro, although the plaque size and yields of infectious virus were decreased. Targeted mutations in binding sites reported to affect interaction with IE4 protein and a putative ORF9 protein binding site were not lethal. Single deletions of ORF62 or ORF71 from cosmids permitted recovery of infectious virus, but recombination events repaired the defective repeat region in some progeny viruses, as verified by PCR and Southern hybridization. VZV infectivity in skin xenografts in the SCID-hu model required ORF62 expression; mixtures of single-copy recombinant OkaΔ62 (rOkaΔ62) or rOkaΔ71 and repaired rOka generated by recombination of the single-copy deletion mutants were detected in some skin implants. Although insertion of ORF62 into the nonnative site permitted replication in cell culture, ORF62 expression from its native site was necessary for cell-cell spread in differentiated human skin tissues in vivo.