bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyethylene/maleic anhydride grafted polyethylene/organic‐montmorillonite nanocomposites. I. Preparation, microstructure, and mechanical properties
Authors: Liang Guodong , Xu Junting , Bao Suping , Xu Weibing 
Published: January 2004

AbstractIn this study, three cationic surfactants (hexadecyltrimethylammonium chloride, hexadecyldimethylbenzylammonium chloride, and octadecyltrimethylammonium chloride) were used to modify montmorillonite and polyethylene (PE)/maleic anhydride grafted polyethylene (PE‐g‐MAH)/organic‐montmorillonite (Org‐MMT) nanocomposites, prepared by two blending processes (direct‐melt blending and solution blending). X‐ray diffractometry and transmission electron microscopy were used to investigate the intercalation behavior and microstructure of composites. Mechanical properties were also tested. It was found that the intercalation effect of PE/PE‐g‐MAH/Org‐MMT could be enhanced by increasing the content of PE‐g‐MMT, using the silicate modified by a cationic surfactant with a benzyl group or long alkyl chain, adopting the solution‐blending method or using high‐density polyethylene as matrix. The degree of crystallinity of composites and the crystalline thickness perpendicular to the crystalline plane [like (110) and (200)] decreased with increasing amounts of PE‐g‐MAH and, under certain prescription, the crystalline thickness of the composite made by the solution method was much smaller than that made by direct‐melt blending. This clearly showed that Org‐MMT and PE‐g‐MAH had a heterogeneous nucleation effect on crystallization of PE from the melt, resulting in a decrease of crystalline thickness, and the heterogeneous nucleation effect was more evident in the nanocomposite made by the solution‐blending method than in that made by the direct‐melt intercalation process. The tensile strength initially increased and then decreased with increasing contents of PE‐g‐MAH. The maximum value in tensile strength (23.3 MPa) was achieved when the concentration of PE‐g‐MAH was 6 wt %. The impact strength increased concomitantly with the content of PE‐g‐MAH; it was 122.2 J/m when the concentration of PE‐g‐MAH was 9 wt %.© 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3974–3980, 2004
Simultaneous covalent immobilization of glucose oxidase and catalase onto chemically modified acrylonitrile copolymer membranes
Authors: Godjevargova T. , Dayal Rajeshwar , Marinov Ivaylo 
Published: January 2004

AbstractUltrafiltration membranes from acrylonitrile copolymer were chemically modified with different concentrations of hydrogen peroxide (from 5 to 30% H2O2). The amount of the amide groups in the modified membranes was determined. The water flow and permeability coefficients of the initial and modified membranes were also researched. The modified membranes were used as carriers for covalent immobilization of the dual enzyme system of glucose oxidase and catalase (GOD+CAT). It was found that the best matrices for immobilization of the dual system were membranes modified with 20% H2O2 and the optimal activity ratio was GOD : CAT = 1 : 5. The glucose conversion efficiency with the dual enzyme system was twice as high as that of bound GOD alone. Some of the basic characteristics (optimum pH, optimum temperature, pH, temperature stability, and storage stability) of the dual enzyme system were determined and compared with characteristics of free and bound enzymes. The catalytic parameters of the enzyme reaction (Km and Vmax) were determined with GOD immobilized alone and with the dual system GOD+CAT. The higher rate observed with the dual enzyme system clearly showed the advantage and the efficiency of the immobilized system. Glucose oxidase without catalase was deactivated by H2O2 more rapidly than the immobilized dual GOD+CAT system. These experimental evidences can be explained by the protecting effect of catalase on glucose oxidase from inhibition by H2O2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4057–4063, 2004
Electrochemically synthesized polypyrrole and Cu‐plated nylon/spandex for electrotherapeutic pad electrode
Authors: Kim Seong Hun , Oh Kyung Wha , Bahk Jae Hyon 
Published: January 2004

AbstractElectroconductive fabrics were prepared to improve the properties of conductive electrode pad material used for electrotherapy when it is subjected to various movements of the human body. Highly stretchable and conductive fabrics were prepared by in situ electrochemical polymerization of polypyrrole (PPy) on nylon/spandex stretchable fabric in aqueous solutions with 0.05M pyrrole and 0.05M anthraquinone‐2‐sulfonic acid, sodium salt monohydrate (AQSA) at room temperature for 2 h. Electroless Cu plating was also applied after chemical polymerization of PPy to improve the conductivity of the fabric pad. Performance of prepared stretchable conductive fabric pad was evaluated in terms of conductivity changes as a function of extension and continuous current application time, and clinical test. As a result, the fabric conductivity was well maintained with extension up to 60% and prolonged treatment time over 30 min. The effect of transcutaneous electrical nerve stimulation (TENS) was observed with prepared TENS pad in this study and conventional TENS pad for medical use. The significant effect of TENS was observed with a pad made of conductive fabric by Cu plating and a conventional TENS pad (P < 0.05, respectively). Even though the efficiency of an experimental pad made of fabric composite with electrochemically polymerized PPy was not as good as conventional TENS pad for medical use in this experiment, it can possibly be used for other applications where relatively low‐strength electrical pulse is required. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4064–4071, 2004
Study on long fiber–reinforced thermoplastic composites prepared by in situ solid‐state polycondensation
Authors: Yan Weixia , Han KeQing , Qin LiuLiang , Yu MuHuo 
Published: January 2004

AbstractLong glass fiber–reinforced thermoplastic composites were prepared by a new process, in situ solid‐state polycondensation (INSITU SSP). In this process reinforcing continuous fibers were impregnated by the oligomer of PET melt, and then the impregnated continuous fibers were cut to a desired length (designated prepreg); finally, the prepreg was in situ polymerized in the solid state to form the high molecular weight matrix. SEM, FTIR spectra, short‐beam shear stress test, flexural strength test, impact strength test, and the intrinsic viscosity measurement were used to investigate the wetting and interfacial adhesion, the mechanical properties of the composite, and the molecular weight of matrix resin in the composite. The results showed that the molecular weight of PET in the matrix resin and mechanical properties could be adjusted by controlling the SSP time and that the high level of interfacial adhesion between reinforcing fibers and matrix resin could be achieved by this novel INSITU SSP process, which are attributed to the good wetting of reinforcing fibers with low molecular weight oligomer melt as the impregnation fluid, the in situ formation of chemical grafting of oligomer chains onto the reinforcing fiber surface, and the in situ formation of the high molecular weight PET chains in the interphase regions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3959–3965, 2004
Evaluation of hydrophobically associated polyacrylamide‐containing aqueous fluids and their potential use in petroleum recovery
Authors: Chagas Beatriz S. , Machado Dilon L. P. , Haag Roberto B. , De Souza Celso R. , Lucas Elizabete F. 
Published: January 2004

AbstractAcrylamide and tridecyl acrylate copolymers were synthesized by micellar copolymerization to obtain water‐soluble, hydrophobically modified polymers. Rheological properties of the obtained polymer solutions were evaluated and compared to those of solutions of a commercial polyacrylamide currently used in the petroleum industry. The behavior of the copolymer solutions was studied as a function of the variation of hydrophobic monomer content incorporated in the copolymer as well as the salt content of the aqueous medium, for diluted and semi‐diluted regimens. Comparative studies of such effects on the intrinsic viscosity and the critical concentration of those polymers were conducted. The increase in hydrophobic monomer content produced a sudden increase in the bulk and absolute viscosity of the polymeric solutions, a trend that was more intense from a certain concentration typical for each polymer. Salt addition led to lower bulk viscosity caused by a stronger interaction among hydrophobic groups, resulting from minimized exposure of such groups and water. The same effect was observed for the critical concentration. A comparison of the synthesized polymers with industrial polyacrylamide showed that the synthesized polymers were characterized by advantageously high shear strength and high salt resistance. However, in the absence of salts, higher copolymer amounts were needed to prepare solutions whose viscosity was the same as that of commercial polyacrylamide. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3686–3692, 2004
Pervaporation study of water and tert‐butanol mixtures
Authors: Guo Wei Fen , Chung Tai‐Shung , Matsuura Takeshi , Wang Rong , Liu Ye 
Published: January 2004

AbstractThe permeation behavior of water/tert‐butanol mixture through Sulzer Pervap2510 hydrophilic poly(vinyl alcohol) membranes was investigated and the effects of feed composition and temperature on separation efficiency of the membranes were studied. The pervaporation experiments were carried out with feed water content varying from 0 to 20 wt % according to the existing industrial needs and with the feed temperature from 60 to 100°C. Over this range, both water flux and separation factor increased with increasing water content and feed temperature. These phenomena may be attributed to (1) the strong interaction between water and the membrane, (2) the decoupling effect of the permeants and the membrane at elevated temperatures, and (3) the steric hindrance effect of branch chain alcohol. The permeability ratio (the ideal separation factor) of water to tert‐butanol across the membrane was calculated and found to follow the same relationship with increasing temperature and water content. Both flux and separation factor obtained from the Pervap2510 membrane in this study were much higher than previous reported values, possible causes for which were analyzed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4082–4090, 2004
Oxygen microwave plasma treatment of silicone elastomer: Kinetic behavior and surface composition
Authors: Olander Björn , Wirsén Anders , Albertsson Ann‐Christine 
Published: January 2004

AbstractSilicone elastomers were surface modified by oxygen microwave plasma under different conditions and the elemental composition was followed by X‐ray photoelectron spectroscopy (XPS). The changes in elemental composition were mapped by a method based on ternary XPS diagrams that we have recently developed. Already at the shortest treatment times, 5 s, the change in surface composition is more than one‐half the maximum change obtained on prolonged exposure. After this initial change, the surface gradually oxidizes toward the final composition. Curve resolutions of C1s and Si2p XPS data showed that the initial jump in surface composition is caused by an oxidation of silicon where one of the two methyl groups are replaced by an oxygen. The second methyl group appears to be more difficult to remove, but as the treatment progresses, the number of oxygen bonded to silicon gradually increases. The dominating form of carbon acts as unoxidized methyl groups throughout the process, but the total carbon percentage decreases as the treatment progresses. This indicates either that the methyl groups are removed without prior oxidation or that the methyl groups are removed shortly after oxidation. A silica‐like surface layer was formed on prolonged plasma treatment under all the investigated conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 4098–4104, 2004
The effect of mutations altering biogenic amine metabolism in Drosophila on viability and the response to environmental stresses
Authors: Gruntenko N. , Chentsova N.A. , Bogomolova E.V. , Karpova E.K. , Glazko G.V. , Faddeeva N.V. , Monastirioti M. , Rauschenbach I. Yu. 
Published: January 2004

AbstractDopamine (DA) content, tyrosine decarboxylase (TDC) activity and survival were studied under normal and environmental stress conditions in the ste and e strains carrying ebony mutation increasing DA level and the octopamineless strain TβhnM18 of Drosophila melanogaster. Wild‐type strains Canton S and Oregon R, and strain p845 from which TβhnM18 strain was derived were used as controls. Sexual dimorphism of TDC activity, DA content, and survival in flies of all D. melanogaster strains under study was found. TβhnM18 mutation sharply reduced TDC activity in females, while ebony had no such effect. DA content and survival under heat stress in TβhnM18 flies did not differ from those in the wild type. ste and e flies had drastically increased DA content under normal conditions, dramatically decreased survival under heat stress, but increased survival under starvation. DA content and survival under heat stress were also studied in the reciprocal hybrids (males) F1 of the cross D. virilis strains 101 (wild type) and 147 with X‐linked mutation, which significantly increases DA content. 147×101 males had a considerably higher DA content and lower survival than 101×147 ones. Individuals of all D. melanogaster strains under study developed the stress reaction, as judged by changes in TDC activity and DA levels. The role of biogenic amines in the stress reaction development and adaptation to environmental stresses in Drosophila is discussed. Arch. Insect Biochem. Physiol. 55:55–67, 2004. © 2004 Wiley‐Liss, Inc.
Morphological and molecular effects of 20‐hydroxyecdysone and its agonist tebufenozide on CF‐203, a midgut‐derived cell line from the spruce budworm, Choristoneura fumiferana
Authors: Hu Wenqi , Cook Barbara J. , Ampasala Dinakara R. , Zheng Sichun , Caputo Guido , Krell Peter J. , Retnakaran Arthur , Arif Basil M. , Feng Qili 
Published: January 2004

AbstractThe morphological and molecular responses of a midgut‐derived cell line of the spruce budworm, Choristoneura fumiferana, to 20‐hydroxyecdysone (20E) and the nonsteroidal ecdysone agonist, tebufenozide (RH‐5992), were investigated. The cells responded to these compounds by clumping, generating filamentous extensions, increased mortality and expression of the transcription factor, Choristoneura hormone receptor 3 (CHR3). This cell line can be used as a model system to study the mode of action of ecdysone and its agonists. With subsequent passaging in ecdysteroid‐containing medium, the degree of clumping increased and the clumping could not be reversed by subculturing in ecdysteroid‐free medium. Cell numbers of the adapted cell lines in 20E and RH‐5992 containing media were not significantly decreased, compared to the control, but both cell lines accumulated less 14C‐labeled RH‐5992 and lost the capability of expressing CHR3 in response to these compounds. Taken together, the cell lines appeared to develop a mechanism to adapt to the toxic effects of these compounds. Arch. Insect Biochem. Physiol. 55:68–78, 2004. © 2004 Wiley‐Liss, Inc.
Role of antioxidant defense during different stages of preadult life cycle in European corn borer (Ostrinia nubilalis, Hubn.): Diapause and metamorphosis
Authors: Jovanović‐Galović A. , Blagojević D.P. , Grubor‐Lajšić G. , Worland R. , Spasić M.B. 
Published: January 2004

AbstractAntioxidant enzymes, total glutathione (GSH), and ascorbic acid (ASA) were determined in whole body homogenates of nondiapausing larvae, diapausing larvae during the diapausing period (October, December, and February), and in pupae emerged from both diapausing and nondiapausing larvae of the European corn borer (Ostrinia nubilalis, Hubn., Lepidoptera: Pyralidae). The activities of catalase, selenium nondependent glutathione peroxidase (GPx), and glutathione‐S‐transferase (GST), as well as the content of GSH and ASA, were found to vary throughout the larval diapause. Compared to diapausing larvae, nondiapausing larvae were higher in levels of catalase, GPx, GST, and dehydroascorbate reductase (DHAR) activity. GSH content was also increased. However, nondiapausing larvae contained less ASA than diapausing ones. Pupae had higher GPx and GST activity and an increased ASA content compared to larvae. The pupae emerged from nondiapausing larvae had higher GST, glutathione reductase (GR), and DHAR activities, but lower GPx activity and ASA content than those emerged from diapausing larvae. Correlation analysis revealed differences in the way the antioxidant level is equilibrated for a particular stage and developmental pattern. The results suggest that cellular antioxidants are involved in both the protection of cells and the regulation of redox levels during the pre‐adult stages of Ostrinia nubilalis. Arch. Insect Biochem. Physiol. 55:79–89, 2004. © 2004 Wiley‐Liss, Inc.
Changes in leucine transport activity in Chironomus riparius larvae after short‐term exposure to potassium dichromate and fenitrothion
Authors: Forcella Matilde , Berra Elisa , Giacchini Roberto , Hanozet Giorgio M. , Parenti Paolo 
Published: January 2004

AbstractThe effect of sublethal concentrations of potassium dichromate and fenitrothion on sodium‐leucine cotransport in brush border membrane vesicles from Chironomus riparius larvae has been investigated. Exposure to potassium dichromate and fenitrothion caused a dose‐ and time‐dependent inhibition of leucine uptake. Transport inhibition is easily detectable at doses 100‐fold lower than LD50. Kinetic experiments showed that inhibition was mainly caused by a decrease of the Vmax (680 ± 53 vs. 382 ± 23 and 555 ± 27 nmol/15s/mg protein in control and exposed larvae to K2Cr2O7 and fenitrothion, respectively). Inhibition is possibly related to a variation of sodium ions permeability as evidenced by increased membrane lipid peroxidation. Appropriate control experiments ruled out that the observed differences could be due to changes in general features of membrane preparations. Transport inhibition observed in larvae exposed to potassium dichromate was accompanied by changes in ascorbate peroxidase and dehydroascorbate reductase activities, whereas those exposed to fenitrothion displayed an increase in transaminase activity. The possible value of leucine uptake as biochemical biomarker is briefly discussed. Arch. Insect Biochem. Physiol. 55:90–101, 2004. © 2004 Wiley‐Liss, Inc.
Developmental toxicity of arecoline, the major alkaloid in betel nuts, in zebrafish embryos
Authors: Chang Bei‐En , Liao Mei‐Hui , Kuo M. Yen‐Ping , Chen Chi‐Hsiang 
Published: January 2004

AbstractBackgroundThe major alkaloid in the betel nut, arecoline, has been reported to be potent in inducing developmentally toxic effects by generally lowering the embryo weight and retarding development of the embryo. This study examined the adverse effects of arecoline and tried to unravel the mechanism through the tools of molecular biology.METHODSArecoline was administered to zebrafish embryos by incubation at concentrations ranging from 0.01–0.04% (wt/vol) and lethality and morphological changes were recorded. The expression of genes was analyzed by reverse transcription‐polymerase chain reaction (RT‐PCR) and whole‐mount in situ hybridization. In addition, the protective effects of several antioxidants were tested.RESULTSThe survival rate of treated embryos during a three‐day incubation significantly declined as the arecoline concentration increased. Treated embryos showed general growth retardation and lower rate of heartbeat. When examined at the 24‐hr stage, the relative amounts of transcripts of p53, p21, and cyclin D1, and the spatial expression patterns of these genes in treated groups, were comparable to those of the untreated early stages of embryos. Finally, the addition of glutathione (GSH) or its precursor, N‐acetyl‐L‐cysteine (NAC), ameliorated the developmental retardation of embryos by arecoline.CONCLUSIONSArecoline‐treated embryos exhibited general developmental retardation in a dose‐dependent manner. Our results from RT‐PCR, in situ hybridization, and antioxidant‐protection experiments indicate that the mechanism underlying growth retardation by arecoline in embryos is predominately due to a general cytotoxic effect induced by depletion of intracellular thiols. Birth Defects Research (Part A) 67:000–000, 2003. © 2003 Wiley‐Liss, Inc.
Analyzing protein–protein interactions in cell membranes
Authors: Nohe Anja , Petersen Nils O. 
Published: January 2004

AbstractInteractions among membrane proteins regulate numerous cellular processes, including cell growth, cell differentiation and apoptosis. We need to understand which proteins interact, where they interact and to which extent they interact. This article describes a set of novel approaches to measure, on the surface of living cells, the number of clusters of proteins, the number of proteins per cluster, the number of clusters or membrane domains that contain pairs of interacting proteins and the fraction of one protein species that interacts with another protein within these domains. These data can then be interpreted in terms of the function of the protein‐protein interactions. BioEssays 26:196–203, 2004. © 2004 Wiley Periodicals, Inc.
A cluster translocation model may explain the collinearity of Hox gene expressions
Authors: Papageorgiou Spyros 
Published: January 2004

AbstractA model is proposed that deals with the observed collinearities (spatial, temporal and quantitative) of Hox gene expression during pattern formation along the primary and secondary axes of vertebrates. In particular, in the proximodistal axis of the developing limb, it is assumed that a morphogen gradient is laid down with its source at the distal tip of the bud. The extracellular signals in every cell of the morphogenetic field are transduced and uniformly amplified so that molecules are produced in the nucleus with appropriate physicochemical properties. These molecules can exert a concentration‐dependent force on the Hox cluster. It is assumed that, before activation, the Hox cluster is packaged as an elongated rigid body inside the chromatin and is covered by a coat that prevents the transcription factors reaching the genes of the cluster. The transcription factors are confined to the interchromatin domain and their density decreases with their distance from the chromatin surface. A gradual increase in the extracellular morphogen concentration causes a corresponding increase in the number of the nuclear molecules and the resulting bigger force pushes the Hox cluster toward the interchromatin domain. The step‐by‐step translocations of the Hox cluster initiate the consecutive exposure of genes to their transcription factors. The model explains how gene activation is triggered and it describes spatial, temporal and quantitative collinearities at the initial stages of gene expression. Some recent experiments of Hox deletions and duplications are accounted for by the model. BioEssays 26:189–195, 2004. © 2004 Wiley Periodicals, Inc.