bluuebunny/crossref_metadata_2025_split huggingface dataset:
SKCaChannels Mediate the Medium But Not the Slow Calcium-Activated Afterhyperpolarization in Cortical Neurons
Authors: Villalobos Claudio , Shakkottai Vikram G. , Chandy K. George , Michelhaugh Sharon K. , Andrade Rodrigo 
Published: April 2004

Many neurons, including pyramidal cells of the cortex, express a slow afterhyperpolarization (sAHP) that regulates their firing. Although initial findings suggested that the current underlying the sAHP could be carried through SKCachannels, recent work has uncovered anomalies that are not congruent with this idea. Here, we used overexpression and dominant-negative strategies to assess the involvement of SKCachannels in mediating the current underlying the sAHP in pyramidal cells of the cerebral cortex.Pyramidal cells of layer V exhibit robust AHP currents composed of two kinetically and pharmacologically distinguishable currents known as the medium AHP current (ImAHP) and the slow AHP current (IsAHP).ImAHPis blocked by the SKCachannel blockers apamin and bicuculline, whereasIsAHPis resistant to these agents but is inhibited by activation of muscarinic receptors. To test for a role for SKCachannels, we overexpressed KCa2.1 (SK1) and KCa2.2 (SK2), the predominant SKCasubunits expressed in the cortex, in pyramidal cells of cultured brain slices. Overexpression of KCa2.1 and KCa2.2 resulted in a fourfold to fivefold increase in the amplitude ofImAHPbut had no detectable effect onIsAHP. As an additional test, we examinedIsAHPin a transgenic mouse expressing a truncated SKCasubunit (SK3-1B) capable of acting as a dominant negative for the entire family of SKCa–IKCachannels. Expression of SK3-1B profoundly inhibitedImAHPbut again had no discernable effect onIsAHP. These results are inconsistent with the proposal that SKCachannels mediateIsAHPin pyramidal cells and indicate that a different potassium channel mediates this current.
Amphibious water‐soluble copolymer. I. Its synthesis and dispersing ability on barium titanate
Authors: Chen Lung‐Pin , Ying Kuo‐Liang , Hsu Kung‐Chung 
Published: April 2004

AbstractAn amphibious water‐soluble copolymer, polyacrylamide/(α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate (PAAM/DAAE), was synthesized and used as a dispersion agent for BaTiO3 particles. PAAM/DAAE was prepared from acrylamide and (α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate under basic conditions through a free‐radical polymerization. The structure of this copolymer was verified with IR and 1H‐NMR spectra. The dispersing effects of PAAM/DAAE were examined through the measurement of the viscosity and sedimentation of BaTiO3 suspensions and the green density. The results indicated that this copolymer could uniformly disperse the particles, reduce the viscosity, stabilize the suspensions, and produce high‐density green compacts. In comparison with a commercial dispersant, the ammonium salt of poly(methylacrylic acid), PAAM/DAAE was clearly more effective. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2232–2239, 2004
Thermal stability of native polybutylene terephthalate
Authors: Shelgaev V. N. , Mikitaev A. K. , Lomakin S. M. , Zaikov G. E. , Koverzanova E. V. 
Published: April 2004

AbstractThe thermal and thermooxidative stability of polybutylene terephthalate (PBTP), synthesized in the presence of the optimal stabilizing system, has been investigated. The basic products of PBTP degradation and the regularities of their formation in the temperature regime close to the temperature regimes of its processing were determined. The investigations conducted allowed recommendations to be made on the temperature regimes of PBTP processing because even a small excess of the chosen temperature (265°C) leads to polymer chain fragmentation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2351–2356, 2004
Sound absorption properties of thermally bonded nonwovens based on composing fibers and production parameters
Authors: Lee Youn Eung , Joo Chang Whan 
Published: April 2004

AbstractThis article reviews the noise absorption capacity of thermally bonded nonwovens in the range of audible frequencies (125–2500 Hz). First, we focus on the effects of the properties of the fibers, which constitute nonwovens, on the sound absorption properties, and then we consider the web orientation angle of nonwovens. We also investigate a composite model of the sound absorption properties of nonwovens, including the surface roughness and panel vibration. We have used an impedance tube interferometer, which provides the normal incidence sound absorption coefficient of materials, for the determination of the noise absorption properties of nonwovens produced under different conditions. The noise absorption capacity of nonwovens depends primarily on the thickness and surface characteristics of specimens, but the effects of the fiber contents are only marginal. Interestingly, when there is a panel in front of nonwovens, the noise absorption capacity increases significantly at low and medium frequencies (250–1000 Hz). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2295–2302, 2004
Phosphonate‐containing bismaleimide resins. II. Preparation and characteristics of reactive blends of phosphonate‐containing bismaleimide and epoxy
Authors: Shu Wei‐Jye , Chin Wei‐Kuo , Chiu Hsiu‐Jung 
Published: April 2004

AbstractTwo kinds of phosphonate‐containing bismaleimide (BMI) monomers, phenyl‐(4,4′‐bismaleimidophenyl) phosphonate and ethyl‐(4,4′‐bismaleimido‐phenyl) phosphonate, were synthesized and added through blending to two epoxy systems for the study of their applications as reactive flame retardants. The thermal behaviors of the BMI monomers in both kinds of epoxy systems, bisphenol and phenol–novolac, were similar. An increase in the BMI contents increased the storage modulus and glass‐transition temperature but slightly reduced the mechanical strength of the epoxy blends. The pyrolysis models of both BMI blends in the two epoxy systems were quite alike. Although the initial pyrolysis temperatures of all the blending systems gradually decreased as the phosphorous content increased, the flame retardancy of all the phosphonate‐containing epoxy systems was promoted significantly by increasing contents of BMI. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2375–2386, 2004
Tl(III) initiated polymerization of methyl methacrylate in micellar phase
Authors: Patra Manabendra , Behera Ajay K. , Behera Rajani K. , Sinha Bijoy K. 
Published: April 2004

AbstractThe polymerization kinetics of methyl methacrylate (MMA) was studied, using Tl(III)‐cyclohexanone (CH) redox system as initiator, in the presence of emulsifier [i.e., sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and thallium triacetate (TX‐100)] over a temperature range of 25–45°C. The effect of various concentrations of MMA, Tl(III), cyclohexanone, H+, and varying ionic strengths on the rate of polymerization, rate of Tl(III) consumption (−RTl), and the percentage of monomer conversion were examined in the presence of 0.015M SDS. The kinetic results of polymerization in the absence and presence of 0.015M SDS were compared in terms of overall activation energy (Ea) for the process. The viscosity‐average molecular weight (MV) of the polymers, obtained in the presence of varying concentrations of anionic surfactant (SDS), was also determined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2480–2485, 2004
Effects of water on the curing and properties of epoxy adhesive used for bonding FRP composite sheet to concrete
Authors: Wu Lixin , Hoa Suong V. , Ton‐That Minh‐Tan 
Published: April 2004

AbstractWhen a concrete surface is contaminated by water due to rain, saline water, ground water, and water jetty treatment, water, alkalis, and other contaminants on the concrete surface may interact with an epoxy adhesive used for bonding fiber‐reinforced polymer composite sheets to concrete. This can influence both the curing rate and the degree of cure of the curing reaction. This in turn can affect the time required for field application. It can also influence the mechanical properties and durability of epoxy adhesives. In this paper, water effects on the curing and properties of two kinds of commercial adhesives were evaluated. Curing kinetics were studied using isothermal DSC analysis. Results showed that water accelerated the curing reaction. However, excess water offsets part of the accelerating effect. While water is typically considered to be harmful to properties of adhesives, it was seen that a small amount (less than 2%) of water improved degree of cure, mechanical properties, and durability of adhesives. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2261–2268, 2004
Proton exchange membranes by grafting of styrene–acrylic acid onto FEP by preirradiation technique. II. Physicochemical properties of the membrane and its sulfonated derivatives
Authors: Phadnis Swati , Patri M. , Hande Varsha R. , Roychoudhury Suhasini , Deb P. C. 
Published: April 2004

AbstractPoly(tetrafluoroethylene‐co‐haxafluoropropylene) (FEP)‐g‐styrene–acrylic acid and its sulfonated derivative membranes were prepared by graft copolymerization of styrene–acrylic acid onto FEP by using preirradiation of γ‐ray technique followed by sulfonation. The physiochemical properties such as ion exchange capacity, water uptake, ionic resistance of the grafted membranes, and their sulfonated derivatives were studied as a function of degree of grafting. These membranes on sulfonation gave acid base, indicating property. The membranes gave yellow color in acidic medium and purple color in alkali medium. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2318–2325, 2004
Complexation of poly(dimethylsiloxane)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) latex with poly(dimethylsiloxane)/poly(vinyl acetate‐co‐butyl acrylate) latex
Authors: Yang Mingjiao , Dan Yi 
Published: April 2004

AbstractTwo latices—the poly(dimethylsiloxane) (PDMS)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) system (PA latex) and the PDMS/poly(vinyl acetate‐co‐butyl acrylate) system (PB latex)—were prepared by seeded emulsion polymerization, and PA/PB complex latices were obtained through the interparticle complexation of the PA latex with the PB latex. In addition, for the further study of the interparticle complexation of the PA latex with the PB latex, copolymer latices [PDMS/methyl methacrylate‐co‐butyl acrylate‐co‐vinyl acetate‐co‐methacrylic acid) (PC)] were prepared according to the monomer recipe of the complex latices and the polymerization process of the component latices. The properties of the obtained polymer latices and complex latices were investigated with surface‐tension, contact‐angle, and viscosity measurements. The mechanical properties of the coatings obtained from the latices were investigated with tensile‐strength measurements. The results showed that, in comparison with the two component latices (PA latex and PB latex) and the corresponding copolymer latices (PC latices), the PA/PB complex latices had lower surface tension, lower viscosities, and better wettability to different substrates. The tensile strengths of the coatings obtained from the complex latices were higher than the tensile strengths of the coatings from the two component latices and copolymer latices. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2522–2527, 2004
Studies on poly(styrene‐co‐maleic anhydride)‐modified polyesteramide‐based anticorrosive coatings synthesized from a sustainable resource
Authors: Zafar Fahmina , Sharmin Eram , Ashraf S. M. , Ahmad Sharif 
Published: April 2004

AbstractPolyesteramide (PEA) coating resin, synthesized from linseed oil, a sustainable resource, was found to show improved physicomechanical and acid‐resistance properties. To further improve these properties in terms of alkali resistance, scratch hardness, and thermal stability and to reduce the baking temperature, we have attempted to incorporate styrene into the polymer backbone through its copolymer with maleic anhydride. The structural elucidation of modified PEA resin (SCPEA) was carried out by FTIR, 1H‐NMR, and 13C‐NMR spectroscopes. The physicomechanical and chemical‐resistance properties were investigated by standard methods and thermal stability was investigated by thermogravimetric analysis method. A comparative study of these properties of PEA and SCPEA was carried out. It was observed that the SCPEA showed better properties than the reported one. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2538–2544, 2004
New polyurethane cationomers with naphthyl and phenyltriazene pendants: Synthesis and properties
Authors: Buruiana Emil C. , Niculescu Violeta , Buruiana Tinca 
Published: April 2004

AbstractTwo new diols bearing triazene moiety, 1‐(α‐naphthyl)‐3,3‐di(2‐hydroxyethyl) triazene‐1 (NT‐D) and 1‐phenyl‐3,3‐di(2‐hydroxyethyl) triazene‐1 (PT‐D), were synthesized from aromatic amines and diethanolamine. These monomers were used as chain coextenders in the two‐step addition reaction between poly(tetramethylene oxide) diol, 2,4‐tolylene diisocyanate, and N‐methyldiethanolamine to obtain photosensitive polyurethanes of elastomer type. Triazene polyurethane cationomers with chlorine counterions were prepared via a quaternization reaction of the above polymers with benzyl chloride. All polyurethanes had a quantity of triazene units between 7.02 and 8.93 wt % polymer, and the content of ammonium quaternary groups in the cationic ones was of 30.56 meq/100 g naphthyl triazene polyurethane cationomer (PUC‐NT) and 30.19 meq/100 g phenyl triazene polyurethane cationomer (PUC‐PT), respectively. Photobehavior of the triazene units in all polymers under continuous Hg‐lamp irradiation was similar to that found for monomers, when both chromophores were transformed during UV irradiation. It is concluded that the PT‐D acts as a more efficient sensitizer in the UV light‐induced reaction but the photolysis in elastomeric films was lower than that observed in solution. The presence of quaternary ammonium structure on the same polymer backbone decreases the constant rates of photolysis. Because the triazene polyurethanes become crosslinked during UV irradiation could be assessed as potential negative‐resist polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2599–2605, 2004
Pore structure of water‐wettable hydrophobic resins based on divinylbenzene and methyl acrylate
Authors: Wei Jia , Zhao Xin , Yan Jun 
Published: April 2004

AbstractHydrophobic, but water‐wettable porous resins based on divinylbenzene (DVB) and methyl acrylate (MA) were prepared with a wide range of pore structures by suspension copolymerization under different conditions. By using purified DVB (98.8%), the specific surface area for the resulting MA/DVB resins could reach high values at high DVB levels, while these resins are wettable by direct contact with water. An increased content of MA significantly increases the porosity of the resins, whereas the solvating power of the porogen affects both pore structure and water‐wettability of the MA/DVB resins profoundly. Treating these MA/DVB resins with ferric chloride in the presence of dichloroethane gives products with larger surface areas and an enhanced water‐wettability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2681–2688, 2004
Studies of sulfonated polyethylene for biliary stent application
Authors: Peng Mei‐Chuan , Lin Jui‐Che , Chen Chiung‐Yu , Wu Jiunn‐Jong , Lin Xi‐Zhang 
Published: April 2004

AbstractPalliative treatment for obstructive jaundice by endoscopic biliary stent insertion is a recent commonly used method. Unfortunately, stent reobstruction may occur within 3 to 6 months as a result of bacterial adhesion and formation of biofilm. Bacterial adhesion was postulated as the initial step of stent clogging and the bacterial enzyme activity of β‐glucuronidase led to the deposition of calcium bilirubinate. In this study, surface sulfonation of the polyethylene lumen was postulated to improve the patency of the biliary stent. Surface modification with sulfonated group formation was carried out with fuming sulfuric acid containing 20 wt % sulfuric trioxide (SO3). The reaction time varied from 1 to 3 h at room temperature. ATR‐FTIR and ESCA techniques showed that the surface amount of sulfonated functionalities increased with sulfonation time. The contact angle of the sulfonated PE, determined by the sessile drop technique, decreased compared to that of unmodified PE, but cannot be detected by the captive bubble method because of the high surface hydrophilicity. SEM micrographs indicated that the sulfonated PE inner lumen remained relatively smooth after extended sulfonation reaction. Adhesion of Escherichia coli to the sulfonated PE stents after 48‐h bile perfusion was about 10‐ to 20‐fold less than that to the unmodified PE, as observed by SEM and surface spreading method. These results indicated that the surface sulfonated groups could effectively decrease the adhesion of E. coli in human bile, probably attributable to the hydrophilic repellence between the bacterial cell membrane and sulfonated groups. This finding suggested that the sulfonated PE tubing could prolong the patency period of plastic stents and may be of great potential as a biliary stent in a real clinical setting. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2450–2457, 2004
Temperature/pH‐sensitive comb‐type graft hydrogels composed of chitosan and poly(N‐isopropylacrylamide)
Authors: Lee Sang Bong , Ha Dong In , Cho Seong Kwan , Kim Seon Jeong , Lee Young Moo 
Published: April 2004

AbstractComb‐type graft hydrogels, composed of chitosan and poly(N‐isopropylacrylamide) (PNIPAAm), were prepared to manifest rapid temperature and pH sensitivity. Instead of directly grafting the NIPAAm monomer onto the chitosan chain, semitelechelic PNIPAAm with carboxyl end group was synthesized by radical polymerization using 3‐mercaptopropionic acid as the chain‐transfer agent, and was grafted onto chitosan having amino groups. The comb‐type hydrogels were prepared with two different graft yields and grafting regions, such as surface‐ and bulk‐grafting, and then compared with a chitosan hydrogel. The synthesis of telechelic PNIPAAm and the formation of amide group were confirmed by using FTIR spectroscopy and gel permeation chromatography. Results from the water state and thermal stability revealed that the introduction of the PNIPAAm side chain disturbed the ordered arrangement of the chitosan molecule, resulting in an increase in the equilibrium water content. Comb‐type graft hydrogels showed rapid temperature and pH sensitivity because of the free‐ended PNIPAAm attached to the chitosan main chain and the chitosan amino group itself, respectively. In particular, the surface graft hydrogel maintained its dimension at low pH, although the chitosan main chain was not crosslinked, whereas chitosan and bulk graft hydrogel were dissolved as a result of the coating effect of pH‐independent PNIPAAm. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2612–2620, 2004
Resistivity of conductive polymer–coated fabric
Authors: Lekpittaya Porntip , Yanumet Nantaya , Grady Brian P. , O'Rear Edgar A. 
Published: April 2004

AbstractPreparation of conductive polymer–coated fabrics was carried out by admicellar polymerization. By this method, a thin layer of conductive polymers (polypyrrole, polyaniline, and polythiophene) was formed on cotton and polyester fabrics by a surfactant template. The effects of monomer concentration, oxidant to monomer ratio, and addition of salt on the resistivity of the resulting fabrics were studied. The results showed that the apparent surface and volume resistivity decreased with an increase in monomer concentration in the range 5–15 mM, but was not strongly dependent on the oxidant to monomer ratio over the range of 1 : 1 to 2 : 1. Addition of 0.5M salt was found to reduce the resistivity significantly. The lowest resistivity obtained was with polypyrrole‐coated fabric, with resistivity around 106 ohm. SEM micrographs of the treated fabric surface showed a filmlike polymer coating, confirming that the fabrics were successfully coated by admicellar polymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2629–2636, 2004
Syntheses and biodegradability of benzylated waste pulps and graft copolymers from PBzs and L‐lactic acid
Authors: Hadano Shingo , Maehara Seiji , Onimura Kenjiro , Yamasaki Hirohito , Tsutsumi Hiromori , Oishi Tutomu 
Published: April 2004

AbstractBenzylated waste pulps (PBzs) were synthesized from treated waste pulp (Pulp), and benzyl chloride with phase transfer catalyst (PTC), and graft copolymers (PBz‐g‐LA) were synthesized from PBzs and L‐lactic acid (LA). Thermal properties, solubility, crystallinity, and biodegradability of the obtained PBzs and graft copolymers were investigated. PBzs with the degree of substitution (DS) higher than 1.5 showed Tg and Tm in DSC measurement. All PBz‐g‐LA exhibited no Tm. However, the graft copolymers obtained from lower DS PBzs having no Tg, exhibited Tg. The solubility of PBzs enhanced with increasing DS, and the crystallinity of PBzs reduced with increasing DS because of hydrophobicity and steric effect of benzyl groups. The solubility of graft copolymers was similar to that of original PBzs. Biodegradation tests for PBzs, Pulp, and graft copolymers were performed using cellulase in 0.1 M acetate buffer solution (pH 5.5) at 37°C. All samples showed biodegradability though the biodegradation rate decreased with increasing DS of PBz. In PBz‐g‐LA, the initial biodegradation rate was faster than that of original PBz because of hydrolysis of LA units. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2658–2664, 2004
Nanocomposites of poly(vinyl chloride) and nanometric calcium carbonate particles: Effects of chlorinated polyethylene on mechanical properties, morphology, and rheology
Authors: Wu Dezhen , Wang Xiaodong , Song Yongzhi , Jin Riguang 
Published: April 2004

AbstractNanocomposites of poly(vinyl chloride) (PVC) and nano‐calcium carbonate (CaCO3) particles were prepared via melt blending, and chlorinated polyethylene (CPE) as an interfacial modifier was also introduced into the nanocomposites through preparing CPE/nano‐CaCO3 master batch. The mechanical properties, morphology, and rheology were studied. A moderate toughening effect was observed for PVC/nano‐CaCO3 binary nanocomposites. The elongation at break and Young's modulus also increased with increasing the nano‐CaCO3 concentration. Transmission electron microscopy (TEM) study demonstrated that the nano‐CaCO3 particles were dispersed in a PVC matrix uniformly, and a few nanoparticles agglomeration was found. The toughening effect of the nano‐CaCO3 particles on PVC could be attributed to the cavitation of the matrix, which consumed tremendous fracture energy. The notched Izod impact strength achieved a significant improvement by incorporating CPE into the nanocomposites, and obtained the high value of 745 J/m. Morphology investigation indicated that the nano‐CaCO3 particles in the PVC matrix was encapsulated with a CPE layer through preparing the CPE/nano‐CaCO3 master batch. The evaluation of rheological properties revealed that the introduction of nano‐CaCO3 particles into PVC resulted in a remarkable increase in the melt viscosity. However, the viscosity decreased with addition of CPE, especially at high shear rates; thus, the processability of the ternary nanocomposites was improved. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2714–2723, 2004