bluuebunny/crossref_metadata_2025 huggingface dataset:
Butadiene polymerization with vanadium–titanium–aluminum catalytic systems
Authors: Mullagaliev I. R. , Kharitonova E. Y. , Urazbaev V. N. , Monakov Y. B.
Published: November 2003

Butadiene polymerization in the presence of mixed vanadium–titanium–aluminum catalytic systems containing various organoaluminum compounds (OACs) was investigated. The main factors influencing the activity and stereospecificity of the [VOCl3–TiCl4–OAC1]–(heating)–OAC2 catalysts [where OAC1 and OAC2 were Al(i‐Bu)3, Al(i‐Bu)2H, or Al(i‐Bu)2Cl] were considered. The kinetic parameters of the process were determined. The high activity and stereospecificity of the multicomponent systems probably accounted for the formation of polymerization active sites with both transition‐metal derivatives in their structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 211–217, 2004
Synthesis and characterization of graft copolymers of hydroxypropyl cellulose with acrylamide and some comonomers
Authors: Chauhan Ghanshyam S. , Sharma Rajeev , Lal Harinder
Published: November 2003

To obtain new polymeric materials for environmental management, we used pine needles from the huge forest of the Western Himalayas as a source of cellulose. Cellulose was derivatized to hydroxypropyl cellulose (HPC), a useful water‐soluble cellulose ether. HPC was graft‐copolymerized with acrylamide (AAm) with benzoyl peroxide as the initiator. At optimum grafting conditions, five different concentrations of the comonomers glycidyl methacrylate, acrylic acid, 2‐hydroxyethyl methacrylate, and acrylonitrile were grafted with AAm. Networks of HPC and AAm were also synthesized by crosslinking reactions with glutaraldehyde as a crosslinker over a range of four different concentrations of crosslinker under acidic conditions. Crosslinked networks of HPC with AAm and a comonomer at one comonomer concentration were also synthesized. Graft copolymers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and swelling behavior. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 545–555, 2004
Thermal stability and dynamic mechanical behavior of acrylic resin and acrylic melamine coatings
Authors: Chattopadhyay D. K. , Rohini Kumar D. B. , Sreedhar B. , Raju K. V. S. N.
Published: November 2003

Acrylic polyols of different hydroxyl numbers consisting of hydroxy ethyl methacrylate, methyl methacrylate, butyl acrylate, and styrene were prepared by free‐radical solution as well as suspension polymerization techniques in the presence of benzoyl peroxide initiator. These polyols were crosslinked with butoxy methyl melamine at a ratio of 85 : 15 in the presence of acid catalyst. The thermal stability of polyols and their corresponding crosslinked films was studied by thermogravimetric (TG) technique. The Broido and Coats–Redfern methods were used to calculate the activation energy of thermal decomposition from standard TG curves. Dynamic mechanical thermal analysis was used to study the dynamic mechanical properties and determination of glass‐transition temperature of acrylic/melamine crosslinked films. The results indicate that the thermal stability of polyols and crosslinked films strongly depends on the hydroxyl number of the acrylic polyols. It was found that acrylic polyols synthesized by suspension polymerization methods upon crosslinking yield more thermally stable and flexible films than polyols prepared by solution polymerization methods. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 27–34, 2004
Effect of electrical field on dipoles in polymer composites
Authors: Švorčík V. , Gardášová R. , Rybka V. , Hnatowicz V. , Červená J. , Plešek J.
Published: November 2003

Orientation of two bipolar compounds embedded in polymer composites was studied. Poly(methyl methacrylate) (PMMA) dissolved in acetone was doped with a cobaltborane derivative of 1,2‐dimethylimidazole and polystyrene (PS) dissolved in toluene was doped with the 3‐(1,2‐dimethyl imidazole)‐borane. To orient the dipoles, the composites were exposed to external electrical field: PMMA composite at the temperature of glass transition (Tg) and PS composite during evaporation of the toluene solvent. The degree of dipole orientation was estimated by the change in relative permittivity (ε) of the resulting composite film. The dependence of the ε on the temperature, frequency, voltage, and dipole concentration was studied. It was found that the dipole's distribution in the composite film was not homogenous. At the Tg, the dipoles in PMMA became oriented by external direct electrical field and the orientation was conserved after cooling to lower temperatures. In a PS‐based composite, the significant permittivity increase was observed already at low‐dopant concentrations. The dipole orientation achieved during solvent evaporation was also permanent and the composite permittivity was an increasing function of the film thickness. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 40–45, 2004
The role of preconditioning on morphology development in layered silicate thermoset nanocomposites
Authors: Tolle Tia Benson , Anderson David P.
Published: November 2003

The impact of preconditioning constituent materials on the morphology development of organically modified montmorillonite–epoxy nanocomposites is examined to determine the sensitivity of exfoliation to material conditions. In situ synchrotron small‐angle X‐ray scattering studies were performed to relate the initiation and levels of exfoliated morphologies with various silicate preconditioning processes. Significantly, exfoliation could be achieved in systems initially considered intercalated by preconditioning through epoxy–silicate mixture aging. The resulting morphologies lead to slightly improved toughness. Implications for nanocomposite morphology development models include the necessity of further investigation of the complexities of both local and global morphologies. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 89–100, 2004
Compatibilization of a poly(butylene terephthalate)/poly(ethylene octene) copolymer blends with different amounts of an epoxy resin
Authors: Aróstegui A. , Nazábal J.
Published: November 2003

New toughened poly(butylene terephthalate) (PBT) materials were obtained by melt blending with 20 wt % poly(ethylene octene) (PEO) copolymer and different levels of a difunctional epoxy resin in a twin‐screw extruder followed by injection‐molding. The presence of neither PEO or epoxy influenced either the phase nature of the two amorphous phases of the blends or the crystallization process of PBT, despite the slight reaction of epoxy with PBT as stated by the observed torque increases. The addition of epoxy led to a decrease in the particle size that stopped due to the concomitant viscosity increase. Supertough PBT‐based blends with an impact strength more than 18‐fold that of PBT were obtained without previous chemical modification of any of the blend components at 1.0 wt % epoxy contents. The interparticle distance was the parameter that controlled notched toughness in these PBT/PEO blends. The adhesion at the interphase was the parameter on which the critical interparticle distance appeared to depend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 260–269, 2004
Reinforced poly(ether sulfone) materials by blending with a semiaromatic liquid crystalline copolyester
Authors: García M. , Eguiazábal J. I. , Nazábal J.
Published: November 2003

Blends based on poly(ether sulfone) (PES) and a semiaromatic liquid crystalline copolyester (R5) were obtained by injection molding across the entire composition range. The blends showed two pure amorphous phases. The fibrillar structure of the skin led to enhancements in the stiffness. The break properties, however, decreased at low LCP contents, due to the expected lack of adhesion between the phases. The increase in the modulus at increasing LCP content led to improvements in tensile strength. The notch sensitivity of PES decreased after the addition of low LCP levels, giving rise to enhancements of almost 600% in the notched impact strength. The unusually enhanced performance of the 20/80 blend, which has been seen previously in another thermoplastic/LCP blend, suggests that the dispersed PES phase in this blend may act as rubber particles do in rubber toughened thermoplastics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 52–59, 2004
Enhanced toughening of poly(propylene) with reclaimed‐tire rubber
Authors: Tantayanon Supawan , Juikham Sukunya
Published: November 2003

The dynamic vulcanization of reclaimed‐tire rubber (RTR) and homopolypropylene (PP) was performed by melt‐mixing using either a sulfur crosslinking agent, maleic anhydride (MA), dicumyl peroxide (DCP), or the combination of MA and DCP, in two consecutive machines, first a two‐roll mill and then a counterrotating twin‐screw extruder. In the case of applying a sulfur crosslinking agent, it was demonstrated that the RTR/PP blend at the ratio of 30/70 had the highest impact strength. This could be attributed to the limitation of carbon black in the blend. When the combination of MA and DCP was applied, the result was higher impact strength of the blend at the same ratio. This could be attributed to not only the cohesion between the polymer chains in each phase, PP phase and rubber phase, but also the interfacial adhesion between PP and RTR chains in these two phases. For comparison, the GRT/PP blends with and without sulfur crosslinking agent were prepared as well. All these blends showed low impact strength, which was nearly the same as that of PP. The effects of different crosslinking agents on dispersion and distribution of rubber domain size, viscosity, and percentage crystallinity were also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 510–515, 2004
Phase structural analyses of polyethylene extrusion coatings on high‐density papers. I. Monoclinic crystallinity
Authors: Furuheim Knut Magne , Axelson David E. , Antonsen Henrik W. , Helle Torbjørn
Published: November 2003

In the present work the morphology of high‐density polyethylene (HDPE) extrusion coating layer on high‐density paper (HDP) has been investigated. An uneven layer with a high content of crystallinity against the paper surface was discovered. The methods applied were solid‐state 13C NMR Spectroscopy and Atomic Force Microscopy. The highly crystalline layer was found to be mainly monoclinic crystallinity. The formation of the monoclinic crystallites was probably initiated by orientation of the polyethylene molecules by drawing, adhesion to the fibrous paper surface, and pressure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 218–225, 2004
Phase structural analyses of polyethylene extrusion coatings on high‐density papers. II. Influence of paper surface properties on the polyethylene morphology
Authors: Furuheim Knut Magne , Axelson David E. , Antonsen Henrik W. , Helle Torbjørn
Published: November 2003

Paper samples of three different qualities were extrusion coated with low‐density polyethylene (LDPE) and high‐density polyethylene (HDPE). The morphological phases of the polyethylene layers have been quantified by 13C solid‐state high‐resolution NMR. Shear forces in the process initiate the formation of the monoclinic crystallites. The surface tensions of the high‐density papers have influence on the degree of interaction between the two materials and how these shear forces work. The paper surface properties will thus have an influence on properties and the size of the monoclinic crystalline mass fraction of the polyethylene coating. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 226–234, 2004
n‐Butyl acrylate based latex interpenetrating polymer networks used as processing modifiers and impact modifiers of poly(vinyl chloride)
Authors: Zhang Liucheng , Pan Mingwang , Zhang Jian
Published: November 2003

A latex interpenetrating polymer network (LIPN), consisting of poly(n‐butyl acrylate), poly(n‐butyl acrylate‐co‐ethylhexyl acrylate), and poly(methyl methacrylate‐co‐ethyl acrylate) and labeled PBEM, with 1,4‐butanediol diacrylate as a crosslinking agent was synthesized by three‐stage emulsion polymerization. The initial poly(n‐butyl acrylate) latex was agglomerated by a polymer latex containing an acrylic acid residue and then was encapsulated by poly(n‐butyl acrylate‐co‐ethylhexyl acrylate) and poly(methyl methacrylate‐co‐ethyl acrylate). A polyblend of poly(vinyl chloride) (PVC) and PBEM was prepared through the blending of PVC and PBEM. The morphology and properties of the polyblend were studied. The experimental results showed that the processability and impact resistance of PVC could be enhanced considerably by the blending of 6–10 phr PBEM. This three‐stage LIPN PBEM is a promising modifier for manufacturing rigid PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1168–1173, 2004
Effects of surfactants on acrylonitrile polymerization initiated by a Cr(VI)–cyclohexanone redox system: A kinetic study
Authors: Patra Manabendra , Behera Ajay K. , Behera Rajani K. , Sinha Bijoy K.
Published: November 2003

The polymerization of acrylonitrile (AN) was kinetically studied with a Cr(VI)–cyclohexanone (CH) redox system as an initiator from 25 to 45° C in the presence of a surfactant. The rate of polymerization and the percentage of the monomer conversion increased as the concentration of the anionic surfactant [sodium dodecyl sulfate (SDS)] increased above its critical micelle concentration. However, the cationic surfactant (cetyltrimethylammonium bromide) reduced the rate considerably at higher concentrations, whereas the nonionic surfactant (TX‐100) had no effect on the rate. The effects of the Cr(VI), CH, AN, and H+ concentrations and the ionic strength on the rates were also examined. The presence of 0.015M SDS reduced the overall activation energy of the polymerization by 5.55 kcal/mol with respect to that in the absence of the surfactant. With increasing SDS concentration, the viscosity‐average molecular weight also increased. A suitable mechanistic scheme was proposed for the polymerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1147–1153, 2004
Blends of poly(ε‐caprolactone‐b‐lactic acid) and poly(lactic acid) for hot‐melt applications
Authors: Stolt Mikael , Viljanmaa Mikko , Södergård Anders , Törmälä Pertti
Published: November 2003

The condensation reaction product of poly(lactic acid) (PLA) and a hydroxyl‐terminated four‐armed poly(ε‐caprolactone) (PCL) was studied by size‐exclusion chromatography, DSC, and NMR. The use of both L‐lactic acid (LLA) and rac‐lactic acid (rac‐LA) was studied and the use of two different catalysts, stannous 2‐ethylhexanoate [Sn(Oct)2] and ferrous acetate [Fe(OAc)2], was also investigated. The thermal stability and adhesive properties were also measured for the different formulations. The characterization results suggested the formation of a blend of PLA and a block‐copolyester of PLA and PCL. The results further indicated partial miscibility in the amorphous phase of the blend showing only one glass‐transition temperature in most cases, although no randomized structures could be detected in the block‐copolymers. The polymerization in the Fe(OAc)2‐catalyzed experiments proceeded slower than in the Sn(Oct)2‐catalyzed experiments. The discoloring of the polymer was minor when Fe(OAc)2 was used as catalyst, but significant when Sn(Oct)2 was used. The ferrous catalyst also caused a slower thermal degradation. Differences in the morphology and in the adhesive properties could be related to the stereochemistry of the poly(lactic acid). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 196–204, 2004
Studies on double networks in natural rubber vulcanizates
Authors: Aprem Abi Santhosh , Joseph Kuruvilla , Thomas Sabu
Published: November 2003

The concept of double networks is a rather new idea, by which one imparts chain orientation in elastomers. Double networks were made in natural rubber vulcanizates cured with a single and a new binary accelerator system. Double networks with different extensions were prepared and their effects on tensile properties were analyzed. The influence of extent of initial cure on double‐network formation was examined. Thermal stability of the double network formed was analyzed by ageing of the double networks and was found to improve with residual extension. Crosslink density of the networks formed was determined by swelling methods and stress–strain analysis. It was found that crosslink density increased with double‐network formation and residual extension. The stress–strain behavior and moduli were analyzed to study the effect of these properties on double‐network formation. Double networks were hardly affected by the binary accelerator system. Based on the studies it was found that residual extension was the major factor determining the final properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1068–1076, 2004
Composites based on jute fibers and phenolic matrices: Properties of fibers and composites
Authors: Razera I. A. T. , Frollini E.
Published: November 2003

Composites based on phenolic matrices and both untreated and alkali and ionized air–treated jute fibers were prepared. Different fiber lengths and fiber content were used to reinforce the phenolic matrices. The jute fibers were characterized with respect to lignin, holocellulose, ash, and humidity contents and also to the crystallinity index. The mechanical properties of fibers were investigated by means of tensile analysis and the morphology by SEM. The untreated and treated jute fiber–reinforced composites were characterized as to water absorption. The mechanical property and morphological aspects of the composites were evaluated by impact strength and photomicrographs obtained from SEM. Among the jute fiber treatments considered in the present work, the treatment with a solution of 5% NaOH presented the best results because: (1) the fiber presented a higher tensile strength, and a larger percentage of elongation at break; (2) the composite reinforced with this fiber presented the highest impact strength results when this was the unique treatment (20% of fiber), as well as when it was combined with ionized air (30% of fiber); and (3) the composite that presented the lowest water uptake was that reinforced with this fiber. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1077–1085, 2004
Synthesis in inverse emulsion and associating behavior of hydrophobically modified polyacrylamides
Authors: Pabon Martial , Corpart Jean‐Marc , Selb Joseph , Candau Françoise
Published: November 2003

An inverse free‐radical emulsion polymerization technique was used to prepare copolymers of acrylamide and two different hydrophobic comonomers: N,N‐dihexylacrylamide (diC6) or N,N‐diphenylacrylamide (diPh). The products of the reaction were high molecular weight hydrophobically modified water‐soluble polymers (HMWSPs) encapsulated within water droplets dispersed in an organic medium. A comparison of the copolymer compositions prepared under different experimental conditions showed that the level of incorporation of diPh in the final copolymer depended strongly on its localization in the emulsion (aqueous or oil phase) and on the nature of the redox initiator pair (water‐soluble or oil‐soluble). The rheological properties of the HMWSPs in aqueous solution were investigated as a function of the comonomer content and the nature of the initiator, using steady‐flow experiments. The thickening properties were found to be directly correlated to the conditions of synthesis and were optimal when the initiator and the hydrophobic comonomer were located in two distinct phases. An examination of the viscosity as a function of shear rate showed that these solutions exhibit typical characteristics of hydrophobically associative polymers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 916–924, 2004
Microhardness studies of PMMA/natural rubber blends
Authors: Mina M. F. , Ania F. , Baltá Calleja F. J. , Asano T.
Published: November 2003

The microhardness, H, of PMMA/natural rubber blends, prepared following the solution method has been investigated by means of the microindentation technique. Hardness changes are correlated with the variation of the glass transition temperature. The influence of temperature and degree of deformation on H were additionally examined. The inclusion of rubber particles in the PMMA matrix is shown to soften the blends. The variation of the micromechanical property at the phase boundary of polymer/rubber particle has been studied. Results reveal that H drastically drops at the interphase. In the case of the drawn materials, the indentation anisotropy (ΔH) is shown to gradually increase with the draw ratio, where ΔH is found to be higher for the PMMA/rubber blend than for the original PMMA. This result is explained by the higher orientation of the PMMA molecules near the periphery of stretched rubber particles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 205–210, 2004
Phase morphology of PP/COC blends
Authors: Šlouf Miroslav , Kolařík Jan , Fambri Luca
Published: November 2003

Phase morphology of polymer blends PP/COC, where PP is polypropylene and COC is a copolymer of ethene and norbornene, was characterized by means of scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). PP/COC blends were prepared by injection molding and their morphology was studied for six different compositions (90/10, 80/20, 70/30, 60/40, 50/50, and 25/75 wt %). The intention was to improve PP properties by forming COC cocontinuous phase, which should impart to the PP matrix higher stiffness, yield stress, and barrier properties. Surprisingly enough, all studied blends were found to have fibrillar morphology. In the 90/10, 80/20, and 70/30 blends, the PP matrix contained fibers of COC, whose average diameter increased with increasing COC fraction. In the 60/40 blend, the COC component formed in the PP matrix both fibers and larger elongated entities with PP fibers inside. The 50/50 blend was formed by COC cocontinuous phase with PP fibers and PP cocontinuous phase with COC fibers. In the 25/75 blend, PP fibers were embedded in the COC matrix. In all blends, the fibers had an aspect ratio at least 20, were oriented in the injection direction, and acted as a reinforcing component, which was proven by stress–strain and creep measurements. According to the available literature, the fibrous morphology formed spontaneously in PP/COC is not common in polymer blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 253–259, 2004
Wood flour: A new filler for the rubber processing industry. II. Cure characteristics and mechanical properties of NBR compounds filled with corona‐treated wood flour
Authors: Vladkova T. G. , Dineff P. D. , Gospodinova D. N.
Published: November 2003

Corona‐treated wood flour was evaluated as a filler for NBR (nitrile butadiene rubber) compounds by studying its influence on their cure characteristics and mechanical properties. The different operating conditions of the corona treatment, such as voltage and duration, which led to different degrees of surface etching, were observed by means of electron microscopy. Accumulation of different oxygen‐containing groups on the wood flour particles' surface was confirmed by means of ESCA. Wood flour–filled materials were thus obtained with varying final properties. The cure characteristics, mechanical parameters, and water adsorption of the composites were estimated to determine an optimum level of the wood flour surface modification. The corona treatment of the wood flour renders it into a semiactive filler. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 883–889, 2004
Melt flow indexer evidence of high‐temperature transitions in molten high‐density polyethylenes
Authors: Hussein Ibnelwaleed A. , Williams Michael C.
Published: November 2003

A melt flow indexer (MFI) was used to investigate high‐temperature transitions in melts of high‐density polyethylene (HDPE). The MFI data were obtained in the range 190–230°C. These transitions were found in the MFI at about 210 and 225°C and reproduced in a Haake melt blender. Polystyrene was used in the blender experiment to demonstrate typical amorphous behavior. For HDPE melts, the MFI–temperature behavior and the torque–temperature data of the blender were found to be alternative images of the same anomalous temperature dependency in the range 210–225°C. Also, the Haake melt blender was able to reproduce the 150°C transition observed by Kolnaar and Keller in the extrusion of HDPE. Regardless of the simplicity of the MFI device, results are in agreement with our previous DSC findings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1309–1313, 2004
Effect of coupling agent on the mechanical properties of fly ash–filled polybutadiene rubber
Authors: Alkadasi Nabil A. N. , Hundiwale D. G. , Kapadi U. R.
Published: November 2003

Fly ash, a waste productof thermal power stations generated in huge quantities, has been posing problems of its disposal. As such it contains a variety of inorganic oxides and is available in finely powdered form. Attempts have been made for its use as a filler in elastomers and plastics. It is important to note that fly ash used in in untreated form does not significantly enhance the mechanical properties of composites. In this work, fly ash treated with silane coupling agent (Si‐69) was used as a filler in polybutadiene rubber (PBR). The comparison of properties of composites filled with treated and untreated fly ash revealed that the composites with treated fly ash showed better reinforcing properties. Thus the silane coupling agent used here promoted adhesion between fly ash and the PBR. The improvement in mechanical properties in general and tensile properties (tensile strength, modulus 100% and modulus 200%, hardness) of the composites in particular were observed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1322–1328, 2004
Properties of crosslinked casein/waterborne polyurethane composites
Authors: Wang Niangui , Zhang Lina , Lu Yongshang , Du Yuming
Published: November 2003

Waterborne polyurethane (WPU) and casein (1 : 1 by weight) were blended at 90°C for 30 min, and then were crosslinked by adding 1–10 wt % ethanedial to prepare a series of sheets. Their structure and properties were characterized by using infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical analysis, and tensile testing. The results indicated that crosslinked blend sheets exhibited a certain degree of miscibility, and exhibited much higher tensile strength and water resistivity than did the WPU, casein, and the uncrosslinked blend from WPU and casein. When the ethanedial content was 2 wt %, the tensile strength and elongation at break of crosslinked sheets achieved 19.5 MPa and 148% in the dry state, and 5.0 MPa and 175% in the wet state, respectively. A 2 wt % content of ethanedial plays an important role in the enhancement of mechanical properties, thermal stability, and water resistivity of the blends of WPU and casein as a result of intermolecular crosslinking. This work provided a new protein plastic with good water resistivity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 332–338, 2004
Influence of processing method on the exfoliation process for organically modified clay systems. I. Polyurethanes
Authors: Rhoney Ian , Brown Steven , Hudson Nicholas E. , Pethrick Richard A.
Published: November 2003

The influence of different processing methods on the nature of the dispersion achieved in the creation of a polyurethane nanocomposite is presented. The nanocomposites were produced using two different types of organically modified montmorillonite clays and a sample of fine particles of silicon nitride as a reference material. Rheological data were used to assess the nature of the dispersion achieved using the different processing methods. The nature of the dispersion produced was characterized using wide‐angle X‐ray scattering measurements of the finally cured products. Dynamic mechanical thermal analysis was used to investigate the effect of the incorporation of clay platelets into the matrix of the polymer. The high‐temperature modulus provides evidence of the interaction between the polymer and the clay platelets; however, surprisingly, the glass transition temperatures of the filled and unfilled materials were almost identical. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1335–1343, 2004
Characterization of two molluscan crystal‐modulating biomineralization proteins and identification of putative mineral binding domains
Authors: Michenfelder Martina , Fu Germaine , Lawrence Camille , Weaver James C. , Wustman Brandon A. , Taranto Laura , Evans John Spencer , Morse Daniel E.
Published: November 2003

Ethylenediamine‐tetraacetic acid extracted water‐soluble matrix proteins in molluscan shells secreted from the mantle epithelia are believed to control crystal nucleation, morphology, orientation, and phase of the deposited mineral. Previously, atomic force microscopy demonstrated that abalone nacre proteins bind to growing step edges and to specific crystallographic faces of calcite, suggesting that inhibition of calcite growth may be one of the molecular processes required for growth of the less thermodynamically stable aragonite phase. Previous experiments were done with protein mixtures. To elucidate the role of single proteins, we have characterized two proteins isolated from the aragonitic component of nacre of the red abalone, Haliotis rufescens. These proteins, purified by hydrophobic interaction chromatography, are designated AP7 and AP24 (aragonitic protein of molecular weight 7 kDa and 24 kDa, respectively). Degenerate oligonucleotide primers corresponding to N‐terminal and internal peptide sequences were used to amplify cDNA clones by a polymerase chain reaction from a mantle cDNA library; the deduced primary amino acid sequences are presented. Preliminary crystal growth experiments demonstrate that protein fractions enriched in AP7 and AP24 produced CaCO3 crystals with morphology distinct from crystals grown in the presence of the total mixture of soluble aragonite‐specific proteins. Peptides corresponding to the first 30 residues of the N‐terminal sequences of both AP7 and AP24 were generated. The synthetic peptides frustrate the progression of step edges of a growing calcite surface, indicating that sequence features within the N‐termini of AP7 and AP24 include domains that interact with CaCO3. CD analyses demonstrate that the N‐terminal peptide sequences do not possess significant percentages of α‐helix or β‐strand secondary structure in solution. Instead, in both the presence and absence of Ca(II), the peptides retain unfolded conformations that may facilitate protein–mineral interaction. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 522–533, 2003
Spectroscopic study of permanganate oxidation reactions of oligonucleotides containing single base mismatches
Authors: Bui Chinh T. , Lambrinakos Andreana , Cotton Richard G. H.
Published: November 2003

The electrophoretic gel‐based chemical cleavage of the mismatch method gives an incomplete view of the DNA conformational changes induced by a single base mismatch. This spectroscopic study investigates the permanganate oxidation reactions with matched and mismatched DNA under constant and variable temperature conditions. The results, which include the oxidation levels, reaction patterns with isosbestic points, color changes, thermal spectra, spectroscopy derivative, and gel separation and melting temperatures, provide a fundamental background for identification of oligonucleotides containing single base mismatches by chemical means. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 628–636, 2003
Experimental evaluation of phospholipids and icodextrin in re-formation of peritoneal adhesions
Authors: Müller S A , Treutner K H , Anurov M , Titkova S , Oettinger A P , Schumpelick V
Published: November 2003

Background

The formation of further adhesions after adhesiolysis is a major problem. Not all agents that are supposed to reduce de novo adhesions can reduce further adhesion formation. The efficacy and safety of intraperitoneally applied phospholipids has been shown previously. This study evaluated the influence of phospholipids and icodextrin on adhesion re-formation.

Methods

In an experimental study on 60 Chinchilla rabbits adhesions were induced by standardized abrasion of defined areas of the ventral abdominal wall, the caecum and the ileum. Open adhesiolysis was performed 10 days later. The animals randomly received either 1·5 per cent phospholipids, 4 per cent icodextrin or Ringer's lactate intraperitoneally. Half of the animals in each group were killed after a further 10 days and the remainder at 20 days. Adhesion formation was assessed by computer-aided planimetry and histopathological examination.

Results

Phospholipids (10 days: P = 0·001; 20 days: P = 0·012) and icodextrin (10 days: P = 0·006; 20 days: P = 0·055) reduced adhesion re-formation after both intervals compared with Ringer's lactate controls.

Conclusion

Phospholipids and icodextrin were effective in preventing re-formation of adhesions.
Persistent increase in the incidence of abdominal aortic aneurysm in Scotland, 1981–2000
Authors: Best V A , Price J F , Fowkes F G R
Published: November 2003

Background

In the 1970s and 1980s, mortality and morbidity rates for abdominal aortic aneurysm (AAA) increased throughout the developed world. As AAAs are associated with similar risk factors to other cardiovascular diseases that have recently decreased in incidence, the incidence of AAA should show a similar declining trend.

Methods

Routinely collected data were obtained on all primary diagnoses of aortic aneurysm resulting in death or hospital discharge in Scotland between 1981 and 2000. Trends in the data were analysed according to sex and age, aneurysm site and type of hospital admission.

Results

Between 1981 and 2000, 42·3 per cent of the 10 822 deaths from aortic aneurysm in Scotland were attributed to the abdominal aorta. Age-adjusted mortality rates for AAA increased 2·6-fold from 2·62 deaths per 100 000 in 1981 to 6·82 per 100 000 in 2000. Hospital admissions for AAA also rose threefold, with increases in both elective admissions (from 3·05 to 7·80 per 100 000) and emergency admissions (from 7·44 to 11·23 per 100 000).

Conclusion

The incidence of AAA has increased over the past 20 years in Scotland. This is unlikely to be due simply to changes in detection and diagnosis, data inaccuracies, coding or ageing of the population. The incidence of both elective and emergency admission for AAA increased, suggesting that a genuine and persistent rise in the incidence of AAA has probably occurred.
Matrix metalloproteinase 2 and 9 activity in patients with colorectal cancer liver metastasis
Authors: Waas E T , Wobbes T , Lomme R M L M , DeGroot J , Ruers T , Hendriks T
Published: November 2003

Background

Matrix metalloproteinases (MMPs) have been reported to play an important role in tumour cell invasion and metastasis. The bioactivity of MMPs in liver metastasis from colorectal cancer was investigated and correlated with clinicopathological variables.

Method

Thirty-two patients underwent resection of colorectal cancer liver metastases. Latent and active forms of MMP were measured in tissue extracts, by means of quantitative gelatin zymography and a fluorometric activity assay.

Results

Broad-spectrum MMP activity, and levels of both active and latent forms of MMP-2 and MMP-9, were higher in tissues containing metastatic tumour than in normal liver tissue. Median metastatic to normal tissue ratios were 15·0 and 17·6 for active and proMMP-2 respectively, and those for active and proMMP-9 were 6·2 and 2·9. The ratios of active to latent enzyme were higher in metastatic tissue than in normal tissue. Lowered MMP-2 activity was associated with large metastatic lesions and increased proMMP-9 levels with preoperative chemotherapy. Both MMP-2 and MMP-9 activity were linked unfavourably to early recurrent disease.

Conclusion

These data suggest a role for MMPs in colorectal cancer liver metastasis, but indicate different roles for individual MMPs.
Lateral pelvic lymph node dissection for advanced lower rectal cancer
Authors: Fujita S , Yamamoto S , Akasu T , Moriya Y
Published: November 2003

Background

The oncological outcome of patients who underwent curative surgery for lower rectal cancer was investigated to clarify whether lateral pelvic lymph node dissection (LPLD) conferred any benefit.

Methods

A total of 246 patients who underwent curative surgery for stage II and III lower rectal cancer (below the peritoneal reflection) between 1985 and 1998 was reviewed. Forty-two of these patients did not undergo LPLD.

Results

Patients who did not undergo LPLD were older, more likely to have anterior resection and pelvic nerve preservation, and had smaller tumours and lymph node metastasis at an earlier stage than those who underwent LPLD. There was no difference in survival among patients with stage II and III disease between the two groups. However, in patients with pathological N1 lymph node metastasis, the 5-year disease-free survival rate was 73·3 per cent in patients who had LPLD compared with 35·3 per cent among those who did not (P = 0·013). Multivariate analysis showed that LPLD was a significant prognostic factor.

Conclusion

LPLD improved the prognosis of patients with stage III disease and a small number of lymph node metastases. A randomized clinical trial is needed to verify the benefit of LPLD.
Comparison of histological features and inflammatory cell reaction in alcoholic, idiopathic and tropical chronic pancreatitis
Authors: Shrikhande S V , Martignoni M E , Shrikhande M , Kappeler A , Ramesh H , Zimmermann A , Büchler M W , Friess H
Published: November 2003

Background

There is increasing evidence that immune mechanisms may be crucial in the development of alcoholic chronic pancreatitis. However, it is not known whether differences in underlying aetiology influence the inflammatory reaction in patients with chronic pancreatitis. The histological features and the pattern of inflammatory cell infiltration were studied in three aetiological forms of chronic pancreatitis: alcoholic, idiopathic and tropical pancreatitis.

Methods

Forty-three patients, ten with alcoholic, 12 with idiopathic and 21 with tropical chronic pancreatitis, were evaluated for the pattern of pancreatic inflammatory cell infiltration and histological features. Ten organ donors served as controls. Haematoxylin and eosin-stained tissue sections were used for histological evaluation. For immunohistochemical characterization of the inflammatory reaction, four antibodies—CD4, CD8, CD45 and CD68—were used. Quantitative evaluation of the various cell infiltrates was performed with computer-assisted image analysis. The inflammatory cell infiltration pattern was also evaluated.

Results

The degree of endophlebitis and the overall density of plasma cells were greater in tropical than in alcoholic chronic pancreatitis. The grade of intralobular fibrosis was significantly higher in tropical chronic pancreatitis compared with the idiopathic form. No significant quantitative differences in the specific cellular infiltrates (CD4, CD8, CD45, CD68) were observed in the three different groups. However, the perivascular inflammation number score was significantly higher in alcoholic compared with idiopathic pancreatitis (P = 0·037), and the perivascular inflammation area score was significantly lower in idiopathic than in alcoholic (P = 0·024) or tropical (P = 0·020) pancreatitis.

Conclusion

Different aetiological forms of chronic pancreatitis result in similar histological features and a comparable inflammatory cell reaction, indicating that the disease, independent of the underlying aetiology, reaches a common immunological stage beyond which it appears to progress as a single distinctive entity.
Randomized clinical trial of multimodal optimization and standard perioperative surgical care
Authors: Anderson A D G , McNaught C E , MacFie J , Tring I , Barker P , Mitchell C J
Published: November 2003

Background

Multimodal optimization of surgical care has been associated with reduced hospital stay and improved physical function. The aim of this randomized trial was to compare multimodal optimization with standard care in patients undergoing colonic resection.

Methods

Twenty-five patients requiring elective right or left hemicolectomy were randomized to receive a ten-point optimization programme (14 patients) or conventional care (11). The groups were similar in terms of age (64 versus 68 years), male : female sex ratio (6 : 8 versus 5 : 6) and Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) score (both 26). Outcome measures were recorded before operation and on postoperative days 1, 7 and 30. They included hand grip strength, lung spirometry, and pain and fatigue scores. Further outcome measures included time to achieve a predetermined mobilization target, time to resumption of normal diet, and length of stay.

Results

Optimization was associated with maintained grip strength, earlier mobilization (46 versus 69 h; P = 0·043), and significantly lower pain and fatigue scores. Patients in the optimization group tolerated a regular hospital diet significantly earlier than controls (48 versus 76 h; P < 0·001). Optimization significantly reduced the median length of hospital stay (3 versus 7 days; P = 0·002).

Conclusion

Optimization of surgical care significantly improved patients' physical and psychological function in the early postoperative period and facilitated early hospital discharge.
Chemical neuroanatomy of the fly's movement detection pathway
Authors: Sinakevitch Irina , Strausfeld Nicholas J.
Published: November 2003

In Diptera, subsets of small retinotopic neurons provide a discrete channel from achromatic photoreceptors to large motion‐sensitive neurons in the lobula complex. This pathway is distinguished by specific affinities of its neurons to antisera raised against glutamate, aspartate, γ‐aminobutyric acid (GABA), choline acetyltransferase (ChAT), and a N‐methyl‐D‐aspartate type 1 receptor protein (NMDAR1). Large type 2 monopolar cells (L2) and type 1 amacrine cells, which in the external plexiform layer are postsynaptic to the achromatic photoreceptors R1–R6, express glutamate immunoreactivity as do directionally selective motion‐sensitive tangential neurons of the lobula plate. L2 monopolar cells ending in the medulla are accompanied by terminals of a second efferent neuron T1, the dendrites of which match NMDAR1‐immunoreactive profiles in the lamina. L2 and T1 endings visit ChAT and GABA‐immunoreactive relays (transmedullary neurons) that terminate from the medulla in a special layer of the lobula containing the dendrites of directionally selective retinotopic T5 cells. T5 cells supply directionally selective wide‐field neurons in the lobula plate. The present results suggest a circuit in which initial motion detection relies on interactions among amacrines and T1, and the subsequent convergence of T1 and L2 at transmedullary cell dendrites. Convergence of ChAT‐immunoreactive and GABA‐immunoreactive transmedullary neurons at T5 dendrites in the lobula, and the presence there of local GABA‐immunoreactive interneurons, are suggested to provide excitatory and inhibitory elements for the computation of motion direction. A comparable immunocytological organization of aspartate‐ and glutamate‐immunoreactive neurons in honeybees and cockroaches further suggests that neural arrangements providing directional motion vision in flies may have early evolutionary origins. J. Comp. Neurol. 468:6–23, 2004. © 2003 Wiley‐Liss, Inc.
Correlation of expression of the actin filament‐bundling protein espin with stereociliary bundle formation in the developing inner ear
Authors: Li Huawei , Liu Hong , Balt Steve , Mann Sabine , Corrales C. Eduardo , Heller Stefan
Published: November 2003

The vertebrate hair cell is named for its stereociliary bundle or hair bundle that protrudes from the cell's apical surface. Hair bundles mediate mechanosensitivity, and their highly organized structure plays a critical role in mechanoelectrical transduction and amplification. The prototypical hair bundle is composed of individual stereocilia, 50–300 in number, depending on the animal species and on the type of hair cell. The assembly of stereocilia, in particular, the formation during development of individual rows of stereocilia with descending length, has been analyzed in great morphological detail. Electron microscopic studies have demonstrated that stereocilia are filled with actin filaments that are rigidly cross‐linked. The growth of individual rows of stereocilia is associated with the addition of actin filaments and with progressively increasing numbers of cross‐bridges between actin filaments. Recently, a mutation in the actin filament‐bundling protein espin has been shown to underlie hair bundle degeneration in the deaf jerker mouse, subsequently leading to deafness. Our study was undertaken to investigate the appearance and developmental expression of espin in chicken inner ear sensory epithelia. We found that the onset of espin expression correlates with the initiation and growth of stereocilia bundles in vestibular and cochlear hair cells. Intense espin immunolabeling of stereocilia was colocalized with actin filament staining in all types of hair cells at all developmental stages and in adult animals. Our analysis of espin as a molecular marker for actin filament cross‐links in stereocilia is in full accordance with previous morphological studies and implicates espin as an important structural component of hair bundles from initiation of bundle assembly to mature chicken hair cells. J. Comp. Neurol. 468:125–134, 2004. © 2003 Wiley‐Liss, Inc.
Basement membrane proteins promote progression of intraepithelial neoplasia in 3‐dimensional models of human stratified epithelium
Authors: Andriani Frank , Garfield Jackie , Fusenig Norbert E. , Garlick Jonathan A.
Published: November 2003

We have developed novel 3‐dimensional in vitro and in vivo tissue models that mimic premalignant disease of human stratified epithelium in order to analyze the stromal contribution of extracellular matrix and basement membrane proteins to the progression of intraepithelial neoplasia. Three‐dimensional, organotypic cultures were grown either on a de‐epidermalized human dermis with pre‐existing basement membrane components on its surface (AlloDerm), on a Type I collagen gel that lacked basement membrane proteins or on polycarbonate membranes coated with purified extracellular matrix proteins. When tumor cells (HaCaT‐II4) were mixed with normal keratinocytes (4:1/normals:HaCaT‐II4), tumor cells selectively attached, persisted and proliferated at the dermal‐epidermal interface in vitro and generated dysplastic tissues when transplanted to nude mice only when grown in the presence of the AlloDerm substrate. This stromal interface was permissive for tumor cell attachment due to the rapid assembly of structured basement membrane. When tumor cells were mixed with normal keratinocytes and grown on polycarbonate membranes coated with individual extracellular matrix or basement membrane components, selective attachment and significant intraepithelial expansion occurred only on laminin 1 and Type IV collagen‐coated membranes. This preferential adhesion of tumor cells restricted the synthesis of laminin 5 to basal cells where it was deposited in a polarized distribution. Western blot analysis revealed that tumor cell attachment was not due to differences in the synthesis or processing of laminin 5. Thus, intraepithelial progression towards premalignant disease is dependent on the selective adhesion of cells with malignant potential to basement membrane proteins that provide a permissive template for their persistence and expansion. © 2003 Wiley‐Liss, Inc.