bluuebunny/crossref_metadata_2025 huggingface dataset:
Innovative polyamide‐based packaging of fresh meat
Authors: Laurino C. , Laurienzo P. , Malinconico M. , Scoponi M. , Sorrentino A. , Vacca P. , Volpe M. G.
Published: April 2004

Innovative polymeric films based on blends of nylon 6 and ethylene‐co‐vinyl alcohol, previously tested by contact with the simulating fat‐containing foods, were further tested as packaging for fresh minced meat. As quality attributes for the shelf‐life evaluation, the microbiological parameters and some chemical–physical parameters were chosen. The changes that occurred during the evaluation period of 6 days were monitored by several means on both the polymer films and the fresh meat. The results suggest that the barrier properties of the polymeric films were shown to play a determinant role in the lipid oxidation, thus confirming the previous evaluation of the simulating foods. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 23–29, 2004
Effect of chemically modified waste rubber powder as a filler in natural rubber vulcanizates
Authors: Yehia A. A. , Mull M. A. , Ismail M. N. , Hefny Y. A. , Abdel‐Bary E. M.
Published: April 2004

Waste rubber powder (RP) was subjected to chemical modification by using different concentrations of oxidizing agents such as nitric acid and 30% hydrogen peroxide solution. This treatment leads to introducing some functional groups onto the surface of RP. The chemically modified RP was incorporated in natural rubber mixes either alone or in combination with carbon black (HAF). The physicomechanical properties of NR vulcanizates obtained were studied and compared to NR vulcanizates filled with untreated RP. It was found that the chemically modified RP improves tensile strength and aging resistance of NR vulcanizates compared with untreated RP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 30–36, 2004
Dynamic mechanical properties of agricultural residues‐filled polystyrene
Authors: Abdel‐Goad Mahmoud A.‐Halim
Published: April 2004

Agricultural residues (cotton straw) were added as very small particles to polystyrene (PS) at different weight ratios by using a melt‐mixing technique. The dynamic mechanical tests were performed over a wide range of temperatures and frequencies by using an ARES rheometer (Rheometrics Scientific) operated in the dynamic mode. The dynamic mechanical properties in terms of the storage modulus (G′), loss modulus (G″), compliance moduli, loss tangent, and dynamic viscosity were studied and compared for PS and PS composite. The results showed that the dynamic mechanical moduli and viscosity were found to increase with the addition of cotton straw and rise further with its loading increasing. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 37–40, 2004
Effect of molecular weight on the rheological properties of atactic poly(vinyl alcohol)/dimethylsulfoxide/water solution
Authors: Lyoo Won Seok , Lee Sung Jun , Kim Joon Ho , Noh Seok Kyun , Ji Byung Chul , Kim Byoung Chul
Published: April 2004

This article describes the molecular weight effect of atactic poly(vinyl alcohol) (a‐PVA) on the rheological properties of 7.5, 10.0, and 12.5 g/dL solutions of a‐PVA with number‐average degrees of polymerization (Pn) of 4000 and 1700 in dimethylsulfoxide/water mixture. a‐PVA with a Pn of 1700 solutions exhibited almost Newtonian flow behavior, whereas high molecular weight a‐PVA, with a Pn of 4000 solutions, exhibited shear‐thinning behavior. On the plot of storage and loss moduli of a‐PVA with a Pn of 1700 solutions, the dynamic storage modulus of a‐PVA, with a Pn of 1700 solutions, was smaller than the dynamic loss modulus over the frequency range of 10−1 to 102 rad/s. However, the dynamic storage modulus of a‐PVA, with a Pn of 4000 solutions, was smaller than the dynamic loss modulus in the sol state and, in the postgel state, the dynamic storage modulus became larger than the dynamic loss modulus, indicating the evolution of viscoelastic solid properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 41–46, 2004
Activation energy, free energy, enthalpy, and entropy changes associated with viscometric changes of extremely to moderately dilute aqueous solutions of polyvinylpyrrolidone at 288.15–313.15 K
Authors: Singh Man , Kumar Sanjay
Published: April 2004

Viscometric behavior of polyvinylpyrrolidone (PVP) was investigated for extremely dilute (0.002–0.010 g dL−1), dilute (0.02–0.10 g dL−1), and moderately dilute (0.20–1.00 g dL−1) solutions at 288.15, 290.15, 293.15, 295.15, 298.15, 300.15, 303.15, 305.15, 308.15, 311.15, and 313.15 K. The experimental data were plotted according to Jones–Dole, Fuoss, and Fedors equations. Intrinsic viscosity ([η]) variation with temperature indicated the existence of different hydrodynamic states of PVP in solution at different temperatures. The PVP was found to show polyelectrolyte behavior in extremely dilute solutions, probably attributable to the presence of partially polarizable >CO groups in the chain. Activation energy (ΔE), differential enthalpy (∂ΔH), entropy (∂ΔS), and free energy (∂ΔG) changes of viscous flow were derived from flow velocity and taken into account for interpretation of the results to better understand the hydrodynamic and conformational behavior of PVP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 47–55, 2004
Propylene polymerization using MgCl2/ethylbenzoate/TiCl4 catalyst: Determination of titanium oxidation states
Authors: Al‐Arifi A. S. N.
Published: April 2004

The chemical interaction of the catalyst MgCl2/ethylbenzoate/TiCl4 with the cocatalysts triethylaluminum and trisobutylaluminum was investigated to establish a relationship between the titanium oxidation states and the catalytic activity, polymer isotacticity, and polymer molecular weight in propylene polymerizations. This interaction was studied using different Al : Ti molar ratios by measuring the changes of the titanium oxidation states at different polymerization times. Both hydrogen and alkyl aluminum caused a reduction of Ti4+ species to lower oxidation states species Ti3+ and Ti2+. However, the Ti4+ species reduction appeared to be incomplete. It was found that the Ti4+ species undergoes a severe reduction as the Al : Ti molar ratio increases from 50 to 230 as overreduction takes place. This change of the Ti3+ species percentage with time was found to correlate with the rate–time profiles of propylene polymerization. From this observation, it would be fair to conclude that the trivalent titanium species is more likely to be the active titanium species for propylene polymerization than the aforementioned catalyst system. On the other hand, hydrogen addition was found to cause an increase in Ti3+ species. The increases in both hydrogen amount and/or Al : Ti molar ratio were found to cause a decrease in both molecular weight and polypropylene isotactic index. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 56–62, 2004
Short‐beam and three‐point‐bending tests for the study of shear and flexural properties in unidirectional‐fiber‐reinforced epoxy composites
Authors: Sideridis E. , Papadopoulos G. A.
Published: April 2004

The bending properties of composite materials are often characterized with simply supported beams under concentrated loads. The results from such tests are commonly based on homogeneous beam equations. For laminated materials, however, these formulas must be modified to account for the stacking sequence of the individual plies. The horizontal shear test with a short‐beam specimen in three‐point bending appears suitable as a general method of evaluation for the shear properties in fiber‐reinforced composites because of its simplicity. In the experimental part of this work, the shear strength of unidirectional‐glass‐fiber‐reinforced epoxy resin composites was determined in different fiber directions with the short‐beam three‐point‐bending test. Also, the elastic constants and flexural properties of the same materials were determined from bending experiments carried out on specimens in the 0, 15, 30, 45, 60, 75, and 90° fiber directions with high span–thickness ratios. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 63–74, 2004
Crosslinking of high‐density polyethylene in the presence of organic peroxides
Authors: Anbarasan Ramasatamy , Babot Odile , Maillard Bernard
Published: April 2004

The crosslinking efficiency of various commercially available organic peroxides (dicumyl peroxide, O,O‐t‐butyl O‐2‐ethylhexylperoxycarbonate, t‐butyl peroxybenzoate, t‐butyl 3,5,5‐trimethylperoxyhexanoate, and t‐butyl 2‐ethylperoxyhexanoate) was tested on high‐density polyethylene (HDPE) in its molten state. The variations of the concentrations of the peroxides versus the crosslinking extent were plotted for these peroxides, and the values were compared. Dicumyl peroxide was found to be the best crosslinking agent for HDPE. The efficiency of the HDPE crosslinking with each peroxy derivative was analyzed on the basis of the behavior of the radicals generated from it. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 75–81, 2004
Pseudothermoset blends of poly (methyl methacrylate) and polypyrrole morphological, thermal, and conductivity studies
Authors: Ashraf S. M. , Ahmad Sharif , Riaz Ufana
Published: April 2004

Blends of poly (methyl methacrylate) (PMMA)/Polypyrrole (PPy) were synthesized by emulsion polymerization of methyl methacrylate (MMA) and in situ oxidative polymerization of pyrrole (Py) with varying concentrations of Py and ferric chloride. The influence of the varying concentrations of ferric chloride, Py, and MMA on the morphological, spectral, thermal, and conductance characteristics of the blends were investigated. Hydrogen bonding between PPy and PMMA was inferred from FTIR studies that indicate blend formation. DSC and TGA analysis of the blends were done. A curious thermal behavior was observed that the blends lost their elasticity and flexibility on heating and turned into rigid and brittle material. DSC thermogram did not show glass transition temperature, indicating molecular and chain reorganization on heating. We have therefore called these blends pseudothermoset. The physicomechanical characteristics of the films of the blends were found to deteriorate with the increased ratio of ferric chloride in the blend, causing a decrease in the conductivity. Maximum conductivity (percolation threshold) was found at 14 wt % loading of Py in the blend (1.6 × 10−3 S cm−1), which was further correlated with the morphology of the films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 82–91, 2004
Diffusion‐controlled polymer dissolution and drug release
Authors: Vrentas J. S. , Vrentas C. M.
Published: April 2004

A model is formulated for diffusion‐controlled polymer dissolution and simultaneous drug release for amorphous, uncrosslinked polymers. Calculated fractional drug release versus time curves are similar to experimental curves reported in the literature. Solutions of the transport equations provide a way of illustrating how polymer type and molecular weight can be used in an attempt to approach a constant drug release rate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 92–99, 2004
Twin‐screw extrusion compounding of polypropylene/organoclay nanocomposites modified by maleated polypropylenes
Authors: Wang Yeh , Chen Feng‐B. , Wu Kai‐C.
Published: April 2004

Polypropylene/organoclay nanocomposites modified with different maleic anhydride grafted polypropylene (PPgMA) compatibilizers were compounded on a twin‐screw extruder. The effectiveness of the feeding sequence and compatibilizer type toward the dispersion of organoclay into PP matrix was critically studied. The composites prepared with side feed appeared to provide better dispersion and modulus improvement over that with hopper feed. The effect of PPgMA compatibilizers, including PB3150, PB3200, PB3000, and E43, with a wide range of maleic anhydride (MA) content and molecular weight was also examined. The structure was investigated with X‐ray diffraction and transmission electron microscopy. The relative complex viscosity curves also revealed a systematic trend with the extent of exfoliation and showed promise for quantifying the hybrid structure of the nanocomposites. Mechanical properties were determined by dynamical mechanical analysis and tensile and impact tests. Maleated polypropylene with low‐melt flow index and moderate MA content enhanced clay dispersion and resulted in significant improvement in tensile modulus of the nanocomposites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 100–112, 2004
Shear flow behavior and oil distribution between phases in thermoplastic vulcanizates
Authors: Jayaraman Krishnamurthy , Kolli Venkata Giri , Kang Sang‐Yoon , Kumar Sharad , Ellul Maria D.
Published: April 2004

The high rate shear flow behavior and the morphology of five different oil‐extended polypropylene (PP)/ethylene‐propylene‐diene monomer (EPDM) thermoplastic vulcanizate blends were investigated with the melt flow rate (MFR) of the PP varying from 0.7 to 20. The ratio of rubber to PP is 70 : 30 in three of the thermoplastic vulcanizates (TPVs) and 50 : 50 in the other two TPVs. The distribution of the high‐temperature oil between the PP melt and the rubber is a key parameter because this will affect the viscosity of the PP/oil medium. The object of this study was to estimate the matrix composition in each of the TPVs at processing temperatures and to compare the shear viscosity of the effective matrix with that of the TPV. To this end, several PP/oil mixtures were prepared and their viscosity curves were correlated with the neat PP melt viscosity curves by means of shift factors varying with oil concentration. The oil distribution between the PP and rubber phases was estimated from TEM micrographs of the TPV blends. The results show that the PPs are mixed with oil to different proportions in the different TPVs and the viscosity curves of these mixtures exhibit the same trends in magnitude as the corresponding TPV viscosity curves. Hence, the shear flow of TPVs can be understood more readily in terms of the effective PP/oil medium flow behavior than in terms of the neat PP melt flow. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 113–121, 2004
Studies on surface tension of poly(vinyl alcohol): Effect of concentration, temperature, and addition of chaotropic agents
Authors: Bhattacharya A. , Ray P.
Published: April 2004

It is generally considered that the H‐bonds are responsible for the stabilization of network of PVA in water. The major types of intermolecular interactions from inorganic salts are responsible for the network of poly(vinyl alcohol) (PVA) and water, which ruptures the multiple H‐bonds between the OH groups of the polymer chains; therefore, various ions possessing abilities to affect these bonds result in salting out. It has been suggested that water molecules in the region of ionic hydration spheres must have strong orientation preferences, which could considerably restrict their ability to reorient and form hydration shells around nearby nonpolar solutes and thus affect the microstructure. In this article, our primary objective was to study the variation of surface tension, as it reflects the change in short‐range forces. Apart from this, we have also studied the surface tension behavior with the variation of concentration and temperature for different molecular weights of PVA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 122–130, 2004
Optical‐limiting properties of poly(arylene ethynylenes) containing thiophene ring
Authors: Zhou Guijiang , Liu Yunqi , Ye Cheng
Published: April 2004

Poly(arylene ethynylenes) containing thiophene ring were synthesized in good yield. In synthesis, pyridine was added to accelerate reaction owing to its phase transfer effect on CuI. The optical‐limiting properties of the prepared polymers were investigated with a Q‐switched Nd : YAG laser at 532 nm with 10‐ns pulse width. The experiments showed that the order of the optical‐limiting response of the polymers is poly(3‐hexyl‐2,5‐thienyleneethylene) (P3) > poly(2,5‐dihexyloxy‐1,4‐benzyleneethylene‐3‐hexyl‐2,5‐thienyleneethylene) (P2) > poly(9‐hexyl‐3,6‐carbazoleethylene‐3‐hexyl‐2,5‐thienyleneethylene) (P1). It can be understood well by the comparison of their conjugation length and D‐A structure. In addition, the results indicated that introducing the electron‐rich aromatic ring into the polymer backbone to enhance the D‐A structure would be an effective way to improve its optical‐limiting property. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 131–135, 2004
Waterborne anionomeric polyurethane–ureas from functionalized fluoropolyethers
Authors: Turri S. , Levi M. , Trombetta T.
Published: April 2004

A family of anionomeric segmented polyurethane–ureas made from α‐ω dimethylol‐terminated perfluoropolyethers (Mn = 1000–2000), isophorone diisocyanate, dimethylol propionic acid, and ethylenediamine was obtained in form of stable aqueous dispersions. The dispersions were characterized by viscometry and dynamic laser light scattering. The main compositive parameters explored were the amount of COOH groups and the length of the fluorinated macromer. The new polyurethane–ureas were characterized by dynamic mechanical analysis obtaining information on modulus, thermal transition, and phase segregation. Surface properties and chemical resistance were estimated through measurements of static contact angles and spot tests with different solvents. Although surface hydrophobicity was not affected by composition, water‐sorption behavior was sensitive to the ionic character (COOH level) of the polymer. Diffusion and permeability coefficients of polymer films, having different carboxyl contents, were estimated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 136–144, 2004
Cotton fabric graft copolymerization using microwave plasma. I. Universal attenuated total reflectance–FTIR study
Authors: Abidi Noureddine , Hequet Eric
Published: April 2004

The effect of microwave plasma on lightweight cotton fabric was investigated. N2‐plasma, O2‐plasma, and Ar‐plasma were obtained using a microwave generator at 2.45 GHz under vacuum. The universal attenuated total reflectance–Fourier transform infrared (UATR–FTIR) instrument was used to monitor the changes created after N2‐, O2‐, and Ar‐plasma treatments. The exposure of cotton fabrics to the plasma for 240 s with a microwave power of 500 W was sufficient to create active carbonyl groups, as shown by the presence of a peak around 1725 cm−1 in the FTIR spectra of the treated cotton fabrics. Ar‐plasma was found to generate more active groups than N2‐ and O2‐plasmas. The active centers created within the cellulose chains were used to initiate copolymerization reactions with vinyl monomers to impart hydrophobic character to lightweight cotton fabric. The efficiency of the grafting process and the presence of grafted monomers on fabric surface were confirmed using UATR–FTIR. Testing of treated fabric revealed that excellent water repellency was obtained. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 145–154, 2004
Rheological analysis of vapor‐grown carbon nanofiber‐reinforced polyethylene composites
Authors: Lozano Karen , Yang Shuying , Zeng Qiang
Published: April 2004

The melt rheological analysis of high‐density polyethylene reinforced with vapor‐grown carbon nanofibers (VGCNFs) was performed on an oscillatory rheometer. The influence of frequency, temperature, and nanofiber concentration (up to 30 wt %) on the rheological properties of composites was investigated. Specifically, the viscosity increase is accompanied by an increase in the elastic melt properties, represented by the storage modulus G′, which is much higher than the increase in the loss modulus G″. The composites and pure PE exhibit a typical shear thinning behavior as complex viscosity decreases rapidly with the increase of shearing frequency. The shear thinning behavior is much more pronounced for the composites with high fiber concentration. The rheological threshold value for this system was found to be around 10 wt % of VGCNF. The damping factor was reduced significantly by the inclusion of nanofibers into the matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 155–162, 2004
Investigation on the cell nucleation and cell growth in microcellular foaming by means of temperature quenching
Authors: Sun Xinghua , Liu Huiju , Li Gang , Liao Xia , He Jiasong
Published: April 2004

The cell nucleation and real‐time cell growth with increasing cell growth time in microcellular foaming were investigated by means of temperature quenching in a supercritical CO2 pressure‐quench process. Samples of uniform size and shape were saturated in a vessel under conditions of 100–180°C and 30 MPa, and then depressurized to the atmosphere in 10 s. After depressurization, these samples were removed from the vessel at prescribed intervals, and immediately immersed in an ice‐water slurry to obtain foamed samples with various cell growth times. It was found that the nucleation density is closely correlated to the gas absorption capacity of the polymer matrix, so that the final cell density should not be adopted as the nucleation density, as done commonly. The change of cell structure and mass density with increasing cell growth time was dominated by gas diffusion behavior, which was strongly influenced by the temperature. The final cell structure was mainly determined by the cell growth step, where gas diffusion played a key role. The final cell density was in direct proportion to the gas remaining in the substrate, which ranged from 6.0 × 109 to 4.7 × 106 cells/cm3. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 163–171, 2004
Functionalization of polypropylene film by radiation grafting of acryloyl chloride and subsequent esterification with Disperse Red 1
Authors: Bucio Emilio , Burillo Guillermina , Del Pilar Carreón‐Castro María , Ogawa Takeshi
Published: April 2004

Polypropylene (PP) films were grafted with acryloyl chloride by γ‐irradiation, and the grafted films were reacted with an azo dye, Disperse Red 1. The films were characterized by X‐ray diffraction, scanning electron microscopy, atomic force microscopy, and differential scanning calorimetry. It was found that the grafting takes place first on the film surface, and with increase in the radiation dose the grafting penetrated inside of the film, decreasing the crystallinity of the PP film. The surface of the films was homogeneous, and a mesophase was observed for the film grafted with the dye through a polarized optical microscope. The dye underwent trans to cis photoreaction, whereby the red films became colorless by the irradiation of UV light at room temperature, although the color was recovered on standing, and more quickly when heated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 172–178, 2004
Effects of dispersed phase composition on thermoplastic polyolefins
Authors: Ha M. H. , Kim B. K. , Kim E. Y.
Published: April 2004

Ternary blends of polypropylene (PP), ethylene–octene copolymer (mPE), and high‐density polyethylene (HDPE) were prepared based on the phase behavior and physical properties of mPE/HDPE binary blends, and the results were interpreted in terms of morphology and both rheological and mechanical properties of the ternary blends as well as the binary blends. It was found that when mPE encapsulates HDPE in the PP matrix, compared to the encapsulation of mPE by HDPE, better blend properties were obtained, presumably because of the compatibilizing effect of mPE between PP and HDPE. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 179–188, 2004
Electrochemical polymerization of toluene in the mixed electrolytes of boron trifluoride diethyl etherate and trifluoroacetic acid
Authors: Li Enhua , Shi Gaoquan , Hong Xiaoyin , Wu Peiyi
Published: April 2004

Poly(methylphenylene) (PMeP) films were prepared by direct oxidation of toluene in the mixed electrolytes of boron trifluoride diethyl etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potential of toluene in pure BFEE was measured to be 1.52 V versus saturated calomel electrode (SCE). This value was much lower than that determined in a neutral medium such as acetonitrile (2.13 V versus SCE). The introduction of TFA into BFEE decreased the oxidation potential of toluene and also improved the properties of as‐formed polymer films. Infrared and Raman spectra confirmed the formation of PMeP films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 189–195, 2004
Preparation of cationic wheat starch by twin‐screw reactive extrusion
Authors: Tara Ahmed , Berzin Françoise , Tighzert Lan , Vergnes Bruno
Published: April 2004

Cationic starches were prepared in a corotating twin‐screw extruder by using wheat starch and two different reagents: 2.3‐epoxypropyltrimethylammonium chloride (Quab 151®) and 3‐chloro 2‐hydroxypropyltrimethylammonium (Quab 188®) in aqueous sodium hydroxide (NaOH). The different factors affecting this reaction were investigated. These factors include the extrusion conditions (feed rate, screw speed, barrel temperature), the reagent chemical structure, the starch plasticizer, and the molar ratio between Quab and NaOH. Degree of substitution (DS) and reaction efficiency (RE) were characterized, as well as starch transformation. High reaction efficiency (90%) can be reached for a low degree of substitution. It appears that the epoxy form of the reagent (Quab 151®) is more efficient in all processing conditions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 201–208, 2004
Preparation and characterization of PVDF/silica hybrid membranes containing sulfonic acid groups
Authors: Kim Dae Sik , Park Ho Bum , Lee Young Moo , Park Young Hoon , Rhim Ji‐Won
Published: April 2004

Organic–inorganic hybrid membranes of poly(vinylidene fluoride)‐cohexafluoropropylene (PVDF‐HFP) and silica composites containing sulfonic acid groups were prepared via in situ polymerization of tetraethoxysilane (TEOS) and sulfosuccinic acid (SSA) using the sol‐gel process. The membranes containing more sulfonic acid groups showed a higher vapor sorption and greater swelling behavior. The bound and free water content of the membrane is proportional to the SSA concentration. However, the hybrid membranes without SSA do not have free water. The ion conductivity of the membranes is proportional to the SSA concentration. Silica content in the hybrid membrane without SSA had great effect on their mechanical properties. Tensile modulus and yield stress increased and yield strain and elongation at break decreased with increased silica content. However, in the case of the hybrid membrane containing SSA modulus, yield stress decreased and yield strain and elongation at break increased with increased silica content due to the weak interactions between the hydrophobic polymer chain and the hydrophilic group of SSA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 209–218, 2004
Evaluation of physical properties and curing characteristics of silica‐filled ethylene–propylene–diene terpolymer in the presence of chloroprene rubber
Authors: Das Amit , Debnath Subhas Chandra , De Debapriya , Basu Dipak Kumar
Published: April 2004

The effect of addition of chloroprene rubber (CR) on the dispersion of silica in EPDM (ethylene–propylene–diene terpolymer) was studied. It was observed that physical properties of the vulcanizates could be significantly increased at the EPDM : CR blend ratio of 92.5 : 7.5. SEM micrographs also indicated that incorporation of CR into EPDM improves the network structure of the resulting vulcanizates. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 196–200, 2004
Synthesis of PMMA‐PTHF‐PMMA and PMMA‐PTHF‐PST linear and star block copolymers
Authors: Macit Hulya , Hazer Baki
Published: April 2004

Combination of cationic, redox free radical, and thermal free radical polymerizations was performed to obtain linear and star polytetramethylene oxide (poly‐THF)‐polymethyl methacrylate (PMMA)/polystyrene (PSt) multiblock copolymers. Cationic polymerization of THF was initiated by the mixture of AgSbF6 and bis(4,4′ bromo‐methyl benzoyl) peroxide (BBP) or bis (3,5,3′,5′ dibromomethyl benzoyl) peroxide (BDBP) at 20°C to obtain linear and star poly‐THF initiators with Mw varying from 7,500 to 59,000 Da. Poly‐THF samples with hydroxyl ends were used in the methyl methacrylate (MMA) polymerization in the presence of Ce(IV) salt at 40°C to obtain poly(THF‐b‐MMA) block copolymers containing the peroxide group in the middle. Poly(MMA‐b‐THF) linear and star block copolymers having the peroxide group in the chain were used in the polymerization of methyl methacrylate (MMA) and styrene (St) at 80°C to obtain PMMA‐b‐PTHF‐b‐PMMA and PMMA‐b‐PTHF‐b‐PSt linear and star multiblock copolymers. Polymers obtained were characterizated by GPC, FT‐IR, DSC, TGA, 1H‐NMR, and 13C‐NMR techniques and the fractional precipitation method. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 219–226, 2004
The impact of oyster dredging on the growth of blue cod, Parapercis colias , in Foveaux Strait, New Zealand
Authors: Carbines Glen , Jiang Weimin , Beentjes Michael P.
Published: April 2004

Little is known about the potential impact of habitat modification by bottom fishing gear on the growth of demersal fishes. An analysis is presented for the growth of blue cod in Foveaux Strait, southern New Zealand, based on otoliths of fish captured from two sites in Foveaux Strait in 1999.

Each site contained two distinct areas of contrasting benthic habitat complexity, one area of relatively ‘complex’ recovering biogenic reef and another area of relatively ‘simple’ sand and gravel, both previously modified by oyster dredging.

Data were fitted to von Bertalanffy growth models for each sex of blue cod from the four areas sampled. No significant difference in growth models was observed for either male or female blue cod compared between the two types of habitat complexity at the eastern site. However, growth differed significantly for both sexes of blue cod from the two habitat types at the western site. Pairwise t‐tests further showed that growth differences only appeared biologically significant for the youngest blue cod sampled (3 years). These fish were, on average, 20% larger in complex biogenic reefs than in simple areas dredged by the oyster fishery.

These results suggest that on‐going disturbance and simplification of seabed habitat by the oyster fishery may impede the growth of juvenile blue cod. Areas of recovering biogenic reef may, therefore, provide important habitat for the recruitment and early development of blue cod in Foveaux Strait. Remedial actions may be required to protect some areas of recovering biogenic reef from further damage, and to allow dredged areas sufficient time to recover if the blue cod fishery and related resources are to be managed effectively.

Copyright © 2004 John Wiley & Sons, Ltd.
Identification of rat faecal, urinary and biliary metabolites of thionorphine, a novel mixed agonist‐antagonist analgesic, using liquid chromatography/electrospray ionization tandem mass spectrometry
Authors: Wei Shu‐xiang , Zhang Zhen‐qing , Wang Xiao‐ying , Guo Ji‐fen
Published: April 2004

The biotransformation of thionorphine (N‐cyclopropylmethyl‐7α‐[(s)‐1‐hydroxy‐1‐methyl‐3‐(2thiophene)‐propyl]‐6,14‐endo‐ethano tetrahydrooripavine), a new analgesic, was in‐vestigated in rats. The results of metabolite analysis by liquid chromatography/electrospray ionization tandem mass spectrometry with positive ion mode, in which a mobile phase of 10mM ammonium acetate (pH 3.0)/acetonitrile (25/75) was used, suggested that thionorphine is biotransformed to two potentially active metabolites, the N‐dealkylated thionorphine (M‐I) and the oxidized thionorphine (M‐II), and subsequently form conjugates with glucuronic acid of both thionorphine and the metabolites. Copyright © 2004 John Wiley & Sons, Ltd.
Adsorption of mercaptoacetic acid on a colloidal silver surface as investigated by Raman spectroscopy
Authors: Castro J. L. , López‐Ramírez M. R. , Centeno S. P. , Otero J. C.
Published: April 2004

The vibration ν(SH) has never been observed in the surface‐enhanced Raman scattering of mercaptoacetic acid recorded in a wide range of pH. This behavior enables us to deduce that the SH group is deprotonated and links to the metal forming an AgS bond as 1‐alkanethiols do. On the contrary, the carboxylic or carboxylate groups do not link to the metal and the carboxylic group is preserved even at pH values under which it should be deprotonated. This fact enables the stabilization of the adsorbed monolayer by removing the electrostatic repulsions between COO‐ groups and by the formation instead of hydrogen bonds between carboxylic groups. Only under rather basic conditions (pH > 8) does the carboxylic groups dissociate, but the νs(OCO) band is neither enhanced nor shifted toward low frequencies. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
A mixed mechanistic‐electrostatic model to explain pH dependence of glycosyl hydrolase enzyme activity
Authors: Olivera‐Nappa Alvaro , Andrews Barbara A. , Asenjo Juan A.
Published: April 2004

Glycosyl hydrolases are a vast group of enzymes that share a common topology at their active site with two acidic residues that are responsible for activity. In spite of their similarity, they exhibit a wide range of pH optima that must depend on other factors. Using structural and mechanistic knowledge about glycosyl hydrolases from families 7, 10, and 16, we have formulated a new mathematical model that can include not only the ionization behavior of the catalytic residues but also as many ionizable residues as desired in the active site. In addition, the model can incorporate electrostatic influences via acid dissociation equilibrium constants and chemical relationships such as hydrogen bonds. The results of the simulations indicate a clear shift in the pH dependence of activity for the enzymes only when a close interrelation (hydrogen bond) between the catalytic and auxiliary residues in the active site is taken into account. This explains the observations from mutagenesis studies that show this type of shift and cannot be explained by a purely electrostatic interaction theory. Moreover, the presence of the kind of chemical interaction proposed could provide stabilization of the activity in the presence of environmental, structural, pH and electrostatic variations. These findings and the implications for the design of new mutagenesis strategies are discussed. The results suggest a way to modify, via site‐directed mutagenesis, the acid dissociation of one of the catalytic residues in the active site independently of the other, which could have clear advantages over the purely electrostatic modifications that usually affect both residues simultaneously. © 2004 Wiley Periodicals, Inc.
Novel synthetic jasmonates as highly efficient elicitors for taxoid production by suspension cultures of Taxus chinensis
Authors: Qian Zhi‐Gang , Zhao Zhen‐Jiang , Tian Wen‐Hong , Xu Yufang , Zhong Jian‐Jiang , Qian Xuhong
Published: April 2004

Suspension cultures of Taxus chinensis were used as a model plant cell system to evaluate novel synthetic jasmonates as elicitors for stimulating the biosynthesis of secondary metabolites. Significant increases in accumulation of taxuyunnanine C (Tc) were observed in the presence of newly synthesized 2‐hydroxyethyl jasmonate (HEJA) and trifluoroethyl jasmonate (TFEJA) without their inhibition on cell growth. Addition of 100 μM HEJA or TFEJA on day 7 led to a high Tc content of 44.3 ± 1.1mg/g or 39.7 ± 1.1 mg/g (at day 21), while the Tc content was 14.0 ± 0.1 mg/g and 32.4 ± 1.6 mg/g for the control and that with addition of 100 μM methyl jasmonate (MJA), respectively. The superior stimulating ability of HEJA and TFEJA over MJA, which was generally considered as the best chemical for eliciting taxoid biosynthesis, suggests that the novel jasmonate analogues may have great potential in application to other cell culture systems for effcient elicitation of plant secondary metabolites. © 2004 Wiley Periodicals, Inc.
Fermentation of biomass‐generated producer gas to ethanol
Authors: Datar Rohit P. , Shenkman Rustin M. , Cateni Bruno G. , Huhnke Raymond L. , Lewis Randy S.
Published: April 2004

The development of low‐cost, sustainable, and renewable energy sources has been a major focus since the 1970s. Fuel‐grade ethanol is one energy source that has great potential for being generated from biomass. The demonstration of the fermentation of biomass‐generated producer gas to ethanol is the major focus of this article in addition to assessing the effects of producer gas on the fermentation process. In this work, producer gas (primarily CO, CO2, CH4, H2, and N2) was generated from switchgrass via gasification. The fluidized‐bed gasifier generated gas with a composition of 56.8% N2, 14.7% CO, 16.5% CO2, 4.4% H2, and 4.2% CH4. The producer gas was utilized in a 4‐L bioreactor to generate ethanol and other products via fermentation using a novel clostridial bacterium. The effects of biomass‐generated producer gas on cell concentration, hydrogen uptake, and acid/alcohol production are shown in comparison with “clean” bottled gases of similar compositions for CO, CO2, and H2. The successful implementation of generating producer gas from biomass and then fermenting the producer gas to ethanol was demonstrated. Several key findings following the introduction of producer gas included: (1) the cells stopped growing but were still viable, (2) ethanol was primarily produced once the cells stopped growing (ethanol is nongrowth associated), (3) H2 utilization stopped, and (4) cells began growing again if “clean” bottled gases were introduced following exposure to the producer gas. © 2004 Wiley Periodicals, Inc.
Influence of β‐subunit on thermal and high‐pressure process stability of tomato polygalacturonase
Authors: Peeters Liesbet , Fachin Diana , Smout Chantal , van Loey Ann , Hendrickx Marc E.
Published: April 2004

Polygalacturonase (PG; E.C. 3.2.1.15) was extracted from tomato fruit and purified by cation‐exchange chromatography. Two peaks containing PG activity were detected: the first denotes a thermolabile PG fraction (PG2) and the second a thermostable fraction (PG1). PG1 is a dimer of PG2 and a heat‐stable protein called the β‐subunit. In contrast to its resistance to heat, PG is easily inactivated at elevated pressure. Although the thermal stability of purified tomato PG1 and PG2 is distinctly different, they show an identical pressure stability. To gain further insight into the thermal and pressure stability of both PG isoenzymes, the in vitro recombination of PG2 and β‐subunit was studied. After severe heat (up to 140°C for 5 min) and pressure (up to 800 MPa for 15 min) treatments, the residual fractions containing the β‐subunit were able to convert PG2 into the heat‐stable PG1, showing the extreme thermal and pressure stability of the β‐subunit. PG1 was detected in heat‐treated tomato juice and, to a lesser extent, in tomato pieces. In contrast, as was the case for purified PG, no pressure‐stable fraction was observed when tomato juice and pieces were treated under pressure. These data clearly show the differing behavior of the PG1–PG2–β‐subunit system under thermal and high‐pressure treatments and offer the possibility of inactivating tomato PG using high pressure without the need for high temperatures. © 2004 Wiley Periodicals, Inc.
Emergency presentation of colorectal cancer is associated with poor 5-year survival
Authors: McArdle C S , Hole D J
Published: April 2004

Background

Previous studies have reported that emergency presentation of colorectal cancer is associated with poor outcome. Many of these studies were small and most were not adjusted for case mix. The aim of this study was to establish, after adjusting for case mix, the magnitude of the differences in postoperative mortality and survival between patients undergoing elective surgery and those presenting as an emergency.

Methods

Three thousand two hundred patients who underwent surgery for colorectal cancer between 1991 and 1994 in Scotland were studied. Five-year survival rates and adjusted hazard ratios were calculated.

Results

Some 1603 (72·4 per cent) of 2214 elective patients had a potentially curative resection compared with 632 (64·1 per cent) of 986 patients who presented as an emergency (P < 0·001). Following curative resection, the postoperative mortality rate was 2·8 per cent after elective and 8·2 per cent after emergency operation (P < 0·001). Overall survival at 5 years was 57·5 per cent after elective and 39·1 per cent after emergency curative surgery (P < 0·001); cancer-specific survival at 5 years was 70·9 and 52·9 per cent respectively (P < 0·001). The adjusted hazard ratio for overall survival after emergency relative to elective surgery was 1·68 (95 per cent confidence interval (c.i.) 1·49 to 1·90; P < 0·001) and that for cancer-specific survival was 1·90 (95 per cent c.i. 1·62 to 2·22; P < 0·001).

Conclusion

Following apparently curative resection for colorectal cancer, there was an excess of both cancer-related and intercurrent deaths in patients who presented as an emergency.
Use of the time–signal intensity curve from dynamic magnetic resonance imaging to evaluate remnant pancreatic fibrosis after pancreaticojejunostomy in patients undergoing pancreaticoduodenectomy
Authors: Tajima Y , Matsuzaki S , Furui J , Isomoto I , Hayashi K , Kanematsu T
Published: April 2004

Background

This study assessed the value of the time–signal intensity curve (TIC) obtained from dynamic magnetic resonance imaging (MRI) in the evaluation of remnant pancreatic fibrosis after pancreaticojejunostomy in patients undergoing pancreaticoduodenectomy.

Methods

Two modes of pancreaticojejunostomy—duct-to-mucosa anastomosis (DMA; 24 patients) and pancreatojejunoserosal anastomosis (PJSA; 22 patients)—were used in 46 consecutive patients undergoing pancreaticoduodenectomy. All patients underwent dynamic contrast-enhanced MRI of the pancreas before pancreaticoduodenectomy. Retrospective review of the pancreatic magnetic resonance images and histological examination of the pancreas were performed, and the patterns of TICs from dynamic MRI were compared with the degree of pancreatic fibrosis. Dynamic MRI of the residual pancreas was carried out for 1–3 years after pancreaticoduodenectomy in 26 patients (14 DMA, 12 PJSA) who had a histologically verified normal pancreas with no fibrosis at the time of pancreaticoduodenectomy.

Results

Evaluation of preoperative dynamic magnetic resonance images showed that a pancreatic TIC with a rapid rise to a peak followed by a rapid decline (type I) was characteristic of a normal pancreas without fibrosis. Pancreatic TICs with a slow rise to a peak followed by a slow decline or a plateau (types II and III) indicated a fibrotic pancreas. Postoperative pancreatic MRI demonstrated that six of 12 patients with a PJSA had a type II TIC, whereas 12 of 14 patients with a DMA had a type I curve (P = 0·046).

Conclusion

The TIC obtained from dynamic MRI is a reliable indicator of fibrosis in the remnant pancreas after pancreaticoduodenectomy. Use of a DMA was associated with a lower risk of pancreatic fibrosis 1–3 years after surgery than a PJSA.
Infrared ray electronic endoscopy combined with indocyanine green injection for detection of sentinel nodes of patients with gastric cancer
Authors: Nimura H , Narimiya N , Mitsumori N , Yamazaki Y , Yanaga K , Urashima M
Published: April 2004

Background

To avoid unnecessary lymphadenectomy in patients with cancer accurate diagnosis of the sentinel lymph node (SLN) is important.

Methods

This report examined the initial clinical use of infrared ray electronic endoscopy (IREE) combined with indocyanine green (ICG) injection for SLN detection in 84 patients with gastric cancer not invading the subserosa (75 T1 N0 M0 and nine T2 N0 M0 tumours, according to tumour node metastasis classification).

Results

There were no adverse events after injection of ICG. At least one SLN was detected in all but one patient by both ICG injection alone and by IREE with ICG. Eleven of the 84 patients had lymph node metastasis. SLNs detected by ICG injection alone did not include metastases in four of 11 patients, whereas IREE with ICG detected SLNs containing lymph node metastases in all 11 patients. Moreover, SLNs illuminated by IREE with ICG included all metastases among the 105 regional lymph nodes in the 11 patients; no metastatic lymph nodes were identified among 154 non-SLNs.

Conclusion

IREE combined with ICG injection may efficiently detect SLNs that contain metastases in patients with gastric cancer.
Influence of volume and specialization on survival following surgery for colorectal cancer
Authors: McArdle C S , Hole D J
Published: April 2004

Background

Previous studies have shown that significant surgeon-related differences in survival exist following surgery for colorectal cancer. It is not clear whether these differences were due to differences in caseload or degree of specialization.

Methods

Outcome in 3200 patients who underwent resection for colorectal cancer between 1991 and 1994 was analysed on the basis of caseload and degree of specialization of individual surgeons. Five-year survival rates, and the corresponding hazard ratios adjusted for case mix, were calculated.

Results

Cancer-specific survival rate at 5 years following curative resection varied among surgeons from 53·4 to 84·6 per cent; the adjusted hazard ratios varied from 0·48 to 1·55. Cancer-specific survival rate at 5 years following curative resection was 70·2, 62·0 and 65·9 per cent for surgeons with a high, medium and low case volume respectively. There were no consistent differences in the adjusted hazard ratios by volume. Cancer-specific survival rate at 5 years following curative resection was 72·7 per cent for those treated by specialists and 63·8 per cent for those treated by non-specialists; the adjusted hazard ratio for non-specialists was 1·35 (95 per cent confidence interval 1·13 to 1·62; P = 0·001).

Conclusion

The differences in outcome following apparently curative resection for colorectal cancer among surgeons appear to reflect the degree of specialization rather than case volume. It is likely that increased specialization will lead to further improvements in survival.
Randomized clinical trial of laparoscopic versus open fundoplication for gastro-oesophageal reflux
Authors: Nilsson G , Wenner J , Larsson S , Johnsson F
Published: April 2004

Background

The aim of this study was to compare the long-term results of laparoscopic and open antireflux surgery in a randomized clinical trial by investigating subjective and objective outcomes.

Methods

Sixty patients with gastro-oesophageal reflux disease (GORD) were randomized to laparoscopic or open 360 ° fundoplication. Subjective evaluation using disease-specific and generic questionnaires and structured interviews, and objective evaluation by endoscopy, oesophageal manometry and 24-h pH monitoring, were performed before operation and 1 month, 6 months and 5 years after surgery.

Results

Two patients in the laparoscopic group had reoperations for hiatal stricture; one patient in the open group had repair of an incisional hernia, and one patient in each group had surgery for intestinal obstruction. There were no differences in the subjective outcomes of diet, sleep, medication, patient satisfaction and symptoms of GORD after 5 years. Nor were there any differences in objective outcomes determined by endoscopy, manometry or 24-h pH monitoring. Well-being was decreased in all patients before operation but was restored to normal or above-normal values after fundoplication, regardless of the type of surgery. Seven of 28 patients in the open group had complaints regarding the scar.

Conclusion

Elimination of GORD symptoms improved well-being and eliminated the need for daily acid suppression in most patients, no matter which procedure was employed. These results were apparent 1 month after the operation and were still valid 5 years later.