bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of wood fibers on the rheological properties of i‐PP/wood fiber composites
Authors: Maiti S. N. , Subbarao R. , Ibrahim Mohd. Nordin
Published: November 2003

The effects of wood fibers on the melt rheological behavior of isotactic poly(propylene) (i‐PP)/wood fiber (WF) composites have been studied at WF concentrations of 0–32.2 vol % at 493 K. Shear stress–shear rate variations obeyed a power law equation, and the composites exhibited shear thinning, which increased with filler content. At a low shear rate, the apparent melt viscosity increased, while melt elasticity, after an initial decrease, also increased with WF concentration. At a higher shear rate, after an initial decrease, the melt viscosity showed an increase, as did melt elasticity, with increase in filler content. A titanate coupling agent, LICA 38, used to modify the wood fiber surface, modified these rheological parameters by functioning as a plasticizer/lubricant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 644–650, 2004
Synthesis and characterization of hindered‐phenol‐containing amine moieties as antioxidants for polypropylene copolymers
Authors: Desai Jigar , Pendyala V. N. S. , Xavier S. F. , Misra A. N. , Nair K. B.
Published: November 2003

(4‐Ethylphenyl)‐3,5‐ditertiarybutyl‐4‐hydroxybenzylamine, 1‐phenyl‐4‐(3,5‐ditertiarybutyl‐4‐hydroxybenzyl)piperazine, and 1‐(3,5‐ditertiarybutyl‐4‐hydroxybenzyl)piperidine were synthesized and characterized, and their performance in polypropylene copolymer (PPCP) was tested by multiple extrusions in a Brabender plasticorder. The thermooxidative stability of PPCP was assessed by the measurement of oxidative induction time at 200 ± 1°C, and the thermal stability was assessed by observation of the change in the melt flow rate. A comparative study of the synthesized antioxidants with the commercially available antioxidant 2,6‐ditertiarybutyl‐4‐methylphenol was made. The presence of phenolic and amino groups influenced the performance of the antioxidants. The performance of the antioxidants influenced the thermal stability of the PPCP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1097–1103, 2004
Effect of adhesive‐coated glass fiber in natural rubber (NR), acrylonitrile rubber (NBR), and ethylene–propylene–diene rubber (EPDM) formulations. I. Effect of adhesive‐coated glass fiber on the curing and tensile properties of NR, NBR, and EPDM formulations
Authors: Rathinasamy P. , Balamurugan P. , Balu S. , Subrahmanian V.
Published: November 2003

Adhesive‐coated glass fibers (3 and 6 mm in length) were added at loadings of 10, 20, and 30 phr in natural rubber (NR), nitrile rubber (NBR), and ethylene–propylene–diene comonomer (EPDM) formulations in both plain and carbon black mixes. The compounds were mixed in a two‐roll mill and were characterized for their cure properties, tensile, tear, and Mullin's effect. In NR mixes, all of the formulations showed reversion in cure behavior, suggesting that NR remained unaffected. In NBR and EPDM mixes, almost all of the mechanical properties of the fiber improved. The result was more significant in EPDM than in NBR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1111–1123, 2004
Effect of adhesive‐coated glass fiber in natural rubber (NR), acrylonitrile rubber (NBR), and ethylene–propylene–diene rubber (EPDM) formulations. II. Effect of cyclic loading, abrasion, and accelerated aging
Authors: Rathinasamy P. , Balamurugan P. , Balu S. , Subrahmanian V.
Published: November 2003

Treated glass fibers (RICS, 3 and 6 mm in length) were added at a concentrations of 10, 20, and 30 phr in natural rubber (NR), nitrile rubber (NBR), and ethylene–propylene–diene comonomer (EPDM) formulations, in both plain and carbon black mixes. The compounds were mixed in two‐roll mill and were evaluated for their resistance to hot‐air aging, abrasion, compression set, Goodrich heat buildup, De Mattia fatigue, and for NR mixes, adhesion in the tensile mode. The vulcanizates of the three rubbers showed resistance to hot‐air aging. Abrasion resistance was poor for NR, and it improved with carbon black addition in the presence of treated glass fiber in NBR. In carbon‐black‐added EPDM vulcanizates, the abrasion resistance and fatigue resistance were better. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1124–1135, 2004
Graded‐index plastic optical fiber with high mechanical properties enabling easy network installations. II
Authors: Ishigure Takaaki , Hirai Miki , Sato Masataka , Koike Yasuhiro
Published: November 2003

It was shown how high mechanical strength should be provided in the high numerical aperture (NA) graded‐index plastic optical fiber (GI POF). In this newly developed GI POF, a copolymer of methyl methacrylate (MMA) and 2,2,2‐trifluoroethyl methacrylate (3FMA) was used to increase the NA. The GI POF we proposed previously was composed of a PMMA homopolymer cladding and a doped PMMA core. It was previously shown that substituting the copolymer P(MMA–3FMA) for the PMMA as the cladding material made little change in the fiber's light‐transmission characteristics. This study focused on mechanical flexibility, which is one of the most important advantages of the POF. It was found that the P(MMA–3FMA)‐clad GI POF had almost the same or superior mechanical strength in addition to the excellent light‐propagation characteristics. It was also found that such excellent mechanical properties were achieved using a small dopant concentration and optimum heat‐drawing conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 410–416, 2004
Effect of thermal hysteresis on the gas permeation properties of 6FDA‐based polyimides
Authors: Fuhrman C. , Nutt M. , Vichtovonga K. , Coleman M. R.
Published: November 2003

The effect of thermal hysteresis on the polymer chain packing and permeation properties of two 6FDA‐based polyimide isomers was investigated. Thermal quenching resulted in a small increase in the fractional free volume of the polyimides with respect to the samples that had been annealed. Quenching from above the glass‐transition temperature also resulted in larger increases in the permeabilities for both 6FDA–6FmDA and 6FDA–6FpDA with respect to annealed samples. Meta‐connected 6FDA–6FmDA exhibited a larger increase in the permeability after quenching than the para‐connected isomer, 6FDA–6FpDA. This larger increase in the permeability for 6FDA–6FmDA may have been due to differences in the effects of the increases in the free volume on the intersegmental resistance to chain motions. Although physical aging over a 3‐month period resulted in a reduction in the permeability of quenched samples of 6FDA–6FpDA, the quenched samples maintained higher permeabilities than the annealed samples. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1174–1182, 2004
Novel polymer electrolyte composed of poly(ethylene oxide), lithium triflate, and benzimidazole
Authors: Chen Hsien‐Wei , Xu Hongyao , Huang Chih‐Feng , Chang Feng‐Chih
Published: November 2003

This work has demonstrated that the incorporation of benzimidazole derivatives, 2,2′‐p‐phenylene‐bisindole (PPBI), enhances the ionic conductivity of a poly(ethylene oxide) (PEO)–based electrolyte by 20 times more than the plain system. Specific interactions among amino group, ethyl oxide, and lithium cation were investigated using differential scanning calorimetry (DSC), FTIR, and alternating current impedance. The DSC characterization confirms that the initial addition of PPBI is able to enhance the PEO crystallinity attributed to the interaction between the negative charge from the amino group and the lithium cation. Three types of complexes are present: complex I is present in the PEO phase, complex II resides at interphase, and complex III is located within the PPBI domain. Complex II plays the key role in stabilizing these two microstructure phases. FTIR spectra confirm that because of the presence of PPBI one is able to dissolve lithium salts more easily than in the plain electrolyte system and thus increase the fraction of free ions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 719–725, 2004
New intumescent flame‐retardant agent: Application to polyurethane coatings
Authors: Wang Jincheng , Li Guang , Yang Shenglin , Jiang Jianming
Published: November 2003

The first part of this investigation focused on the synthesis and characterization of a new type of intumescent flame‐retardant (IFR) agent. Four steps were used in the synthesis process. The structure was characterized by FTIR, magic‐angle spinning nuclear magnetic resonance (MAS‐NMR) 13C spectroscopy, and elemental analysis. The addition of an IFR agent into polyurethane (PU) varnish led to an improvement in its carbonization and flame‐retardant (FR) properties. The second part focused on the evaluation of such characteristics as FR property, thermal stability of IFR/PU‐based coatings, rheology of IFR/PU‐based coating solutions, and mechanical properties such as hardness, adhesion, and flexibility of IFR/PU‐based dry coating films. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1193–1206, 2004
Electrospinning of ethyl–cyanoethyl cellulose/tetrahydrofuran solutions
Authors: Zhao Shengli , Wu Xiaohui , Wang Linge , Huang Yong
Published: November 2003

In this study, electrospinning was used to fabricate ethyl–cyanoethyl cellulose [(E‐CE)C] fiber from a solution of (E‐CE)C/tetrahydrofuran. The diameter of the thinnest fiber fabricated during the electrospinning was about 200 nm. It was found that the diameters of the fibers and their distribution depend on the processing parameters and properties of the solution, such as viscosity, temperature, and concentration, for example. The morphology of the fiber was also observed by SEM. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 242–246, 2004
Thermal cure behavior of unsaturated polyester/phenol blends
Authors: Chiu Hsien‐Tang , Jeng Ruey‐Er , Chung Jung‐Sheng
Published: November 2003

Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to detect and simulate the cure behavior of unsaturated polyester (UP), phenol, and UP/phenol blends and to calculate and predict the cure rate, cure temperature, conversion, and changes in the glass‐transition temperature along with various cure orders in order to obtain the optimum parameters for processing. With dynamic scanning and isothermal DSC procedures and Borchardt–Daniels dynamic software, cure data for the UP resin were obtained, 90% of the conversion rate at 100°C being achieved after 15 min. However, for the phenol and UP/phenol blends, gradually increasing the temperature was found to be best for curing according to the DSC and DMA test results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1041–1058, 2004
Hydrogels of modified ethylenediaminetetraacetic dianhydride gelatin conjugated with poly(ethylene glycol) dialdehyde as a drug‐release matrix
Authors: Rathna G. V. N.
Published: November 2003

Hydrogels have been recognized as versatile biomaterials in biomedical applications. This article describes the synthesis and characterization of a poly(ethylene glycol) (PEG) dialdehyde derivative, the modification of gelatin with ethylenediaminetetraacetic dianhydride (EDTAD), and the conjugation of PEG dialdehyde for enhanced hydrophilicity, biocompatibility, and flexibility. Hydrogels of gelatin conjugated with various percentages of PEG dialdehyde (10–30%), 35% EDTAD‐modified gelatin, and 12% PEG dialdehyde conjugated with 31% EDTAD‐modified gelatin with or without 1% chlorhexidine were prepared. For all the synthesized gel formulations, the swelling kinetics and drug release in pH 7.4 and pH 4.5 buffers at 37°C were studied. Gels of PEG‐conjugated gelatin, 35% EDTAD‐modified gelatin, and 12% PEG conjugated with 31% EDTAD‐modified gelatin, with or without 1% chlorhexidine, showed significantly improved swelling ratios in comparison with gelatin. The drug release was unaffected by an increase in the percentage of PEG conjugation with gelatin. Complete drug release was recorded within 48 h in the pH 4.5 buffer, whereas in the pH 7.4 buffer, the drug release was accomplished within 128 h. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1059–1067, 2004
Synthesis and properties of self‐crosslinkable polyurethane–urea with silsesquioxane formation
Authors: Zhang Tao , Xi Kai , Chen Hong , Yu Xuehai
Published: November 2003

Based on the typical two‐step polyurethane–urea synthesis, a new series of self‐crosslinkable polyurethane (PU)–urea formulations, consisting of poly(tetramethylene oxide) and 4,4′‐diphenyl methane diisocyanate, and extended by ethylenediamine (EDA)/aminoethylaminopropyltrimethyoxysilane (AEAPS), were prepared. FTIR, ESCA, WAXD, DSC, and mechanical properties of samples were recorded. The results show that the self‐crosslinkable polyurethane–urea could be crosslinked by hydrolysis of the trimethyloxysiloxane group to form the silsesquioxane structure. These structures represent a kind of nanosize, cagelike, chemical crosslink site as well as filler, which affect the properties of PU. The morphology, varied with different ratios of EDA/AEAPS, was also discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 190–195, 2004
Thermal property of epoxy/SiO2 hybrid material synthesized by the sol–gel process
Authors: Weng Wei‐Hsiang , Chen Hui , Tsai Song‐Po , Wu Jen‐Chin
Published: November 2003

Organic–inorganic hybrid materials synthesized by the sol–gel process have been developed for several years. This synthesis method can effectively overcome the defects of conventional composite materials. In this investigation, epoxy/SiO2 hybrid material was synthesized by a sol–gel process with a precursor system. Tetraethoxysilane, water, and ethanol were mixed in appropriate proportions, varying the amounts of catalyst, alkalinity, and acidity, and then processed by a hydrolysis‐condensation reaction at room temperature. The product synthesized with this process is called a precursor. The coupling agent γ‐glycidoxypropyl‐methyldiethoxysilane (KBE‐402) was used to modify the surface of the silica. The role of the coupling agent was to add covalent bonding between epoxy resin and silica, which reinforced the interfacial force of the hybrid material. The epoxy resin was mixed with precursor in different proportions and then cured at 170°C for 1 h. The thermal property of the epoxy/SiO2 hybrid materials was studied by thermogravimetric analysis and DSC. From the results, we found the precursor prepared with acidity catalyst was better than that prepared with alkalinity catalyst. Coupling agent improved the thermal property of epoxy/SiO2 hybrid materials, especially when the temperature was high and the suitable amount of the coupling agent for the hybrid system was 5%. The glass‐transition temperature of the hybrid materials was increased to adapt to the content of precursor from 80 to 113°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 532–537, 2004
Highly stabilized papain conjugated with water‐soluble phospholipid polymer chain having a reacting terminal group
Authors: Miyamoto Daisuke , Watanabe Junji , Ishihara Kazuhiko
Published: November 2003

A novel water‐soluble and biocompatible phospholipid polymer, poly(2‐methacryloyloxyethyl phosphorylcholine) (PMPC), was synthesized using a photoinduced living radical polymerization technique for modification of the enzyme. The PMPC had a reactive carboxylic group on a terminal, and its molecular weight and molecular weight distribution were regulated. The PMPC was reacted with the amino groups of papain via amide bonds to form a conjugate (P‐PMPC). The modification degrees with PMPC chains on the conjugate were 22% (P‐PMPC22) and 42% (P‐PMPC42) versus the total number of amino groups of papain. The stability of the P‐PMPC was evaluated in a buffered solution (pH 6.1) at 25 and 40°C. The helix content of the P‐PMPC was slightly below that of native papain. However, the secondary structure of the P‐PMPC was maintained at its initial level for 28 days at both temperatures. The enzymatic activity after the conjugation was about 40% of the native enzyme, but it was maintained about over 75% of the initial enzymatic activity even when it was stored at 40°C for 28 days. This result is due to inhibition of self‐digestion and a change in the ternary structure of papain by the PMPC chains. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 827–832, 2004
The influence of the diluent system on the porous structure formation of copolymers based on 2‐vinylpyridine and divinylbenzene. Diluent system. III. heptane/methylethylketone
Authors: Luz Cosme Tadeu L. , Coutinho Fernanda M. B.
Published: November 2003

The effects of the diluent mixture's composition and crosslinking degree [divinylbenzene (DVB)] on the porous characteristics of the anion‐exchange resins based on 2‐vinylpyridine (2VP) and DVB, synthesized by suspension polymerization, in the presence of a diluent mixture constituted of heptane (HEP) and methyl ethyl ketone (MEK) at different proportions, were evaluated. The resins were characterized by mercury porosimetry, nitrogen adsorption (Brunauer–Emmett–Teller (BET) method surface area determination), apparent density, and swelling in methanol. The optical appearance of the copolymer beads was examined by optical microscopy. It was found that the development of porosity was attained whenever the content of methyl ethyl ketone in the diluent mixture was increased for all DVB contents employed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 666–669, 2004
Synthesis of a new conjugated polymer based on benzimidazole and its sensory properties using the fluorescence‐quenching effect
Authors: Choi Ho Wook , Kim Youn Suk , Yang Nam Choul , Suh Dong Hack
Published: November 2003

A new anionic conjugated polymer containing a fluorene group in the main chain was designed and synthesized from poly(2,7‐(9,9′‐dihexylfluorene)‐5,5′‐bibenzimidazole) (PFBI). The polymer showed strong blue emission with high quantum efficiency (0.64) at 450 nm in MeOH and the dramatic quenching effect by Methyl Viologen (MV2+). The fluorescence‐quenching effect results from the weak complex formation between an anionic polymer and electron acceptors such as bipyridinium derivatives. The linear Stern–Volmer constant (Ksv) was 3.7×105 M−1 for MV2+. The newly synthesized polymer is expected to show the applicability for biological and chemical sensors. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 900–904, 2004
Study on the morphology and properties of metallocene polyethylene and ethylene/vinyl acetate blends
Authors: Wu Tong , Li Ying , Zhang Da‐Lun , Liao Shuang‐Quan , Tan Hui‐Min
Published: November 2003

Two commercial polymer materials, metallocene linear low density polyethylene (m‐LLDPE) and ethylene/vinyl acetate copolymer (EVA) have been used to form binary blends of various compositions. The mechanical properties, morphology, rheological behavior, dynamic mechanical properties, and crystallization of m‐LLDPE/EVA blends were investigated. It was found that with the addition of EVA, the fluidity and processability of m‐LLDPE were significantly improved, and the introduction of polar groups in this system showed no significant changes in mechanical properties at lower EVA content. As verified by morphology observation and differential scanning calorimetry analysis, miscible blends were formed within certain weight ratios. Dynamic mechanical property studies showed that flexibility of the blends was enhanced in comparion with pure m‐LLDPE, where the peak value of loss modulus shifted to lower temperature and its intensity was enhanced as EVA content increased, indicating the existence of more amorphous regions in the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 905–910, 2004
Mechanical and dynamic mechanical studies of epoxy/VAc‐EHA/HMMM IPN–jute composite systems
Authors: Datta Chandan , Basu Diya , Roy Abhishek , Banerjee Amarnath
Published: November 2003

Epoxy [50:50 mixture of Di‐Glycidyl Ether of Bis‐Phenol A (DGEBA) and Epoxidized Novolac (EPN)] was solution blended with Vinyl Acetate‐2‐ Ethylhexylacrylate (VAc‐EHA) resin in aqueous medium, in varying weight fractions, with Hexamethoxymethylmelamine (HMMM) as a crosslinker and data was compared with a control. The present work was aimed to optimize the tensile strength, dynamic mechanical strength, impact strength, and toughness by preparing a blend followed by jute composites of a semi‐ and full interpenetrating network (IPN). In control experiments epoxy alone was crosslinked (semi‐IPN), whereas the DGEBA‐EPN and VAc‐EHA/HMMM were crosslinked separately (full‐IPN), using jute as the substrate for making composites. Composites of full‐IPN systems of epoxy/VAc‐EHA system had higher moduli and UTS than the semi‐IPN systems. Dynamic mechanical study showed that full‐IPN systems have higher Tg values than semi‐IPN systems. The impact strength increases with increasing proportions of VAc‐EHA copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 958–963, 2004
Radical copolymerization of N‐(4‐acetyl phenyl)‐ maleimide and styrene: Monomer reactivity ratios and thermal properties
Authors: Soykan Cengiz , Erol İbrahim
Published: November 2003

Copolymers containing N‐(4‐acetyl phenyl)maleimide (NAPMI) and styrene (ST) at different compositions have been prepared by radical copolymerization. FTIR, 1H‐, and 13C NMR and elemental analysis techniques were used on the identification of polymers. The monomer reactivity ratios were estimated using the Kelen‐Tüdös (KT) and Fineman‐Ross (FR) graphical methods. Structural parameters of the copolymers were obtained calculating the dyad monomer sequence fractions. A thermal study of the obtained copolymers related to the N‐(4‐acetyl phenyl)maleimide content has been carried out taking into account several theories predicting the depence of the glass transition temperature on the copolymers composition. The Tgs are linearly distributed between Tgs of homopolymers and in all cases, single, well‐defined Tgs are obtained. Glass transition temperatures increase with the increase of molar fraction of N‐(4‐acetylphenyl)maleimide. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 964–970, 2004
Synthesis and characterization of nanosized polypyrrole–polystyrene composite particles
Authors: Xu Xiao‐Jun , Gan Leong‐Ming , Siow Kok‐Siong , Wong Ming‐Keong
Published: November 2003

Nanosized polypyrrole–polystyrene (PPy–PS) composite particles were synthesized by the polymerization of pyrrole on PS nanoparticles in the presence of FeCl3. The PS nanoparticles were prepared from microemulsion polymerizations using the cationic nonpolymerizable surfactant cetyltrimethylammonium bromide (CTAB), the nonionic polymerizable surfactant ω‐methoxy[poly(ethylene oxide)40]undecyl α‐methacrylate (PEO–R–MA‐40), or the cationic polymerizable surfactant ω‐acryloyloxyundecyltrimethylammonium bromide (AUTMAB). For the latexes stabilized by CTAB, the resulting PPy–PS composite particles exhibited relatively poor colloidal stability and the pressed pellets exhibited relatively low electrical conductivities (∼10−7–10−3 S cm−1). However, for the latexes stabilized by polymerizable surfactants, the resulting PPy–PS composite particles exhibited relatively good colloidal stability and relatively high conductivities (∼10−5–10−1 S cm−1). The effect of polymerizable surfactants on the colloidal stability of composite particles and the conducting mechanism of the composites are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1360–1367, 2004
Supramolecular assembly of collagen triblock peptides
Authors: Martin Raquel , Waldmann Lars , Kaplan David L.
Published: November 2003

The relationship between primary sequence and collagen triple‐helix formation is relatively well characterized, while higher levels of structural assembly from these sequences is poorly understood. To address this gap, a new collagen‐like triblock peptide design was used to study the relationship between amino acid sequence and supramolecular assembly. Four collagen‐like peptides with the sequence (Glu)5(Gly–Xaa–Hyp–Gly–Pro–Hyp)6(Glu)5 and corresponding to Xaa = alanine, proline, serine, or valine, and an analogous peptide without the glutamic acid end blocks, were solubilized in water at high concentrations (20–150 mg/mL) and analyzed in optical polarizing microscopy and transmission electron microscopy. Some of the peptides self‐assembled into supramolecular structures, the nature of which was determined by the core collagen‐like sequence. The globular end blocks appeared necessary for these short triple‐helix‐forming peptides to spontaneously organize into supramolecular structures in solution and also provided enhanced thermal stability based on CD analysis. The results indicate a strong dependence of the peptide triblock assembly behavior on the identity of the guest residue Xaa; nematic order when Xaa was valine, no organization when Xaa was serine, and banded spherulites displaying a cholesteric‐like twist when Xaa was proline or alanine. According to these results, the identity of the amino acid in position Xaa of the triplet Gly–Xaa–Yaa dramatically determined the type of supramolecular assembly formed by short triple helices based on collagen‐triblock like sequences. Moreover, the structural organization observed for these collagen‐triblock peptides was analogous to some assemblies observed for native collagen in vivo and in vitro. The amino acid sequence in the native collagen proteins may therefore be a direct determinant of the different supramolecular architectures found in connective tissues. © 2003 Wiley Periodicals, Inc. Biopolymers 70:435–444, 2003
Fluorescence properties of labeled proteins near silver colloid surfaces
Authors: Maliwal Badri P. , Malicka Joanna , Gryczynski Ignacy , Gryczynski Zygmunt , Lakowicz Joseph R.
Published: November 2003

The fluorescence properties of a monolayer of labeled avidin molecules were studied near silver island films. We first adsorbed a monolayer of biotinylated‐BSA as a base that was used to capture labeled avidin molecules. For labeled avidin on silver island films, we observed an increase of the fluorescence intensity of between 18 and 80 with one‐photon excitation and up to several hundredfold or larger with two‐photon excitation. The probes were moderately more photostable in the presence of silver islands. There was also a dramatic decrease in the lifetimes with the amplitude‐weighted values decreasing from 7‐ to 35‐fold. The data suggest that these spectral changes are due to both increased rates of excitation near the metallic particles and increases in the rates of radiative decay. Because these silver island surfaces are very heterogeneous, we are hopeful that larger increases in intensity and photostability can be obtained for probes situated at an optimal distance from the ideal island surfaces. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 585–594, 2003
Nondestructive analyses of unsaturated fatty acid species in dietary oils by attenuated total reflectance with Fourier transform IR spectroscopy
Authors: Yoshida Satoshi , Yoshida Hiroshi
Published: November 2003

The aim of this study was to develop a nondestructive method to quantitate relative amounts of n‐3 and n‐6 polyunsaturated fatty acid (PUFA) species in vegetable oils and oil seeds using Fourier transform IR spectroscopy (FTIR). The alkene CH stretching vibrations of unsaturated fatty acids in oils showed IR absorption bands with various peak positions and intensities at around 3010 cm−1, depending on the extent of unsaturation and PUFA species. With the aid of partial least‐squares regression analysis, the FTIR measurement could practically predict the content of each PUFA species in the oil to be tested. A calculation method was also presented to directly find PUFA species in oils from the FTIR spectra. This technique was applied to dried soybean seeds to demonstrate a nonhomogenous distribution of saturated fatty acids and PUFAs, as well as glycans, in soybean cross sections. © 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 70: 604–613, 2003
Volumetric characterization of homopolymeric amino acids
Authors: Noudeh Gholamreza D. , Taulier Nicolas , Chalikian Tigran V.
Published: November 2003

We have determined the partial molar volumes, expansibilities, and adiabatic compressibilities for poly(L‐alanine), poly(L‐proline), and poly(L‐threonine) within the temperature range of 18–55°C. In addition, we have determined at 25°C changes in volume, ΔV, and adiabatic compressibility, ΔKS, associated with the coil‐to‐helix transitions of poly(L‐lysine) and poly(L‐glutamic acid) and the α‐to‐β transition of poly(L‐lysine). We have interpreted our volumetric data as suggesting that poly(L‐alanine) and poly(L‐proline) are not fully unfolded and, probably, retain some solvent‐inaccessible core. Further, we propose that poly(L‐threonine) is fully unfolded with the majority of its atomic groups being solvent‐exposed. Near zero changes in volume and compressibility accompanying the coil‐to‐helix transitions of poly(L‐lysine) and poly(L‐glutamic acid) suggest that, in the absence of fortuitous compensations, the coil‐to‐helix transitions of the polypeptides do not result in any significant enhancement of solute hydration. By contrast, the α‐to‐β transition of poly(L‐lysine) causes slight but statistically significant increases in volume and compressibility, an observation that may suggest that the β‐sheet conformation of poly(L‐lysine) is slightly less hydrated than its α‐helical conformation. In general, our results provide a quantitative volumetric description of the hydration properties of the homopolymeric polypeptides investigated. Such characterizations should prove useful in developing an understanding of the role that solvent plays in the stabilization/destabilization of folded protein structures and protein complexes. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 563–574, 2003
Hydrophobic tendencies of polar groups as a major force in molecular recognition
Authors: Chalikian Tigran V.
Published: November 2003

Proteins and nucleic acids are able to adopt their native conformation and perform their biological role only in the presence of water with which they actively interact in a mutually modifying way. Traditionally, hydrophobic effect has been considered to be the major factor stabilizing biopolymeric structures. However, solvent reorganization around polar groups is an event thermodynamically more unfavorable than solvent reorganization around nonpolar groups. Consequently, burial of polar groups with formation of complementary solute‐solute hydrogen bonds out of contact with water is an energetically favorable process that also provides a major force driving macromolecular association and folding. In contrast to nonpolar groups, polar groups may form their complementary intra‐ or intersolute hydrogen bonds out of contact with water only provided that an appropriate solute structure has been formed with properly positioned hydrogen bond donors and acceptors. Formation of such structures is disfavored entropically and may not be possible due to steric reasons. However, the interior of a folded protein, α‐helices and β‐sheets, double helical nucleic acid structures, and protein‐ligand interfaces all provide rigid matrices where polar groups may form their complementary hydrogen bonds. For these structures, the inward drive of polar groups represents a considerable stabilizing factor. © 2003 Wiley Periodicals, Inc. Biopolymers 70: 492–496, 2003
Meta-analysis of randomized clinical trials comparing open and laparoscopic inguinal hernia repair
Authors: Memon M A , Cooper N J , Memon B , Memon M I , Abrams K R
Published: November 2003

Background

The aim was to conduct a meta-analysis of the randomized evidence to determine the relative merits of laparoscopic (LIHR) and open (OIHR) inguinal hernia repair.

Methods

A search of the Medline, Embase, Science Citation Index, Current Contents and PubMed databases identified all randomized clinical trials that compared OIHR and LIHR and were published in the English language between January 1990 and the end of October 2000. The meta-analysis was prepared in accordance with the Quality of Reporting of Meta-analyses (QUOROM) statement. The six outcome variables analysed were operating time, time to discharge from hospital, return to normal activity and return to work, postoperative complications and recurrence rate. Random effects meta-analyses were performed using odds ratios and weighted mean differences.

Results

Twenty-nine trials were considered suitable for meta-analysis. Some 3017 hernias were repaired laparoscopically and 2972 hernias were repaired using an open method in 5588 patients. For four of the six outcomes the summary point estimates favoured LIHR over OIHR; there was a significant reduction of 38 per cent in the relative odds of postoperative complications (odds ratio 0·62 (95 per cent confidence interval (c.i.) 0·46 to 0·84); P = 0·002), 4·73 (95 per cent c.i. 3·51 to 5·96) days in time to return to normal activity (P < 0·001), 6·96 (95 per cent c.i. 5·34 to 8·58) days in time to return to work (P < 0·001) and 3·43 (95 per cent c.i. 0·35 to 6·50) h in time to discharge from hospital (P = 0·029). There was a significant increase of 15·20 (95 per cent c.i. 7·78 to 22·63) min in the mean operating time for LIHR (P < 0·001). The relative odds of short-term recurrence were increased by 50 per cent for LIHR compared with OIHR, although this result was not statistically significant (odds ratio 1·51 (95 per cent c.i. 0·81 to 2·79); P = 0·194).

Conclusion

LIHR was associated with earlier discharge from hospital, quicker return to normal activity and work, and significantly fewer postoperative complications than OIHR. However, the operating time was significantly longer and there was a trend towards an increase in the relative odds of recurrence after laparoscopic repair.
Comparison of P-POSSUM risk-adjusted mortality rates after surgery between patients in the USA and the UK
Authors: Bennett-Guerrero E , Hyam J A , Shaefi S , Prytherch D R , Sutton G L , Weaver P C , Mythen M G , Grocott M P , Parides M K
Published: November 2003

Background

The Physiological and Operative Severity Score for the enUmeration of Mortality and morbidity (POSSUM) criteria have been used to assess surgical risk in patients in the UK. The aim was to determine how applicable these criteria are to patients undergoing surgery in the USA.

Methods

Two cohorts of patients undergoing major non-cardiac surgery were followed prospectively in the USA (n = 1056) and the UK (n = 1539). Each patient was assigned a risk score for preoperative physiological status and operative severity using the established POSSUM criteria. Death in hospital was the primary outcome measure. For each patient a predicted risk of death was calculated from Portsmouth POSSUM (P-POSSUM) methodology using an established equation. The relationships between predicted and observed mortality rates in each cohort were investigated by means of multivariate logistic regression.

Results

Within each cohort, an increase in risk estimated by P-POSSUM predicted an increase in observed mortality rate (P < 0·001). For any given risk level, however, mortality rates were significantly higher in the UK cohort than in the US cohort (odds ratio 4·50 (95 per cent confidence interval 2·81 to 7·19); Z = 6·25, P < 0·001).

Conclusion

An increase in predicted risk, based on the P-POSSUM methodology, was associated with a higher mortality rate in patients from both countries. However, risk-adjusted mortality rates following major surgery were four times higher in the UK cohort. These marked differences warrant validation in a larger number of centres.
Symptoms and anal sphincter morphology following primary repair of third-degree tears
Authors: Davis K , Kumar D , Stanton S L , Thakar R , Fynes M , Bland J
Published: November 2003

Background

Approximately 0·6–9 per cent of vaginal deliveries are complicated by third-degree tears. The precise impact of such injuries on future pelvic floor function remains unknown. The aim of this study was to define the extent of structural and physiological damage to the anal sphincter and to investigate anorectal function in women who sustained third-degree tears during vaginal delivery.

Methods

Fifty-six women who sustained a third-degree tear were investigated prospectively. All patients had a primary repair of the anal sphincter complex, and were assessed by anorectal physiology and endoanal ultrasonography at a mean of 3·6 months. Symptoms were assessed by direct personal interview and also by a self-completed questionnaire.

Results

Forty-four patients had a persistent anal sphincter defect on ultrasonography. The mean resting and squeeze anal canal pressures were significantly lower in patients with a combined defect than in those in whom the repair was intact (P = 0·036 and P = 0·005 respectively). At direct interview three patients volunteered current symptoms of faecal and/or urinary incontinence whereas 32 reported bothersome symptoms on the questionnaire (P < 0·001).

Conclusion

The anatomical and physiological damage sustained during third-degree tears appears to be much greater than is generally appreciated. Primary repair does not provide lasting integrity. A self-administered questionnaire appears to be more accurate in defining the symptomatology.
Prevalence of multiple endocrine neoplasia type 1 in young patients with apparently sporadic primary hyperparathyroidism or pancreaticoduodenal endocrine tumours
Authors: Langer P , Wild A , Hall A , Celik I , Rothmund M , Bartsch D K
Published: November 2003

Background

The appropriate treatment for a sporadic endocrine tumour may be different from those that present as part of the multiple endocrine neoplasia type 1 (MEN1) syndrome. As primary hyperparathyroidism (pHPT) and pancreaticoduodenal endocrine tumours (PETs) are the most common organ manifestations of MEN1, the prevalence of germline mutations in the MEN1 gene was determined in young patients with apparently sporadic pHPT or PETs.

Methods

Eighteen of 705 patients with pHPT and 11 of 93 patients with PETs operated on between 1987 and 2001 had no family history of MEN1, only one organ manifestation and were aged 40 years or less at the time of diagnosis. Fifteen patients with pHPT and eight with PETs agreed to MEN1 gene mutation analysis, which was performed by single-strand conformational variant analysis and direct DNA sequencing.

Results

Two of 15 patients (13·3 (95 per cent confidence interval (c.i.) 1·6 to 40·4) per cent) with apparently sporadic pHPT had a MEN1 germline mutation. Both mutations were found in patients with pHPT due to multiglandular disease, whereas the remaining 13 patients had a solitary adenoma. None of the eight patients with PETs carried a MEN1 germline mutation.

Conclusion

Sporadic pHPT due to multiglandular disease in patients younger than 40 years may represent the first organ manifestation of MEN1 despite a negative family history.
Decline in admission rates for acute appendicitis in England
Authors: Kang J Y , Hoare J , Majeed A , Williamson R C N , Maxwell J D
Published: November 2003

Background

The incidence of acute appendicitis declined in western countries between the 1930s and the early 1990s. The aim of this study was to determine time trends in hospital admissions for acute appendicitis in England between 1989–1990 and 1999–2000, and in population mortality rates for appendicitis from 1979 to 1999.

Methods

Hospital Episode Statistics for admissions were obtained from the Department of Health and mortality data from the Office for National Statistics.

Results

Between 1989–1990 and 1999–2000, age-standardized hospital admission rates for acute appendicitis decreased by 12·5 per cent in male patients and by 18·8 per cent in female patients. The proportions of admissions that resulted in operation remained stable. Admission rates for non-specific mesenteric lymphadenitis fell. Admission rates for abdominal pain increased between 1989–1990 and 1995–1996, at which time the International Classification of Diseases codes changed. Between 1995–1996 and 1999–2000, admission rates for abdominal pain declined. Analysis of age-specific admission rates for acute appendicitis and abdominal pain from 1989–1990 to 1995–1996 showed that the decline in acute appendicitis could not be accounted for by a change in diagnostic practice. Mortality rates for acute appendicitis remained stable over the study period.

Conclusion

Admission rates for acute appendicitis declined over the study period. This decline cannot be explained by reclassification.
Immunonutrition
Authors: Kirk H J , Heys S D
Published: November 2003

Has clinical potential, but much more research is required
Ischaemia–reperfusion is an event triggered by immune complexes and complement
Authors: Chan R K , Ibrahim S I , Verna N , Carroll M , Moore F D , Hechtman H B
Published: November 2003

Background

Reperfusion injury is a common clinical problem that lacks effective therapy. Two decades of research implicating oxygen free radicals and neutrophils has not led to a single successful clinical trial.

Methods

The aim was to review new clinical and preclinical data pertaining to the alleviation of reperfusion injury. A review of the literature was undertaken by searching the MEDLINE database for the period 1966–2003 without language restrictions.

Results and conclusion

Evidence now points to complement and immune complexes as critical players in mediating reperfusion injury. Ischaemia is postulated to induce a phenotypical cellular change through the surface expression of a neoantigen. Preformed circulating natural IgM antibodies are then trapped and complement is activated. Final events leading to reperfusion injury include formation of the membrane attack complex and mast cell degranulation.
Chiral Bis(amino alcohol)oxalamide Gelators—Gelation Properties and Supramolecular Organization: Racemate versus Pure Enantiomer Gelation
Authors: Makarević Janja , Jokić Milan , Raza Zlata , Štefanić Zoran , Kojić‐Prodić Biserka , Žinić Mladen
Published: November 2003

Four new chiral bis(amino alcohol)oxalamides (1–4: amino alcohol=leucinol, valinol, phenylglycinol, and phenylalaninol, respectively) have been prepared as low‐molecular‐weight organic gelators. Their gelation properties towards various organic solvents and mixtures were determined and these were then compared to related bis(amino acid) oxalamide gelators. Spectroscopic (FTIR, 1H NMR) and X‐ray diffraction studies revealed that the primary organization motif of (S,S)‐1 and racemate 1 (rac‐1) in lipophilic solvents involved the formation of inverse bilayers. The X‐ray crystal structure of (S,S)‐1 also shows this type of bilayer organization. The crystal structure of rac‐2 reveals meso bilayers of hydrogen‐bonded aggregates. Within the bilayers formed, the gelator molecules are connected by cooperative hydrogen bonding between oxalamide units and OH groups, while the interbilayer interactions are realized through lipophilic interactions between the iBu groups of leucinol. Oxalamide meso‐1 lacks any gelation ability and crystallizes in monolayers. In dichloromethane rac‐1 forms an unstable gel; this is prone to crystallization as a result of the formation of symmetrical meso bilayers. In contrast, in aromatic solvents rac‐1 forms stable gels; this indicates that enantiomeric bilayers are formed. Oxalamide rac‐1 is capable of gelling a volume of toluene three times larger than (S,S)‐1. A tranmission electron microscopy investigation of rac‐1 and (S,S)‐1 toluene gels reveals the presence of thinner fibers in the former gel, and, hence, a more compact network that is capable of immobilizing a larger volume of the solvent. The self‐assembly of these types of gelator molecules into bilayers and subsequent formation of fibrous aggregates can be explained by considering the strength and direction of aggregate forces (supramolecular vectors) in three‐dimensional space.
Electron Density Investigation of a Push–Pull Ethylene (C14H24N2O2⋅H2O) by X‐ray Diffraction atT= 21 K
Authors: Forni Alessandra , Destro Riccardo
Published: November 2003

The electron charge distribution in a strongly twisted push–pull ethylene [PPE, 3‐(1,3‐diisopropyl‐2‐imidazolidinylidene)‐2,4‐pentanedione] has been determined by low temperature (T= 21 K) single‐crystal X‐ray diffraction analysis. The derived electronic properties are consistent with a zwitterionic molecule, as indicated by a charge transfer of 0.82(16) efrom thepushto thepullmoieties and a charge polarization of 0.29(7) eon the olefinic bond. A dipole moment of 12(3) D has been determined, which compares well with ab initio theoretical results in terms of both modulus and orientation. The second moments, which have also been obtained with good precision, characterize PPE as a highly quadrupolar molecule. The special electronic features of the molecule confer particular topological properties to the electron density distribution, as evidenced by comparison with “standard” organic molecules. The crystallographic asymmetric unit of the present system includes one water molecule, which is hydrogen bonded to PPE. Its topological properties have also been investigated, together with an analysis of the hydrogen bonds involved.
A new privacy and authentication protocol for end‐to‐end mobile users
Authors: Lee Cheng‐Chi , Yang Chao‐Chen , Hwang Min‐Shiang
Published: November 2003

In this papecr, we propose a new privacy and authentication scheme for end‐to‐end mobile users. There are three goals in our scheme. The first allows two end‐to‐end mobile users to communicate privately each other. The second allows two end‐to‐end mobile users to distribute a session key simply. The third allows two end‐to‐end mobile users to mutually authenticate. Copyright © 2003 John Wiley & Sons, Ltd.
Detection of antigen‐specific T cells by cytokine flow cytometry: the use of whole blood may underestimate frequencies
Authors: Hoffmeister Bodo , Bunde Torsten , Rudawsky Ina Maria , Volk Hans‐Dieter , Kern Florian
Published: November 2003

Antigen‐specific T cells may be detected and enumerated by short‐term ex vivo antigen‐specific stimulation followed by cytokine flow cytometry. Most frequently, intracellular IFN‐γ is used to identify T cells specific for cytomegalovirus (CMV), Epstein‐Barr virus or HIV. Some researchers use whole blood, others peripheral blood mononuclear cells (PBMC) in this assay; however, the performance of the two systems has never been directly compared. Blood was drawn from previously characterized healthy CMV‐positive donors, and CMV‐derived peptides or CMV lysate were used as stimulants. In an initial series of experiments, lithium‐heparin was identified as the best coagulant to be used. Dose‐response curves were established using concentrations between 0.1 and 40 μg/ml of peptides and between 0.1 and 20 μg/ml of virus lysate, respectively. IFN‐γ‐positive T cells were expressed as percent of the reference population, and frequencies measured in whole blood and PBMC were compared. Maximum responses were consistently higher in PBMC than in whole blood and were reached at lower concentrations of stimulant. In several instances, responses identified with PBMCwere not at all detected with whole blood. In summary, studies using whole blood in this type of assay are likely to underestimate the frequencies of antigen‐specific T cells.