bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and characterization of poly(N‐vinyl‐2‐pyrrolidone) grafted sodium alginate hydrogel beads for the controlled release of indomethacin
Authors: Işıklan Nuran , İnal Murat , Yiğitoğlu Mustafa
Published: July 2008

Graft copolymers of sodium alginate (NaAlg) with N‐vinyl‐2‐pyrrolidone were prepared using azobisisobutyronitrile as initiator. The graft copolymers (NaAlg‐g‐PVP) were characterized with Fourier transform infrared spectroscopy, elemental analysis, and differential scanning calorimetry. Polymeric hydrogel beads of NaAlg and NaAlg‐g‐PVP were prepared by crosslinking method using glutaraldehyde (GA) as a crosslinker in the hydrochloric acid catalyst (HCl) and these beads were used to deliver anti‐inflammatory drug, indomethacin (IM). Chemical stability of the IM after encapsulation into beads was confirmed by FTIR. Preparation conditions of the NaAlg‐g‐PVP beads were optimized by considering the percentage entrapment efficiency, particle size, swelling capacity and their release data. In vitro release studies were performed in simulated gastric fluid (pH 1.2) for the initial 2 h, followed by simulated intestinal fluid (pH 7.4) for 4 h. Effects of GA concentration, exposure time to GA, drug/polymer (d/p) ratio, and concentration of HCl on the release of IM were discussed. It was observed that IM release from the beads decreased with increasing GA concentration and exposure time. IM release also decreases with increasing d/p ratio and HCl concentration. The highest IM release was obtained to be 77% for beads crosslinked with 0.027M GA. Swelling experiments were also performed to compute molecular mass between crosslinks of the beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Formation of a bicontinuous structure membrane of polyvinylidene fluoride in diphenyl ketone diluent via thermally induced phase separation
Authors: Yang J. , Li D. W. , Lin Y. K. , Wang X. L. , Tian F. , Wang Z.
Published: July 2008

The polyvinylidene fluoride (PVDF)‐diphenyl ketone (DPK) mixture was studied as a new system to prepare PVDF membranes via thermally induced phase separation (TIPS). The phenomena of liquid–liquid phase separation was found in this mixture when the temperature of mixture was decreasing and the PVDF concentration was less than 30 wt %. Using DPK as diluent, PVDF membrane with bicontinuous structure was obtained without necessity to add a nonsolvent or a stretching process further. The phase diagram of PVDF‐DPK system was also constructed to help investigate the effect of PVDF concentration and coarsening temperature on morphology of resulting membrane. The experiments showed that high coarsening temperatures and low PVDF concentrations resulted in the formation of the large pore size membrane. The strength of the wet membrane was decreasing with decreasing PVDF concentration. On condition that the PVDF concentration was larger than 30 wt %, thermally induced solid–liquid separation occurred and bicontinuous structure disappeared. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Study on radiation‐induced grafting of hydrophilic monomers onto chitosan
Authors: Dergunov Sergey A. , Nam Irina K. , Maimakov Tauzhan P. , Nurkeeva Zauresh S. , Shaikhutdinov Erengaip M. , Mun Grigoriy A.
Published: July 2008

The graft polymerization of 2‐Hydroxyethyl acrylate, 2‐Hydroxyethyl methacrylate, and N‐vinylpyrrolidone onto chitosan in aqueous solution initiated by γ‐ray irradiation was carried out. The effect of various conditions such as the absorbed dose, concentration of monomer, and solvent on grafting was investigated. The grafting yield increased with the increase in absorbed dose. The degree of grafting increased with increase in the radiation dose. The obtained graft copolymers showed the solubility in water in wide pH interval. The interactions between grafted chitosan copolymers with sodium dodecyl sulfate (SDS) were studied in an aqueous solution. It was found that there is a narrow molar ratio of SDS/cation (∼ 0.40–0.70) depending on different grafted copolymers, at which the turbidity of SDS‐grafted chitosan complex has a maximum due to the formation of water insoluble interpolymer aggregates via the SDS attached on the polymer chain. The turbidity falls sharply with the further addition of excessive SDS, which forms micelle in the solution and causes the de‐aggregation of the interpolymer aggregates and also because of the precipitation of complexes and returns to the original level. The morphologic properties of thin films of SDS‐ grafted chitosan complex were investigated. It was observed that upon heating the insoluble complex of SDS and grafted chitosan in water, superstructures were formed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation, characterization, and cellular interactions of collagen‐immobilized PDMS surfaces
Authors: Keranov I. , Vladkova T. , Minchev M. , Kostadinova A. , Altankov G.
Published: July 2008

Multistep procedure to biofunctionalization of (poly)dimethylsiloxane (PDMS) surfaces is present here, including plasma‐based Ar+ beam treatment; acrylic acid grafting; and flexible PEG spacer coupling prior to the collagen immobilization by peptide synthesis reaction. The success of any step of the surface modification is controlled by XPS analysis, contact angle measurements, SEM, and AFM observations. To evaluate the effect of PEG chain length, three diNH2PEGs (2000, 6000, and 20,000 D) of relative long polymer chain were employed as a spacer, expecting that a long flexible spacer could provide more conformational freedom for the collagen molecules and fibroblast reorganization to further cellular matrix formation. Human fibroblast cells were used as a model to evaluate the biological response of the collagen‐immobilized PDMS surfaces. It is found that the earlier described biofunctionalization is one more road to improvement of the cellular interaction of PDMS, the last one being the best when PEG spacer with moderate chain length, namely of 6000 D, is used. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of novel polyphenol species derived from bis(4‐aminophenyl)ether: Substituent effects on thermal behavior, electrical conductivity, solubility, and optical band gap
Authors: Kaya İsmet , Yıldırım Mehmet
Published: July 2008

In this study, four different Schiff bases namely 4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (2‐HBA), 4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (4‐HBA), 4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (3,4‐HBA), and 4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (HMBA) were synthesized. These Schiff bases were converted to their polymers that have generate names of poly‐4,4′‐oxybis[N‐(2‐hydroxybenzilidene)aniline] (P‐2‐HBA), poly‐4,4′‐oxybis[N‐(4‐hydroxybenzilidene)aniline] (P‐4‐HBA), poly‐4,4′‐oxybis[N‐(3,4‐dihydroxybenzilidene)aniline] (P‐3,4‐HBA), and poly‐4,4′‐oxybis[N‐(4‐hydroxy‐3‐methoxybenzilidene)aniline] (PHMBA) via oxidative polycondensation reaction by using NaOCl as the oxidant. Four different metal complexes were also synthesized from 2‐HBA and P‐2‐HBA. The structures of the compounds were confirmed by FTIR, UV‐vis, 1H and 13C NMR analyses. According to 1H NMR spectra, the polymerization of the 2‐HBA and 4‐HBA largely maintained with COC coupling, whereas the polymerization of the 3,4‐HBA and HMBA largely maintained with CC coupling. The characterization was made by TG‐DTA, size exclusion chromatography and solubility tests. Also, electrical conductivity of the polymers and the metal complex compounds were measured, showing that the synthesized polymers are semiconductors and their conductivities can be increased highly via doping with iodine ions (except PHMBA). According to UV–vis measurements, the optical band gaps (Eg) were found to be 3.15, 2.06, 3.23, 3.02, 2.61, 2.47, 2.64, 2.42, 2.83, 2.77, 2.78, and 2.78 for 2‐HBA, P‐2‐HBA, 4‐HBA, P‐4‐HBA, 3,4‐HBA, P‐3,4‐HBA, HMBA, PHMBA, 2‐HBA‐Cu, 2‐HBA‐Co, P‐2‐HBA‐Cu, and P‐2‐HBA‐Co, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Biodegradable polymeric micro‐nanofibers by electrospinning of polyester/polyether block copolymers
Authors: Detta N. , El‐Fattah A. A. , Chiellini E. , Walkenström P. , Gatenholm P.
Published: July 2008

Two block copolymers consisting of biodegradable segments of poly(ethylene glycol) (PEG) and poly(ε‐caprolactone) (PCL) with slight different lengths of soft hydrophilic segments (PEG) and molecular weight were produced. The copolymer with shorter PEG segments and higher molecular weight was named copolymer A, while the other copolymer B. Both copolymers were dissolved in dichloromethane at the same concentration (5% w/v) and electrospun. Different combinations of spinning voltage (SV) and distance needle to collector were used. Electrospun A copolymer showed curly and uniform fibers with an average diameter of 2 μm, while B copolymer fibers were straight, uneven, and much thinner (submicrometric). In the latter case, fiber bundles and beads were also present. Viscosity measurements on the solutions before spinning showed a viscosity of 13.0 mPa s for A copolymer solution and 5.5 mPa s for B copolymer. The mechanical properties on dog‐bone shaped samples from the electrospun material evidenced that A copolymer had much higher stress and elongation at break but approximately the same elastic modulus as compared to B copolymer. Fiber morphology and mechanical properties of electrospun block copolymers are deeply influenced by different amount and length of soft and hard segments, and block copolymers can be the best suited systems to fit several applications because of the broad range of properties they show upon changing the composition ratio and molecular weight of components. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Influence of surface modification on the dispersion of nanoscale α‐Al2O3 particles in a thermoplastic polyurethane matrix
Authors: Chen Cheng‐Ho , Mao Ching‐Feng , Tsai Ming‐Shyong , Yen Fu‐Su , Lin Jian‐Min , Tseng Ching‐Hui , Chen Heng‐Yi
Published: July 2008

In this study, two types of nanoscale α‐Al2O3 particles were used for preparation of α‐Al2O3/thermoplastic polyurethane (TPU) composites. These α‐Al2O3 particles were either coated or uncoated with stearic acid. For the uncoated α‐Al2O3/TPU composite, the results of field‐emission scanning electron microscopy (FE‐SEM) and energy dispersive X‐ray spectrometry indicate that uncoated α‐Al2O3 particles are significantly aggregated together. This aggregation is due to the poor compatibility between the inorganic filler (α‐Al2O3) and the organic matrix (TPU). The size of clusters is in the range from 5 to 20 μm. For the coated α‐Al2O3/TPU composite, FE‐SEM results indicate that most coated α‐Al2O3 particles are well dispersed in the TPU matrix. This phenomenon results from the effect of surface modifier (i.e., stearic acid) on α‐Al2O3 particles. Stearic acid can act as a compatibilizer to bridge the boundary between the TPU matrix and the α‐Al2O3 particle. Stearic acid is not only a suitable surface modifier for the nanoscale α‐Al2O3 particle, but also a good dispersant for the dispersion of nanoscale α‐Al2O3 particles in the TPU matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Crystallization, orientation morphology, and mechanical properties of biaxially oriented starch/polyvinyl alcohol films
Authors: Wang Jing , Lu Yafei , Yuan Huilin , Dou Peng
Published: July 2008

Biaxially oriented starch/polyvinyl alcohol (PVA) films were prepared by stretching starch/PVA blend precursor films that were fabricated by extrusion casting via a twin‐screw extruder. Investigations on crystallization, orientation morphology, and mechanical properties of extrusion cast and stretched starch/PVA films were carried out by using differential scanning calorimetry, scanning electron microscope, wide angle X‐ray diffraction (WAXD), and tensile testing. The fresh extrusion‐cast starch/PVA films, which were almost amorphous, can crystallize spontaneously when aged at room condition. A good compatibility between starch and PVA was obtained by extrusion‐casting technology. The well‐developed molecular orientation, which did not occur along the machine direction during the extruding process, was observed in stretched film samples. Stretching unaged films can induce crystallization and the orientation of crystalline structures during stretching, resulting in the changes in diffraction peaks of WAXD patterns. The effect of stretch ratio and the orientation distribution in the plane of the film on mechanical properties of stretched films was studied, and the equal biaxially oriented films were found to exhibit in‐plane isotropy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Compatibilization of poly(vinyl chloride) and polystyrene blends with poly(styrene‐co‐n‐methylolacrylamide)
Authors: Escobar D. , Mendizabal E. , González‐Núñez R.
Published: July 2008

In this work, the compatibilization of blends of plasticized polyvinyl chloride (PVC) and polystyrene (PS) with poly(styrene‐co‐n‐methylolacrylamide) (PSnMA) was investigated. The PSnMA was synthesized by emulsion polymerization with different amounts of n‐methylolacrylamide (nMA). Particle size and phase behavior was determined by scanning electron microscopy, and mechanical properties were determined in an Universal Testing Machine. Micrographs revealed that an appreciable size reduction of the dispersed phase was achieved when small amounts of PSnMA were added to the blend, and as the amount of nMA was increased, particle size decreased. When the (PVC/PS/PSnMA) blend was subjected to solvent extraction to remove PS and unreacted PVC, the residue showed a single Tg. Tensile modulus and the ultimate strength of the blends increased with PSnMA content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Enhancement of PVC/ENR blend properties by poly(methyl acrylate) grafted oil palm empty fruit bunch fiber
Authors: Raju Gunasunderi , Ratnam Chantara Thevy , Ibrahim Nor Azowa , Rahman Mohammad Zaki Ab. , Yunus Wan Md Zin Wan
Published: July 2008

Effect of oil palm empty fruit bunch (OPEFB) fiber and poly(methyl acrylate) grafted OPEFB on several mechanical properties of poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends were studied. The composites were prepared by mixing the fiber and the PVC/ENR blends using HAKEE Rheomixer at the rotor speed of 50 rpm, mixing temperature 150°C, and mixing period of 20 min. The fiber loadings were varied from 0 to 30% and the effect of fiber content in the composites on their ultimate tensile strength (UTS), Young's modulus, elongation at break, flexural modulus, hardness, and impact strength were determined. An increasing trend was observed in the Young's modulus, flexural modulus, and hardness with the addition of grafted and ungrafted fiber to the PVC/ENR blends. However the impact strength, UTS, and elongation at break of the composites were found to decrease with the increase in fiber loading. An increase in elongation at break and UTS and decrease in the flexural and Young's modulus was observed with the addition of PMA‐g‐OPEFB fiber compared to ungrafted fiber. This observation indicates that grafting of PMA onto OPEFB impart some flexibility to the blend. The morphology of cryogenically fractured and tensile fracture surfaces of the composites, examined by a scanning electron microscope shows that the adhesion between the fiber and the matrix is improved upon grafting of the OPEFB fiber. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
In situ development of Zn/Cd‐incorporated poly(esteramide‐urethane) from sustainable resource
Authors: Zafar Fahmina , Ashraf S. M. , Ahmad Sharif
Published: July 2008

It was for the first time we attempted to develop zinc and cadmium incorporated linseed oil based poly(esteramide‐urethane) [Zn/Cd‐LPEAUr], and investigated their structure, mechanism, and properties. The resin was synthesized in situ by the reaction of linseed oil derived fatty amide diol [HELA], divalent zinc/cadmium acetate and toluylene‐2, 4 (6), diisocyanate [TDI; 2–12 wt %] with minimal solvent. The structural elucidation of Zn/Cd‐LPEAUr was carried out by FTIR, 1H‐NMR, and 13C‐NMR spectral techniques. TGA and DSC techniques were used to measure the thermal stability and curing behavior of these resins, respectively. The physicomechanical and chemical/corrosion resistance properties were investigated by standard laboratory methods. The performance of Zn/Cd‐LPEAUr coating was compared with reported oil based polyesteramide. Antibacterial test of the resins were performed by agar diffusion method against E. coli and S. aureus, and compared with those of petroleum‐based metal containing polyurethanes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
LiClO4 doped cellulose acetate as biodegradable polymer electrolyte for supercapacitors
Authors: Selvakumar M. , Bhat D. Krishna
Published: July 2008

The possibility of producing a biodegradable polymer electrolyte based on cellulose acetate (CA) with varied concentration of LiClO4 for use in supercapacitors has been investigated. The successful doping of the CA films has been analyzed by FTIR and DSC measurements of the LiClO4 doped CA films. The ionic conductivity of the films increased with increase in salt content and the maximum ionic conductivity obtained for the solid polymer electrolyte at room temperature was 4.9 × 10−3 Ω−1 for CA with 16% LiClO4. The biodegradation of the solid polymer electrolyte films have been tested by soil burial, degradation in activated sludge, and degradation in buffer medium methods. The extent of biodegradation in the films has been measured by AC Impedance spectroscopy and weight loss calculations. The study indicated sufficient biodegradability of the materials. A p/p polypyrrole supercapacitor has been fabricated and its electrochemical characteristics and performance have been studied. The supercapacitor showed a fairly good specific capacitance of 90 F g−1 and a time constant of 1 s. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Electrospun self‐assembled nanofiber yarns
Authors: Mondal Abhijit , Borah Ritutapan , Mukherjee Avishek , Basu Sandip , Jassal Manjeet , Agrawal Ashwini K.
Published: July 2008

A technique for making self‐assembled electrospun (E‐spun) nanofiber yarns from poly(acrylonitrile) in a single step is described. The process involved formation of the nanofiber yarn directly within the electrospinning zone and its removal before it can reach the counter‐electrode. The yarn is presumably formed due to splitting of the main jet into numerous nanojets and their reassembly into a single entity midway between the two electrodes. The process was found to occur at a particular field strength, which varied considerably with the concentration of the polymer dope. The gross morphology of yarns and the alignment of nanofibers in the yarn were evaluated by scanning electron microscopy (SEM). The rationale behind the formation of the yarn like structure has been explained. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Polypropylene/clay nanocomposites prepared by in situ grafting‐melt intercalation with a novel cointercalating monomer
Authors: Song Pingan , Tong Lifang , Fang Zhengping
Published: July 2008

Polypropylene (PP)/clay nanocomposites were prepared by melt‐compounding PP with organomontmorillonite (OMT), using maleic anhydride grafted polypropylene (PP‐g‐MA) as the primary compatibilizer and N‐imidazol‐O‐(bicyclo pentaerythritol phosphate)‐O‐(ethyl methacrylate) phosphate (PEBI) as the cointercalating monomer. X‐ray diffraction patterns indicated that the larger interlayer spacing of OMT in PP was obtained due to the cointercalation monomer having a large steric volume and the d‐spacing further increased with the addition of PP‐g‐MA, as evidenced by transmission electron microscopy. Thermogravimetric analysis revealed that the PEBI‐containing PP nanocomposites exhibited better thermal stability than PEBI‐free PP composites. Dynamic mechanical analysis demonstrated that the storage modulus was significantly enhanced, and the glass transition temperature (Tg) shifted slightly to low temperature with the incorporation of clay for PP/OMT hybrids. PEBI‐containing PP/OMT composites gave a lower Tg value because of the strong internal plasticization effect of PEBI in the system. Cone calorimetry showed that the flame‐retardancy properties of PP nanocomposites were highly improved with the incorporation of PEBI. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation and characterization of composites of polyethylene with polypyrrole‐coated wollastonite
Authors: Ong Chu Kuen , Ray Sudip , Cooney Ralph P. , Edmonds Neil R. , Easteal Allan J.
Published: July 2008

Composite sheets of polyethylene and polypyrrole‐coated wollastonite were prepared by extrusion and compression molding. Four compatibilizers were also evaluated, poly(ethylene‐co‐methyl acrylate) (EMA), maleated polyethylene (MAPE), poly(ethylene‐co‐vinyl alcohol) (EVOH), and poly(vinyl alcohol) (PVOH). The composite materials were characterized using X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy (SEM), Raman spectroscopy, and mechanical properties determined by tensile tests. SEM micrographs showed that significantly improved interactions occurred between the PE matrix and polypyrrole‐coated wollastonite particles in the presence of EMA, MAPE, and EVOH. Raman spectroscopy confirmed that the polypyrrole coating on the wollastonite particles was not thermally degraded during melt processing. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Perfluorinated coatings and terracotta: An impregnation study
Authors: Youssef Ali , Pabon Martial , Woelflé Emmanuel , Severac Romain , Gilbert Robert G.
Published: July 2008

The mechanisms of penetration onto terracotta of two commercially available perfluorinated acrylates were studied: Zonyl®225, a solvent‐based perfluorinated polyacrylate containing two unfluorinated acrylic or vinylic monomers; and Zonyl®329, an aqueous dispersion synthesized from comparable monomers plus a vinylic silane. Two application methods were used: by immersion of the substrate for 15 h and by multiple brush strokes, with pauses between strokes. Application effectiveness was assessed by measuring the depth of penetration into terracotta. The results of coating were examined by optical and electron microscopy, including elemental analysis. When the impregnating agent was applied by extended immersion, both solvent‐based and aqueous dispersion exhibited higher penetration depths with increasing concentrations. When applied using multiple brush strokes, the solvent‐based solution exhibited the same trend as that in immersion; however, the aqueous dispersion showed no penetration beyond ∼ 0.12 mm. This limited depth of penetration is shown to be a result of partial drying between brush strokes, but also as a result of porosity restrictions and electrostatic interactions between the positively charged polymer colloids in the dispersion and the negatively charged terracotta surface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of hypochlorite treatment on performance of hollow fiber membrane prepared from polyethersulfone/N‐methyl‐2‐pyrrolidone/tetronic 1307 solution
Authors: Arahman Nasrul , Maruyama Tatsuo , Sotani Tomohiro , Matsuyama Hideto
Published: July 2008

Polyethersulfone (PES) hollow fiber membrane was prepared by blending with nonionic surfactant Tetronic 1307 to improve its hydrophilicity. The membranes were posttreated by hypochlorite solution of 10, 100, 500, and 2000 ppm. The effect of hypochlorite treatment on the performance of PES membrane was investigated. Experimental results showed that the water permeability of treated membrane was two to three times higher than that of untreated membrane in case of blend membrane prepared from PES/N‐methyl‐2‐pyrrolidone (NMP)/Tetronic 1307 solution. On the other hand, hypochlorite treatment has no effect on water permeability of the membrane prepared from PES/NMP solution. Elemental analysis and ATR–FTIR measurement results indicated that hypochlorite treatment led to decomposition and leaching out of Tetronic 1307 component from the membrane. The change of membrane surface structure by the hypochlorite treatment was confirmed by atomic force microscopy measurement. The hypochlorite treatment brought about no significant impact on the mechanical property of the membranes. This indicated that the hypochlorite treatment of PES membrane prepared with surfactant was a useful way to improve the water permeability without the decrease of membrane strength. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effect of the structure of silane‐coupling agent on dynamic mechanical properties of dental resin‐nanocomposites
Authors: Sideridou Irini D. , Karabela Maria M.
Published: July 2008

This work was aimed at the study by dynamic mechanical analysis (DMA) of dental composites consisted of a Bis‐GMA/TEGDMA (50/50 wt/wt) matrix and silica nanoparticles (Aerosil OX50) as filler, silanized with various silanes. The silanes used were 3‐[(1,3(2)‐dimethacryloyloxypropyl)‐2 (3)‐oxycarbonylamido] propyltriethoxy‐silane (UDMS), 3‐methacryloxypropyl‐trimethoxysilane (MPS), octyltrimethoxysilane (OTMS), blends of UDMS/OTMS (50/50 wt/wt), or MPS/OTMS (50/50 wt/wt). The total amount of silane was kept constant at 10% by weight fraction relative to the filler weight. The silanized nanoparticles were mixed with the dimethacrylate matrix (60% filler by weight fraction). The composites were light cured and tested by DMA for the determination of storage modulus (E′), loss modulus (E″), tangent delta (tan δ), and glass transition temperature (Tg). Measurements were performed in samples immediately after curing and samples stored in water at 37°C for 1, 7, 30, or 120 days. OTMS‐composite in which OTMS does not form covalent bond with the dimethacrylate matrix showed lower elastic modulus both in dry and wet conditions. The ability of bifunctional UDMS for crosslinking was found not to increase the elastic behavior of the composite, as it was expected, compared with that of MPS‐composite, because of the high amount of the silane used. After immersion in water the elastic modulus of OTMS‐composite remained constant, while that of the other composites increased after 1 day and then remained constant up to 120 days. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
2,2‐Bis[4‐(3,4‐dicarboxyphenoxy) phenyl]propane dianhydride (BPADA)‐based polyimide membranes for pervaporation dehydration of isopropanol: Characterization and comparison with 4,4′‐(hexafluoroisopropylidene) diphthalic anhydride (6FDA)‐based polyimide membranes
Authors: Xiao Shude , Feng Xianshe , Huang Robert Y. M.
Published: July 2008

Polyimides were synthesized from one‐step polycondensation of BPADA and various diamines and were characterized with GPC, FTIR, NMR, DSC, and TGA. Polyimide membranes were prepared, and their hydrophilicity was estimated by contact angles and the free energies of interfacial interactions. Pervaporation properties were investigated for the dehydration of isopropanol, and comparisons were made between BPADA‐based membranes and 6FDA‐based membranes. The concentration coefficients of BPADA‐based membranes were calculated from the linear moiety contribution method based on the results from 6FDA‐based membranes, and they were compared to understand the effects of the feed concentration on pervaporation properties. The effects of temperature on permeation flux were studied with permeation activation energies for total flux and water flux in permeates. Moiety contribution factors for activation energies were used to correlate permeation flux and monomer moieties in the polymers, and reasonable results were obtained for BPADA. It is revealed that steric effects of monomers may change the diffusion properties, while functional groups are favorable to the changes in sorption properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Genomic organization of thepara‐sodium channel α‐subunit genes from the pyrethroid‐resistant and ‐susceptible strains of the diamondback moth
Authors: Sonoda Shoji , Tsukahara Yoshitaka , Ashfaq Muhammad , Tsumuki Hisaaki
Published: July 2008

We examined the genomic organization of thepara‐sodium channel α‐subunit gene of the diamondback moth,Plutella xylostella(L.). The nucleotide sequence contained 34 putative exons, which covered almost the entire coding region of the gene producing 1,889 amino acid residues. Deduced amino acid identity to thehscplocus ofHeliothis virescenswas 84%. Comparison of deduced amino acid sequences of the permethrin‐resistant and ‐susceptible strains showed two substitutions other thankdrandsuper‐kdr‐like substitutions. They were Ala to Thr (A1060T) and Pro to Ser (P1836S) at the linker region of the domains II–III and the carboxyl terminus, respectively. Furthermore, we developed PCR amplification protocols for the rapid detection of both substitutions. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley‐Liss, Inc.
Characterization ofAnopheles minimusCYP6AA3 expressed in a recombinant baculovirus system
Authors: Boonsuepsakul Soamrutai , Luepromchai Ekawan , Rongnoparut Pornpimol
Published: July 2008

Metabolism by cytochrome P450 monooxygenases is a major mechanism implicated in resistance of insects to insecticides, including pyrethroids. We previously isolated the cytochrome P450 CYP6AA3 from deltamethrin‐selected resistant strain ofAnopheles minimusmosquito, a major malaria vector in Thailand. In the present study, we further investigated the role of CYP6AA3 enzyme in deltamethrin metabolism in vitro. The CYP6AA3 was expressed inSpodoptera frugiperda(Sf9) insect cells via baculovirus‐mediated expression system. The enzymatic activity of CYP6AA3 in deltamethrin metabolism was characterized after being reconstituted withAn. minimusNADPH‐cytochrome P450 reductase and a NADPH‐regenerating system. The contribution of CYP6AA3 responsible for deltamethrin metabolism was determined by measurement of deltamethrin disappearance following the incubation period and deltamethrin‐derived compounds were detected using combined gas chromatography mass spectrometry analysis. 3‐Phenoxybenzaldehyde was a major product of CYP6AA3‐mediated deltamethrin metabolism. Deltamethrin degradation and formation of metabolites were NADPH‐dependent and inhibited by piperonyl butoxide. Deltamethrin was catalyzed by CYP6AA3 with an apparentKmof 80.0 ± 2.0 andVmaxof 60.2 ± 3.6 pmol/min/pmol P450. Furthermore, deltamethrin cytotoxicity assays by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) and trypan blue dye exclusion were examined in Sf9 insect cells, with and without expression of CYP6AA3. Results revealed that CYP6AA3 could play a role in detoxifying deltamethrin in the cells. Thus, the results of this study support the role of CYP6AA3 in deltamethrin metabolism. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley‐Liss, Inc.
Aflatoxin B1 detoxification by CYP321A1 in Helicoverpa zea
Authors: Niu Guodong , Wen Zhimou , Rupasinghe Sanjeewa G. , Zeng Ren Sen , Berenbaum May R. , Schuler Mary A.
Published: July 2008

The polyphagous corn earworm Helicoverpa zea frequently encounters aflatoxins, mycotoxins produced by the pathogens Aspergillus flavus and A. parasiticus, which infect many of this herbivore's host plants. While aflatoxin B1 metabolism by midgut enzymes isolated from fifth instars feeding on control diets was not detected, this compound was metabolized by midgut enzymes isolated from larvae consuming diets supplemented with xanthotoxin, coumarin, or indole‐3‐carbinol, phytochemicals that are likely to co‐occur with aflatoxin in infected host plants. Of the two metabolites generated, the main derivative identified in midguts induced with these chemicals and in reactions containing heterologously expressed CYP321A1 was aflatoxin P1 (AFP1), an O‐demethylated product of AFB1. RT‐PCR gel blots indicated that the magnitude of CYP321A1 transcript induction by these chemicals is associated with the magnitude of increase in the metabolic activities of induced midgut enzymes (coumarin>xanthotoxin>indole 3‐carbinol). These results indicate that induction of P450s, such as CYP321A1, plays an important role in reducing AFB1 toxicity to H. zea. Docking of AFB1 in the molecular models of CYP321A1 and CYP6B8 highlights differences in their proximal catalytic site volumes that allow only CYP321A1 to generate the AFP1 metabolite. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley‐Liss, Inc.
The citation advantage of open‐access articles
Authors: Norris Michael , Oppenheim Charles , Rowland Fytton
Published: July 2008

Four subjects—ecology, applied mathematics, sociology, and economics—were selected to assess whether there is a citation advantage between journal articles that have an open‐access (OA) version on the Internet compared to those articles that are exclusively toll access (TA). Citations were counted using the Web of Science, and the OA status of articles was determined by searching OAIster, OpenDOAR, Google, and Google Scholar. Of a sample of 4,633 articles examined, 2,280 (49%) were OA and had a mean citation count of 9.04 whereas the mean for TA articles was 5.76. There appears to be a clear citation advantage for those articles that are OA as opposed to those that are TA. This advantage, however, varies between disciplines, with sociology having the highest citation advantage, but the lowest number of OA articles, from the sample taken, and ecology having the highest individual citation count for OA articles, but the smallest citation advantage. Tests of correlation or association between OA status and a number of variables were generally found to weak or inconsistent. The cause of this citation advantage has not been determined.
Information organization and retrieval using a topic maps‐based ontology: Results of a task‐based evaluation
Authors: Yi Myongho
Published: July 2008

As information becomes richer and more complex, alternative information‐organization methods are needed to more effectively and efficiently retrieve information from various systems, including the Web. The objective of this study is to explore how a Topic Maps‐based ontology approach affects users' searching performance. Forty participants participated in a task‐based evaluation where two dependent variables, recall and search time, were measured. The results of this study indicate that a Topic Maps‐based ontology information retrieval (TOIR) system has a significant and positive effect on both recall and search time, compared to a thesaurus‐based information retrieval (TIR) system. These results suggest that the inclusion of a Topic Maps‐based ontology is a beneficial approach to take when designing information retrieval systems.
Selecting manuscripts for a high‐impact journal through peer review: A citation analysis of communications that were accepted by Angewandte Chemie International Edition, or rejected but published elsewhere
Authors: Bornmann Lutz , Daniel Hans‐Dieter
Published: July 2008

All journals that use peer review have to deal with the following question: Does the peer review system fulfill its declared objective to select the “best” scientific work? We investigated the journal peer‐review process at Angewandte Chemie International Edition (AC‐IE), one of the prime chemistry journals worldwide, and conducted a citation analysis for Communications that were accepted by the journal (n = 878) or rejected but published elsewhere (n = 959). The results of negative binomial‐regression models show that holding all other model variables constant, being accepted by AC‐IE increases the expected number of citations by up to 50%. A comparison of average citation counts (with 95% confidence intervals) of accepted and rejected (but published elsewhere) Communications with international scientific reference standards was undertaken. As reference standards, (a) mean citation counts for the journal set provided by Thomson Reuters corresponding to the field “chemistry” and (b) specific reference standards that refer to the subject areas of Chemical Abstracts were used. When compared to reference standards, the mean impact on chemical research is for the most part far above average not only for accepted Communications but also for rejected (but published elsewhere) Communications. However, average and below‐average scientific impact is to be expected significantly less frequently for accepted Communications than for rejected Communications. All in all, the results of this study confirm that peer review at AC‐IE is able to select the “best” scientific work with the highest impact on chemical research.
Main‐path analysis and path‐dependent transitions in HistCite™‐based historiograms
Authors: Lucio‐Arias Diana , Leydesdorff Loet
Published: July 2008

With the program HistCite™ it is possible to generate and visualize the most relevant papers in a set of documents retrieved from the Science Citation Index. Historical reconstructions of scientific developments can be represented chronologically as developments in networks of citation relations extracted from scientific literature. This study aims to go beyond the historical reconstruction of scientific knowledge, enriching the output of HistCite™ with algorithms from social‐network analysis and information theory. Using main‐path analysis, it is possible to highlight the structural backbone in the development of a scientific field. The expected information value of the message can be used to indicate whether change in the distribution (of citations) has occurred to such an extent that a path‐dependency is generated. This provides us with a measure of evolutionary change between subsequent documents. The “forgetting and rewriting” of historically prior events at the research front can thus be indicated. These three methods—HistCite, main path and path dependent transitions—are applied to a set of documents related to fullerenes and the fullerene‐like structures known as nanotubes.
Visualization of health‐subject analysis based on query term co‐occurrences
Authors: Zhang Jin , Wolfram Dietmar , Wang Peiling , Hong Yi , Gillis Rick
Published: July 2008

A multidimensional‐scaling approach is used to analyze frequently used medical‐topic terms in queries submitted to a Web‐based consumer health information system. Based on a year‐long transaction log file, five medical focus keywords (stomach, hip, stroke, depression, and cholesterol) and their co‐occurring query terms are analyzed. An overlap‐coefficient similarity measure and a conversion measure are used to calculate the proximity of terms to one another based on their co‐occurrences in queries. The impact of the dimensionality of the visual configuration, the cutoff point of term co‐occurrence for inclusion in the analysis, and the Minkowski metric power k on the stress value are discussed. A visual clustering of groups of terms based on the proximity within each focus‐keyword group is also conducted. Term distributions within each visual configuration are characterized and are compared with formal medical vocabulary. This investigation reveals that there are significant differences between consumer health query‐term usage and more formal medical terminology used by medical professionals when describing the same medical subject. Future directions are discussed.
Robust Tris‐Cyclometalated Iridium(III) Phosphors with Ligands for Effective Charge Carrier Injection/Transport: Synthesis, Redox, Photophysical, and Electrophosphorescent Behavior
Authors: Zhou Guijiang , Wang Qi , Ho Cheuk‐Lam , Wong Wai‐Yeung , Ma Dongge , Wang Lixiang , Lin Zhenyang
Published: July 2008

With the target to design and develop new functionalized green triplet light emitters that possess distinctive electronic properties for robust and highly efficient phosphorescent organic light‐emitting diodes (PHOLEDs), a series of bluish–green to yellow–green phosphorescent tris‐cyclometalated homoleptic iridium(III) complexes [Ir(ppy‐X)3] (X=SiPh3, GePh3, NPh2, POPh2, OPh, SPh, SO2Ph, Hppy=2‐phenylpyridine) have been synthesized and fully characterized by spectroscopic, redox, and photophysical methods. By chemically manipulating the lowest triplet‐state character of Ir(ppy)3 with some functional main‐group 14–16 moieties on the phenyl ring of ppy, a new family of metallophosphors with high‐emission quantum yields, short triplet‐state lifetimes, and good hole‐injection/hole‐transporting or electron‐injection/electron‐transporting properties can be obtained. Remarkably, all of these IrIII complexes show outstanding electrophosphorescent performance in multilayer doped devices that surpass that of the state‐of‐the‐art green‐emitting dopant Ir(ppy)3. The devices described herein can reach the maximum external quantum efficiency (ηext) of 12.3 %, luminance efficiency (ηL) of 50.8 cd A−1, power efficiency (ηp) of 36.9 Lm W−1 for [Ir(ppy‐SiPh3)3], 13.9 %, 60.8 cd A−1, 49.1 Lm W−1 for [Ir(ppy‐NPh2)3], and 10.1 %, 37.6 cd A−1, 26.1 Lm W−1 for [Ir(ppy‐SO2Ph)3]. These results provide a completely new and effective strategy for carrier injection into the electrophosphor to afford high‐performance PHOLEDs suitable for various display applications.
Mono‐ and Dinuclear Palladium(II) N,S‐Heterocyclic Carbene Complexes with N Spacers and their Suzuki Coupling Activities
Authors: Yen Swee Kuan , Koh Lip Lin , Huynh Han Vinh , Hor T. S. Andy
Published: July 2008

Mixed‐ligand N,S‐heterocyclic carbene (NSHC) complexes, trans‐[PdBr2(NSHC)(Py)] (NSHC=3‐benzyl‐ or 3‐propyl‐benzothiazolin‐2‐ylidene), have been obtained from bridge‐cleavage reactions of the dinuclear complex, [Pd(μ‐Br)Br(NSHC)]2, in pyridine at room temperature. Use of neutral N‐bidentate donors (L=pyrazine, 1,2‐bis(4‐pyridyl)ethane, 4,4′‐bipyridine and trans‐1,2‐bis(4‐pyridyl)ethylene) yields the dinuclear spacer‐bridged [Pd2Br4(NSHC)2(μ‐L)] complexes. The X‐ray single‐crystal structures of the pyridyl, bridging pyrazine and 1,2‐bis(4‐pyridyl)ethane complexes are reported. These air‐stable complexes are active in the Suzuki–Miyaura coupling reactions of selected aryl bromides. The dinuclear complexes are generally more active than their mononuclear pyridyl analogues. The benzyl derivatives consistently outperform the n‐propyl counterparts.
Optimal predictive densities and fractional moments
Authors: Taufer Emanuele , Bose Sudip , Tagliani Aldo
Published: July 2008

The maximum entropy approach used together with fractional moments has proven to be a flexible and powerful tool for density approximation of a positive random variable. In this paper we consider an optimality criterion based on the Kullback–Leibler distance in order to select appropriate fractional moments. We discuss the properties of the proposed procedure when all the available information comes from a sample of observations. The method is applied to the size distribution of the U.S. family income. Copyright © 2008 John Wiley & Sons, Ltd.
MECP2 promoter methylation and X chromosome inactivation in autism
Authors: Nagarajan Raman P. , Patzel Katherine A. , Martin Michelle , Yasui Dag H. , Swanberg Susan E. , Hertz‐Picciotto Irva , Hansen Robin L. , Van de Water Judy , Pessah Isaac N. , Jiang Ruby , Robinson Wendy P. , LaSalle Janine M.
Published: July 2008

Epigenetic mechanisms have been proposed to play a role in the etiology of autism. This hypothesis is supported by the discovery of increased MECP2 promoter methylation associated with decreased MeCP2 protein expression in autism male brain. To further understand the influence of female X chromosome inactivation (XCI) and neighboring methylation patterns on aberrant MECP2 promoter methylation in autism, multiple methylation analyses were performed on brain and blood samples from individuals with autism. Bisulfite sequencing analyses of a region 0.6 kb upstream of MECP2 in brain DNA samples revealed an abrupt transition from a highly methylated region in both sexes to a region unmethylated in males and subject to XCI in females. Chromatin immunoprecipitation analysis demonstrated that the CCCTC‐binding factor (CTCF) is bound to this transition region in neuronal cells, consistent with a chromatin boundary at the methylation transition. Male autism brain DNA samples displayed a slight increase in methylation in this transition region, suggesting a possible aberrant spreading of methylation into the MECP2 promoter in autism males across this boundary element. In addition, autistic female brain DNA samples showed evidence for aberrant MECP2 promoter methylation as an increase in the number of bisulfite sequenced clones with undefined XCI status for MECP2 but not androgen receptor (AR). To further investigate the specificity of MECP2 methylation alterations in autism, blood DNA samples from females and mothers of males with autism were also examined for XCI skewing at AR, but no significant increase in XCI skewing was observed compared to controls. These results suggest that the aberrant MECP2 methylation in autism brain DNA samples is due to locus‐specific rather than global X chromosome methylation changes.
An Age‐Stratified Poisson Model for Comparing Trends in Cancer Rates Across Overlapping Regions
Authors: Li Yi , Tiwari Ram C. , Zou Zhaohui
Published: July 2008

The annual percent change (APC) has been used as a measure to describe the trend in the age‐adjusted cancer incidence or mortality rate over relatively short time intervals. The yearly data on these age‐adjusted rates are available from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute. The traditional methods to estimate the APC is to fit a linear regression of logarithm of age‐adjusted rates on time using the least squares method or the weighted least squares method, and use the estimate of the slope parameter to define the APC as the percent change in the rates between two consecutive years. For comparing the APC for two regions, one uses a t‐test which assumes that the two datasets on the logarithm of the age‐adjusted rates are independent and normally distributed with a common variance. Two modifications of this test, when there is an overlap between the two regions or between the time intervals for the two datasets have been recently developed. The first modification relaxes the assumption of the independence of the two datasets but still assumes the common variance. The second modification relaxes the assumption of the common variance also, but assumes that the variances of the age‐adjusted rates are obtained using Poisson distributions for the mortality or incidence counts. In this paper, a unified approach to the problem of estimating the APC is undertaken by modeling the counts to follow an age‐stratified Poisson regression model, and by deriving a corrected Z ‐test for testing the equality of two APCs. A simulation study is carried out to assess the performance of the test and an application of the test to compare the trends, for a selected number of cancer sites, for two overlapping regions and with varied degree of overlapping time intervals is presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rejoinder
Authors: Bouza C. N.
Published: July 2008

Article http://dx.doi.org/10.1002/bimj.4710360113

Letter to the editor http://dx.doi.org/10.1002/bimj.200810429