bluuebunny/crossref_metadata_2025_split huggingface dataset:
Noncatalytic hydrogenation of natural rubber latex
Authors: Mahittikul A. , Prasassarakich P. , Rempel G. L. 
Published: December 2006

AbstractHydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene‐based elastomers. Natural rubber latex (NRL) could be hydrogenated to a strictly alternating ethylene–propylene copolymer using diimide generated in an in situ system. The diimide generated using the in situ technique for hydrogenation of NRL was accomplished by thermolysis of p‐toluenesulfonyl hydrazide (TSH). A molar ratio of TSH to double bonds equal to 2 : 1 was found to be the optimum ratio to provide a high percentage of hydrogenation. 95% Degree of saturation of NRL was achieved in o‐xylene. Hydrogenated products are characterized by FTIR and NMR spectroscopy. The thermal stability of hydrogenated rubber was improved as shown from the results of thermogravimetric analysis. From the differential scanning calorimetry measurement, the glass transition temperature of the hydrogenated product did not appear to change. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2885–2895, 2007
Properties of polymer‐modified mortars based on methyl methacrylic latexes with emulsifier contents and various monomer ratios
Authors: Hyung Wongil , Mun Kyungju , Kim Wanki 
Published: December 2006

AbstractThis study investigates the effects of the emulsifier content and monomer ratio on the typical properties of the polymer‐modified mortars with methyl‐methacrylate–butyl‐acrylate (MMA/BA) and methyl‐methacrylate–ethyl‐acrylate (MMA/EA) latexes and obtains basic data necessary to develop appropriate latexes for cement modifiers. The polymer‐modified mortars using the MMA/BA and MMA/EA latexes polymerized with emulsifier contents and at various monomer ratios are prepared for different polymer–cement ratios, and tested to obtain the particle size of the polymer latexes, the glass transition temperature of the polymer film, air contents, water–cement ratios, flexural and compressive strengths, water absorption, and chloride ion penetration. From the test results, the polymer‐modified mortars using MMA/BA and MMA/EA latexes with the mix proportions of synthesis having emulsifier contents of 5–6% and monomer ratios of 50 : 50 to 60 : 40 for the appropriate mix proportions can be recommended for practical applications. The basic properties of the polymer‐modified mortars are more affected by the polymer–cement ratio rather than the monomer ratio and emulsifier content, and are improved over unmodified mortar. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3010–3018, 2007
Synthesis and evaluation of novel injectable and biodegradable polyglycolide‐based composites
Authors: Xie Dong , Park Jong‐Gu , Zhao Jun 
Published: December 2006

AbstractNovel 3‐arm methacrylate‐endcapped biodegradable polyglycolide prepolymer was synthesized and characterized. Injectable and in situ curable composites formulated with the liquid prepolymer and bioabsorbable β‐tricalcium phosphate were prepared. The pastelike composites were cured at room temperature using a redox‐initiation system. The initial compressive strengths (CSs), curing time, exotherm, and degree of conversion of the cured composites were determined. The composites showed initial yield CS ranging from 20.1 to 92.3 MPa, modulus from 0.73 to 5.65GPa, ultimate strength from 119.9 to 310.5 MPa, and toughness from 630 to 3930 N mm. Increasing filler content increased yield strength and modulus but decreased ultimate strength and toughness. Diametral tensile strength test showed the same trend as did CS test. Increasing filler content also increased curing time but decreased exotherm and degree of conversion. During the course of degradation, all the materials showed a significant burst degradation behavior within 24 h, followed by a significant increase in strength between Day 1 and Day 3, and then continuous degradation until no strength was detected. The composites with higher filler content retained their strengths longer but those with lower filler contents lost their strengths in 45 or 60 days. The degradation rate is filler‐content dependent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2977–2984, 2007
Microphase separation, stress relaxation, and creep behavior of polyurethane nanocomposites
Authors: Xia Hesheng , Song Mo , Zhang Zhongyi , Richardson Mel 
Published: December 2006

AbstractThe stress relaxation and creep behavior of blank polyurethane (PU) and PU/clay nanocomposites were investigated. The relaxation time spectrum and retardant time spectrum were derived according to the generalized Maxwell model and Voigt model with a Tikhonov regularization method, respectively. The characteristic relaxation time was identified with the corresponding relaxation process. At a small strain, the relaxation was mainly attributed to uncoiling/disentangling of soft segment chain network in the soft phase, with a single characteristic relaxation time in the range of 5–100 s. The increase in the hard segment content leads to a decrease in the relaxation time, and the addition of clay leads to an increase in the relaxation time. At large strains, the multipeak relaxations occurred, and they were attributed to the breakup of interconnected hard domains and pullout of soft segment chains from hard domains, together with the disentangling of soft segment chain network in the soft phase. The creep results are consistent with those of the stress relaxation. The relaxation and creep behavior were related to microphase separation of PU. This study suggested that the relaxation spectrum can be used to examine the complicated relaxation processes for a multiphase and multicomponent polymer system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2992–3002, 2007
Adsorption of guanosine, cytidine, and uridine on a β‐cyclodextrin derivative grafted chitosan
Authors: Xiao Jian Bo 
Published: December 2006

AbstractA β‐cyclodextrin derivative grafted chitosan (CDD‐C) was synthesized with chitosan and carboxymethyl‐β‐cyclodextrin (β‐CD). Its structure was characterized by elemental, infrared spectra, and X‐ray diffraction analyses. The degree of substitution by the carboxymethyl‐β‐CD moiety achieved 0.27 with the addition of DMF to the reaction solution. The results are in agreement with the expectations. The static adsorption properties for guanosine, cytidine, and uridine were studied. Experimental results demonstrated that CDD‐C had higher adsorption capability for guanosine than cytidine and uridine, and the adsorption capacity for guanosine was 74.20 mg/g. The adsorption capacity was greatly influenced by pH, time, and temperature. The introduction of chitosan enhanced the adsorption ability and adsorption selectivity of β‐CD for guanosine. This novel derivative of chitosan is expected to have wide applications in separation, concentration, and analysis of guanosine, cytidine, and uridine in biological sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3050–3055, 2007
Chitosan‐grafted poly(hydroxyethyl methacrylate‐co‐glycidyl methacrylate) membranes for reversible enzyme immobilization
Authors: Yakup Arıca M. , Yilmaz Meltem , Bayramoğlu Gülay 
Published: December 2006

AbstractEpoxy group‐containing poly(hydroxyethyl methacrylate/glycidyl methacrylate), p(HEMA/GMA), membrane was prepared by UV initiated photopolymerization. The membrane was grafted with chitosan (CH) and some of them were chelated with Fe(III) ions. The CH grafted, p(HEMA/GMA), and Fe(III) ions incorporated p(HEMA/GMA)‐CH‐Fe(III) membranes were used for glucose oxidase (GOD) immobilization via adsorption. The maximum enzyme immobilization capacity of the p(HEMA/GMA)‐CH and p(HEMA/GMA)‐CH‐Fe(III) membranes were 0.89 and 1.36 mg/mL, respectively. The optimal pH value for the immobilized GOD preparations is found to have shifted 0.5 units to more acidic pH 5.0. Optimum temperature for both immobilized preparations was 10°C higher than that of the free enzyme and was significantly broader at higher temperatures. The apparent Km values were found to be 6.9 and 5.8 mM for the adsorbed GOD on p(HEMA/GMA)‐CH and p(HEMA/GMA)‐CH‐Fe(III) membranes, respectively. In addition, all the membranes surfaces were characterized by contact angle measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3084–3093, 2007
Swelling and mechanical behavior of modified poly(vinyl alcohol)/laponite nanocomposite membranes
Authors: Nair Shubhangi H. , Pawar Kiran C. , Jog Jyoti P. , Badiger Manohar V. 
Published: December 2006

AbstractNanocomposite (NC) membranes based on hydrophobically modified PVA and laponite were synthesized with varying laponite content in the feed. The incorporation of laponite in NC membranes was investigated by FTIR spectroscopy and thermogravimetric analysis. The swelling ratio of membranes was determined as a function of temperature and laponite content. Swelling studies of NC membranes exhibited the decrease in swelling with an increase in laponite content in the NC membranes. The swelling ratio of NC membrane with 20% laponite slightly increased with an increase in temperature. Dynamic mechanical analysis showed the systematic increase in storage modulus with laponite content, which indicates the enhancement of mechanical property upon laponite addition. There was also a decrease in the tan δ peak values of NC membranes with an increase in laponite content in NCs. The permeabilities through NC membranes as a function of solute size and laponite content were studied and the results showed molecular screening based on size. The permeability of solute reduced due to the presence of well‐dispersed laponite in the NC. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2896–2903, 2007
Nonisothermal cure kinetics of DGEBA with novel aromatic diamine
Authors: Ghaemy M. , Barghamadi M. , Behmadi H. 
Published: December 2006

AbstractThe effect of the molar ratio of diglycidyl ether of a bisphenol‐A based epoxy (DGEBA) and synthesized 4‐phenyl‐2,6‐bis(4‐aminophenyl)pyridine (PAP) as curing agent during nonisothermal cure reaction by the Kissinger, Ozawa, and isoconversional equations was studied. The cure mechanism was studied by FTIR analysis. Kinetic analysis of the curing reaction of DGEBA at two different concentrations (42 and 32 phr) of the curing agent was studied by using DSC analysis. With an increasing PAP content, the pre‐exponential factor increased by increasing collision probability between epoxide and primary or secondary amine groups in noncataltyic or catalytic modes. The activation energy also increased because of the increasing content of crosslink density. The activation energies obtained from three equations were in good agreement. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3076–3083, 2007.
Structural, morphological, and dynamic mechanical properties of Zn‐filled Nylon 11
Authors: Pande S. A. , Kelkar D. S. , Peshwe D. R. 
Published: December 2006

AbstractNylon 11 samples were filled with metal (Zn) fillers of two different concentrations (1 and 5% w/w) each. The samples in the form of disc were obtained by using hot press molder. The structural properties have been investigated using density measurement and wide angle X‐ray diffraction (WAXD) technique. The morphology of pure and Zn‐filled samples has been studied using scanning electron microscopy. Glass transition (Tg) temperature was determined using dynamic mechanical thermal analyzer (DMTA). The result shows that there is slight crystal modification due to the addition of metal fillers (Zn), and the crystallinity has improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3094–3098, 2007
Polyimides 7: Synthesis, characterization, and properties of novel soluble semifluorinated poly(ether imide)s
Authors: Kute Vijay , Banerjee Susanta 
Published: December 2006

AbstractThree novel diamine monomers (VI, VII, and VIII) were synthesized. These diamine monomers lead to a number of semifluorinated poly(ether imide)s when reacted with different commercially available dianhydrides like pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA), 2,2‐bis (3,4‐dicarboxyphenyl) hexafluoropropene (6FDA), and oxydiphthalic dianhydride (ODA) by thermal imidization route. Elemental analyses, IR and NMR techniques were used to characterize the monomers and polymers. The resulting polymers exhibited weight average molar masses up to 1.78 × 105 g mol−1 in GPC with respect to polystyrene standard and have very good solubility in several organic solvents such as NMP, DMF, DMAC, DMSO, chloroform, and THF. Very good solubility of these polymers in CDCl3 enables their complete characterization by proton as well as 13C‐NMR techniques. The polymers showed very high thermal stability with decomposition temperature (5% weight loss) up to 511°C in air and high glass transition temperature up to 311°C depending upon the exact repeating unit structure. The polymer films showed high modulus (up to 2.9 GPa) as was evaluated by DMA. The polymers also showed very low water absorption (0.16%), low dielectric constant (2.35 at 1MHz) and very good optical transmission. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3025–3044, 2007
Kinetic study of the curing of mixtures of DGEBA and five‐membered cyclic carbonates with lanthanum triflate as cationic initiator
Authors: Cervellera Roser , Ramis Xavier , Salla Josep M. , Mantecón Ana , Serra Angels 
Published: December 2006

AbstractMixtures of diglycidylether of bisphenol A (DGEBA) with 1,3‐benzodioxolane‐2‐one (CC) or 4‐phenoxymethyl‐1,3‐dioxolane‐2‐one (PGEC) were cured in the presence of lanthanum triflate. FTIR/ATR was used to study the evolution of carbonate and epoxide groups to follow the reactive processes that take place during curing. DSC was applied to study the thermal characteristics of the curing process and to determine the glass‐transition temperatures of the cured materials. The kinetics of the curing was studied isothermally by means of FTIR and the kinetic model was selected through the isokinetic relationships. DSC experiments were used to study the kinetics in nonisothermal conditions by means of isoconversional procedures and the Coats–Redfern and Criado methodologies. By TMA we could monitor the evolution of the shrinkage during isothermal curing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2875–2884, 2007
Superoxide Compounds of the Large Pseudo‐Alkali‐Metal Ions Tetramethylammonium, ‐Phosphonium, and ‐Arsonium
Authors: Dietzel Pascal D. C. , Kremer Reinhard K. , Jansen Martin 
Published: December 2006

AbstractCompounds of the three large cations tetramethylammonium, tetramethylphosphonium, and tetramethylarsonium with the superoxide radical anion were synthesized by either metathesis or ion exchange in liquid ammonia. They were obtained from concentrated solutions as ammoniates in the form of long needle‐shaped single crystals. [N(CH3)4]‐(O2)⋅3NH3 crystallizes in the monoclinic crystal system, whereas the two compounds [E(CH3)4](O2)⋅2NH3 (E=P, As) are isostructural and belong to the orthorhombic crystal system. The cation–anion packing in all three crystal structures is related to the sodium chloride structure. All structures contain hydrogen bonds between the ammonia molecules and between ammonia and the superoxide. The solvent of crystallization was easily released from the crystals upon complete removal of the solvent from the reaction vessel, leading to polycrystalline samples. The Raman spectra of all three solvent‐free compounds show the symmetric stretching mode of the superoxide ion at about 1123 cm−1. The desolvated [N(CH3)4](O2) was investigated by powder X‐ray diffraction, and the crystal structure was solved by ab initio simulated annealing methods by using rigid‐body models of the constituent molecular ions. The superoxide ion shows rotational disorder. The magnetic susceptibility of tetramethylammonium superoxide follows the Curie–Weiss law with a high‐temperature effective magnetic moment of 1.66(3) μB and a paramagnetic Curie temperature of Θ=−13(6) K. Complementary electron paramagnetic resonance spectroscopy revealed that the average g factor is temperature‐dependent. It decreased from 2.15 at 10 K to 1.66 at 100 K, possibly due to the onset of rotational motion of the superoxide ion and in accordance with the lower‐than‐expected effective magnetic moment.
Dose‐linear pharmacokinetics of oleanolic acid after intravenous and oral administration in rats
Authors: Jeong Dong Won , Kim Young Hoon , Kim Hui Hyun , Ji Hye Young , Yoo Sun Dong , Choi Won Rack , Lee Soo Min , Han Chang‐Kyun , Lee Hye Suk 
Published: December 2006

AbstractThe pharmacokinetics of oleanolic acid was evaluated in vitro and in vivo. From Caco‐2 cell permeation studies, oleanolic acid was a low permeability compound with no directional effects, suggesting a low in vivo absorption mediated by a passive diffusion. Oleanolic acid was metabolically unstable following incubation with rat liver microsomes in the presence of NADPH. After intravenous injection at doses of 0.5, 1 and 2 mg/kg doses, oleanolic acid showed dose‐linear pharmacokinetics as evidenced by unaltered CL (28.6–33.0 ml/min/kg), Vss (437–583 ml/kg), dose‐normalized AUC (16.0–17.9 µg min/ml based on 1 mg/kg) and t1/2 (41.9–52.7 min). Following oral administration of oleanolic acid at doses of 10, 25 and 50 mg/kg, Tmax, t1/2, dose‐normalized Cmax (66–74 ng/ml based on 25 mg/kg) and dose‐normalized AUC (5.4–5.9 µg min/ml based on 25 mg/kg) were comparable between 25 and 50 mg/kg dose, but the plasma concentrations at 10 mg/kg dose were not measurable as they were below the limit of quantitation (2 ng/ml). The absolute oral bioavailability was 0.7% for oral doses of 25 and 50 mg/kg. The extent of urinary excretion was minimal for both i.v. and oral doses. The very low oral bioavailability of oleanolic acid could be due to a poor absorption and extensive metabolic clearance. Copyright © 2007 John Wiley & Sons, Ltd.
In vitro activation of the corticosteroid ciclesonide in animal nasal mucosal homogenates
Authors: Sato H. , Nave R. , Nonaka T. , Mochizuki T. , Takahama S. , Kondo S. 
Published: December 2006

AbstractCiclesonide, a new corticosteroid for allergic rhinitis, is administered as an inactive parent compound that is converted by esterases to the pharmacologically active metabolite, desisobutyryl‐ciclesonide (des‐CIC). This study investigated the in vitro activation of ciclesonide in nasal mucosa of multiple animal species. Nasal mucosal homogenates from rats, guinea‐pigs, rabbits and dogs were incubated with ciclesonide 0.5 µmol/l (0.271 µg/ml) or 5 µmol/l (2.71 µg/ml) for up to 120 min. Concentrations of ciclesonide and des‐CIC were measured by high‐performance liquid chromatography with tandem mass spectrometry. Ciclesonide was metabolized to des‐CIC in nasal mucosal homogenates of each species. The initial velocities of des‐CIC formation ranged from 0.0038 to 0.0150 nmol/min/mg protein and 0.0319 to 0.0983 nmol/min/mg protein in nasal mucosal homogenates incubated with ciclesonide 0.5 µmol/l and 5 µmol/l, respectively. Furthermore, the initial velocities of ciclesonide metabolism ranged from 0.0032 to 0.0142 nmol/min/mg protein and 0.0445 to 0.1316 nmol/min/mg protein in nasal mucosal homogenates incubated with ciclesonide 0.5 µmol/l and 5 µmol/l, respectively. This study confirms that ciclesonide is converted to des‐CIC in nasal mucosal homogenates without any marked differences among animal species. Copyright © 2007 John Wiley & Sons, Ltd.
The influence of grafted polymer architecture and fluid hydrodynamics on protein separation by entropic interaction chromatography
Authors: Coad Bryan R. , Steels Bradley M. , Kizhakkedathu Jayachandran N. , Brooks Donald E. , Haynes Charles A. 
Published: December 2006

AbstractEntropic interaction chromatography (EIC) provides efficient size‐based separation of protein mixtures through the entropy change associated with solute partitioning into a layer of hydrophilic homopolymer that has been end‐grafted within the pores of a macroporous chromatography support. In this work, surface‐initiated atom‐transfer radical polymerization (ATRP) is used to prepare a library of EIC stationary phases covering a wide range of grafted‐chain densities and molecular weights. Exhaustive chain cleavage and analysis by saponification and GPC‐MALLS, respectively, show that the new ATRP synthesis procedure allows for excellent control over graft molecular weight and polydispersity. The method is used to prepare high‐density grafts (up to 0.164 ± 0.005 chains/nm2) that extend the range of EIC applications to include efficient buffer‐exchange and desalting of protein preparations. Reducing the graft density allows for greater partitioning of high molecular weight solutes, extending the linear range of the selectivity curve. Increasing graft molecular weight also alters selectivity, but more directly affects column capacity by increasing the volume of the grafted layer. Protein partitioning in high‐density EIC columns is found to decrease with mobile‐phase velocity (u). Although solute mass transfer resistances leading to an increase in plate height can explain this effect, pressure drop data across the column are indicative of weak convective flow through at least a fraction of the grafted architecture. Modeling of the grafted brush properties in the presence of solvent flow by subjecting a self‐consistent‐field theory representation of the brush to a viscous shear force predicts that the grafted chains will tilt and elongate in the direction of flow. The shear force may therefore act to reduce the number of conformations available to chains, increasing their rigidity without significantly altering the thickness of the grafted layer. A reduction in protein partitioning is then predicted when the dependence on u of the solute entropy loss is stronger than that of the grafted polymer, a condition met at high graft densities. Biotechnol. Bioeng. 2007;97: 574–587. © 2006 Wiley Periodicals, Inc.
Fatal ischemic stroke related to nonpermissive peripheral artery access for percutaneous aortic valve replacement
Authors: Berry Colin , Cartier Raymond , Bonan Raoul 
Published: December 2006

AbstractThis report describes an 85 year‐old man who underwent percutaneous aortic valve replacement (PAVR). With a logistic euroSCORE of 37%, the patient had been refused surgical aortic valve replacement because of an unacceptably high peri‐operative risk. During the PAVR procedure, severe resistance was encountered when advancing the 21 Fr delivery catheter through the left iliac artery despite pre‐dilatation with a 7 mm balloon. Following this, PAVR was promptly achieved without difficulty, with excellent valve positioning, no peri‐valvular leak and good hemodynamics. However, transesophageal echocardiography revealed a mobile echogenic mass within the outflow tract of the left ventricle. The mass was retrieved with a cardiac bioptome manipulated via the left femoral artery through a 9 Fr sheath. A right cerebral ischemic stroke manifested shortly after the post‐procedure and the patient died on the fourth post‐operative day. Post‐mortem findings revealed a left subclavian artery occlusion by iliac vascular tissue. This report highlights the imperative for device‐specific vascular access screening criteria and the need to minimize device size in order to safely accomplish PAVR. © 2006 Wiley‐Liss, Inc.