bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of fly ash silica and precipitated silica fillers on the viscosity, cure, and viscoelastic properties of natural rubber
Authors: Thongsang S. , Sombatsompop N. , Ansarifar A.
Published: April 2008

The viscosity, cure properties, storage, and loss moduli and tan δ of natural rubber (NR) filled with the same amounts of precipitated silica (PSi) and fly ash silica (FASi) fillers were measured. The fillers were treated with bis[3‐triethoxysilylpropyl‐]tetrasulfide (TESPT), or, used in the rubber untreated. TESPT is a sulfur‐containing bi‐functional organosilane that chemically adheres silica to rubber and also prevents silica from interfering with the reaction mechanism of sulfur cure. The dispersion of PSi and FASi in the rubber was investigated using scanning electron microscope (SEM). The effects of silica type and loading and surface treatment on the aforementioned properties were of interest. The SEM results showed that the FASi particles were larger in size and had a wider particle size distribution when compared with the PSi particles. The viscosity of the compounds decreased progressively with mixing time, and the compounds with FASi had a lower viscosity than those filled with PSi. The treatment with Si69 had no beneficial effect on the dispersion of the fillers in the rubber matrix. At low temperatures, the type and loading of the filler had no effect on the storage and loss moduli of the compounds, but the effect was more pronounced at high temperatures. There was also evidence from the tan δ and glass transition temperature (Tg) measurements that some limited interaction between the filler particles and rubber had occurred because of TESPT. Copyright © 2008 John Wiley & Sons, Ltd.
Structure and properties of polypropylene/clay nanocomposites compatibilized by solid‐phase grafted polypropylene
Authors: Ding Chao , He Hui , Guo Baochun , Jia Demin
Published: April 2008

Polypropylene/organic‐montmorillonite (PP/OMMT) nanocomposites were prepared via a solid‐phase PP graft (TMPP) with a higher grafting level as the compatibilizer. The effects of the compatibilizer on the structure and properties of PP/OMMT nanocomposites were investigated. The structure of the nanocomposites were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that when the weight ratio of TMPP and OMMT is greater than 1:1, the OMMT can be dispersed in PP matrix uniformly at the nanoscale. The mechanical properties of the nanocomposites reached a maximum when the weight ratio of TMPP and OMMT is 1:1, although more uniform dispersion was achieved at a higher content of TMPP. The mechanical properties of the nanocomposites decrease with the content of TMPP. The crystallization behavior, dynamic rheological property, and thermal stability of the nanocomposites were investigated by differential scanning calorimetry (DSC), dynamic rheological analysis, and thermal gravimetric analysis (TGA), respectively. Due to the synergistic effects of TMPP and OMMT on the crystallization of PP, the crystallization peak temperature of the nanocomposites increased remarkably compared with that of the neat PP. TMPP shows β‐phase nucleating ability and OMMT promotes the development of β‐phase crystallite. The nanocomposites show restricted melt flow and enhanced temperature sensitivity compared with the neat PP. The thermal stability of the nanocomposites is obviously improved compared with that of the neat PP. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers.
Analysis of galanthamine‐type alkaloids by capillary gas chromatography–mass spectrometry in plants
Authors: Berkov Strahil , Bastida Jaume , Viladomat Francesc , Codina Carles
Published: April 2008

Galanthamine, an acetylcholinesterase inhibitor used for the treatment of Alzheimer's disease, and galanthamine‐type alkaloids are synthesised in different plants of the family Amaryllidaceae. A capillary gas chromatographic–mass spectroscopic (CGC‐MS) method for the separation of 7 galanthamine type alkaloids, including galanthamine and epigalanthamine, is described in the present paper. A simple method for the routine quantification of galanthamine in plants was developed using pre‐packed columns with diatomaceous earth (Isolute HM‐N), allowing simultaneous preparation of a large number of samples. Galanthamine showed excellent linearity in the range from 50 to 1000 µg/mL and the limit of quantification was 5 µg/mL in total ion current mode and 1.6 ng/mL in selected ion monitoring mode. The recovery of galanthamine was more than 90%. Interday reproducibility (RSD) of the extraction was 2.74%. A method to find and to microextract Amaryllidaceae alkaloids in low‐mass plant samples is also described. Copyright © 2008 John Wiley & Sons, Ltd.
Preparative separation of the saponin lancemaside a from Codonopsis lanceolata by centrifugal partition chromatography
Authors: Shirota Osamu , Nagamatsu Kumi , Sekita Setsuko , Komoto Noriko , Kuroyanagi Masanori , Ichikawa Makoto , Ohta Sanae , Ushijima Mitsuyasu
Published: April 2008

Introduction. Lancemaside A is a saponin that inhibits decreases in blood testosterone level and thus prevents or ameliorates symptoms associated with male climacteric disorder. Our initial attempt to preparative isolation of lancemaside A from the saponin fraction of Codonopsis lanceolata roots by a preparative HPLC did not give a clear result.

Objective. To develop a simple and efficient method for the preparative isolation of lancemaside A from the hot water extract of C. lanceolata roots using centrifugal partition chromatography (CPC).

Methodology. The saponin fraction obtained from the hot water extract of C. lanceolata roots was used as the sample for preparative‐scale separation of lancemasides by CPC using n‐hexane:n‐butanol:methanol:0.1% aqueous formic acid (3:4:1:6, v/v) as the two‐phase solvent system. The upper phase (organic phase) of the two‐phase solvent system was used as the mobile phase, and 0.5 g of saponin fraction was applied for separation by CPC. Each fraction that was separated by CPC was analysed by HPLC, and the fractions containing each of the separated compounds were pooled together, and then were purified by simple preparative HPLC.

Results. The demonstrated separation sequence, hot water extraction, DIAION HP‐20 column chromatography, CPC and preparative HPLC, yielded lancemaside A, foetidissimoside A and astersaponin Hb in their pure forms.

Conclusion. The simple and efficient method for the preparative isolation of lancemaside A along with two other saponins, foetidissimoside A and astersaponin Hb, from the saponin fraction of C. lanceolata was established using CPC.
Solid‐phase microextraction for determining twelve orange flavour compounds in a model beverage emulsion
Authors: Mirhosseini Hamed , Tan Chin Ping , Yusof Salmah , Hamid Nazimah Sheikh Abdul
Published: April 2008

Solid‐phase microextraction (SPME) coupled to gas chromatography has been applied for the headspace analysis (HS) of 12 target flavour compounds in a model orange beverage emulsion. The main volatile flavour compounds studied were: acetaldehyde, ethyl acetate, α‐pinene, ethyl butyrate, β‐pinene, myrcene, limonene, γ‐terpinene, octanal, decanal, linalool and citral (neral plus geranial). After screening the fibre type, the effect of other HS‐SPME variables such as adsorption temperature (25–55°C), extraction time (10–40 min), sample concentration (1–100% w/w), sample amount (5–10 g) and salt amount (0–30% w/w) were determined using a two‐level fractional factorial design (25−2) that was expanded further to a central composite design. It was found that an extraction process using a carboxen–polydimethylsiloxane fibre coating at 15ºC for 50 min with 5 g of diluted emulsion 1% (w/w) and 30% (w/w) of sodium chloride under stirring mode resulted in the highest HS extraction efficiency. For all volatile flavour compounds, the linearity values were accurate in the concentration ranges studied (r2 > 0.97). Average recoveries that ranged from 90.3 to 124.8% showed a good accuracy for the optimised method. The relative standard deviation for six replicates of all volatile flavour compounds was found to be less than 15%. For all volatile flavour compounds, the limit of detection ranged from 0.20 to 1.69 mg/L. Copyright © 2008 John Wiley & Sons, Ltd.
Evaluation of viability assays for anthocyanins in cultured cells
Authors: Elisia Ingrid , Popovich David G. , Hu Chun , Kitts David D.
Published: April 2008

The MTT [3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide] assay is a widely accepted cytotoxicity assay which can produce inaccurate results due to possible interference with the antioxidant property of anthocyanins. Alternative methods to the MTT assay, such as BrdU (DNA‐based) and CellTiter‐Glo (ATP‐based) assays were evaluated to assess anthocyanin cytotoxicity, derived from blackberry in LNCaP, MCF‐7 and MDA‐MB‐453 cell lines. The standard cell counting method was the reference assay. Greater correlation of cell viability values following anthocyanin exposure was obtained from multiple cell lines with the alternative assays when compared with cell counting. MTT and cell counting results were not always correlated, albeit this was a function of cell type. In particular, poor correlations between cell counting and MTT procedures used to assess cytotoxicity of anthocyanins were observed in the MDA‐MB‐453 cell lines. Comparison of cytotoxicity derived from alternative assays and the MTT assays with the cell counting method was dependent on the assay procedure and the cell type. The LC50 of blackberry crude extract ranged from 0.4 to 9.4 mg/mL between assays and across all cell lines, whereas a semi‐purified anthocyanin extract was not cytotoxic. Cytotoxicity evaluation of polyphenolic‐rich extracts using BrdU and CellTiter‐Glo assays as alternatives to the MTT method is recommended. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of coinitiator type on initiation efficiency of two‐component photoinitiator systems based on Eosin
Authors: Popielarz Roman , Vogt Otmar
Published: April 2008

Effect of coinitiator structure on relative initiation efficiency of two‐component Eosin/coinitiator systems has been evaluated quantitatively in polymerization of poly(ethylene glycol) diacrylate as an example monomer. The initiation efficiency has been measured by the Fluorescence Probe Technique (FPT), using Eosin both as a photoinitiator component and as a fluorescent probe. A LED/fiber optic‐based measurement system has been developed and applied in this study. It has been found that from among 17 compounds tested, the following coinitiators form most efficient photoinitiating systems in combination with Eosin, when exposed to visible light: coinitiator, relative efficiency = triethanolamine, 1.0; 2,6‐diisopropyl‐N,N‐dimethylaniline, 0.70; 2‐benzyl‐2‐(dimethylamino)‐4′‐morpholinobutyrophenone (Irgacure 369), 0.91; carbon tetrabromide, 2.1; [4‐[(2‐hydroxytetradecyl)oxy]phenyl]phenyliodonium hexafluoroantimonate (SarCat 1012), 28. These relative efficiencies refer to the following component concentrations: [Eosin] = 8.6 × 10−4M, (0.05% by weight); [coinitiator] = 4.3 × 10−2M. The factors affecting the initiation efficiency of the systems studied are discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3519–3532, 2008
Hydrophilic graft modification of a commercial crystalline polyolefin
Authors: Shin Jihoon , Chang Andrew Y. , Brownell Lacie V. , Racoma Ira O. , Ozawa Coreen H. , Chung Ho‐Yong , Peng Shufu , Bae Chulsung
Published: April 2008

Hydroxy‐functionalized isotactic poly(1‐butene) was synthesized using transition metal‐catalyzed regioselective CH borylation at the side chain of the commercial polyolefin and subsequent oxidation of the boronic ester functionality. Functionalization up to ∼ 19 mol % of the termini of the ethyl side chain occurred without significant side reactions that could alter the polymer chain length. Esterification of the hydroxy group in the polymer with 2‐bromoisobutyl bromide generated a side chain‐functionalized polyolefin macroinitiator. Atom transfer radical polymerization of tert‐butyl acrylate from the macroinitiator produced a high molecular‐weight graft copolymer of the polyolefin, isotactic poly(1‐butene)‐graft‐poly(tert‐butyl acrylate) (PB‐g‐PtBA). Finally, the hydrolysis of the tert‐butoxy ester group of PB‐g‐PtBA created an amphiphilic polyolefin, isotactic poly(1‐butene)‐graft‐poly(acrylic acid), which contained a short carboxylic acid‐functionalized polymer block at the side chain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3533–3545, 2008
Functionalization of surface‐grafted polymethylhydrosiloxane thin films with alkyl side chains
Authors: Thami Thierry , Nasr Gihane , Bestal Hanan , Van Der Lee Arie , Bresson Bruno
Published: April 2008

Thin films of crosslinked polymethylhydrosiloxane (PMHS) have been grafted on silica using the sol–gel process allowing further functionalization by effective quantitative hydrosilylation of SiH groups by olefins within the network. Postfunctionalization gives the polysiloxane network with n‐alkyl side chains. The PMHS coating was prepared by room temperature polycondensation of a mixture of methyldiethoxysilane HSiMe(OEt)2 monomer and triethoxysilane HSi(OEt)3 (TH) as crosslinker. The surface‐attached films are chemically stable and covalently bonded to the silica surface. Subsequently, films were functionalized without delamination. We showed by FTIR spectroscopy how the crosslinking ratio and the molecular size of the alkenes precursors influence the extent of the hydrosilylation reaction of SiH groups in the PMHS network. We have determined that quasi‐full olefin addition catalyzed by a platinum complex occurred within soft networks of less than 5% TH with 1‐alkenes CH2CH(CH2)n‐2CH3 of various alkyl chain lengths (n = 5, 11, 17). Powders of PMHS gel were also modified with 1‐alkenes by hydrosilylation. The SiH groups within the soft gel (5% crosslinked) were fully functionalized as shown by 29Si and 1H solid‐state NMR. The structure of functionalized polysiloxane with n‐octadecyl and n‐dodecyl side chains was studied by FTIR, wide angle X‐ray diffraction, and DSC showing crystallization of the long n‐alkyl chains in the network. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3546–3562, 2008
Real‐time FTIR monitoring of the mechanism of initiation of isobutylene polymerizations by epoxide/Lewis acid systems
Authors: Hayat Soytaş Serap , Puskas Judit E. , Kulbaba Kevin
Published: April 2008

Real‐time Fourier Transformation Infrared (FTIR) spectroscopy with a fiber optic transmission probe (TR) was used to monitor the polymerization of isobutylene (IB) initiated by α‐methylstyrene epoxide (MSE) and 1,2‐epoxi‐2,4,4‐trimethylpentane (TMPO‐1) in conjunction with TiCl4 and BCl3. In the presence of an equimolar amount of BCl3, MSE and TMPO‐1 underwent ring opening via SN1 mechanism. In contrast to TiCl4‐coinitiated reactions, no oligoether formation via SN2 mechanism was observed. TMPO‐1 with excess BCl3 initiated IB polymerization, yielding a telechelic PIB carrying α‐primary OH and ω‐tertiary Cl functionalities with 70% initiator efficiency. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3611–3618, 2008
Impact of the clay organic modifier on the morphology of polymer–clay nanocomposites prepared by in situ free‐radical polymerization in emulsion
Authors: Greesh Nagi , Hartmann Patrice C. , Cloete Valeska , Sanderson Ronald D.
Published: April 2008

Poly(styrene‐co‐butyl acrylate) copolymers were prepared by free‐radical random copolymerization of styrene and butyl acrylate in emulsion in the presence of 10% of surface‐modified sodium montmorillonite (Na‐MMT). The objective of this work was to evaluate the impact of the clay organic modifier in terms of its chemical structure, its degree of interaction within the clay galleries surface, and its ability to copolymerize with monomers, on the morphology and properties of the final nanocomposite prepared. Na‐MMT was modified using different organic modifiers, namely: sodium 1‐allyloxy‐2‐hydroxypropyl (Cops), 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS), N‐isopropylacrylamide (NIPA), and sodium 11‐methacryloyloxy‐undecan‐1‐yl sulfate (MET), respectively. The morphology and properties of the nanocomposites obtained were found to be dependant on the clay organic modifier. X‐ray diffraction (XRD) and transmission electron microscopy indicated that, nanocomposites at 10% clay loading with Cops‐, NIPA‐, and MET‐modified clays, yielded intercalated to partially exfoliated structures, whereas AMPS‐modified clay gave a nanocomposite with a fully exfoliated structure. All polymer–clay nanocomposites were found to be more thermally stable than neat poly(S‐co‐BA) as were determined by TGA. However, nanocomposites with intercalated structures exhibited greater thermal stability relative to fully exfoliated ones. Furthermore, nanocomposites with exfoliated structures exhibited higher storage moduli (GI) than partially exfoliated once, whereas intercalated structure showed the lowest GI values. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3619–3628, 2008
Thermogelling behaviors of poly(caprolactone‐b‐ethylene glycol‐b‐caprolactone) triblock copolymer in the presence of hyaluronic acid
Authors: Kim In Yong , Yoo Mi Kyong , Kim Bom Chol , Park In Young , Lee Hyun Chul , Cho Chong Su
Published: April 2008

In this article, we studied the effect of hyaluronic acid (HA) on thermogelation of poly(caprolactone‐b‐ethylene glycol‐b‐caprolactone) (PCL‐PEG‐PCL) aqueous solution designed as an injectable system for prevention of postsurgical tissue adhesion. The PCL‐PEG‐PCL triblock copolymers were simply synthesized by ring‐opening polymerization of ε‐caprolactone (CL) in the presence of PEG as a polymeric initiator. The synthesized copolymers were confirmed by proton nuclear magnetic resonance (1H‐NMR) spectroscopy. Possible interactions between HA and PCL‐PEG‐PCL triblock copolymers in the blend were evaluated by Fourier‐transform infrared spectroscopy (FTIR). The effect of HA on the micellization of PCL‐PEG‐PCL aqueous solution was investigated by dye solubilization method and electrophoretic lighting scattering (ELS) spectrophotometer. Also, the thermogelling behaviors of the PCL‐PEG‐PCL triblock copolymers in the presence of HA and their mechanism were investigated by test tube inverting method, 13C‐NMR, 1H‐NMR, Advanced Rheometic Expansion System (ARES), and differential scanning calorimetry (DSC). The PCL‐PEG‐PCL/HA blend aqueous solutions undergo the sol‐gel‐sol transition in response to an increase in temperature (10–60 °C) and the gelation of the PCL‐PEG‐PCL was rather accelerated by HA. Presumably, this accelerated gelation seems to arise from the attractive interactions between them and the effect of chain confinement in the micelle corona region. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3629–3637, 2008
Kinetics of dispersion polymerization: Effect of medium composition
Authors: Jiang Sheng , Sudol E. David , Dimonie Victoria L. , El‐Aasser Mohamed S.
Published: April 2008

The effect of the medium composition (monomer and solvent) on the kinetics of dispersion polymerization of methyl methacrylate (MMA) was studied via reaction calorimetry. It was found that increasing the monomer concentration increased the reaction rate; the exponent of the dependency of the initial reaction rate on the MMA concentration was found to be 0.93. Narrow particle size distributions were achieved at the lower monomer concentrations (0.24–0.81 mol/L) and a minimum size (2.45 μm) was found at an intermediate concentration (0.44 mol/L). The average molecular weight of the PMMA increased and the molecular weight distribution broadened with increasing monomer concentration. During a dispersion polymerization, the MMA concentration was found to decrease linearly with conversion in both phases, whereas the ratio of concentrations in the particles and continuous phase ([M]p/[M]c) remained constant (0.47) with partitioning favoring the continuous phase. The average number of free radicals per particle in MMA dispersion polymerization was estimated to be high from the nucleation stage onward (>5000). The increasing rate during the first ∼ 40% conversion was primarily caused by the increasing volume of the polymer particle phase. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3638–3647, 2008
Synthesis of chiral micelles and nanoparticles from amino acid based monomers using RAFT polymerization
Authors: Skey Jared , O'reilly Rachel K.
Published: April 2008

Homopolymers of tbutyl acrylate (PtBuA) and a monosubstituted acrylamide (PAM) having an amino acid moiety in the side chain, N‐acryloyl‐(L)‐phenylalanine methyl ester 1, have been synthesized by Reversible Addition‐Fragmentation Chain Transfer (RAFT) polymerization. Diblock copolymers of these homopolymers were also synthesized by chain extending PtBuA with monomer 1 and after modification, using simple acid deprotection chemistries of the acrylate block to afford a poly (acrylic acid) block, an optically active amphiphilic diblock copolymer was isolated. The optically active amphiphilic diblock copolymers, which contain chiral amino acid moieties within the hydrophobic segment, were then self‐assembled to afford spherical micelles which were subsequently crosslinked throughout the shell layer to afford robust chiral nanoparticles. The hydrodynamic diameters (Dh) of the block copolymer micelles and nanoparticles were measured by dynamic light scattering (DLS) and the dimensions of the nanoparticles were determined using tapping‐mode atomic force microscopy (AFM) and transmission electron microscopy (TEM). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3690–3702, 2008
An efficient solid‐state polycondensation method for synthesizing stereocomplexed poly(lactic acid)s with high molecular weight
Authors: Fukushima Kazuki , Kimura Yoshiharu
Published: April 2008

Simultaneous solid‐state polycondensation (SSP) of the powdery prepolymers of poly(L‐lactic acid) (PLLA) and poly(D‐lactic acid) (PDLA) can produce entire stereocomplexed poly(lactic acid)s (sc‐PLA) with high molecular weight and can be an alternative synthetic route to sc‐PLA. Ordinary melt polycondensations of L‐ and D‐lactic acids gave the PLLA and PDLA prepolymers having medium molecular weight which were pulverized for blending in 1:1 ratio. The resultant powder blends were then subjected to SSP at 130–160 °C for 30 h under a reduced pressure of 0.5 Torr. Some of the products thus obtained attained a molecular weight (Mw) as high as 200 kDa, consisting of stereoblock copolymer of PLLA and PDLA. A small amount of the stereocomplex should be formed in the boundaries of the partially melted PLLA and PDLA where the hetero‐chain connection is induced to generate the blocky components. The resultant SSP products showed predominant stereocomplexation after their melt‐processing in the presence of the stereoblock components in spite of containing a small amount of racemic sequences in the homo‐chiral PLLA and PDLA chains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3714–3722, 2008
Syntheses of multicyclic poly(ether sulfone)s from 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane and 4,4′‐bis(4‐chlorophenyl) sulfones
Authors: Kricheldorf Hans R. , Bornhorst Kirstin
Published: April 2008

5,5′,6,6′‐Tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane (TTSBI) was polycondensed with 4,4′‐dichlorodiphenyl sulfone (DCDPS) or with 4,4′‐bis(4‐chlorophenyl sulfonyl) biphenyl (BCSBP) in DMSO. Concentration and feed ratio were optimized to avoid gelation and to obtain a maximum yield of multicyclic polyethers free of functional groups. Regardless of these reaction conditions, only low fractions of perfect multicycles were obtained from DCDPS apparently due to steric hindrance of ring closure. Under the same conditions high fractions of perfect multicycles were achieved with the longer and more flexible DCSBP. The reaction products were characterized by MALDI‐TOF mass spectrometry, 1H‐NMR spectroscopy viscosity, and DSC measurements. Relatively low glass transition temperatures (Tgs ≈ 160–175 °C) were found. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3732–3739, 2008
RAFT synthesis of amphiphilic (A‐ran‐B)‐b‐C diblock copolymers with tunable pH‐sensitivity
Authors: Hu Ying Qian , Kim Min Sang , Kim Bong Sup , Lee Doo Sung
Published: April 2008

RAFT homopolymerization of 2‐(diisopropylamino)ethyl methacrylate (DPA) and 2‐(diethylamino)ethyl methacrylate (DEA) and their random copolymerization were investigated. The random copolymers of DPA‐ran‐DEA were synthesized and used as macro‐CTA to prepare poly(DPA‐ran‐DEA)‐b‐poly(N‐(2‐hydroxypropyl) methacrylamide) amphiphilic block copolymers. The 1H NMR and GPC measurements confirmed the successful synthesis of these copolymers. The potentiometric titration results showed that the pKb values of these copolymers were in the range of 6.7 ∼ 7.7 and linearly varied with the DPA/DEA composition, regardless of the block length of HPMA. The pH‐induced micellization in PBS solution was verified by fluorescence spectroscopy. The dynamic light scattering evaluation showed that the hydrodynamic diameters of these micelles are between 37 ∼ 43 nm © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3740–3748, 2008
Dispersibility of clay and crystallization kinetics for in situ polymerized PET/pristine and modified montmorillonite nanocomposites
Authors: Hwang Sung Yeon , Lee Wan Duk , Lim Jung Seop , Park Ki Hong , Im Seung Soon
Published: April 2008

Nanocomposite materials composed of poly (ethylene terephthalate) (PET) and montmorillonite (MMT) clays were prepared by in situ polymerization. Samples consisted of PET blended with various quantities of either pristine (Na+‐MMT) or organically modified MMT (A10‐MMT). The morphology and thermal and mechanical properties were evaluated for each sample. TEM micrographs, acquired at a 20 nm resolution, provide direct evidence of exfoliation of the clay particles into the PET matrix and show the effect of the alkyl‐modifier on clay dispersibility. The dispersion of PET/A10‐MMT was greater than that observed for the PET/Na+‐MMT nanocomposites. The greatest degree of exfoliation occurred for PET/A10‐MMT 0.5 wt %. However, PET/Na+‐MMT exhibited higher crystallization temperatures and rates suggesting that Na+‐MMT is a more efficient nucleating agent. Both mechanically and thermally, PET/A10‐MMT nanocomposites exhibited superior properties over pure PET. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1022–1035, 2008
Effects of compression cycles and precompression pressure on the repeatability of piezoresistivity for carbon black‐filled silicone rubber composite
Authors: Wang Luheng , Ding Tianhuai , Wang Peng
Published: April 2008

We studied the influences of the compression cycles and the precompression pressure on the piezoresistivity of carbon black‐filled silicone rubber composite. The experimental results show that if the load pressure is less than the maximum pressure in the precompression cycle, the repeatability of the piezoresistivity is improved with the increase of the compression cycles. Once the load pressure surpasses the maximum pressure in the precompression cycle, the piezoresistivity of the composite is changed distinctly. The experimental phenomena are explained and described qualitatively by analyzing the changes in the composite resistance under the zero pressure and the slippage of the molecule chain during the compression. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1050–1061, 2008
Crystal structure and morphologies of polypropylene homopolymer and propylene‐ethylene random copolymer: Effect of the substituted 1,3,5‐benzenetrisamides
Authors: Wang Jingbo , Dou Qiang , Chen Xianyi , Li Di
Published: April 2008

Four different substituted 1,3,5‐benzenetrisamides were synthesized and two of them were reported for the first time. Their effects on the crystal structure and morphologies of the iPP homopolymer (PPH) and propylene‐ethylene random copolymers (PPR) were investigated. The results showed that they had versatile nucleating ability among the different crystal forms of PPH. The N,N′,N′′‐tris‐tert‐butyl‐1,3,5‐benzene‐tricarboxamide, N,N′,N′′‐tris‐cyclohexyl‐1,3,5‐benzene‐tricarboxamide, and N,N′,N′′‐tris‐isopropyl‐1,3,5‐benzene‐tricarboxamide suppressed the formation of detectable spherulites with the common α‐form of the PPH, as well as the N,N′,N′′‐n‐butyl‐1,3,5‐benzene‐tricarboxamide induced the spherulites of the β‐form. The combination of the ethylene segment and the nucleating agent facilitated the formation of the γ‐form. These trisamides had limited effects on the packing of the PPH segments but induced more compacted packing of the PPRs. The nucleation mechanism of such compounds was discussed for the first time, it was found that the nucleation ability of these compounds rooted in matching of their dimension of the b‐axis with dimension of the c‐axis of iPP, and their butterfly‐shape further enhanced it. The (001) face of the trisamides was in contact with the (010) face of iPP. This epitaxial crystallization led to preferential growth along the b‐axis, and the ethylene segment indeed enhanced this effect. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1067–1078, 2008
Where does all the helium that we use come from?
Authors: Manning David A. C.
Published: April 2008

Helium occurs naturally in association with geological fluids and is regarded by economists as a mineral commodity. Commercially, helium is obtained as a by‐product from natural gas reservoirs that typically have concentrations of up to 1% He by volume (STP). Existing sources of helium within the USA are expected to decline in parallel with declining natural gas production. Huge reserves of helium occur in Algeria, Qatar and Russia, which are likely to dominate production for the next several decades. In this context, political and economic factors that affect hydrocarbon gas production may influence the availability and price of helium. Copyright © 2008 John Wiley & Sons, Ltd.
A review of stable isotope techniques for N2O source partitioning in soils: recent progress, remaining challenges and future considerations
Authors: Baggs E. M.
Published: April 2008

Nitrous oxide is produced in soil during several processes, which may occur simultaneously within different micro‐sites of the same soil. Stable isotope techniques have a crucial role to play in the attribution of N2O emissions to different microbial processes, through estimation (natural abundance, site preference) or quantification (enrichment) of processes based on the 15N and 18O signatures of N2O determined by isotope ratio mass spectrometry. These approaches have the potential to become even more powerful when linked with recent developments in secondary isotope mass spectrometry, with microbial ecology, and with modelling approaches, enabling sources of N2O to be considered at a wide range of scales and related to the underlying microbiology. Such source partitioning of N2O is inherently challenging, but is vital to close the N2O budget and to better understand controls on the different processes, with a view to developing appropriate management practices for mitigation of N2O. In this respect, it is essential that as many of the contributing processes as possible are considered in any study aimed at source attribution, as mitigation strategies for one process may not be appropriate for another. To aid such an approach, here the current state of the art is critically examined, remaining challenges are highlighted, and recommendations are made for future direction. Copyright © 2008 John Wiley & Sons, Ltd.
Application of nitrogen stable isotope analysis in size‐based marine food web and macroecological research
Authors: Jennings Simon , Barnes Carolyn , Sweeting Christopher J. , Polunin Nicholas V. C.
Published: April 2008

Interacting human and environmental pressures influence the structure and dynamics of marine food webs. To describe and predict the effects of these pressures, theoretical advances need to be supported by a capacity to validate the underlying models and assumptions. Here, we review recent applications of nitrogen stable isotope analysis in marine food web and macroecological research, with a focus on work that has paralleled a resurgence of interest in the development and application of size‐based models. Nitrogen stable isotope data have been used to estimate intra‐ and inter‐specific variation in trophic level, predator‐prey size ratios, transfer efficiency, food chain length, relationships between predator and prey species diversity and the dynamics of energy use. Many of these estimates have contributed to the development, testing and parameterisation of food web and ecosystem models, some of which have been used to establish baselines for assessing the scale of human impacts. The interpretation of results depends on assumed fractionation but, when supported by sensitivity analyses and experimental validation, nitrogen stable isotope data provide valuable insights into the structuring of marine communities and ecosystems. Copyright © 2008 John Wiley & Sons, Ltd.
Stable carbon and nitrogen isotopes and quality traits of fossil cereal grains provide clues on sustainability at the beginnings of Mediterranean agriculture
Authors: Aguilera Mònica , Araus José Luis , Voltas Jordi , Rodríguez‐Ariza Maria Oliva , Molina Fernando , Rovira Núria , Buxó Ramon , Ferrio Juan Pedro
Published: April 2008

We present a novel approach to study the sustainability of ancient Mediterranean agriculture that combines the measurement of carbon isotope discrimination (Δ13C) and nitrogen isotope composition (δ15N) along with the assessment of quality traits in fossil cereal grains. Charred grains of naked wheat and barley were recovered in Los Castillejos, an archaeological site in SE Spain, with a continuous occupation of ca. 1500 years starting soon after the origin of agriculture (ca. 4000 BCE) in the region. Crop water status and yield were estimated from Δ13C and soil fertility and management practices were assessed from the δ15N and N content of grains. The original grain weight was inferred from grain dimensions and grain N content was assessed after correcting N concentration for the effect of carbonisation. Estimated water conditions (i.e. rainfall) during crop growth remained constant for the entire period. However, the grain size and grain yield decreased progressively during the first millennium after the onset of agriculture, regardless of the species, with only a slight recovery afterwards. Minimum δ15N values and grain N content were also recorded in the later periods of site occupation. Our results indicate a progressive loss of soil fertility, even when the amount of precipitation remained steady, thereby indicating the unsustainable nature of early agriculture at this site in the Western Mediterranean Basin. In addition, several findings suggest that barley and wheat were cultivated separately, the former being restricted to marginal areas, coinciding with an increased focus on wheat cultivation. Copyright © 2008 John Wiley & Sons, Ltd.
Elucidation of nitrate reduction pathways in anaerobic bioreactors using a stable isotope approach
Authors: Mazéas Laurent , Vigneron Vassilia , Le‐Ménach Karyn , Budzinski Hélène , Audic Jean‐Marc , Bernet Nicolas , Bouchez Théodore
Published: April 2008

Leachate recirculation allows an increase of moisture content and the enhancement of the anaerobic digestion of wastes in landfill. Since there is no ammonia elimination process in landfill when leachate is recirculated, NH may accumulate. One strategy for NH removal is to treat aerobically the leachate outside the landfill to convert NH into NO. When nitrified leachate is recirculated, denitrification should occur in the waste. We have previously shown that wastes have a large capacity to convert nitrate into N2. Nevertheless, in some cases we observed nitrate reduction without gaseous nitrogen production. Using a stepwise multiple regression models, H2S concentration was the unique parameter found to have a negative effect on N2 production. We then suspected that dissimilatory nitrate reduction to ammonium (DNRA) occurred in the presence of H2S. In order to verify this hypothesis, 15N nitrate injections were performed into microcosms containing different H2S concentrations. The ammonium 15N enrichment was measured using an elemental analyser coupled to an isotope ratio mass spectrometer. In the two microcosms containing the highest H2S concentrations, the ammonium was 15N enriched and at the end of the experiment all the added nitrate was converted into ammonium. For the two microcosms containing the lowest H2S concentrations, no 15N enrichment of ammonium was observed. This isotopic approach has allowed us to demonstrate that, in the presence of significant concentrations of H2S, denitrification is replaced by DNRA. Copyright © 2008 John Wiley & Sons, Ltd.
Are frequent radiographs necessary in the management of closed forearm fractures in children?
Authors: Bochang Chen , Katz Kalman , Weigl Daniel , Jie Yang , Zhigang Wang , Bar-On Elhanan
Published: April 2008

Introduction

A prospective pooled case series was used to assess the value of frequent radiographic examinations during treatment of closed forearm fractures in children from major university pediatric medical centers in Israel and China.

Methods

The sample consisted of 202 consecutive children (mean age 7 years; range 3–12 years) with closed forearm fractures treated nonoperatively. Children with open, growth-plate fractures or fractures associated with dislocation of the nearby joint (i.e., monteggia fractures) were excluded. In 28 children who had torus fractures, radiographic examination was performed at the time of cast removal, 3 weeks after the start of treatment. In 63 children who had stable fractures that did not require reduction (undisplaced or minimally displaced, complete or greenstick), radiographic examination was performed 1 week after the start of treatment and again at cast removal 4–6 weeks later. In the remaining 111 children with complete, displaced, or greenstick fractures (all with angulation of more than 15°) who underwent closed reduction, an additional X-ray was taken 2 weeks after cast placement. All children (except those with torus fractures) were followed clinically, without further radiographic examination, for 3 months after cast removal.

Results

Radiographs at cast removal showed good union in all stable fractures, indicating that additional X-rays on cast removal would have had no added value. In the children with unstable fractures, only 9 showed redisplacement with angulation of more than 15° on repeated X-rays during the first 2 weeks after cast placement. All 9 underwent successful re-reduction. On clinical evaluation 3 months after cast removal, all patients in the sample had full range of elbow and forearm motion. Repeated fracture did not occur in any of the patients.

Conclusions

On the basis of these results, radiographs are recommended 2 weeks after cast placement for greenstick or complete fractures. At the time of cast removal, if clinical examination does not show signs of nonunion or malalignment, no radiographic examination is necessary.
Effects of cardiac resynchronization therapy on coronary blood flow: Evaluation by transthoracic Doppler echocardiography☆
Authors: Valzania Cinzia , Gadler Fredrik , Winter Reidar , Braunschweig Frieder , Brodin Lars‐Åke , Gudmundsson Petri , Boriani Giuseppe , Eriksson Maria J.
Published: April 2008

Background:

Relatively limited and conflicting data are available on the effects of cardiac resynchronization therapy (CRT) on coronary blood flow (CBF).

Aims:

To investigate changes in the left anterior descending coronary artery (LAD) flow under different CRT pacing modes by means of transthoracic Doppler echocardiography (TTE).

Methods:

Twenty‐two responders to CRT (67±11 years) with idiopathic dilated cardiomyopathy underwent TTE assessment of LAD flow and Tissue Velocity Imaging during 4 programming modes: intrinsic conduction (IC), right ventricular pacing (RV), simultaneous biventricular pacing (BVP), BVP with left ventricular (LV) pre‐activation.

Results:

Mean coronary flow velocity (CFV) was increased by simultaneous BVP (p=0.0063 vs. IC) and BVP with LV pre‐activation (p<0.0001 vs. IC; p=0.027 vs. simultaneous BVP). Peak CFV and LAD flow velocity/time integral were highest during BVP with LV pre‐activation. A reduction in septal‐to‐lateral delay and an increase in peak systolic velocity in the basal septum were observed during simultaneous BVP and BVP with LV pre‐activation.

Conclusions:

In CRT responders with idiopathic dilated cardiomyopathy, an increase in LAD flow, assessed by TTE, was observed during simultaneous BVP and BVP with LV pre‐activation. This was associated with an improvement in regional myocardial contraction and a decrease in intraventricular dyssynchrony.
Transplantation of adipose derived stromal cells is associated with functional improvement in a rat model of chronic myocardial infarction
Authors: Mazo Manuel , Planat‐Bénard Valérie , Abizanda Gloria , Pelacho Beatriz , Léobon Bertrand , Gavira Juan José , Peñuelas Iván , Cemborain Arantxa , Pénicaud Luc , Laharrague Patrick , Joffre Carine , Boisson Marie , Ecay Margarita , Collantes Maria , Barba Joaquin , Casteilla Louis , Prósper Felipe
Published: April 2008

Aims:

To determine the effect of transplantation of undifferentiated and cardiac pre‐differentiated adipose stem cells compared with bone marrow mononuclear cells (BM‐MNC) in a chronic model of myocardial infarction.

Methods:

Ninety‐five Sprague–Dawley rats underwent left coronary artery ligation and after 1month received by direct intramyocardial injection either adipose derived stem cells (ADSC), cardiomyogenic cells (AD‐CMG) or BM‐MNC from enhanced‐Green Fluorescent Protein (eGFP) mice. The control group was treated with culture medium. Heart function was assessed by echocardiography and 18F‐FDG microPET. Cell engraftment, differentiation, angiogenesis and fibrosis in the scar tissue were also evaluated by (immuno)histochemistry and immunofluorescence.

Results:

One month after cell transplantation, ADSC induced a significant improvement in heart function (LVEF 46.3±9.6% versus 27.7±8% pre‐transplant) and tissue viability (64.78±7.2% versus 55.89±6.3% pre‐transplant). An increase in the degree of angiogenesis and a decrease in fibrosis were also detected. Although transplantation of AD‐CMG or BM‐MNC also had a positive, albeit smaller, effect on angiogenesis and fibrosis in the infarcted hearts, this benefit did not translate into a significant improvement in heart function or tissue viability.

Conclusion:

These results indicate that transplantation of adipose derived cells in chronic infarct provides a superior benefit to cardiac pre‐differentiated ADSC and BM‐MNC.
Responses to pain in school‐aged children with experience in a neonatal intensive care unit: Cognitive aspects and maternal influences
Authors: Hohmeister Johanna , Demirakça Süha , Zohsel Katrin , Flor Herta , Hermann Christiane
Published: April 2008

Previously, it was shown that school‐aged (9–14yr) preterm and fullterm children with neonatal pain exposure exhibit elevated heat pain thresholds and heightened perceptual sensitization to tonic painful heat when tested under standard conditions [Hermann C, Hohmeister J, Demirakca S, Zohsel K, Flor H. Long‐term alteration of pain sensitivity in school‐aged children with early pain experiences. Pain 2006;125:278–85]. Here, changes in the psychosocial context of pain responses in these children, who had been hospitalized ≥7 days after birth including ≥3 days of treatment in a neonatal intensive care unit (NICU), are reported. Nineteen preterm (≤31 weeks gestational age) and 20 fullterm children (≥37 weeks gestational age) with NICU experience, recruited retrospectively and selected based on strict exclusion criteria, and 20 fullterm control children participated. Preterm NICU children endorsed more pain catastrophizing as compared to controls. Mothers of preterm children, who had been more severely ill and had been hospitalized longer than fullterm NICU children, were more likely to engage in solicitous pain‐related behavior. Maternal influence was also assessed by comparing heat pain thresholds and perceptual sensitization to tonic painful heat obtained in the presence versus absence (i.e. standard testing conditions) of the mother. In all three groups, maternal presence was associated with increased heat pain thresholds. Control children habituated significantly more to tonic heat when their mother was present. The NICU children showed overall significantly less habituation than the controls; there was no modulating effect of maternal presence. Especially in highly vulnerable children such as preterms, neonatal pain exposure and prolonged hospitalization may, aside from neuronal plasticity, promote maladaptive pain‐related cognitions and foster parental behavior that reinforces the child's pain response.
Protein kinase C protects from DNA damage‐induced necrotic cell death by inhibiting poly(ADP‐ribose) polymerase‐1
Authors: Hegedűs Csaba , Lakatos Petra , Oláh Gábor , Tóth Balázs I. , Gergely Szabolcs , Szabó Éva , Bíró Tamás , Szabó Csaba , Virág László
Published: April 2008

The goal of the current study, conducted in freshly isolated thymocytes was (1) to investigate the possibility that the activation of poly(ADP‐ribose) polymerase‐1 (PARP‐1) in an intact cell can be regulated by protein kinase C (PKC) mediated phosphorylation and (2) to examine the consequence of this regulatory mechanism in the context of cell death induced by the genotoxic agent. In cells stimulated by the PKC activating phorbol esters, DNA breakage was unaffected, PARP‐1 was phosphorylated, 1‐methyl‐3‐nitro‐1‐nitrosoguanidine‐induced PARP activation and cell necrosis were suppressed, with all these effects attenuated by the PKC inhibitors GF109203X or Gö6976. Inhibition of cellular PARP activity by PKC‐mediated phosphorylation may provide a plausible mechanism for the previously observed cytoprotective effects of PKC activators.
Treating Leick with like: response to criticisms of the use of entanglement to illustrate homeopathy
Authors: Milgrom Lionel R.
Published: April 2008

In criticising papers which recently appeared in Homeopathy, Leick claims that no double blind randomised clinical trials (DBRCTs) show that homeopathy is efficacious, and that specific effects of substances diluted beyond Avogadro's limit are implausible. He states that generalised entanglement models should be able to improve the design of experiments to test ultra-high dilutions, and disparages the authors' understandings of quantum physics. The paper responds to those criticisms. Several DBRCTs have shown that homeopathy has effects which are not due to placebo and these are now supported by preclinical work. This area of theory is in its infancy and it is unreasonable to expect it to have generated experiments at this stage. The authors have used accepted interpretations of quantum theory: Leick's view is coloured by skepticism concerning homeopathy.