bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water and alcohol(s): what's the difference? A proton NMR and DFT study of hetero‐association with pyridine
Authors: Lomas John S. , Maurel François 
Published: May 2008

AbstractHetero‐association of water and some simple aliphatic alcohols with pyridine in benzene has been studied by 1H nuclear magnetic resonance (NMR) spectroscopy at very low donor concentration, where self‐association is negligible. Association constants for the formation of 1:1 and 2:1 pyridine:water complexes can then be determined without recourse to ad hoc computer programmes. That for association of a second pyridine with water is about 10 times lower than for the first. Reaction parameters for the first association with water are very similar to those for the alcohols, whereas the reaction enthalpy for the second association is somewhat smaller. The chemical shift of the OH protons and the HCOH coupling constants for alcohols at high dilution in benzene are almost identical with gas‐phase data. The change in chemical shift upon association with pyridine correlates with the free energy of the reaction. Quantum mechanical calculations [BPE0 functional, 6‐311+G(d,p) basis set and a polarized continuum model of the solvent (IEFPCM)] have been run on complexes of pyridine with water, both 1:1 and 2:1, and with four alcohols. Calculated reaction enthalpies are in qualitative and, in some cases, almost quantitative agreement with the experimental data. The association constants for 1:1 complexation of pyridine with alcohols follow a rough Taft correlation in terms of polar substituent constants. Substituent size, even in the case of very bulky groups, seems to be unimportant. Copyright © 2008 John Wiley & Sons, Ltd.
Comparative nucleophilic reactivities in carboxylate, phosphinate, and thiophosphate esters cleavage
Authors: Ghosh Kallol K. , Bal Sunita , Kolay Sancheeta , Shrivastava Ashish 
Published: May 2008

AbstractNucleophilic substitution reaction of p‐nitrophenyl acetate (PNPA), p‐nitrophenyldiphenyl phosphinate, and pesticide parathion with different α‐nucleophiles [I] have been studied at 27 °C in different pH in the presence of a novel cationic surfactant. The kinetic study was performed spectrophotometrically under pseudo‐first order conditions with the α‐nucleophile in excess. The pKa of nucleophiles have also been determined by kinetic method. In the presence of surfactant, the rate constant increased with increasing surfactant concentration up to a limiting value. This behavior has been analyzed in quantitative terms on the basis of pseudo‐phase model of micellar catalysis. Finally the nucleophilic reactivity of hydroxamate ions has been compared with other α‐nucleophiles, like oxime, hydroxybenzotriazole, and 2‐iodosobenzoic acid (IBA). The order of cleavage of electrophilic centers, that is, CO, PO, and PS have also been discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Changes of electron density in the OHN hydrogen bond upon proton transfer in complexes of phenols with trimethylamine: DFT study
Authors: Kwiatkowska Emilia , Majerz Irena 
Published: May 2008

AbstractThe intermolecular hydrogen bonds in phenol–trimethylamine complexes were investigated by Bader Atom in Molecules (AIM) theory. The AIM parameters of the bond critical points (BCPs) of the O···H, N···H, and CO bonds as well as those of the phenol ring critical point (RCP) were analyzed as functions of the proton‐transfer degree. Transfer of the proton from donor to acceptor changes not only the electron density of the hydrogen bridge, but also the electron cloud in the proton donor. The differences between the proton donors in relation to their pKavalues are seen in the systematic changes of the AIM parameters. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis and characterization of amphiphilic cationic symmetrical ABCBA pentablock terpolymer networks: Effect of hydrophobic content
Authors: Triftaridou Aggeliki I. , Loizou Elena , Patrickios Costas S. 
Published: May 2008

AbstractGroup transfer polymerization was employed for the preparation of six amphiphilic terpolymer networks comprising the hydrophilic, pH‐responsive 2‐(dimethylamino)ethyl methacrylate (DMAEMA), the neutral hydrophilic methoxy hexa(ethylene glycol) methacrylate (HEGMA), and the hydrophobic n‐butyl methacrylate (BuMA). 1,4‐Bis(methoxytrimethylsiloxymethylene)cyclohexane was used as a bifunctional initiator, whereas ethylene glycol dimethacrylate served as the crosslinker to interconnect the linear terpolymer precursors to three‐dimensional terpolymer network structures. Five of the terpolymer networks were model, with linear chains between crosslinks of precise length. Four of the five model networks were based on ABCBA pentablock terpolymers with theoretical structure DMAEMA5‐b‐BuMAn/2‐b‐HEGMA10‐b‐BuMAn/2‐b‐DMAEMA5 with n values equal to 5, 10, 20, and 30. The model network based on the equimolar statistical terpolymer and the nonmodel randomly crosslinked terpolymer network were also prepared. The molecular weights and compositions of the linear pentablock terpolymer precursors to the networks were found to be close to the theoretically expected, while the network sol fractions were found to be relatively low. The degrees of swelling of the networks in water were found to decrease with increasing the hydrophobic content, whereas those in THF exhibited the opposite trend. Small‐angle neutron scattering in deuterium oxide indicated structural organization in the most hydrophobic pentablock terpolymer networks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4420–4432, 2008
Substituents effect on the properties of sulfonated polyimide copolymers
Authors: Miyatake Kenji , Yasuda Tomohiro , Watanabe Masahiro 
Published: May 2008

AbstractA series of sulfonated polyimide (SPI) copolymers containing methyl, methoxy, or fluorine groups were synthesized to elucidate the substituents effect on their proton conducting properties as well as thermal, hydrolytic, and oxidative stability for polymer electrolyte membrane fuel cell applications. SPIs of high molecular weight (Mw > 200 kDa, Mn > 80 kDa) along with the ion exchange capacity (IEC) varying between 1.34 and 1.91 mequiv/g were obtained, which gave tough, ductile, and flexible membranes by solution casting. The thermal properties of the SPIs were dominated by the electronic structure of the sulfonated aromatic rings. The electron‐donating methyl groups lowered the thermal decomposition temperature. The hydrolytic and oxidative stability was roughly in the order of IEC (the higher IEC membranes were less stable). Fluorine groups, either as F or CF3, had negative effect on the hydrolytic and oxidative stability. In the water uptake and proton conductivity, hydrophobic components are rather more influential than the substituents. It was found out that the SPI(5, 8, 0.7) containing bis(phenoxy)biphenylene sulfone moieties as a rigid hydrophobic component showed the best balanced properties in terms of the stability and the proton conductivity for its rather low IEC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4469–4478, 2008
Synthesis of proton‐conducting block copolymer membranes composed of a fluorinated segment and a sulfonic acid segment
Authors: Matsumoto Kozo , Ozaki Fumiaki , Matsuoka Hideki 
Published: May 2008

AbstractDiblock copolymer membranes having a fluorinated segment and a sulfonic acid segment were prepared by living radical polymerization, solution casting, and crosslinking, followed by heat treatment. Diblock copolymers of 2,3,4,5,6‐pentafluorostyrene (PFS)/4‐(1‐methylsilacyclobutyl)styrene (SBS) and neopentyl styrenesulfonate (SSPen) (poly(PFS‐co‐SBS)‐b‐polySSPen)s were synthesized by nitoroxy‐mediated living radical polymerization. Self‐standing crosslinked membranes were obtained by casting a THF solution of the block copolymer with Pt catalyst. Heat treatment of the membrane at 230 °C induced decomposition of the neopentyl sulfonate esters to provide block copolymer membranes having a fluorinated segment and a free sulfonic acid segment. It was confirmed that the block copolymer with a high sulfonic acid content exhibited high ion exchange capacity and high proton conductivity as well as high thermal stability. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4479–4485, 2008
Living cationic polymerization of dihydrofuran and its derivatives
Authors: Yonezumi Motomasa , Kanaoka Shokyoku , Aoshima Sadahito 
Published: May 2008

AbstractCationic polymerization of 2,3‐dihydrofuran (DHF) and its derivatives was examined using base‐stabilized initiating systems with various Lewis acids. Living cationic polymerization of DHF was achieved using Et1.5AlCl1.5 in toluene in the presence of THF at 0 °C, whereas it has been reported that only less controlled reactions occurred at 0 °C. Monomer‐addition experiments of DHF and the block copolymerization with isobutyl vinyl ether demonstrated the livingness of the DHF polymerization: the number–average molecular weight of the polymers shifted higher with low polydispersity as the polymerization proceeded after the monomer addition. Furthermore, this base‐stabilized cationic polymerization system allowed living polymerization of ethyl 1‐propenyl ether and 4,5‐dihydro‐2‐methylfuran at −30 and −78 °C, respectively. In the polymerization of 2,3‐benzofuran, the long‐lived growing species were produced at −78 °C. The obtained polymers have higher glass transition temperatures compared to poly(acyclic alkyl vinyl ether)s. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4495–4504, 2008
Synthesis and properties of fluorene or carbazole‐based alternating copolymers containing Si and vinylene units in the main chain
Authors: Naga Naofumi , Tagaya Nanae , Noda Hiroyuki , Imai Takahiro , Tomoda Haruhiko 
Published: May 2008

AbstractAlternating copolymerization of 9,9‐dihexyl‐2,7‐dibromofluorene (HFl), N‐hexyl‐2,7‐dibromocarbazole (2,7‐HCz) or N‐hexyl‐3,6‐dibromocarbazole (3,6‐HCz) with Si‐containing divinyl or diallyl compounds, divinyldimethylsilane, divinyldiphenylsilane, 1,3‐divinyltetramethyldisiloxane, 1,4‐bis(dimethylvinylsilyl)benznene, diallyldimethylsilane, or diallyldiphenylsilane has been investigated using Mizoroki‐Heck reaction with a Pd catalyst. The corresponding alternating copolymers were obtained in good yield. The alternating copolymers from HFl or 2,7‐HCz showed good solubility in typical organic solvents. On the other hand, the copolymer with 3,6‐HCz became insoluble due to the crosslinking. Photophysical properties of the resulting copolymers were investigated with UV–vis absorption and photoluminescence spectroscopy. All the copolymers showed absorption peak derived from π–π* transition at around 340 nm, which was blue shifted in comparison with that of the corresponding homopolymer. Whereas emission peaks of the copolymers of the cast film were red shifted in comparison with that of the homopolymers. Multiple broad absorption peaks, which would be derived from intramolecular charge transfer through σ–π moiety, were also detected in the range from 390 to 450 nm in the spectra of the copolymers containing Si‐vinylene unit. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4513–4521, 2008
Monodisperse ultrafine polystyrene nanoparticles prepared by a semicontinuous microemulsion polymerization
Authors: Kong Xuanfeng , Wu Qian , Hu Wancheng , Wang Zhaoqun 
Published: May 2008

AbstractMonodisperse ultrafine polystyrene nanoparticles have been successfully prepared under low levels of surfactant through a novel semicontinuous microemulsion polymerization, in which the first part of monomer (St1) is added dropwise while the subsequent supply to the polymerizing system is delivered in one potion. Polystyrene nanoparticles with number‐average diameter of 17.4 nm and polydispersity index of 1.06 were obtained using low level of surfactant/monomer weight ratio of 0.20. Influencing of parameters including amount of St1, solid content, initiator, reaction temperature, and cosurfactant on the resultant particle size and size distribution were investigated. The mechanism of nucleation and particle growth was discussed as well. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4522–4528, 2008
Synthesis and self‐assembly in water of coil‐rod‐coil amphiphilic block copolymers with central π‐conjugated sequence
Authors: de Cuendias Anne , Ibarboure Emmanuel , Lecommandoux Sébastien , Cloutet Eric , Cramail Henri 
Published: May 2008

AbstractThe purpose of this study is to correlate the nano‐organization in water of coil‐rod‐coil amphiphilic block copolymers constituted of a conjugated segment to their optoelectronic properties. The ABA block copolymer structures, easily achieved via coupling reactions, are based on conjugated rod of dihexylfluorene and 3,4‐ethylenedioxythiophene units linked to two flexible poly(ethylene oxide) or poly[(ethylene oxide)‐ran‐(propylene oxide)] chains. These well‐defined copolymers exhibited a range of specific morphologies in water, a good solvent of coil blocks and a bad solvent of the conjugated rod. Particularly, vesicles and micelles with spherical, cylindrical, or elongated shape were noticed. Correlations were attempted to be established between the weight percent of the conjugated sequence contained in the copolymers, the morphology of the nanostructures obtained by self‐assembly in solution and the resulting optical properties. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4602–4616, 2008
Fingerprinting the degradation product patterns of different polyester‐ether networks by electrospray ionization mass spectrometry
Authors: Höglund Anders , Hakkarainen Minna , Kowalczuk Marek , Adamus Grazyna , Albertsson Ann‐Christine 
Published: May 2008

AbstractFingerprinting of the degradation product patterns by electrospray ionization mass spectrometry (ESI‐MS) was evaluated as a tool to monitor the degree of degradation in polyester‐ether networks. Four different crosslinked caprolactone (CL) and/or 1,5‐dioxepan‐2‐one (DXO) networks were subjected to hydrolytic degradation in aqueous solution at 37 °C for up to 147 days. After predetermined time periods, the water‐soluble degradation products were analyzed by ESI‐MS and tandem ESI‐MS. In addition, changes in pH, mass loss, and copolymer composition were determined. In the case of more slowly hydrolyzed CL‐rich (co)polymers, CL and/or DXO oligomers terminated by hydroxyl and carboxyl end groups were predominantly formed as degradation products. However, on prolonged hydrolysis oligomers with attached crosslinking agent dominated the degradation product patterns of more easily hydrolyzed DXO‐rich (co)polymers. It was shown that in the recorded mass spectra the variation of intensities in the series of ions corresponding to DXO and CL/DXO oligomers with or without attached crosslinking agent could be utilized to monitor the extent of hydrolytic degradation in the polyester matrix and the disruption of the network structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4617–4629, 2008
Preliminary results of a longitudinal study of changes in cognitive function in breast cancer patients undergoing chemotherapy with doxorubicin and cyclophosphamide
Authors: Jansen Catherine E. , Dodd Marylin J. , Miaskowski Christine A. , Dowling Glenna A. , Kramer Joel 
Published: May 2008

AbstractObjectives: Recent studies suggest that standard dose chemotherapy for breast cancer may cross the blood–brain barrier. However, the evidence for chemotherapy‐induced cognitive impairments in breast cancer patients is inconsistent. The purposes of this study in a sample of newly diagnosed patients with breast cancer were to (1) evaluate cognitive function prior to the administration of chemotherapy; (2) assess changes in cognitive function over time; and (3) evaluate potential relationships between cognitive function and anxiety, depression, fatigue, hemoglobin level, menopausal status, and perception of cognitive function.Methods: Thirty women with breast cancer completed neuropsychological testing before the initiation of chemotherapy and after four cycles of doxorubicin and cyclophosphamide. Descriptive statistics were used to summarize sample characteristics, and paired t‐tests were carried out to evaluate for changes in neuropsychological test scores prior to and following completion of chemotherapy. Linear mixed model analyses were used to determine whether significant changes in neuropsychological test scores remained after controlling for anxiety, depression, fatigue, hemoglobin level, menopausal status, and perceived cognitive function.Results: Significant decreases in visuospatial skill (p<0.001) and total cognitive scores (p=0.001) were found following chemotherapy. In addition, a significant improvement was found in executive function (p=0.014). Of note, these changes remained significant even after controlling for anxiety, depression, fatigue, hemoglobin level, menopausal status, and perceived cognitive function.Conclusions: Data from this study supported the hypothesis that chemotherapy may have a negative impact on select domains of cognitive function. Copyright © 2008 John Wiley & Sons, Ltd.
Carbon Nanotube Synthesis in Atmospheric Pressure Glow Discharge: A Review
Authors: Nozaki Tomohiro , Okazaki Ken 
Published: May 2008

AbstractThis review presents recent developments of formation techniques related to atmospheric pressure glow discharge. The description specifically emphasizes their application to carbon nanotube (CNT) synthesis based on our recent work. High‐purity vertically aligned single‐walled CNTs are producible only when an atmospheric pressure glow discharge is applied: even moderate pressure such as 20 kPa preferentially synthesizes multi‐walled CNTs. Lower operating pressures are known to produce carbon nanofibers exclusively. A tentative reaction mechanism is discussed based on plasma‐induced substrate heating and on‐line gas analysis in the plasma sheath. Finally, concluding and prospective remarks are presented briefly.magnified image
Recent contributions to the study of past permafrost
Authors: French Hugh 
Published: May 2008

AbstractThis paper reviews recent literature, published between 2002 and 2007, concerning the previous existence of permafrost (past permafrost) that formed during the cold periods of the Pleistocene in the northern mid‐latitudes. Some past permafrost continues to be preserved today as relict permafrost in the higher northern latitudes. Given that global climate warming models predict widespread thaw of permafrost in the coming century, it is surprising that little attention has been given to the insights that past and relict permafrost offer as to the nature and duration of permafrost thaw. Copyright © 2008 John Wiley & Sons, Ltd.
Response of citrus peelminer Marmara gulosa Guillén and Davis (Lepidoptera: Gracillariidae) stages to various insecticides
Authors: Grafton‐Cardwell Elizabeth E , Montez Gregory M , Reagan Christopher A , Dunn Richard A , Ouyang Yuling 
Published: May 2008

AbstractBACKGROUND: Egg and larval stages of citrus peelminer Marmara gulosa Guillén and Davis infesting zucchini squash Cucurbita pepo L. var ‘Revenue’ were exposed in the laboratory to a wide range of insecticide classes used in California citrus (organophosphate, carbamate, pyrethroid, neonicotinoid, insect growth regulator, fermentation products and sulfur) to determine peelminer response with and without a non‐ionic adjuvant or oil.RESULTS: All of the insecticides tested except sulfur reduced egg hatch and mine initiation. When the larval stage was treated, only buprofezin failed to reduce larval and pupal development. Cyfluthrin and spinosad, with the addition of adjuvant or oil, and abamectin combined with oil allowed no survivors at 7 days after treatment (DAT). The slower‐acting insect growth regulators pyriproxyfen and diflubenzuron applied in combination with adjuvant or oil allowed no survival of peelminer 21 DAT. A field trial showed 62.6–68.5% reduction in mined citrus fruit after two applications of diflubenzuron and no significant improvement of control with the addition of cyfluthrin.CONCLUSION: Bioassays indicate that M. gulosa is relatively susceptible to a wide range of insecticide classes in the laboratory. Lack of efficacy experienced in field trials would then be due to characteristics of the fruit or canopy that limit coverage, rather than to the effectiveness of the insecticides. Copyright © 2008 Society of Chemical Industry
Quantum‐corrected Monte Carlo analysis of scaling behavior of nano‐scale InGaAs high electron mobility transistors
Authors: Fujishiro Hiroki I. , Kawabata Takahiro , del Alamo Jesús A. 
Published: May 2008

AbstractThe performance of InGaAs HEMTs with gate length (Lg) scaled down to 10 nm is estimated using quantum‐corrected Monte Carlo (MC) simulations. Thinner gate barrier results in better scaling properties. A nearly universal relationship of subthreshold slope (S) and DIBL on a scaling parameter (γ) that represents the aspect ratio of Lg and characteristics length (λ) can be seen. After further optimization to reduce λ, through a reduction in barrier and/or channel thickness, the InGaAs HEMT could become a likely candidate to enter the CMOS roadmap beyond Si. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Drive current of ultrathin Ge‐on‐insulator n‐channel MOSFETs
Authors: Azuma Y. , Mori T. , Tsuchiya H. 
Published: May 2008

AbstractIn this paper, we study a drive current of ultrathin Ge‐on‐Insulator (GOI) n ‐channel MOSFETs based on a quantum‐corrected Monte Carlo device simulation. We found that the drive current of GOI n ‐channel MOSFETs significantly decreases by considering electron transfer to the higher X valleys from the lowest L valleys due to the phonon scattering. However, under quasi‐ballistic transport, the GOI n ‐channel MOSFETs with Ge (111) surface orientation are demonstrated to provide substantially higher drive current than the Si‐based MOSFETs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermoelastic damping in GaAs micromechanical resonators
Authors: Okamoto Hajime , Ito Daisuke , Onomitsu Koji , Yamaguchi Hiroshi 
Published: May 2008

AbstractDamping of the mechanical motion is one of the factors that limit the sensitivity of mechanical resonators. For the development of high‐sensitivity transducers, it is important to understand the damping mechanism of the resonators and minimize the damping effect. Here, we show that the damping of a GaAs microcantilever strongly depends on the temperature and it is minimized at around 50 K. This temperature dependence of the damping is mainly caused by the thermoelastic damping effect, which is generated by the strain‐induced temperature gradient in the GaAs cantilever. The minimization of the mechanical damping at around 50 K is due to the suppression of the thermal expansion of GaAs at this temperature, which eliminates the temperature gradient in the cantilever. This result indicates that the sensitivity of GaAs resonators can be improved by adjusting the operating temperature. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)