bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deuterium isotope effects on 13C chemical shifts of nitromalonamide
Authors: Hansen Poul Erik 
Published: May 2008

AbstractThe OH chemical shift of the enol form of nitromalonamide is found at 18.9 ppm both in DMSO‐d6 and in DMF‐d7 indicating a very strong hydrogen bond. The OH chemical shift is insensitive to temperature changes. Contrary to the large OH chemical shift, a small two‐bond deuterium isotope effect of 0.135 ppm due to deuteration at the OH position is found at the enolic carbon. This is confirmed by density functional theory calculations. The observed effects are interpreted as due to an equilibrium between identical enolic forms. These show a strong OH·O hydrogen bond as well as a NH·ONO hydrogen bond. Copyright © 2008 John Wiley & Sons, Ltd.
Structure elucidation and complete NMR spectral assignments of four new diterpenoids from Smallantus sonchifolius
Authors: Dou De‐Qiang , Tian Fang , Qiu Ying‐Kun , Kang Ting‐Guo , Dong Feng 
Published: May 2008

AbstractFour new diterpenoids, named smaditerpenic acid A–D, together with five known compounds, were isolated from the H2O extract of the leaves of Smallantus sonchifolius (yacon) cultivated in Liaoning, China and their structures were elucidated on the basis of one‐ and two‐dimensional NMR (including 1H, 13C‐NMR, 1H1H COSY, HSQC, TOCSY, HMBC, and ROESY), electrospray ionization mass spectrometry (ESI‐MS), and chemical methods. Copyright © 2008 John Wiley & Sons, Ltd.
Temperature dependence of nonequivalent potential wells for pyridinium ion reorientation in pyridinium tetrachloroiodate(III), PyHICl4, studied by 1H14N nuclear quadrupole double resonance
Authors: Seliger J. , Žagar V. , Asaji T. , Konnai A. 
Published: May 2008

AbstractThe reorientation of a pyridinium ion in the paraelectric and antiferroelectric phase of PyHICl4 is investigated using 1H14N nuclear quadrupole double resonance (NQDR). The 14N nuclear quadrupole resonance frequencies are measured. The temperature variations of the principal values of the time‐averaged electric‐field‐gradient (EFG) tensor at the nitrogen position are used to determine the occupation probabilities of the six orientations of a pyridinium ion in both crystallographic phases. The energy difference between various orientations is determined. The molar transition entropy associated with the reorientation of the pyridinium ions is calculated and compared to the experimental value. Copyright © 2008 John Wiley & Sons, Ltd.
1H and 13C assignments of five cembrenes from guggul
Authors: Bai Shi , Jain Mahendra 
Published: May 2008

AbstractChemical shift assignments of 1H and 13C of five cembrene compounds isolated from the hexane extract of guggul, the resin of Commiphora mukul, are reported. Using 1H, 13C, and 2D NMR methods their structures were determined as cembrene (1‐isopropyl‐4,8,12‐trimethyl‐cyclotetradeca‐2,4,7,11‐tetraene), cembrene A (1‐isopropenyl‐4,8,12‐trimethyl‐cyclotetradeca‐4,8,12‐triene), cembrenol (1‐isopropyl‐4,8,12‐trimethyl‐cyclotetradeca‐3,7,11‐trienol), mukulol (1‐isopropyl‐4,8,12‐trimethyl‐ cyclotetradeca‐3,7,11‐trienol), and verticillol (4,8,12,15,15‐pentamethyl‐bicyclo[9.3.1]pentadeca‐3,7‐dien‐12‐ol). Copyright © 2008 John Wiley & Sons, Ltd.
Nucleolar re‐activation is delayed in mouse embryos cloned from two different cell lines
Authors: Svarcova O. , Dinnyes A. , Polgar Z. , Bodo S. , Adorjan M. , Meng Q. , Maddox‐Hyttel P. 
Published: May 2008

AbstractAim of this study was to evaluate and compare embryonic genome activation (EGA) in mouse embryos of different origin using nucleolus as a marker. Early and late 2‐cell and late 4‐cell stage embryos, prepared by in vitro fertilization (IVF), parthenogenetic activation (PG), and nuclear transfer of mouse embryonic fibroblast (MEF) and mouse HM1 embryonic stem cells (HM1), were processed for autoradiography following 3H‐uridine incubation (transcriptional activity), transmission electron microscopy (ultrastructure) and immunofluorescence (nucleolar proteins; upstream binding factor, UBF and nucleophosmin, B23). All early 2‐cell embryos showed transcriptional activity only in nucleoplasm, not over nucleolar precursor bodies (NPBs). UBF was diffusely localized to cytoplasm and B23 to cytoplasm and nucleoplasm. Late 2‐cell IVF and PG embryos displayed transcription over nucleoplasm and NPBs. Ultrastructurally, the latter were developing into functional nucleoli. NT‐MEF and NT‐HM1 embryos displayed transcription over nucleoplasm, but not over NPBs. Development of NPBs into nucleoli was lacking. UBF was in both groups localized to nucleoplasm or distinctly to presumptive NPBs. B23 was distinctly localized to NPBs. All 4‐cell embryos presented nucleoplasmic transcription and developing fibrillo‐granular nucleoli. UBF and B23 were distinctly localized to nucleoli. However, whereas fully transformed reticulated fibrillo‐granular nucleoli were found in IVF and PG embryos, NT‐MEF and ‐HM1 embryos displayed early NPBs transformation. In conclusion, despite normal onset of EGA in cloned embryos, activation of functional nucleoli was one cell cycle delayed in NT embryos. NT‐MEF embryos displayed normal targeting but delayed activation of nucleolar proteins. Contrary, in NT‐HM1 embryos, both of these processes were delayed. Mol. Reprod. Dev. 76: 132–141, 2009. © 2008 Wiley‐Liss, Inc.
Cross‐linked polybenzimidazole membranes for high temperature proton exchange membrane fuel cells with dichloromethyl phosphinic acid as a cross‐linker
Authors: Noyé Pernille , Li Qingfeng , Pan Chao , Bjerrum Niels J. 
Published: May 2008

AbstractPhosphoric acid doped polybenzimidazole (PBI) membranes have been covalently cross‐linked with dichloromethyl phosphinic acid (DCMP). FT‐IR measurements showed new bands originating from bonds between the hydrogen bearing nitrogen in the imidazole group of PBI and the CH2 group in DCMP. The produced cross‐linked membranes show increased mechanical strength, making it possible to achieve higher phosphoric acid doping levels and therefore higher proton conductivity. Oxidative stability is significantly improved and thermal stability is sufficient in a temperature range of up to 250°C, i.e. within the temperature range of operation of PBI‐based fuel cells. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis and kinetics of graft polymerization of methyl methacrylate from the RAFT coordinated surface of nano‐TiO2
Authors: Hojjati Behnaz , Charpentier Paul A. 
Published: May 2008

AbstractPolymer chains of PMMA were grown from nano titania (n‐TiO2) by the reversible addition‐fragmentation chain transfer polymerization process. The mechanism and kinetics of MMA polymerization from both solution and “grafted from” n‐TiO2 were studied. The RAFT agent, 4‐cyano‐4‐(dodecylsulfanylthiocarbonyl) sulfanyl pentanoic acid, with an available carboxyl group was used to anchor onto the n‐TiO2 surface, with the SC(SC12H25) moiety used for subsequent RAFT polymerization of MMA to form n‐TiO2/PMMA nanocomposites. The functionalization of n‐TiO2 was determined by FTIR, XPS, partitioning studies, and thermal analysis. The livingness of the polymerization was verified using NMR and GPC, while the dispersion of the inorganic filler in the polymer was studied using electron microscopy, FTIR, and thermal analysis. The monomer conversion and molecular weight kinetics were explored for the living RAFT polymerization, both in solution and grafted from n‐TiO2, with first‐order kinetics being observed in both cases. Increased graft density on n‐TiO2 led to a lower rate of polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3926–3937, 2008
Hydrophilic, cationic large‐core star polymers and polymer networks: Synthesis and physicochemical characterization
Authors: Kafouris Demetris , Gradzielski Michael , Patrickios Costas S. 
Published: May 2008

AbstractGroup transfer polymerization was used to prepare hydrophilic, cationic large‐core star polymers (LCSPs) and networks of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) and ethylene glycol dimethacrylate (EGDMA) in a two‐step procedure involving the synthesis of linear DMAEMA arms, followed by their crosslinking using a mixture of DMAEMA monomer and EGDMA crosslinker. The degree of polymerization of the linear chains prepared in the first step was kept constant, while the composition of the crosslinking mixture was varied systematically at a constant amount of crosslinker. The monomer/crosslinker molar ratio determined whether LCSPs or polymer networks would be produced. In particular, a high monomer/crosslinker molar ratio led to the formation of networks, whereas LCSPs were formed when a low monomer/crosslinker molar ratio was used. The absolute weight‐average molecular weight of the LCSPs was determined using static light scattering, whereas their hydrodynamic radii and radii of gyration were determined using dynamic light scattering and small‐angle neutron scattering, respectively. The sol fraction extracted from the networks decreased as the monomer/crosslinker molar ratio increased. The degrees of swelling of all of the networks were measured as a function of pH and were found to increase below pH 7. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3958–3969, 2008
Synthesis and properties of polythiophene derivatives containing triphenylamine moiety and their photovoltaic applications
Authors: Li Yaowen , Xue Lili , Xia Haijian , Xu Bin , Wen Shanpeng , Tian Wenjing 
Published: May 2008

AbstractA series of novel soluble polythiophene derivatives containing triphenylamine moiety were synthesized by Grignard metathesis (GRIM) method. The structures of the polymers were characterized and their physical properties were investigated. High molecular weight (Mn up to 25,800 g/mol) and thermostable polymers were obtained. The absorption spectra demonstrated that the absorption wavelength of the polymers could be tuned dramatically by introducing thiophene units in the main chain of the polymers. Photoluminescence spectra indicated that there was intramolecular energy transfer from the side chain to the main chain, and the maximum emission was red‐shifted gradually with the increase of thiophene units in the main chain. Cyclic voltammetry displayed that the polymers possessed relatively high oxidation potential, which promised good air stability and high open circuit voltage for photovoltaic cells application. Finally, bulk heterojunction photovoltaic devices were fabricated by using the polymers as donors and (6,6)‐phenyl C61‐butyric acid methyl ester (PCBM) as acceptor. The maximal open circuit voltage of the photovoltaic cells reached 0.71–0.87 V and the power conversion efficiencies of the devices were measured between 0.014% and 0.45% under white light at 100 mW/cm2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3970–3984, 2008
Synthesis and characterization of oligo(oxyethylene)/carbosilane copolymers for thermoset elastomers via ADMET
Authors: Matloka Piotr P. , Kean Zachary , Greenfield Meghan , Wagener Kenneth B. 
Published: May 2008

AbstractAcyclic diene metathesis (ADMET) polymerization has been used to synthesize latent reactive processable elastomers constructed of carbosilane and polyether segments. Two types of latent modes have been introduced: “chain‐internal” and “chain‐end” sites through the use of labile silicon methoxy functionalities. These latent reactive groups are inert when exposed to metathesis conditions allowing formation of the linear copolymer; subsequently exposure to moisture triggers hydrolysis of the methoxy groups and formation of a chemically crosslinked thermoset. The thermoset's mechanical response can be potentially varied from plastic to elastic behavior, depending on the ratio of carbosilane and oligooxyethylene monomers employed. Different lengths of glycols and numbers of methylene groups between them in the polymer backbone have been investigated to explore structure/property relationship. Polymers composed of oligooxyethylenes with eight methylene groups in between them exhibited fully amorphous character, while the ones with up to 20 methylene groups between glycol units showed their semicrystalline nature. The concentration of “chain‐internal” and “chain‐end” crosslink sites enhances strength; modification to the run length and structure of the soft phase enhances elasticity. Resultant materials have been subjected to mechanical tests using Instron; generated stress/strain curves have shown plastic and elastic behavior. Depending on the composition obtained samples have shown moduli from 0.3 to 115 MPa, tensile strengths from 0.6 to 10 MPa and elongations from 20 to 700%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3992–4011, 2008
Understanding the role of Arg96 in structure and stability of green fluorescent protein
Authors: Stepanenko Olesya V. , Verkhusha Vladislav V. , Shavlovsky Michail M. , Kuznetsova Irina M. , Uversky Vladimir N. , Turoverov Konstantin K. 
Published: May 2008

AbstractArg96 is a highly conservative residue known to catalyze spontaneous green fluorescent protein (GFP) chromophore biosynthesis. To understand a role of Arg96 in conformational stability and structural behavior of EGFP, the properties of a series of the EGFP mutants bearing substitutions at this position were studied using circular dichroism, steady state fluorescence spectroscopy, fluorescence lifetime, kinetics and equilibrium unfolding analysis, and acrylamide‐induced fluorescence quenching. During the protein production and purification, high yield was achieved for EGFP/Arg96Cys variant, whereas EGFP/Arg96Ser and EGFP/Arg96Ala were characterized by essentially lower yields and no protein was produced when Arg96 was substituted by Gly. We have also shown that only EGFP/Arg96Cys possessed relatively fast chromophore maturation, whereas it took EGFP/Arg96Ser and EGFP/Arg96Ala about a year to develop a noticeable green fluorescence. The intensity of the characteristic green fluorescence measured for the EGFP/Arg96Cys and EGFP/Arg96Ser (or EGFP/Arg96Ala) was 5‐ and 50‐times lower than that of the nonmodified EGFP. Intriguingly, EGFP/Arg96Cys was shown to be more stable than EGFP toward the GdmCl‐induced unfolding both in kinetics and in the quasi‐equilibrium experiments. In comparison with EGFP, tryptophan residues of EGFP/Arg96Cys were more accessible to the solvent. These data taken together suggest that besides established earlier crucial catalytic role, Arg96 is important for the overall folding and conformational stability of GFP. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Lycotoxin‐1 insecticidal peptide optimized by amino acid scanning mutagenesis and expressed as a coproduct in an ethanologenic Saccharomyces cerevisiae strain
Authors: Hughes Stephen R. , Dowd Patrick F. , Hector Ronald E. , Panavas Tadas , Sterner David E. , Qureshi Nasib , Bischoff Kenneth M. , Bang Sookie S. , Mertens Jeffrey A. , Johnson Eric T. , Li Xin‐Liang , Jackson John S. , Caughey Robert J. , Riedmuller Steven B. , Bartolett Scott , Liu Siqing , Rich Joseph O. , Farrelly Philip J. , Butt Tauseef R. , Labaer Joshua , Cotta Michael A. 
Published: May 2008

AbstractNew methods of safe biological pest control are required as a result of evolution of insect resistance to current biopesticides. Yeast strains being developed for conversion of cellulosic biomass to ethanol are potential host systems for expression of commercially valuable peptides, such as bioinsecticides, to increase the cost‐effectiveness of the process. Spider venom is one of many potential sources of novel insect‐specific peptide toxins. Libraries of mutants of the small amphipathic peptide lycotoxin‐1 from the wolf spider were produced in high throughput using an automated integrated plasmid‐based functional proteomic platform and screened for ability to kill fall armyworms, a significant cause of damage to corn (maize) and other crops in the United States. Using amino acid scanning mutagenesis (AASM) we generated a library of mutagenized lycotoxin‐1 open reading frames (ORF) in a novel small ubiquitin‐like modifier (SUMO) yeast expression system. The SUMO technology enhanced expression and improved generation of active lycotoxins. The mutants were engineered to be expressed at high level inside the yeast and ingested by the insect before being cleaved to the active form (so‐called Trojan horse strategy). These yeast strains expressing mutant toxin ORFs were also carrying the xylose isomerase (XI) gene and were capable of aerobic growth on xylose. Yeast cultures expressing the peptide toxins were prepared and fed to armyworm larvae to identify the mutant toxins with greatest lethality. The most lethal mutations appeared to increase the ability of the toxin α‐helix to interact with insect cell membranes or to increase its pore‐forming ability, leading to cell lysis. The toxin peptides have potential as value‐added coproducts to increase the cost‐effectiveness of fuel ethanol bioproduction. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.
Microstructure and soft magnetic properties of nanocrystalline (Co0.77Si0.135B0.095)90Fe7Nb3 alloy
Authors: Iturriza N. , Zhukov A. , Val J. J. del , Murillo N. , González J. 
Published: May 2008

AbstractMicrostructure and magnetic hysteretic properties of (Co0.77Si0.135B0.095)90Fe7Nb3 amorphous ribbons submitted to current annealing (current density of 56 A/mm2 during 2 minutes), to develop the nanocrystallization state, are reported. Temperature dependencies of the saturation magnetization, remanence and coercivity are explained by considering the presence of two crystalline phases, namely: nanocrystals of bcc‐Fe,Co(Si) and fcc‐Co grains and the remaining amorphous matrix. A significant magnetic hardening is observed above the Curie point of the residual amorphous matrix, which could be ascribed to an exchange and a dipolar decoupling of the nanograins. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Confinement effect in CdTe nanocrystals embedded in silica thin films
Authors: Levichev S. , Rolo A. G. , Chahboun A. , Conde O. , Kovalev A. I. , Wainstein D. L. , Gomes M. J. M. 
Published: May 2008

AbstractIn this paper we report on the optical and structural properties of CdTe nanoparticles embedded in silica matrix grown by the radio‐frequency (RF) magnetron sputtering technique with subsequent annealing in vacuum. Optical transmittance, Raman scattering, X‐ray photoelectron spectroscopy (XPS), grazing incidence X‐ray diffraction (GIXRD) and photoluminescence (PL) were used to study the grown samples. GIXRD shows the presence of the cubic phase of CdTe nanocrystals (NCs) in the silica matrix, with size ranging from 2.5 nm to 10.5 nm. Raman spectroscopy illustrates features linked to LO phonons in the CdTe structure. The absorption spectra of annealed samples demonstrate shoulders on the absorption in the range 650–700 nm, in agreement with the PL emission observed at 650–725 nm. However, the blue shift observed in the NCs bandgap in relationship with their size was below the expected level. We attribute this feature to the graded interface between the NCs and the matrix, which causes a weak confinement of carriers in CdTe NCs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tailoring the diameter, density and number of walls of carbon nanotubes through predefined catalyst particles
Authors: Schäffel F. , Rümmeli M. H. , Kramberger C. , Queitsch U. , Mohn E. , Kaltofen R. , Pichler T. , Büchner B. , Rellinghaus B. , Schultz L. 
Published: May 2008

AbstractWe have explored the influence of predefined gas phase prepared catalyst particles on carbon nanotube (CNT) properties such as their diameter and number of walls. During the catalyst preparation particles are simultaneously deposited onto a substrate for chemical vapour deposition as well as on a witness grid for analysis in transmission electron microscopy. This allows us to obtain precise information on the starting catalyst material on one side and the CNT product on the other. Clear correlations between the catalyst's size and the CNT diameter and number of walls have been found. Our results indicate a dependence of the resultant CNT on the volume to surface area ratio of the catalyst particle and fit well with our understanding of cap formation at CNT nucleation. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetocaloric effect in nanogranular glass coated microwires
Authors: Ilyn M. I. , Zhukova V. , Santos J. D. , Sánchez M. L. , Prida V. M. , Hernando B. , Larin V. , González J. , Tishin A. M. , Zhukov A. 
Published: May 2008

AbstractThermal dependences of the magnetic susceptibility of the glass‐coated microwires with compositions Fe3P and SnMn prepared by the Taylor–Ulitovski method have been determined. Direct measurements of the adiabatic temperature change revealed ΔTad of 0.04 K in the SnMn and ΔTad of 0.02 K in the Fe3P microwires on the field change of 12 kOe. Temperatures of the peak values of MCE were found to be of ∼215 K and ∼320 K respectively. The variation of magnetic properties of the Fe3P wires with the change of their diameters was observed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band structure effects on the Be(0001) acoustic surface plasmon energy dispersion
Authors: Silkin V. M. , Pitarke J. M. , Chulkov E. V. , Diaconescu B. , Pohl K. , Vattuone L. , Savio L. , Hofmann Ph. , Farı’︁as D. , Rocca M. , Echenique P. M. 
Published: May 2008

AbstractWe report first‐principles calculations of acoustic surface plasmons on the (0001) surface of Be, as obtained in the random‐phase approximation of many‐body theory. The energy dispersion of these collective excitations has been obtained along two symmetry directions. Our results show a considerable anisotropy of acoustic surface plasmons, and underline the capability of experimental measurements of these plasmons to map the electron–hole excitation spectrum of the quasi two‐dimensional Shockley surface state band that is present on the Be(0001) surface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Grafting organic polymer films on surfaces of carbon nanotubes by surface electroinitiated emulsion polymerization
Authors: Tessier Lorraine , Chancolon Jérôme , Alet Pierre‐Jean , Trenggono Adhitya , Mayne‐L'Hermite Martine , Deniau Guy , Jégou Pascale , Palacin Serge 
Published: May 2008

AbstractDiazonium salts coupled with vinylic monomers were able to functionalize carpets of carbon nanotubes by electro‐activation in aqueous media. Hence, nano‐sized carbon surfaces were shown to react with active radical species in solution through a new covalent grafting process called Surface Electroinitiated Emulsion Polymerization (SEEP), where diazonium salts are used both to initiate the polymerization of vinylic monomers in solution and to form a primer grafted polyphenylene‐like layer on the carbon surface. SEM and TEM analyses revealed that ultrathin polymer films are grafted on the sidewalls of carbon nanotubes. XPS spectroscopy further confirmed the functionalization of multi‐walled carbon nanotubes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)