bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and characterization of optically active polystyrene via a chiral nitroxide‐mediated polymerization
Authors: Zhou Nianchen , Xu Wenjian , Zhang Yu , Zhu Jian , Zhu Xiulin 
Published: January 2006

Abstract2,2,6,6‐Tetramethyl‐4‐[d‐(+)‐10‐camphorsulfonyl]‐1‐piperidinyloxy was synthesized and used as a chiral nitroxide for the bulk polymerizations of styrene initiated with benzoyl peroxide (BPO), tetraethylthiuram disulfide (TETD), and thermal initiation. The results showed that the polymerizations proceeded in a controlled/living way; that is, the kinetics presented approximately first‐order plots, and the number‐average molecular weights of the polymers with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight) increased with the monomer conversion linearly. The molecular weight distributions in the case of thermal initiation were narrower than those in the case of BPO and TETD, whereas the polymerization rate with BPO or TETD as an initiator was obviously faster than that with thermal initiation. In addition, successful chain‐extension reactions were carried out, and the structures of the obtained polymers were characterized by gel permeation chromatography and 1H NMR. The specific rotations of the polymers were also measured by polarimetric analysis. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1522–1528, 2006
Synthesis of novel benzoxazines containing glycidyl groups: A study of the crosslinking behavior
Authors: Andreu R. , Espinosa M. A. , Galià M. , Cádiz V. , Ronda J. C. , Reina J. A. 
Published: January 2006

AbstractBenzoxazines derived from aniline and 4‐hydroxybenzoic acid and from phenol and 4‐aminobenzoic acid were prepared with two different synthetic approaches. When the carboxylic group reacted with epichlorohydrin, glycidylic derivatives M‐1 and M‐2, respectively, were obtained. The ring opening of benzoxazine and epoxy took place simultaneously with no catalyst for both monomers. Likewise, both ring‐opening polymerizations took place when boron trifluoride monoethylamine (BF3·MEA) or 4‐(N,N‐dimethylamino)pyridine was used as a catalyst for M‐1. However, for M‐2, when BF3·MEA was used as a catalyst, the epoxy and benzoxazine ring openings could be distinguished, and a polyether intermediate containing benzoxazine side chains could be obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1529–1540, 2006
Synthesis and characterization of fluorinated telomers containing vinylidene fluoride and hexafluoropropene from 1,6‐diiodoperfluorohexane
Authors: Mladenov G. , Ameduri B. , Kostov G. , Mateva R. 
Published: January 2006

AbstractThe synthesis of original fluorinated (co)telomers containing vinylidene fluoride (VDF) or VDF and hexafluoropropene (HFP) was achieved by radical telomerizations and (co)telomerizations of VDF (or VDF and HFP) in the presence of 1, 6‐diiodoperfluorohexane via a semisuspension process.tert‐Butyl peroxypivalate (TBPPi) was used as an efficient thermal initiator. The numbers of VDF and VDF/HFP base units in the (co)telomers were determined by19F and1H NMR spectroscopy. They ranged from 10 to 190 VDF base units. Fluorinated telomers of various molecular weights (1200–12,600 g/mol) were obtained by the alteration of the initial [1,6‐diiodoperfluorohexane]0/[fluoroalkenes]0and [TBPPi]0/[fluoroalkenes]0molar ratios. The thermal properties of these fluorinated (co)telomers, such as the glass‐transition temperature and melting temperature, were examined. As expected, these telomers exhibited good thermal stability. They were stable at least up to 350 °C. The compounds containing more than 30 VDF units were crystalline, whereas all those containing VDF‐co‐HFP were amorphous with elastomeric properties, whatever the number was of the fluorinated base units. The structures of I–(VDF)n–RF–(VDF)m–I and I–(HFP)x(VDF)n–RF–(VDF)m(HFP)y–I (co)telomers were obtained, and the defects of the VDF chain and the CH2CF2I and CF2CH2I functionalities were studied successfully (where RF= C6F12). The functionality in the iodine atoms was modified: the higher the VDF content in the telomers, the lower the normal end functionality (CH2CF2I) and the higher the reversed extremity (CF2CH2I). In addition, the percentage of defects increased when the number of VDF units increased. The molecular weights and molecular weight distributions of different telomers and cotelomers were also studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1470–1485, 2006
Vinyl polymerization of norbornene by bis(nitro‐substituted‐salicylaldiminate)nickel(II)/methylaluminoxane catalysts
Authors: Carlini Carlo , Martinelli Marco , Galletti Anna Maria Raspolli , Sbrana Glauco 
Published: January 2006

AbstractThe polymerization of norbornene has been investigated in the presence of different bis(salicylaldiminate)nickel(II) precursors activated by methylaluminoxane. These systems are highly active in affording nonstereoregular vinyl‐type polynorbornenes (PNBs) with high molecular weights. The productivity of the catalytic systems is strongly enhanced (up to 35,000 kg of PNB/mol of Ni × h) when electron‐withdrawing nitro groups are introduced on the phenol moiety. On the contrary, the presence of bulky alkyl groups on the N‐aryl moiety of the ligand does not substantially affect the activity or characteristics of the resulting PNBs. The catalytic performances are also markedly influenced by the reaction parameters, such as the nature of the solvent, the reaction time, and the monomer/Ni and Al/Ni molar ratios. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1514–1521, 2006
Chain microstructure of homogeneous ethylene‐1‐alkene copolymers and characteristics of single site catalysts using a direct13C NMR peak method. Part III. Application to ethylene–propylene copolymers showing no inversion
Authors: Karssenberg F. G. , Piel C. , Hopf A. , Mathot V. B. F. , Kaminsky W. 
Published: January 2006

AbstractAll relevant13C NMR signals of two series of seven homogeneous ethylene–propylene copolymers were used to fit the second‐order Markov reactivity ratios of the catalysts and the theoretical feeds. The copolymers cover a very broad range of comonomer incorporations, from about 10 to 93%, and show only primary (1,2) insertions. For both series, solutions are found with reliabilities >>99.5%. The reactivity ratios,r112= 2.54,r121= 0.12,r212= 2.05, andr221= 0.29 for the used Zirconocone andr112= 1.69,r121= 0.32,r212= 1.56, andr221= 0.51 for the hafnocene, provide direct information about the metallocenes, the kinetics, and the chain microstructure. With these results, the direct peak method demonstrates that the use of all relevant13C NMR peaks enables accurate second‐order Markov modeling, revealing subtle differences between copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 747–755, 2006
Influence of the efficacy of interfacial modification on the coarsening of cocontinuous PS/HDPE blends during quiescent annealing
Authors: Yuan Zhenhua , Favis Basil D. 
Published: January 2006

AbstractThis article studies the quiescent annealing of three different cocontinuous polystyrene/high‐density polyethylene blends modified with two types of interfacial agents of widely different efficacies. Quantitative analysis of phase growth was obtained using mercury porosimetry. In a previous work, it was shown that one of these modifiers, a symmetrical diblock copolymer, has a high affinity for the interface and demonstrates virtually no micelle formation prior to saturation of the blend interface. The other modifier, a hydrogenated SEBS of 70/30 composition, forms micelles at elevated concentrations of modifier. In this study, it is shown that the cocontinuous phase size grows linearly without modifier, whereas the addition of both interfacial modifiers significantly suppresses the PE/PS phase coarsening and results in nonlinear phase growth behavior. The effect of the diblock copolymer on suppressing coarsening, however, is much more effective than that for the triblock case clearly supporting the tendency toward micelle formation for that latter modifier. In the case of unmodified PE/PS, the driving force for capillary pressure effects is so high that it is the capillary instability phenomena that dominate the coarsening and hence result in a linear growth of pore size with annealing time. When interfacial modifiers are added, the influence of reduced interfacial tension and lower pore size polydispersity significantly diminishes both capillary pressure effects and capillary instability phenomena. In that case, capillary pressure becomes the main rate determining step resulting in a nonlinear dependence of pore size with annealing time. It is shown that both the viscosity of the phases and the temperature of annealing can strongly influence coarsening behavior at low levels of interfacial modifier. Under all those conditions, however, nonlinear phase growth for the partially compatibilized system was maintained. These results clearly show that careful quantitative coarsening experiments using mercury porosimetry can be used as a tool to analyze the efficacy of interfacial modifiers for highly continuous or cocontinuous systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 711–721, 2006
Collapse and swelling of poly(N‐isopropylacrylamide‐co‐sodium acrylate) copolymer brushes grafted on a flat SiO2 surface
Authors: Cheng He , Liu Guangming , Wang Chengqing , Zhang Guangzhao , Wu Chi 
Published: January 2006

AbstractPoly(N‐isopropylacrylamide‐co‐sodium acrylate) copolymer brushes grafted on SiO2‐coated quartz crystal surface were prepared with a surface‐immobilized initiator. The collapse and swelling of the thermally sensitive copolymer brushes in water were studied with quartz crystal microbalance in situ. The frequency and dissipation changes with the temperature increasing in the range 20–38 °C indicate that the brushes undergo a continuous collapse transition. Our results show that the copolymer brushes collapse to a state where the brushes were prepared. A hysteresis was observed in the cooling process. Fourier transform infrared (FTIR) results revealed that the formation of some additional hydrogen bonds within the copolymer chains at their collapsed state is responsible for the hysteresis. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 770–778, 2006
Two calorimetric glass transitions do not necessarily indicate immiscibility: The case of PEO/PMMA
Authors: Lodge Timothy P. , Wood Elizabeth R. , Haley Jeffrey C. 
Published: January 2006

AbstractDifferential scanning calorimetry has been used to examine blends of a poly(ethylene oxide) (PEO), Mn = 300 g/mol, and a poly(methylmethacrylate) (PMMA), Mn = 10,000 g/mol, across the complete composition range. The relatively low molar mass of the PEO minimizes interference from crystallization. In the midrange of composition, ∼25–70% PEO, two broad, but distinct, glass transitions are resolved. These are interpreted as distinct glass transitions of the two components, as anticipated by the self‐concentration model of Lodge and McLeish. The composition dependence of the observed transitions is well described by the self‐concentration approach, using lengthscales of approximately two‐thirds of the Kuhn length. The results are compared with previous measurements on PEO/PMMA blends and other miscible systems. The principal, general conclusion is that one should actually expect two glass transitions in a miscible polymer blend or polymer solution; the rule of thumb that two transitions indicate immiscibility is incorrect. Furthermore, attempts to rationalize two transitions on the basis of incomplete segmental mixing, or other unspecified “nanoheterogeneity,” may not be justified in many cases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 756–763, 2006
Effect of ethanol on folding of hen egg‐white lysozyme under acidic condition
Authors: Sasahara Kenji , Nitta Katsutoshi 
Published: January 2006

AbstractThe equilibrium and kinetics of folding of hen egg‐white lysozyme were studied by means of CD spectroscopy in the presence of varying concentrations of ethanol under acidic condition. The equilibrium transition curves of guanidine hydrochloride‐induced unfolding in 13 and 26% (v/v) ethanol have shown that the unfolding significantly deviates from a two‐state mechanism. The kinetics of denaturant‐induced refolding and unfolding of hen egg‐white lysozyme were investigated by stopped‐flow CD at three ethanol concentrations: 0, 13, and 26% (v/v). Immediately after dilution of the denaturant, the refolding curves showed a biphasic time course in the far‐UV region, with a burst phase with a significant secondary structure and a slower observable phase. However, when monitored by the near‐UV CD, the burst phase was not observed and all refolding kinetics were monophasic. To clarify the effect of nonnative secondary structure induced by the addition of ethanol on the folding/unfolding kinetics, the kinetic m values were estimated from the chevron plots obtained for the three ethanol concentrations. The data indicated that the folding/unfolding kinetics of hen lysozyme in the presence of varying concentrations of ethanol under acidic condition is explained by a model with both on‐pathway and off‐pathway intermediates of protein folding. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Fungicide control of mushroom cobweb disease caused by Cladobotryum strains with different benzimidazole resistance profiles
Authors: Grogan Helen M 
Published: January 2006

AbstractThe benzimidazole fungicides thiabendazole and carbendazim, and the imidazole fungicide prochloraz‐Mn, were tested for their efficacy in controlling cobweb disease of mushrooms caused by two Cladobotryum isolates. Isolate 202A was benzimidazole‐sensitive in vitro and cobweb growth on the casing was well controlled by both benzimidazole fungicides in cropping experiments. Carbendazim also controlled the development of spotting symptoms much more effectively than thiabendazole. A second isolate (192B1) was benzimidazole‐resistant and was highly resistant to thiabendazole in vitro but it showed some sensitivity to carbendazim in vitro at moderate to high concentrations. Despite this, carbendazim did not control disease symptoms in cropping experiments, confirming that isolate 192B1 is cross‐resistant to other benzimidazole fungicides. Both isolates showed some sensitivity to prochloraz‐Mn in vitro. This fungicide gave between 45% and 65% control of cobweb growth on the casing caused by either 202A or 192B1 but gave no control of spotting symptoms. Reducing the fungicide application volume did not give enhanced disease control. The emergence of benzimidazole resistance reduces the value of benzimidazoles in the control of mushroom pathogens. However, the lack of effective alternatives means they continue to have utility in cases where pathogens are still sensitive but this requires regular monitoring of pathogen populations for resistance. Copyright © 2006 Society of Chemical Industry
Effect of dose rate and mixtures of fungicides on selection for QoI resistance in populations of Plasmopara viticola
Authors: Genet Jean‐Luc , Jaworska Grazyna , Deparis Francine 
Published: January 2006

AbstractResistance to QoI fungicides (strobilurins, famoxadone and fenamidone) in populations of Plasmopara viticola (Berk & Curt) Berlese & de Toni developed soon after their introduction in France and Italy. Current resistance management strategies include limitation of the number of applications, use of mixtures and alternation of fungicides with different modes of action. The selection pressure resulting from QoI fungicides applied alone or in mixtures with non‐QoI fungicides was investigated in whole plant experiments under controlled conditions. QoI‐resistant populations of P. viticola gradually reverted to full sensitivity following consecutive transfers to untreated plants, suggesting that resistant phenotypes were less competitive than sensitive ones. When cycled on QoI‐treated plants, reduction in sensitivity was greater for the QoI fungicide which had greater intrinsic activity on P. viticola. Sensitivity decreased at each subsequent cycle, resulting in almost full resistance after four generations. Mixture experiments indicated that selection pressure was affected most by the dose of the QoI fungicide and the nature of the partner fungicide. Folpet delayed selection pressure most effectively when it was associated with famoxadone or azoxystrobin. Mancozeb was least effective at reducing the rate of selection compared with the QoI alone, and fosetyl‐aluminium was intermediate. Higher rates of selection were recorded when the dose of the QoI fungicide, solo or in a mixture, was increased from 1 to 4 µg ml−1. Increasing the dose of the non‐QoI partner fungicide in the mixture from 10 to 30 µg ml−1 resulted in reduced selection pressure. These results suggest that the choice of the fungicide partner and its dosage in the mixture can significantly affect the success of QoI resistance management strategies under practical conditions. Copyright © 2006 Society of Chemical Industry
A wedge disclination dipole interacting with a circular inclusion
Authors: Liu Y. W. , Fang Q. H. , Jiang C. P. 
Published: January 2006

AbstractThe problem involving the interaction effects between a wedge disclination dipole and an elastic circular inclusion is investigated. Utilizing the Muskhelishvili complex variable method, the closed form solutions are derived for complex potentials and stress fields due to a wedge disclination dipole located near the circular inclusion. The strain energy and the force acting on the disclination dipole center are also calculated. The influence of the orientation and the location of the disclination dipole as well as the material elastic dissimilarity upon the equilibrium position of the disclination dipole is discussed in detail. The results show that for certain combinations of materials constants, the disclination dipole has a stable equilibrium point near the inclusion. Moreover, the force on the disclination dipole is very much affected by the orientation of the disclination dipole. The present solutions contain previously known results as the special cases. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation on the optical and structural properties of spin coated CeO2–TiO2 thin films
Authors: Ghodsi F. E. , Tepehan F. Z. 
Published: January 2006

AbstractEquimolar CeO2–TiO2 multi layer (3–7) thin films were prepared by spin coating technique in different spin speed (1500–4000 rpm), by using sol–gel route. The dependence of deposition conditions on the optical and structural properties of the films was investigated. Scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS) were employed to analyze the structural properties of the films. Optical constants (refractive index, absorption coefficient, energy band gap, etc.) were determined in the 200–1100 nm wavelength range by transmission spectrophotometry. It was found that with increasing spinning rate from 1500 rpm to 4000 rpm the thickness of the films decrease from 440 nm to 229 nm while the refractive index and the absorption coefficient at 550 nm wavelength increase from 1.80 to 2.16, and 599.83 cm–1 to 1174.60 cm–1 respectively. The thickness, refractive index, and absorption coefficient of the films at 550 nm wavelength increase from 235 nm to 548 nm, 1.85 to 2.00, and 553.90 cm–1 to 1347.00 cm–1 respectively with increasing the number of coating layers from 3 to 7. The optical band gap has a value of 3.19 eV for indirect transition and is independent of spin speed and number of layers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hysteresis phenomena in (La0.83Bi0.17)0.67Ca0.33MnO3
Authors: Xia Z. C. , Zeng F. R. , Hu M. T. , Dong B. , Liu G. , Wang Y. , Feng X. N. , Liu L. , Tang C. Q. , Yuan S. L. 
Published: January 2006

AbstractThe temperature dependence of the resistance and magnetization of Bi3+‐doped (La0.83Bi0.17)0.67Ca0.33MnO3 is investigated, for which both thermal and magnetic hysteresis phenomena are observed. In a lower applied magnetic field range of 0 < H < 0.5 T and a temperature range of 110 < T < 200 K, a two‐step magnetization behavior with an enhanced magnetoresistance effect is observed. According to the experimental results, it is surmised that the hysteresis behavior results mainly from the coexistence of charge ordered (CO) and ferromagnetic (FM) domains, for which the CO domains have relaxation and pinning effects on the growth and rotation of FM domains. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature dependence of the energy gap of InxSe1–x compounds
Authors: Michalewicz Anna , Nowak Marian , Kępińska Mirosława 
Published: January 2006

AbstractThe optical absorption for photon energies of InxSe1–x thin films was used to determine the variation of the energy gap and the Urbach energy as a function of temperature in the range from 80 to 340 K at photon energies hν = 1.24 to 2.6 eV. The data were analyzed using the Varshni relation [Physica 34, 149 (1967)] for the temperature dependence of semiconductor band gaps. The formula by Yang et al. [cf., e.g., J. Phys. Chem. Solids 65, 1015 (2004)] for the temperature dependence of the energy width of the Urbach absorption edge was also used. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The isotope effect in disordered strongly coupled superconductors
Authors: Mierzyńska M. , Wysokiński K. I. 
Published: January 2006

AbstractThe isotope effect in disordered strongly coupled superconductors has been studied. Weakly disordered bulk s‐ and d‐wave superconductors as well as strongly disordered homogeneous and granular thin films have been considered. To treat strong coupling s‐wave superconductors Eliashberg theory has been used and the weak localization effects on isotope coefficient (IC) calculated within this approach. The interesting point is that weak localization effects known to properly describe degradation of transition temperature of s‐wave superconductors have been found to decrease the isotope coefficient of impure material with respect to pure samples. This is in contrast to the strong increase of IC induced by magnetic impurities in s‐wave or nonmagnetic impurities in d‐wave spin singlet superconductors. We have also calculated the change of isotope coefficient for both homogeneous and granular thin films and found that the effect of disorder in granular materials on the isotope coefficient is similar to that observed in high‐temperature superconductors. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparative study of helium atom diffusion via an interstitial mechanism in nickel and palladium
Authors: Xia Jixing , Hu Wangyu , Yang Jianyu , Ao Bingyun , Wang Xiaolin 
Published: January 2006

AbstractAt low temperatures, helium atoms diffuse primarily by an interstitial mechanism due to the lower activation energy. Using a modified analytic embedded‐atom model (MAEAM) and the molecular dynamics method, a study of the interstitial diffusion for helium atoms in perfect nickel and palladium was performed. Consequently, the diffusion coefficient was calculated from the jump‐frequency method. The temperature dependency of the diffusion coefficient was found to agree well with the Arrhenius relation. The activation energies of the interstitial mechanism in these two metals were obtained by fitting to the Arrhenius relation, and the results agree with the available experimental and other theoretical data. In addition, by comparing the diffusion activation energies of helium atoms in nickel and palladium, it is found that the helium atom is less mobile in palladium than in nickel. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)