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971.
Ian W Hamley Valeria Castelletto Nágila MPS Ricardo Maria EN Pinho Colin Booth David Attwood Zhuo Yang 《Polymer International》2007,56(1):88-92
Small‐angle X‐ray scattering was used to characterise aqueous micellar gels of triblock copolymers E137S18E137, E82S9E82, E76S5E76, E62P39E62, and of two mixtures: E137S18E137 and E62P39E62 (Mix 1) and E82S9E82 and E62P39E62 (Mix 2), each 50/50 wt%. E = oxyethylene, CH2CH2O; S = oxyphenylethylene, OCH2CH(C6H5); and P = oxypropylene, OCH2CH(CH3). Within the concentration and temperature ranges investigated (30–40 wt% copolymer, 20–80 °C), spherical micelles of copolymers E137S18E137, E82S9E82 and E62P39E62 packed into body‐centred cubic (BCC) structures. Gels of E76S5E76 were stable only at high concentrations and low temperatures, and a 70 wt% copolymer solution at T = 30 °C formed a hexagonal gel consistent with cylindrical micelles. It is likely that the mixed copolymers would form two distributions of micelles, and more complex structures were expected. However, gels of Mix 2 had well‐ordered BCC structures, while the less ordered gels of Mix 1 were also best characterised as BCC. Copyright © 2006 Society of Chemical Industry 相似文献
972.
A highly efficient Suzuki cross-coupling reaction between phenyl bromide and phenylboronic acid catalyzed by the palladium complex Pd[tBuNH(S)NHP(O)(OiPr)2-S]2Cl2 in acetonitrile, toluene, THF or DMF has been investigated. The bases we have employed for this reaction were Na2CO3, K2CO3 or Cs2CO3. It was established that using DMF and K2CO3 at 100 °C shows excellent yields of the product at the catalyst amount of 0.1 mmol. The cross-coupling reactions of iodo- and chloro-benzene with phenylboronic acid were also investigated. The influence of the halide nature was as expected. 相似文献
973.
Oliver Klein Maria Minguet Bonvehi Francisco Aguilar-Parrilla Nadine Jagerovic José Elguero Hans-Heinrich Limbach 《Israel journal of chemistry》1999,39(3-4):291-299
Using dynamic solid state 15N CPMAS NMR spectroscopy (CP ≡ cross polarization, MAS ≡ magic-angle spinning), the kinetics of degenerate intermolecular triple proton and deuteron transfers in the cyclic trimers of 15N-labeled polycrystalline 4-nitropyrazole (4NO2P) and 4-bromopyrazole (4BrP) have been studied as a function of temperature and are compared to the kinetics of triple proton transfer in bulk solid 3,5-dimethylpyrazole (DMP) studied previously. The results show that the transfer kinetics in the new trimers are much faster than in DMP. However, the kinetic HHH/HHD/HDD/DDD isotope effects of 4NO2P are similar to those of DMP. These effects indicate a single barrier for the triple proton transfers where all three protons lose zero-point energy in the transition state, as expected for a structure with three compressed hydrogen bonds. At low temperatures, strong deviations from an Arrhenius-behavior are observed which are described in terms of a modified Bell tunneling model and a concerted proton motion. The barrier for the triple proton transfer in 4NO2P and 4BrP is substantially smaller than in DMP. As there is no correlation with the electronic properties of the substituents, we assign this finding to steric effects where the bulky methyl groups of DMP in the 3- and 5-positions hinder the hydrogen bond compression, in contrast to 4NO2P and 4BrP exhibiting substitutents in the 4-position. These results lead to a minimum energy pathway of the proton transfer following in the absence of steric hindering the hydrogen bond correlation line q1 = f(q2), established previously, where q1 represents the deviation of the proton from the hydrogen bond center and q2 the N…N distance. Tunneling occurs at constant N…N distances. 相似文献
974.
Jewgenij Botaschanjan Manfred Broy Alexander Gruler Alexander Harhurin Steffen Knapp Leonid Kof Wolfgang Paul Maria Spichkova 《Formal Aspects of Computing》2008,20(6):637-662
Formal verification of software systems is a challenge that is particularly important in the area of safety-critical automotive systems. Here, approaches like direct code verification are far too complicated, unless the verification is restricted to small textbook examples. Furthermore, the verification of application logic is of limited use in industrial context, unless the underlying operating system and the hardware are verified, too. This paper introduces a generic model stack, allowing the verification of all system layers as well as the concrete application models being used in the upper layers. The presented models and proofs close the gap between the correctness proof for the lower layers of car electronics developed at the Saarland University and the verification procedure for distributed applications developed at the Technische Universität München. 相似文献
975.
Existing corrosion protection technologies for aluminium alloys utilising chromates are environmentally damaging and extremely toxic. This paper presents a preliminary investigation into rare earth diphenyl phosphates as new environmentally benign corrosion inhibitors. Full immersion weight loss experiments, cyclic potentiodynamic polarisation measurements and Raman spectroscopy were used in this study. Results show cerium diphenyl phosphate (Ce(dpp)3) acts as a cathodic inhibitor, decreasing cathodic current density and Ecorr by passivating cathodic intermetallic particles on the alloy surface. Mischmetal diphenyl phosphate (Mm(dpp)3) acts a mixed inhibitor, shifting Ecorr to more noble values, decreasing cathodic current density, increasing the breakdown potential and suppressing pitting. 相似文献
976.
Vladimiros P. Lougovois Maria K. Kolovou Ioannis N. Savvaidis & Michael G. Kontominas 《International Journal of Food Science & Technology》2008,43(7):1286-1294
The spoilage potential of fresh musky octopus ( Eledone moschata ) was determined by evaluating the changes in biochemical and physical properties, microbial growth and sensory quality of the mantle and tentacles, over a period of 18 days. Whole musky octopus, stored in melting ice from the time of harvest, had a storage life of 10 days. Early deterioration in the sensory quality resulted primarily from autolytic reactions. Pseudomonas spp. dominated the spoilage flora, reaching an average count of 108 CFU g−1 at the end of the trial. The bacterial metabolic end products (trimethylamine, total volatile bases) were not useful as objective indicators of freshness, and measurements of pH would only provide an indicator of decomposition. Changes in the dielectric properties of the mantle were reflective of quality deterioration, but could not yield precise information on the storage history of the cephalopod. The common sulphide producer, Shewanella putrefaciens , was not a major spoiler of ice-stored musky octopus. 相似文献
977.
Else Breval Maria Klimkiewicz Chiping Wang Joseph P. Dougherty Ann Crespi 《Journal of the American Ceramic Society》2007,90(8):2664-2666
Annealing of a sintered pellet of Pb0.9175 La0.055 Zr0.975 Ti0.025 O3 in air without any precautions against PbO evaporation results in a core–shell microstructure with a solid PLZT core and a porous ZrO2 -rich shell. 相似文献
978.
Maria D. Salazar-Villalpando David A. BerryTodd H. Gardner 《International Journal of Hydrogen Energy》2008
Partial oxidation of methane (POM) was studied over Rh/(Ce0.56Zr0.44)O2−x, Rh/(Ce0.91Gd0.09)O2−x, Rh/(Ce0.71Gd0.29)O2−x and Rh/(Ce0.88La0.12)O2−x. The effect of catalyst reducibility and redox cycles was investigated. It was found that the type of doped-ceria support and its reducibility played an important role in catalyst activity. It was also observed that redox cycles had a positive influence on H2 production, which was enhanced as the number of redox cycle increased. Results of carbon formation are discussed as a function of ionic conductivity. Temperature programmed reduction (TPR) profiles, BET surface area, ionic conductivity and XRD patterns were determined to characterize catalysts. Catalytic tests revealed that of the materials tested, Rh/(Ce0.56Zr0.44)O2−x was the most active material for the production of syngas, which correlates with its TPR profile. It was observed that doping CeO2 with Zr, rather than with La or Gd caused an enhanced reducibility of Rh/supported-ceria catalysts. 相似文献
979.
Rinaldo Cervellati Emanuela Greco Stefano Costa Maria Clelia Guerra Ester Speroni 《International Journal of Food Science & Technology》2008,43(10):1866-1870
The antioxidant capacities and the total phenolic content in cocoa liquor directly manufactured chocolate from an artisan manufacturer were measured using different in vitro methods (BR, TEAC, and Folin–Ciocalteu Reagent). These parameters were then compared with those of a chocolate made by a leading manufacturing company producing chocolate and cocoa‐containing products. A statistical analysis of the collected data showed that the antioxidant properties of the artisan‐made chocolate are significantly better than those of the factory‐produced one. These results were ascribed to the fact that all the bioactive components in the cocoa beans are better preserved in the artisan‐made chocolate. 相似文献
980.
Maria Elena De Giuli Dean Fantazzini Mario Alessandro Maggi 《Computational Economics》2008,31(2):161-180
In this paper we present a new model to assess the firm value and the default probability by using a bivariate contingent
claim analysis and copula theory. First we discuss an unfeasible case, given the current derivative market on corporate bonds,
which involves univariate digital options to compute the risk neutral probabilities. We then discuss a feasible model, which
considers risky interest rates, instead. Moreover, we develop in this framework a new methodology to extract default probabilities
from stock prices, only, going beyond the standard KMV-Merton model. Besides, the non-observability of the Merton model’s
state variable requires numerical methods, but the results can be unstable with noisy risky data. We show how the null price
can be used as a useful barrier to separate an operative firm from a defaulted one, and to estimate its default probability.
We then present an empirical application with both operative and defaulted firms to show the advantages of our approach.
相似文献