952 resultados para Scheurl, Christoph, 1481-1542.


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An investigation of the parameters as aniline: MnO(2) and temperature on synthesis of polyaniline/MnO(2) composites was performed. The composites were chemically prepared in H(2)SO(4) media using different aniline: MnO(2) ratios at 0 degrees C. After the ratio optimization, the syntheses were performed at 20 degrees C. The polyaniline/MnO(2) composites were characterized by scanning electron microscopy (SEM), ultraviolet-visible, near infrared and infrared spectroscopic techniques. Composites obtained with a uniform, homogeneous and thicker coating of polyaniline films under oxide was considered as the best condition for synthesis.

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The kinetics and the thermodynamics of electrochemical intercalation of lithium into CeO(2)-TiO(2) films prepared by the sol-gel process were studied by galvanostatic intermittent titration technique (GITT) as function of the depth of lithium intercalation. The open-circuit-potential versus x in Li(x)(CeO(2)-TiO(2)) curve consists of two straight lines with different slopes, one in the range of 0.03 <= x <= 0.09 and the other of 0.09 < x <= 0.15. The standard Gibbs energy for lithium intercalation Delta G(1)(0) was 6kJ/mol for x = 0.09 in Li(x)(CeO(2)-TiO(2)) at room temperature. The chemical diffusion coefficient value, D(Li+), of lithium intercalation into thin film oxide was 2.14.10(-11) cm(2)/s at x = 0.15, and the value of the component diffusion coefficient D(Li+),(k) was about one order of magnitude lower than the coefficient of chemical diffusion.

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The electrochemical characteristics of the AA2024 aluminium alloy modified with octadecyltrimethoxysilane (ODTMS) + polyaniline (PANi) and propiltrimethoxysilane (PTMS) + (PANi) were studied in the present work. The results show that the different protective coatings shift the values of corrosion and pit potentials to more positive values making the system nobler and indicate that the double film ODTMS + PANi present the best protection against corrosion characteristics, that is probably due to the two contributions: anodic protection associated with the barrier effect.

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The synthesis and characterization of some pyrazoline compounds of 1,3-diketones with hydrazine derivatives, namely, 1-(S-benzyldithiocarbazate)-3-methyl-5-phenyl-5-hydroxypyrazoline (1); 1-(2-thiophenecarboxylic)-3-methyl-5-phenyl-5-hydroxypyrazoline (2); 1-(2-thiophenecarboxylic)-3,5-dimethyl-5-hydroxypyrazoline (3); 1-(S-benzyldithiocarbazato)-3-methyl-5-phenylpyrazole (4); 1-(2-thiophenecarboxylic)-3-methyl-5-phenylpyrazole (5) and 1-(S-benzyldithiocarbazate)-3,5-dimethylpyrazole (6) are reported. Studies by IR, ((1)H, (13)C)-NMR spectroscopies and single crystal X-ray diffraction revealed that compounds (1)(,) (2) and (3) are formed as pyrazoline, whereas (4) and (5) are formed as pyrazole derivatives only under acidic conditions. Compound (1) crystallizes in orthorhombic P2(1)2(1)2(1), a = 6.38960(10) angstrom, b = 12.9176(3) angstrom, c = 21.2552(5) angstrom, (2) crystallizes in monoclinic, P2(1)/n, a = 11.3617(2) angstrom, b = 8.4988(2) angstrom, c = 92.8900(10)angstrom and beta = 92.8900(5)degrees, (3) crystallizes in monoclinic, C2/c, a = 15.9500(5) angstrom, b = 9.3766(3) angstrom, c = 16.6910(5)angstrom and beta = 113.825(2)degrees, (4) crystallizes in monoclinic, P2(1)/c, a = 15.228(4) angstrom, b = 5.5714(13) angstrom, c = 19.956(5)angstrom and beta = 91.575(7)degrees and (6) crystallizes in orthorhombic, P2(1)2(1)2(1), a = 5.3920(2) angstrom, b = 11.2074(5) angstrom, c = 21.885(1)angstrom . The (3) derivative represents the first pyrazoline compound prepared from 2,4-pentanedione and characterized crystallographically.

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Essential oils are good candidates for the substitution of conventional medicinal treatments. Many articles and patents for their use have been published in recent years. The most attractive aspects of using essential oils as medicaments are their natural source and rapid permeability. Besides permeability, the solubility behavior of a drug is a key determinant of its oral bioavailability. Based on these characteristics, the aim of this study was to synthesize an essential oil derivative compound, using the raw oil extracted from Syzygium aromaticum L., without previous purification. The Eugenol molecular modification may diminish the problems of water solubility and bioavailability. The Eugenyl acetate molecule was characterized and its molecular modification investigated, including its structural properties and stereochemistry. This study was performed applying techniques, such as carbon-13 nuclear magnetic resonance spectroscopy (C-13 NMR), X-ray crystallographic analysis (XRD), powder X-ray diffraction (PXRD) and microscopic recording.

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This study examines the question of how language teachers in a highly technologyfriendly university environment view machine translation and the implications that this has for the personal learning environments of students. It brings an activity-theory perspective to the question, examining the ways that the introduction of new tools can disrupt the relationship between different elements in an activity system. This perspective opens up for an investigation of the ways that new tools have the potential to fundamentally alter traditional learning activities. In questionnaires and group discussions, respondents showed general agreement that although use of machine translation by students could be considered cheating, students are bound to use it anyway, and suggested that teachers focus on the kinds of skills students would need when using machine translation and design assignments and exams to practice and assess these skills. The results of the empirical study are used to reflect upon questions of what the roles of teachers and students are in a context where many of the skills that a person needs to be able to interact in a foreign language increasingly can be outsourced to laptops and smartphones.

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This study examines the question of how language teachers in a highly technology-friendly university environment view machine translation and the implications that this has for the personal learning environments of students. It brings an activity-theory perspective to the question, examining the ways that the introduction of new tools can disrupt the relationship between different elements in an activity system. This perspective opens up for an investigation of the ways that new tools have the potential to fundamentally alter traditional learning activities. In questionnaires and group discussions, respondents showed general agreement that although use of machine translation by students could be considered cheating, students are bound to use it anyway, and suggested that teachers focus on the kinds of skills students would need when using machine translation and design assignments and exams to practice and assess these skills. The results of the empirical study are used to reflect upon questions of what the roles of teachers and students are in a context where many of the skills that a person needs to be able to interact in a foreign language increasingly can be outsourced to laptops and smartphones.