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991.
Alan Patrick da SilvaGisele de Freitas Gauze Narcimário Pereira CoelhoCleuza Conceição da Silva Ernani Abicht Basso 《Tetrahedron letters》2011,52(1):62-64
The hydrazine addition to isothiocyanoterpenes to produce thiosemicarbazides occurs with excellent yields. The reaction rate to conversion of the camphene-based (NCS1), R-(+)-limonene-based (NCS2), and (−)-α-bisabolol-based (NCS3) isothiocyanoterpene derivatives in the respective thiosemicarbazides was experimentally studied. It was observed that NCS3 reacts two times faster than NCS2 and 3.5 times faster than NCS1. A complete theoretical investigation of the transition states of these reactions was accomplished, showing that the difference in the reaction rates can be explained by the differences in the electrophilic character of the -NCS group and the relative stability of the proposed transition states. 相似文献
992.
Márcia R. S. Silva Mary C. F. Alves S. J. G. Lima L. E. B. Soledade Elaine C. Paris E. Longo A. G. Souza Iêda M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2009,97(2):559-564
Sr(Ti,Nd)O3 was synthesized in order to evaluate the influence of the amount of neodymium on the thermal and structural properties of
SrTiO3. The synthesis was carried out using the polymeric precursor method. A small mass gain was observed for the SrTiO3 and SrTi0.98Nd0.02O3 samples accompanied by an exothermic peak in the DTA curves. Other steps at higher temperatures are assigned to the combustion
of the organic material and carbonate. Elimination of defects by previous calcination of the precursors is responsible by
the short and long range ordering of the perovskite. Cubic phase was obtained for undoped and doped SrTiO3. 相似文献
993.
In this work we show that it is possible to obtain a generalized statistical mechanics (thermostatistics) based on Renyi entropy, to be maximized with adequate constraints. The equilibrium probability distribution thus obtained has a very interesting property. Indeed, it reminds us the statistical distribution proposed by Tsallis, known to conveniently describe a variety of phenomena in nonextensive systems. Moreover, some examples are worked out in order to illustrate the main features of the herein introduced formalism. 相似文献
994.
Simone Manéglier-Lacordaire Pierre Besançon Jacques Rivet Jean Flahaut 《Journal of Non》1975,18(3):439-454
The glasses of the germanium-tellurium-sulphur ternary system were investigated in order to determine the formation and crystallization processes. Vitreous samples were prepared by quenching. The vitreous transition and crystallization temperatures, together with microhardnesses, were measured throughout the vitreous region. The latter was sub-divided into several zones, and the behaviour of the glasses in each of these zones was analyzed separately. 相似文献
995.
Jos�� Fl��vio Marcelino Borges Marlon Luiz Hneda Andr�� Maur��cio Brinatti Jo?o Batista Marimon da Cunha Jadir Aparecido Rosa Jos�� Domingos Fabris 《Hyperfine Interactions》2011,203(1-3):9-15
A sample of the coarse sand fraction from the soil material of the A-horizon (0?C0.2 m from the soil surface) of a dusky red magnetic Oxisol was submitted to high-energy mechanical milling for different times. This assay aimed mainly at (a) monitoring the individualization of strongly aggregated mineral particles, and (b) measuring the effect of the milling pressure on the mineralogy changes of the material. These data are also intended to experimentally subside any physical model describing the mechanical behavior of the superficial soil layer that is subjected to intensive machine management, in agriculture fields. Powder X-ray data reveal that some mineralogical phases, notably gibbsite, disappear soon after the first few hours milling. The 298 K-transmission Mössbauer spectrum for the non-milled sand sample shows a qualitatively typical pattern for the sand fraction of basalt derived soils, with magnetically ordered sextets, assignable mainly to hematite and maghemite, and an intense central (super)paramagnetic Fe3?+? doublet. For the milled samples, spectra revealed progressive spectral reduction of the magnetic hyperfine structure, with concomitant increase of relative subspectral areas due to (super)paramagnetic phases, as the milling time increased. This result is consistent with the reduction of measured saturation magnetization, from 4.96(8) J T???1 kg???1, for the non-milled sample, to 3.26(7) J T???1 kg???1, for the sample milled for 8 hours. 相似文献
996.
Rafael Germano Santana Derisvaldo Rosa Paiva Roberto da Silva Gomes Adriana Karla C. A. Reis 《Magnetic resonance in chemistry : MRC》2013,51(5):316-319
The complete assignment of the 1H and 13C NMR spectra of various 2‐acetamido‐3‐mercapto‐3‐methyl‐N‐aryl‐butanamides and 2‐acetamide‐3‐methyl‐3‐nitrososulfanyl‐N‐aryl‐butanamides with p‐methoxy, o‐chloro and m‐chloro substituents is reported. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
997.
The aim of this note is to clarify a minor mistake in the article: Some Applications of the Hodge-de Rham Decomposition to Ricci solitons. 相似文献
998.
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