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211.
M. Manso S. Valadas S. Pessanha A. Guilherme I. Queralt A.E. Candeias M.L. Carvalho 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010
This work comprises the use of energy dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD) and Fourier transformed infrared (FTIR) techniques for the study of the composition of twentieth century traditional Japanese color sticks. By using the combination of analytical techniques it was possible to obtain information on inorganic and organic pigments, binders and fillers present in the sticks. The colorant materials identified in the sticks were zinc and titanium white, chrome yellow, yellow and red ochre, vermillion, alizarin, indigo, Prussian and synthetic ultramarine blue. The results also showed that calcite and barite were used as inorganic mineral fillers while Arabic gum was the medium used. EDXRF offered great potential for such investigations since it allowed the identification of the elements present in the sample preserving its integrity. However, this information alone was not enough to clearly identify some of the materials in study and therefore it was necessary to use XRD and FTIR techniques. 相似文献
212.
José Carlos N. de Araujo Guilherme F. Marranghello 《General Relativity and Gravitation》2009,41(6):1389-1406
We study the generation of a stochastic gravitational wave (GW) background produced by a population of neutron stars (NSs)
which go over a hadron-quark phase transition in its inner shells. We obtain, for example, that the NS phase transition, in
cold dark matter scenarios, could generate a stochastic GW background with a maximum amplitude of h
BG ~ 10−24, in the frequency band ν
obs ≃ 20–2,000 Hz for stars forming at redshifts of up to z ≃ 20. We study the possibility of detection of this isotropic GW background by correlating signals of a pair of Advanced
LIGO observatories. 相似文献
213.
Guilherme R. de Oliveira Heibbe Cristhian B. de Oliveira Wender Alves Silva Valter Henrique Carvalho da Silva José Ricardo Sabino Felipe T. Martins 《Structural chemistry》2012,23(6):1667-1676
Chalcones are ??,??-unsaturated aromatic ketones which can present a wide range of biological activities. Here, the structure of the chalcone (E)-1-(4-biphenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one was determined by single crystal X-ray diffraction technique and compared to those of similar compounds whose crystal structures are available in the Cambridge Structural Database. These comparisons have allowed us to conclude that electron delocalization is abrogated through the biphenyl and carbonyl moieties, while resonance effects are increased through the trimethoxyphenyl group and the olefin carbons. Single-molecule calculations of the asymmetric unit using the DFT method have strengthened these structural relationships, since experimental and theoretical molecular geometries were similar. For instance, the global minimum for the optimized structure occurs when one of the four dihedral angles on the bridge between the two rings of biphenyl is 40.25°, a value close to that of the corresponding torsion determined by single crystal X-ray diffraction analysis [41.7(3)°]. Our theoretical approaches further suggest another stable conformer for different torsions around this bridge, although this conformer was not found in the crystal phase because C?CH···?? intermolecular interactions contributing to assemble the supramolecular architecture of the studied compound keep only the conformer observed. Other face-to-face ??···?? stacking interactions and C?CH···?? contacts are also responsible for the crystal assembly. 相似文献
214.
Removal of methylene blue dye from an aqueous media using superabsorbent hydrogel supported on modified polysaccharide 总被引:8,自引:0,他引:8
Paulino AT Guilherme MR Reis AV Campese GM Muniz EC Nozaki J 《Journal of colloid and interface science》2006,301(1):55-62
The removal of methylene blue (MB) in water with the superabsorbent hydrogel (SH) formed by modified gum arabic, polyacrylate, and polyacrylamide was investigated. The SH exhibited excellent performance in MB absorption. The maximum absorption capacity was 48 mg of the dye per g of SH, representing 98% of the MB removed. Experimental parameters were used as follows: pH 8, hydrogel mass 50 mg, and initial concentration of MB 50 mg L(-1). In a procedure with an individual solution of orange II, an opposite effect related to the MB was observed: the hydrogel only absorbed water, resulting in an orange II-richer solution. The orange II concentration in solution increased about 50 times (relative to the initial concentration). In another experiment using an aqueous mixture of orange II and MB, the SH absorbed the MB exclusively. Compared to the MB, the orange II is separated from water by SH selectivity-absorption through an inverse process. This effect was attributed to the formation of a ionic complex between the imine groups of MB and the ionized carboxylic groups of SH. 相似文献
215.
Stolichnov I Colla E Setter N Wojciechowski T Janik E Karczewski G 《Physical review letters》2006,97(24):247601
Field effect transistors with ferroelectric gates would make ideal rewritable nonvolatile memories were it not for the severe problems in integrating the ferroelectric oxide directly on the semiconductor channel. We propose a powerful way to avoid these problems using a gate material that is ferroelectric and semiconducting simultaneously. First, ferroelectricity in semiconductor (Cd,Zn)Te films is proven and studied using modified piezoforce scanning probe microscopy. Then, a rewritable field effect device is demonstrated by local poling of the (Cd,Zn)Te layer of a (Cd,Zn)Te/CdTe quantum well, provoking a reversible, nonvolatile change in the resistance of the 2D electron gas. The results point to a potential new family of nanoscale one-transistor memories. 相似文献
216.
Using molecular dynamics simulations we investigate the structure of a system of particles interacting through a continuous core-softened interparticle potential. We found for the translational order parameter t a local maximum at a density rho(t-max) and a local minimum at rho(t-min)>rho(t-max). Between rho(t-max) and rho(t-min), the t parameter anomalously decreases upon increasing pressure. For the orientational order parameter Q(6) a maximum was observed at a density rho(t-max)相似文献
217.
Prof. Fernanda Andreia Rosa Samara Mendes de Souza Melo Dr. Karlos Eduardo Pianoski Julia Poletto Mariellen Guilherme dos Santos Dr. Michael Jackson Vieira da Silva Dr. Danielle Lazarin-Bidóia Dr. Hélito Volpato Prof. Sidnei Moura Prof. Celso Vataru Nakamura 《ChemistryOpen》2021,10(10):931-938
A series of 60 4-aminomethyl 5-aryl-3-substituted isoxazoles were synthesized by an efficient method and evaluated in vitro against Leishmania amazonensis and Trypanosoma cruzi, protozoa that cause the neglected tropical diseases leishmaniasis and Chagas disease, respectively. Thirteen compounds exhibited a selective index greater than 10. The series of 3-N-acylhydrazone isoxazole derivatives bearing the bithiophene core exhibited the best antiparasitic effects. 相似文献
218.
Teixeira Fernanda Vieira Alves Guilherme Liberato Ferreira Marcus Henrique Taveira Stephania Fleury da Cunha-Filho Marcílio Sérgio Soares Marreto Ricardo Neves 《Journal of Thermal Analysis and Calorimetry》2018,133(1):365-370
Journal of Thermal Analysis and Calorimetry - The composition and temperature dependence of viscosity and configuration entropy of glasses with chemical composition close to that used for CHROMPIC... 相似文献
219.
Adney Luís A. da Silva Guilherme G. G. Castro Mariana M. V. M. Souza 《Journal of Thermal Analysis and Calorimetry》2012,109(1):33-38
Lanthanum strontium chromite (LSC) powders were synthesized by the combustion method, using five different fuels (urea, glycine, ethylene glycol, ??-alanine, and citric acid). The ignition of the reagent mixture with urea takes a longer time, and more gases are released by combustion. A calcination step is essential for a good crystallization of the perovskite phase. X-ray diffraction patterns showed formation of perovskite phase and a small amount of SrCrO4 for the sample synthesized with urea after calcination. The crystallite sizes are in the range of 23?C33?nm. Scanning electron microscopy revealed the porosity of the powders and the presence of agglomerates, formed by fine particles of different shapes. Thermogravimetric analysis showed a large mass loss for the sample synthesized with citric acid, probably caused by the absence of ignition, with primary polymerization of the precursor reagents. 相似文献
220.