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11.
P. J. Mendes J. M. Gil N. Ayres de Campos R. Peichl A. Weidinger 《Hyperfine Interactions》1983,16(1-4):791-794
The perturbation felt by181Hf probes in a181HfTa lattice loaded with 30 at% hydrogen was observed by PAC as a function of temperature. Three different interactions were identified: 1) ΝQ1=433 (6) MHz, η=0.45 2) ΝQ2=142 (9) MHz, η=0.9, and 3) ΝQ?0, σ=4–14 Μ?1 which are attributed to the Β?, ε? and α-phase in TaH system, respectively. 相似文献
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Leornardo S. Mendes 《Analytica chimica acta》2003,493(2):219-231
Fourier transform-near infrared (FT-NIR) and FT-Raman spectrometries have been used to design partial least squares (PLS) calibration models for the determination of the ethanol content of ethanol fuel and alcoholic beverages. In the FT-NIR measurements the spectra were obtained using air as reference, and the spectral region for PLS modeling were selected based on the spectral distribution of the relative standard deviation in concentration. In the FT-Raman measurements hexachloro-1,3-butadiene (HCBD) has been used as an external standard. In the PLS/FT-NIR modeling for ethanol fuel analysis 50 ethanol fuel standards (84.9-100% (w/w)) were used (25 in the calibration, 25 in the validation). In the PLS/FT-Raman modeling 25 standards were used (13 in the calibration, 12 in the validation). The PLS/FT-NIR and FT-Raman models for beverage analysis made use of 24 standards (0-100% (v/v)). Twelve of them contained sugars (1-5% (w/w)), one-half was used in the calibration and the other half in the validation. Different spectral pre-processing were used in the PLS modeling, depending on the type of sample investigated. In the ethanol fuel analysis the FT-NIR pre-processing was a 17 points smoothed first derivative and for beverages no spectral pre-processing was used. The FT-Raman spectra were pre-processed by vector normalization in the ethanol fuel analysis and by a second derivative (17 points smoothing) in the beverage analysis. The PLS models were used in the analysis of real ethanol fuel and beverage samples. A t-test has shown that the FT-NIR model has an accuracy equivalent to that of the reference method (ASTM D4052) in the analysis of ethanol fuel, while in the analysis of beverages, the FT-Raman model presents an accuracy equivalent to the reference method. The limits of detection for NIR and Raman calibration models were 0.05 and 0.2% (w/w), respectively. It has also been shown that both techniques, present better results than gas chromatography (GC) in evaluating the ethanol content of beverages. 相似文献
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Literature data on distribution ratios (Dw) of Np(V) and Pa(V) for the AG1-X8 resin are scarce whereas those related on resin capacity factors (k′) values for TEVA, TRU and U/TEVA resins are absent. Therefore, batch extraction experiments for Pa(V) and Np(V) from HCl and HNO3 media were realized, at tracer scale, with AG1-X8 and EIChroM resins (TEVA, TRU and U/TEVA). Based on the new Dw and k′ values obtained in this study, a new protocol for Pa/Np separation has been developed leading to a better separation factor of 105 and a chemical yield of 97 ± 3% and 99 ± 1% for Pa and Np, respectively. A separation of 231Pa from uranium matrix was successfully tested. 相似文献
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Quantitative analysis of biogenic polyamines in distilled drinks by direct electrospray ionization tandem mass spectrometry using a nanocontainer 下载免费PDF全文
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Maria Andrea Mendes Formiga Melo Marco Aurélio Rodrigues de Melo Andrea Suame Gouvea Costa Pontes Ana Flávia Félix Farias Manoel Barbosa Dantas Clediana Dantas Calixto Antonio Gouveia de Souza José Rodrigues de Carvalho Filho 《Journal of Thermal Analysis and Calorimetry》2014,117(2):845-849
Vegetable oils with variable proportions of oleic, linoleic, and linolenic acids are more susceptible to oxidative processes. In this subject, this study evaluates the physical chemical properties and oxidative stability of non-conventional oils such as andiroba, babassu, sesame, oiticica, jatropha, and grape through accelerated oxidation techniques (pressurized differential scanning calorimetry, Rancimat and PetroOxy). It was verified that babassu and andiroba oil do not showed detectable induction period presenting high oxidative stability; moreover, it was observed that the enthalpic events occurred in 1.19, >10, 0.53, 0.49, 0.49, and 0.60 h for the andiroba oil, babassu oil, sesame seeds, jatropha, oiticica oils, and grapes, respectively, stimulating the conclusion of greater stability for the babassu oil. 相似文献