Análise quantitativa por fluorescência de raios X com dispersão por energia pelo método da transmissão aplicada à amostras geológicas

Three certified samples of different matrices (Soil-5, SL-1/IAEA and SARM-4/SABS) were quantitatively analysed by energy dispersive X-ray fluorescence with radioisotopic excitation. The observed errors were about 10-20% for the majority of the elements and less than 10% for Fe and Zn in the Soil-5, Mn in SL-1, and Ti, Fe and Zn in SARM-4 samples. Annular radioactive sources of Fe-55 and Cd-109 were utilized for the excitation of elements while a Si(Li) semiconductor detector coupled to a multichannel emulation card inserted in a microcomputer was used for the detection of the characteristic X-rays. The fundamental parameters method was used for the determination of elemental sensitivities and the irradiator or transmission method for the correction of the absorption effect of characteristic X-rays of elements on the range of atomic number 22 to 42 (Ti to Mo) and excitation with Cd-109. For elements in the range of atomic number 13 to 23 (Al to V) the irradiator method cannot be applied since samples are not transparent for the incident and emergent X-rays. In order to perform the absorption correction for this range of atomic number excited with Fe-55 source, another method was developed based on the experimental value of the absorption coefficients, associated with absorption edges of the elements.Foi realizada a análise quantitativa de três amostras certificadas de diferentes matrizes (Soil-5/IAEA, SL-1/IAEA e SARM-4/SABS) através da fluorescência de raios X por dispersão de energia e excitação radioisotópica. Os erros observados foram em torno de 10 a 20% para a maioria dos elementos e inferiores a 10% para Fe e Zn na amostra Soil-5, Mn na amostra SL-1 e Ti, Fe e Zn na amostra SARM-4. Para a excitação dos elementos presentes foram empregadas as fontes radioativas anelares de Fe-55 e Cd-109, enquanto que na detecção dos raios X característicos utilizou-se um detector de Si(Li), acoplado a uma placa analisadora de pulsos multicanal, inserida em um microcomputador. O método dos parâmetros fundamentais foi utilizado na determinação da sensibilidade elementar e o método do irradiador ou da transmissão na correção dos efeitos de absorção dos raios X característicos de elementos de número atômico entre 22 e 42 (Ti ao Mo) e excitação com Cd-109. Para elementos na faixa de número atômico entre 13 e 23 (Al ao V), o método do irradiador não pode ser aplicado, pois a amostra não é transparente aos raios X incidentes e emergentes, e um outro método baseado nas medidas experimentais dos coeficientes de absorção com Cd-109, associados aos saltos de absorção e excitação com Fe-55 foi então desenvolvido a fim de se efetuar a correção da absorção para esta faixa de número atômico

Study on vinasse dynamics in soil usin energy dispersive X-ray fluorescence with radioisotopic excitation

The distribution of S, Cl, K and Ca along the profiles of two soils of different texture (Red Yellow Podzolic and Dark Red Latosol) treated with amounts of vinasse equivalent to 4000 m³/ha were studied using energy dispersive X-ray fluorescence, observing a significant increase in the contents of these elements. The same effect was observed for Cu, Zn, Rb and Sr contents in soils treated with vinasse as compared to the control. The concentrations of Al, Si, Ti, Mn, Fe and Zr could also be evaluated but no significant variation was observed due to the high soil initial concentrations of these elements as compared to the low concentrations in the vinasse. Annular radioactive sources of Fe-55 and Cd-109 were employed for the excitation of these elements in the soil samples, treated or not with vinassse. For the detection of the characteristic X-rays, a Si (Li) semiconductor detector was used, coupled to a multichannel emulation card inserted in a microcomputer.A distribuição de S, Cl, K e Ca ao longo de perfis de dois solos de diferentes texturas (Podzólico Vermelho Amarelo e Latossolo Vermelho Escuro), tratados com uma dose de vinhaça equivalente a 4000 m³/ha, foi estudada utilizando a fluorescência de raios X por dispersão de energia, observando-se um acréscimo significativo dos teores destes elementos. O mesmo efeito foi observado nos teores de Cu, Zn, Rb e Sr nos solos tratados com vinhaça em relação às testemunhas. As concentrações de Al, Si, Ti, Mn, Fe e Zr também puderam ser avaliadas, mas não houve variação nos perfis, devido à alta concentração inicial nos solos acompanhada de baixa concentração na vinhaça. Na excitação dos elementos presentes nas amostras de solo tratados ou não com vinhaça foram empregadas fontes radioativas anelares de Fe-55 e Cd-109, e na detecção dos raios X característicos um detector semicondutor de Si (Li), acoplado a uma placa analisadora de pulsos multicanal, inserida em um microcomputador

Análise quantitativa por fluorescência de raios X com dispersão por energia pelo método da transmissão aplicada à amostras geológicas

Three certified samples of different matrices (Soil-5, SL-1/IAEA and SARM-4/SABS) were quantitatively analysed by energy dispersive X-ray fluorescence with radioisotopic excitation. The observed errors were about 10-20% for the majority of the elements and less than 10% for Fe and Zn in the Soil-5, Mn in SL-1, and Ti, Fe and Zn in SARM-4 samples. Annular radioactive sources of Fe-55 and Cd-109 were utilized for the excitation of elements while a Si(Li) semiconductor detector coupled to a multichannel emulation card inserted in a microcomputer was used for the detection of the characteristic X-rays. The fundamental parameters method was used for the determination of elemental sensitivities and the irradiator or transmission method for the correction of the absorption effect of characteristic X-rays of elements on the range of atomic number 22 to 42 (Ti to Mo) and excitation with Cd-109. For elements in the range of atomic number 13 to 23 (Al to V) the irradiator method cannot be applied since samples are not transparent for the incident and emergent X-rays. In order to perform the absorption correction for this range of atomic number excited with Fe-55 source, another method was developed based on the experimental value of the absorption coefficients, associated with absorption edges of the elements.Foi realizada a análise quantitativa de três amostras certificadas de diferentes matrizes (Soil-5/IAEA, SL-1/IAEA e SARM-4/SABS) através da fluorescência de raios X por dispersão de energia e excitação radioisotópica. Os erros observados foram em torno de 10 a 20% para a maioria dos elementos e inferiores a 10% para Fe e Zn na amostra Soil-5, Mn na amostra SL-1 e Ti, Fe e Zn na amostra SARM-4. Para a excitação dos elementos presentes foram empregadas as fontes radioativas anelares de Fe-55 e Cd-109, enquanto que na detecção dos raios X característicos utilizou-se um detector de Si(Li), acoplado a uma placa analisadora de pulsos multicanal, inserida em um microcomputador. O método dos parâmetros fundamentais foi utilizado na determinação da sensibilidade elementar e o método do irradiador ou da transmissão na correção dos efeitos de absorção dos raios X característicos de elementos de número atômico entre 22 e 42 (Ti ao Mo) e excitação com Cd-109. Para elementos na faixa de número atômico entre 13 e 23 (Al ao V), o método do irradiador não pode ser aplicado, pois a amostra não é transparente aos raios X incidentes e emergentes, e um outro método baseado nas medidas experimentais dos coeficientes de absorção com Cd-109, associados aos saltos de absorção e excitação com Fe-55 foi então desenvolvido a fim de se efetuar a correção da absorção para esta faixa de número atômico.197206Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

The role of boundary conditions on the dynamics of green coffee beans in a rotated dryer

[EN] Coffee drying and roasting are usually performed in rotated dryers; therefore, the study of particle dynamics in this equipment is of great relevance to improve their efficiency and hence the quality of the final product. Thus, this work aimed to investigate experimentally and numerically the dynamics of coffee beans in a rotary dryer. The Euler-Euler model was employed to reproduce the particle velocity profile in the rolling regime under different boundary conditions. The results shown that the lower specularity coefficient (0.01), which characterizes the smooth wall and free slip condition, reproduced the bed behavior that most resembled the experimental one. On the other hand, the other coefficients (0.1 and 1.0) showed an increasing deformation in the bed surface, different from the observed experimental behavior. It was also verified that, as the filling degree increases, the bed surface deformation becomes more pronounced.The authors would like to thank FAPEMIG, CNPq and CAPES for the financial resources assigned to carry out this work.Machado, M.; Resende, I.; Lima, R.; Brandão, R.; Pivello, M.; Nascimento, S.; Duarte, C.... (2018). The role of boundary conditions on the dynamics of green coffee beans in a rotated dryer. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 331-338. https://doi.org/10.4995/IDS2018.2018.7455OCS33133

Stationary solutions for the parity-even sector of the CPT-even and Lorentz-covariance-violating term of the standard model extension

In this work, we focus on some properties of the parity-even sector of the CPT-even electrodynamics of the standard model extension. We analyze how the six non-birefringent terms belonging to this sector modify the static and stationary classical solutions of the usual Maxwell theory. We observe that the parity-even terms do not couple the electric and magnetic sectors (at least in the stationary regime). The Green's method is used to obtain solutions for the field strengths E and B at first order in the Lorentz- covariance-violating parameters. Explicit solutions are attained for point-like and spatially extended sources, for which a dipolar expansion is achieved. Finally, it is presented an Earth-based experiment that can lead (in principle) to an upper bound on the anisotropic coefficients as stringent as $(\widetilde{\kappa}_{e-}) ^{ij}<2.9\times10^{-20}.$Comment: 8 pages, revtex style, revised published version, to appear in EPJC (2009

Maitotoxin-4, a Novel MTX Analog Produced by Gambierdiscus excentricus

Maitotoxins (MTXs) are among the most potent toxins known. These toxins are produced by epi-benthic dinoflagellates of the genera Gambierdiscus and Fukuyoa and may play a role in causing the symptoms associated with Ciguatera Fish Poisoning. A recent survey revealed that, of the species tested, the newly described species from the Canary Islands, G. excentricus, is one of the most maitotoxic. The goal of the present study was to characterize MTX-related compounds produced by this species. Initially, lysates of cells from two Canary Island G. excentricus strains VGO791 and VGO792 were partially purified by (i) liquid-liquid partitioning between dichloromethane and aqueous methanol followed by (ii) size-exclusion chromatography. Fractions from chromatographic separation were screened for MTX toxicity using both the neuroblastoma neuro-2a (N2a) cytotoxicity and Ca2+ flux functional assays. Fractions containing MTX activity were analyzed using liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS) to pinpoint potential MTX analogs. Subsequent non-targeted HRMS analysis permitted the identification of a novel MTX analog, maitotoxin-4 (MTX4, accurate mono-isotopic mass of 3292.4860 Da, as free acid form) in the most toxic fractions. HRMS/MS spectra of MTX4 as well as of MTX are presented. In addition, crude methanolic extracts of five other strains of G. excentricus and 37 other strains representing one Fukuyoa species and ten species, one ribotype and one undetermined strain/species of Gambierdiscus were screened for the presence of MTXs using low resolution tandem mass spectrometry (LRMS/MS). This targeted analysis indicated the original maitotoxin (MTX) was only present in one strain (G. australes S080911_1). Putative maitotoxin-2 (p-MTX2) and maitotoxin-3 (p-MTX3) were identified in several other species, but confirmation was not possible because of the lack of reference material. Maitotoxin-4 was detected in all seven strains of G. excentricus examined, independently of their origin (Brazil, Canary Islands and Caribbean), and not detected in any other species. MTX4 may therefore serve as a biomarker for the highly toxic G. excentricus in the Atlantic area

Consistency analysis of a nonbirefringent Lorentz-violating planar model

In this work analyze the physical consistency of a nonbirefringent Lorentz-violating planar model via the analysis of the pole structure of its Feynman propagators. The nonbirefringent planar model, obtained from the dimensional reduction of the CPT-even gauge sector of the standard model extension, is composed of a gauge and a scalar fields, being affected by Lorentz-violating (LIV) coefficients encoded in the symmetric tensor $\kappa_{\mu\nu}$. The propagator of the gauge field is explicitly evaluated and expressed in terms of linear independent symmetric tensors, presenting only one physical mode. The same holds for the scalar propagator. A consistency analysis is performed based on the poles of the propagators. The isotropic parity-even sector is stable, causal and unitary mode for $0\leq\kappa_{00}<1$. On the other hand, the anisotropic sector is stable and unitary but in general noncausal. Finally, it is shown that this planar model interacting with a $\lambda|\varphi|^{4}-$Higgs field supports compactlike vortex configurations.Comment: 11 pages, revtex style, final revised versio