Caracterização e Predição de Propriedades Físicas e Químicas de Destilados de Petróleo por Ressonância Magnética Nuclear (RMN)

Separar os componentes individuais do petróleo é praticamente impossível, assim a maneira mais conveniente de se analisar destilados de petróleo é por meio da determinação de suas composições químicas e de suas propriedades visto que muitas delas estão relacionadas com a constituição química. Neste trabalho, quatro amostras de petróleo com °API entre 34,9 e 17,9 foram submetidos à destilação PEV (ponto de ebulição verdadeiro) seguindo a norma ASTM D 2892, o que permitiu a obtenção de 42 destilados. A técnica CPMG e a sequência de Gradiente de Campo Pulsado PFGSTE, foram aplicadas para a obtenção dos Tempos de Relaxação (T2) e Coeficiente de Difusão (D) respectivamente. Valores de T2 entre 4,64s a 60,47ms e de D na faixa de 1,6x10-11m2/s a 759,7x10-11, quando correlacionados com a Teb (31 a 400°C), MM (67,59 a 344,54 g/mol) e °API (23,4 a 94,1) dos destilados, apresentaram uma forte tendência com essas propriedades. Os tempos de relaxação medidos por RMN de baixo campo (RMN-BC) foram correlacionados com os valores dos índices de aromaticidade determinados por RMN de alta resolução. Estudos de RMN de baixo campo em conjunto com Destilação Simulada (SimDis) normatizada pela ASTM D7169 demonstraram que RMN-BC é uma alternativa rápida e viável para determinação da distribuição de cadeia carbônica de destilados

Interaction-induced chaos in a two-electron quantum-dot system

A quasi-one-dimensional quantum dot containing two interacting electrons is analyzed in search of signatures of chaos. The two-electron energy spectrum is obtained by diagonalization of the Hamiltonian including the exact Coulomb interaction. We find that the level-spacing fluctuations follow closely a Wigner-Dyson distribution, which indicates the emergence of quantum signatures of chaos due to the Coulomb interaction in an otherwise non-chaotic system. In general, the Poincar\'e maps of a classical analog of this quantum mechanical problem can exhibit a mixed classical dynamics. However, for the range of energies involved in the present system, the dynamics is strongly chaotic, aside from small regular regions. The system we study models a realistic semiconductor nanostructure, with electronic parameters typical of gallium arsenide.Comment: 4 pages, 3ps figure

A semiquantal approach to finite systems of interacting particles

A novel approach is suggested for the statistical description of quantum systems of interacting particles. The key point of this approach is that a typical eigenstate in the energy representation (shape of eigenstates, SE) has a well defined classical analog which can be easily obtained from the classical equations of motion. Therefore, the occupation numbers for single-particle states can be represented as a convolution of the classical SE with the quantum occupation number operator for non-interacting particles. The latter takes into account the wavefunctions symmetry and depends on the unperturbed energy spectrum only. As a result, the distribution of occupation numbers $n_s$ can be numerically found for a very large number of interacting particles. Using the model of interacting spins we demonstrate that this approach gives a correct description of $n_s$ even in a deep quantum region with few single-particle orbitals.Comment: 4 pages, 2 figure

Tests for skewness and kurtosis in the one-way error component model

This paper derives tests for skewness and kurtosis for the panel data one-way error component model. The test statistics are based on the between and within transformations of the pooled OLS residuals, and are derived in a moment conditions framework. We establish the limiting distribution of the test statistics for panels with large cross-section and fixed time-series dimension. The tests are implemented in practice using the bootstrap. The proposed methods are able to detect departures away from normality in the form of skewness and kurtosis, and to identify whether these occur at the individual, remainder, or both error components. The finite sample properties of the tests are studied through extensive Monte Carlo simulations, and the results show evidence of good finite sample performance

Application of the RMF mass model to the r-process and the influence of mass uncertainties

A new mass table calculated by the relativistic mean field approach with the state-dependent BCS method for the pairing correlation is applied for the first time to study r-process nucleosynthesis. The solar r-process abundance is well reproduced within a waiting-point approximation approach. Using an exponential fitting procedure to find the required astrophysical conditions, the influence of mass uncertainty is investigated. R-process calculations using the FRDM, ETFSI-Q and HFB-13 mass tables have been used for that purpose. It is found that the nuclear physical uncertainty can significantly influence the deduced astrophysical conditions for the r-process site. In addition, the influence of the shell closure and shape transition have been examined in detail in the r-process simulations.Comment: to be published in Phys. Rev. C, 22 pages, 9 figure

Carbonation of alkaline paper mill waste to reduce CO2 greenhouse gas emissions into the atmosphere

International audienceThe global warming of Earth's near-surface, air and oceans in recent decades is a direct consequence of anthropogenic emission of greenhouse gases into the atmosphere such as CO2, CH4, N2O and CFCs. The CO2 emissions contribute approximately 60% to this climate change. This study investigates experimentally the aqueous carbonation mechanisms of an alkaline paper mill waste containing about 55 wt% portlandite (Ca(OH)2) as a possible mineralogical CO2 sequestration process. The overall carbonation reaction includes the following steps: (1) Ca release from portlandite dissolution, (2) CO2 dissolution in water and (3) CaCO3 precipitation. This CO2 sequestration mechanism was supported by geochemical modelling of final solutions using PHREEQC software, and observations by scanning electron microscope and X-ray diffraction of final reaction products. According to the experimental protocol, the system proposed would favour the total capture of approx. 218 kg of CO2 into stable calcite/ton of paper waste, independently of initial CO2 pressure. The final product from the carbonation process is a calcite (ca. 100 wt%)-water dispersion. Indeed, the total captured CO2 mineralized as calcite could be stored in degraded soils or even used for diverse industrial applications. This result demonstrates the possibility of using the alkaline liquid–solid waste for CO2 mitigation and reduction of greenhouse effect gases into the atmosphere

Mineral sequestration of CO2 by aqueous carbonation of coal combustion fly-ash

International audienceThe increasing CO2 concentration in the Earth's atmosphere, mainly caused by fossil fuel combustion, has led to concerns about global warming. A technology that could possibly contribute to reducing carbon dioxide emissions is the in-situ mineral sequestration (long term geological storage) or the ex-situ mineral sequestration (controlled industrial reactors) of CO2. In the present study, we propose to use coal combustion fly-ash, an industrial waste that contains about 4.1 wt.% of lime (CaO), to sequester carbon dioxide by aqueous carbonation. The carbonation reaction was carried out in two successive chemical reactions, first, the irreversible hydration of lime. CaO + H2O → Ca(OH)2 second, the spontaneous carbonation of calcium hydroxide suspension. Ca(OH)2 + CO2 → CaCO3 + H2O A significant CaO–CaCO3 chemical transformation (approximately 82% of carbonation efficiency) was estimated by pressure-mass balance after 2 h of reaction at 30 °C. In addition, the qualitative comparison of X-ray diffraction spectra for reactants and products revealed a complete CaO–CaCO3 conversion. The carbonation efficiency of CaO was independent on the initial pressure of CO2 (10, 20, 30 and 40 bar) and it was not significantly affected by reaction temperature (room temperature “20–25”, 30 and 60 °C) and by fly-ash dose (50, 100, 150 g). The kinetic data demonstrated that the initial rate of CO2 transfer was enhanced by carbonation process for our experiments. The precipitate calcium carbonate was characterized by isolated micrometric particles and micrometric agglomerates of calcite (SEM observations). Finally, the geochemical modelling using PHREEQC software indicated that the final solutions (i.e. after reaction) are supersaturated with respect to calcium carbonate (0.7 ≤ saturation index ≤ 1.1). This experimental study demonstrates that 1 ton of fly-ash could sequester up to 26 kg of CO2, i.e. 38.18 ton of fly-ash per ton of CO2 sequestered. This confirms the possibility to use this alkaline residue for CO2 mitigation

ArDM: first results from underground commissioning

The Argon Dark Matter experiment is a ton-scale double phase argon Time Projection Chamber designed for direct Dark Matter searches. It combines the detection of scintillation light together with the ionisation charge in order to discriminate the background (electron recoils) from the WIMP signals (nuclear recoils). After a successful operation on surface at CERN, the detector was recently installed in the underground Laboratorio Subterr\'aneo de Canfranc, and the commissioning phase is ongoing. We describe the status of the installation and present first results from data collected underground with the detector filled with gas argon at room temperature.Comment: 6 pages, 3 figures, Light Detection In Noble Elements (LIDINE 2013