ESCOAMENTO de Materiais Viscoplásticos: Dam Break Flow

Ao longo do último século, o Dam Break Flow vem sendo estudado por muitos autores. A compreensão deste tipo de fenômeno é de grande relevância, uma vez que envolve aplicações em barragens que oferecem múltiplos benefícios para a humanidade. Porém, o rompimento de uma dessas barragens pode trazer consequências indesejáveis e imensuráveis para a sociedade e para o setor de mineração, por exemplo. Neste trabalho estamos interessados em entender como o número de Froude e as propriedades não-newtonianas, particularmente a viscoplasticidade, afetam o perfil de interface do escoamento e a distância alcançada pelo material após o Dam Break Flow. Tais resultados são comparados com o deslocamento de um fluido newtoniano. Através de uma simples abordagem experimental, uma solução de material viscoplástico ou newtoniana incialmente armazenada em um reservatório é instantaneamente liberada. As imagens do escoamento são capturadas durante o teste de duas maneiras diferentes. Uma é feita utilizando uma câmera CCD e a outra é através da Velocimetria por Imagem de Partícula. A partir das imagens obtidas pela câmera CCD, obtém-se um mapa do escoamento, com as suas respectivas velocidades, nível de líquido, formato das interfaces ar-líquido e distância percorrida pelo material são observadas. Já os resultados obtidos com o PIV, são para determinar o campo de velocidade dos momentos iniciais do Dam Break Flow para os diferentes tipos de materiais estudados. Neste trabalho, é mostrado que a plasticidade do material tem total influência sobre a distância alcançada pelo escoamento e também resultam em instabilidades ao longo do mesmo. Foi ainda identificado que o fluido viscoplástico alcança velocidades iniciais maiores que o caso newtoniano. Porém, no decorrer do escoamento, decrescem rapidamente. Quando analisado o caso viscoplástico para um leito com rugosidade, nota-se que para uma superfície lisa, há deslizamento do material de forma significativa para altos valores de plasticidade. Através da análise com PIV, foi constatado que a velocidade de frente de onda é um pouco menor do que a velocidade máxima obtida pelo escoamento. Palavras chave: Dam Break Flow, material viscoplástico, PIV, plasticidade, deslizamento

Identificação de novos inibidores de urease de interesse agrícola.

FertBio 2014

Exploring the Subtle Effect of Aliphatic Ring Size on Minor Actinide-Extraction Properties and Metal Ion Speciation in Bis-1,2,4-Triazine Ligands

Calling all actinides! Bis-1,2,4-triazine ligands bearing five-membered rings were synthesized and evaluated as actinide-selective extractants. Tuning the size of the aliphatic ring leads to subtle changes in actinide-extraction properties. The origins of these changes were elucidated at the molecular level, paving the way for the rational design of improved actinide-selective extractants for reprocessing of spent nuclear fuel., The synthesis and evaluation of three novel bis-1,2,4-triazine ligands containing five-membered aliphatic rings are reported. Compared to the more hydrophobic ligands 1–3 containing six-membered aliphatic rings, the distribution ratios for relevant f-block metal ions were approximately one order of magnitude lower in each case. Ligand 10 showed an efficient, selective and rapid separation of AmIII and CmIII from nitric acid. The speciation of the ligands with trivalent f-block metal ions was probed using NMR titrations and competition experiments, time-resolved laser fluorescence spectroscopy and X-ray crystallography. While the tetradentate ligands 8 and 10 formed Ln$^{III}$ complexes of the same stoichiometry as their more hydrophobic analogues 2 and 3, significant differences in speciation were observed between the two classes of ligand, with a lower percentage of the extracted 1:2 complexes being formed for ligands 8 and 10. The structures of the solid state 1:1 and 1:2 complexes formed by 8 and 10 with Y$^{III}$, Lu$^{III}$ and Pr$^{III}$ are very similar to those formed by 2 and 3 with Ln$^{III}$. Ligand 10 forms Cm$^{III}$ and Eu$^{III}$ 1:2 complexes that are thermodynamically less stable than those formed by ligand 3, suggesting that less hydrophobic ligands form less stable An$^{III}$ complexes. Thus, it has been shown for the first time how tuning the cyclic aliphatic part of these ligands leads to subtle changes in their metal ion speciation, complex stability and metal extraction affinity

Eficiência no solo e estabilidade térmica de novos inibidores de urease.

FertBio 2014

Efeito de novos inibidores de urease no desenvolvimento de Pennisetum glaucum L.

FertBio 2014

Programa de melhoramento genético de pupunha na Embrapa, IAC e INPA.

Estado da arte; Recursos genéticos; Estratégias de melhoramento; Desenvolvimento experimental.bitstream/item/30975/1/Doc205.pd

Schiff bases: A short review of their antimicrobial activities

AbstractSchiff bases are aldehyde- or ketone-like compounds in which the carbonyl group is replaced by an imine or azomethine group. They are widely used for industrial purposes and also exhibit a broad range of biological activities. This short review compiles examples of the most promising antimalarial, antibacterial, antifungal, and antiviral Schiff bases. An overview of synthetic methodologies used for the preparation of Schiff bases is also described

Modeling and Flowsheet Design of an Am Separation Process Using TODGA and H₄TPAEN

Recycling americium from spent fuels is an important consideration for the future nuclear fuel cycle, as americium is the main contributor to the long-term radiotoxicity and heat power of the final waste, after separation of uranium and plutonium using the PUREX process. The separation of americium alone from a PUREX raffinate can be achieved by co-extracting lanthanide (Ln(III)) and actinide (An(III)) cations into an organic phase containing the diglycolamide extractant TODGA, and then stripping Am(III) with selectivity towards Cm(III) and lanthanides. The water soluble ligand H4TPAEN was tested to selectively strip Am from a loaded organic phase. Based on experimental data obtained by Jülich, NNL and CEA laboratories since 2013, a phenomenological model has been developed to simulate the behavior of americium, curium and lanthanides during their extraction by TODGA and their complexation by H4TPAEN (complex stoichiometry, extraction and complexation constants, kinetics). The model was gradually implemented in the PAREX code and helped to narrow down the best operating conditions. Thus, the following modifications of initial operating conditions were proposed: • An increase in the concentration of TPAEN as much as the solubility limit allows. • An improvement of the lanthanide scrubbing from the americium flow by adding nitrates to the aqueous phase. A qualification of the model was begun by comparing on the one hand constants determined with the model to those measured experimentally, and on the other hand, simulation results and experimental data on new independent batch experiments. A first sensitivity analysis identified which parameter has the most dominant effect on the process. A flowsheet was proposed for a spiked test in centrifugal contactors performed with a simulated PUREX raffinate with trace amounts of Am and Cm. If the feasibility of the process is confirmed, the results of this test will be used to consolidate the model and to design a flowsheet for a test on a genuine PUREX raffinate. This work is the result of collaborations in the framework of the SACSESS European Project