An experimental study of the partitioning of trace elements between rutile and silicate melt as a function of oxygen fugacity

Subduction zone or arc magmas are known to display a characteristic depletion of High Field Strength Elements (HFSE) relative to other similarly incompatible elements, which can be attributed to the presence of the accessory mineral rutile (TiO2) in the residual slab. Here we show that the partitioning behavior of vanadium between rutile and silicate melt varies from incompatible (~0.1) to compatible (~18) as a function of oxygen fugacity. We also confirm that the HFSE are compatible in rutile, with D(Ta) > D(Nb) >> (D(Hf) >/~ D(Zr), but that the level of compatibility is strongly dependent on melt composition, with partition coefficients increasing about one order of magnitude with increasing melt polymerization (or decreasing basicity). Our partitioning results also indicate that residual rutile may fractionate U from Th due to the contrasting (over 2 orders of magnitude) partitioning between these two elements. We confirm that, in addition to the HFSE, Cr, Cu, Zn and W are compatible in rutile at all oxygen fugacity conditions

Inline Plasma Analysis as Tool for Process Monitoring in Laser Micro Machining for Multi-layer Materials

AbstractLaser micro machining is an innovative manufacturing technology with a wide range of processable materials and a high level of flexibility. Especially for processing multi-layer materials it is a tool for surface structuring and subsequent functionalization. The manufacturing of e.g. conductor paths for solar cells or batteries requires specific ablation depths on multi-layer materials in order to reveal conducting layers as functional conductor paths. To achieve an ablation of a specific, layer an in-line process monitoring can be used to warrant a robust manufacturing preventing damage on further surface layers. With regards on the need of material specific ablation parameters, this paper addresses the development of a measurement system based on laser induced breakdown spectroscopy (LIBS) as a tool for real-time process monitoring by in-line plasma analysis. The presented results show the specific plasma emission variation at layer interfaces, which can be used for real-time feedback process control with the goal of minimizing the ablation of further layers

Estado de jogo : uma proposta pedagógica a partir de práticas lúdicas

O presente trabalho tem como objetivo apresentar uma proposta pedagógica, composta por seis aulas com base em práticas lúdicas desenvolvidas e pesquisadas pelo autor. As aulas ministradas demonstraram que os participantes atingiram um estado de jogo. Este trabalho também aborda algumas das referências de estudos presentes na literatura que utilizam de conceitos parecidos e que já foram sistematizados, auxiliando no desenvolvimento da compreensão das práticas propostas. A proposta pedagógica foi desenvolvida durante o Estágio de Docência II do autor, que ministrou as aulas de Teatro no Colégio de Aplicação da UFRGS para alunos do Segundo Ano do Ensino Médio. A proposta desenvolvida é composta por quatro momentos que buscam estimular o prazer de jogar, instigando a disponibilidade e trazendo o aluno jogador para o momento presente, resultando em uma série de benefícios à realização de basicamente qualquer jogo que o indivíduo possa ser apresentado

A política externa brasileira para a África de Lula a Temer: mudança matricial em meio à crise

Brazilian foreign policy towards Africa has suffered a major inflection from the 2000s. The rise to power of Luiz Inácio (Lula) da Silva underscored a clear change in Brazilian Foreign Policy paradigms, leading to a resumption of the assignment of importance to the African continent. Since Dilma Rousseff’s first term, started in 2011, relations with the continent have lost weakened as a result of internal and external constraints, although they have maintained their relevance to the country — both politically and economically. With Michel Temer’s rise to power in 2016, there was a reorientation in Brazilian foreign policy general lines, calling into question the space occupied by the African continent throughout the 2000s. This paper, thus, seeks to analyze the impact imposed by the Temer administration to the Brazilian foreign policy to Africa. To this end, it relies mainly on the works of Charles Herman (1990), with the aim of analyzing the different levels of foreign policy change, and of Ricardo Sennes (2003), in order to demonstrate that the foreign policy matrix that marked the Lula and Rousseff governments is distinct from that of Temer government. A política externa brasileira para a África sofreu inflexão durante os anos 2000. A posse de Luiz Inácio (Lula) da Silva marcou uma clara mudança nos paradigmas da política externa brasileira, acarretandoa retomada da atribuição de importância ao continente africano. A partir do primeiro mandato de Dilma Rousseff, em 2011, as relações com o continente vivenciaram um enfraquecimento, resultado decondicionamentos internos e externos, ainda que tenham mantido sua relevância para a política externa brasileira tanto em termos políticos, quanto econômicos. Com a ascensão de Michel Temer ao poder, em2016, operou-se uma reorientação nas linhas gerais da política externa brasileira, colocando em questão o espaço ocupado pelo continente africano ao longo dos anos 2000. Nesse sentido, este trabalho avalia os impactos que a política externa brasileira para o continente africano sofreu a partir de Temer. Para tanto, apoia-se sobretudo nos trabalhos de Charles Hermann (1990), com o intuito de analisar os diferentes níveis de mudança de política externa; e de Ricardo Sennes (2003), com o objetivo de demonstrar que a matriz de política externa que marcou os governos Lula e Dilma é distinta daquela do governo Temer

Development of a biosponge based on Luffa cylindrica and crosslinked chitosan for Allura red AC adsorption

A new bioadsorbent from Luffa cylindrica and cross-linked chitosan was proposed in the present study. Luffa was used as a natural support medium for chitosan crosslinked with glutaraldehyde (LCsG) and epichlorohydrin (LCsE). Biosponges were applied to remove Allura red from aqueous solutions. LCsG and LCsE were produced using different concentrations of chitosan (1%, 3% and 5% (m v−1)) and crosslinking agents (0.5%, 1.0% and 1.5% (v v−1)). Based on the FT-IR spectra, functional groups characteristic of chitosan crosslinked with glutaraldehyde and epichlorohydrin confirmed the crosslinking. In addition, the biosorbent revealed highly efficient functional groups and morphology with irregularities favorable for adsorption. It was found that the increase in the percentage of glutaraldehyde and epichlorohydrin increased the sample's swelling degree, and the degree of cross-linking was greater than 80% for all LCsG. The results regarding the degree of swelling and degree of crosslinking corroborated with the evaluation of the biosponge's adsorptive potential. The Sips model predicted the equilibrium isotherms, with a maximum adsorption capacity of 89.05 mg g−1 for LCsG and 60.91 mg g−1 for LCsE. The new procedure was successful. Luffa was excellent support for chitosan, resulting in an attractive, low-cost bioadsorbent, preventing renewable sources

The Macquarie Deformation-DIA facility at the Australian Synchrotron: A tool for high-pressure, high-temperature experiments with synchrotron radiation

The Macquarie University Deformation-DIA (MQ D-DIA) multi-anvil apparatus at the Australian Synchrotron provides a new experimental facility that enables simultaneous high-pressure and high-temperature in situ synchrotron experimentation in Australia. The MQ D-DIA can be easily deployed at any of a number of beamlines at the Australian Synchrotron, and we describe its installation at the x-ray absorption spectroscopy beamline, which enables in situ x-ray absorption near-edge spectroscopy and energy-scanning x-ray diffraction. A simple, reliable, and x-ray transparent high-pressure cell assembly has been developed for the D-DIA for which load/pressure and heater power/temperature relationships have been calibrated using in situ x-ray diffraction and "offline"mineral equilibration experiments. Additionally, we have mapped temperature distribution within the assembly using a new quantitative electron microprobe mapping technique developed for fine-grained polyphase samples. We are now investigating the speciation of geologically important trace elements in silicate melts (e.g., Zr, U, and Th) measured in situ under high pressure and temperature conditions corresponding to the Earth's mantle. Pressure-dependent changes in speciation influence partitioning behavior, and therefore the distribution in the Earth, of many trace elements. However, previous ex situ investigations are hampered by uncertainty as to whether high-pressure speciation can be faithfully recorded in samples recovered to ambient conditions. We present preliminary results showing an increase in the coordination number of Zr dissolved as a trace component of a sodium-rich silicate melt with pressure. These results also indicate that silicate melt composition exerts a strong influence on Zr speciation.We acknowledge the support from the Australian Research Council LIEF grant (Grant No. LE120100076) to Macquarie University, the Australian National University, and Monash University. We also acknowledge the facilities and the scientific and technical assistance of Microscopy Australia at the Advanced Imaging Precinct, Australian National University, a facility that is funded by the University, and State and Federal Governments, and in particular the assistance of Jeff Chen with EPMA analysis. N.F. acknowledges the support from a Ph.D. scholarship funded through Australian Research Council Grant No. FL130100066 awarded to Professor Hugh O’Neill. G.M. acknowledges support from the Australian Research Council (Grant No. DE160100169)

Caraterização por Microssonda Eletrônica dos Teores de Cloro de Apatitas e sua Importância nos Estudos de Traços de Fissão

Apatite Fission Track Analysis (AFTA) provides important information for geochronology and is used in different tectonic settings. For example, in the study of sedimentary basins it helps estimate subsidence rates and dates periods of uplift of source areas and tectonic pulses. In geomorphology AFTA also helps to quantify rates of erosion and long-term continental denudation. The chlorine contents in apatites influences the ages obtained from fission track dating. Commonly, apatites with more than 0,4 wt% chlorine yield older ages than fluorapatites (Laslett, et al., 1987), because the stability of the tracks changes as chlorine content increases and consequently chlorine rich-apatites are more resistant to the temperature changes than fluorapatites (Green, 1992). We investigated this problem by first determining the chlorine contents of apatites with the microprobe before apatite fission track dating. We studied four samples of the sandstones from the Reconcavo and Camamu Basins using a total of 198 spots in different apatites. We calibrated CAMECA SX50 electron microprobe using 30 spots from the crystal fragment Durando apatite standard, which has a mean chlorine value of 0,42 wt%. The comparison of the chlorine contents of the apatites of these basins with the ages obtained by AFTA indicates some changes in the individual grains in two samples. These changes are related with the current chlorine content in the apatites, once the individual ages are sometimes distributed as straight line, whose inclination is function of the chlorine content. In the other hand, two samples with modest chlorine content there was not this linear correlation

Petrografia das rochas vulcânicas do Pontal Hardy, Ilha Greenwich, arquipélago Shetland do Sul, Antártica : resultados preliminares

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Xenólitos mantélicos do Cerro Agua Poca, província de La Pampa, Argentina : estudo de caso

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