Resumo. O presente artigo visa introduzir aspectos implicados nos estudos sobre as dinâmicas migratórias no Oriente Médio e Norte da África (MENA). Nesse sentido, apresentamos algumas dinâmicas históricas de definição dos territórios do que se considera a região MENA, assim como colocamos em relevo a participação desses países no contexto das crises migratórias e humanitárias que tem caracterizado as dinâmicas de mobilidade na e da região. Em tal contexto chamamos à atenção para a politização dos fenômenos migratórios e para as ainda esparsas iniciativas de estudos e pesquisas que analisem as dinâmicas migratórias de países da região MENA para o sul global. Por fim, o artigo introduz as discussões sobre as migrações na região MENA que integram o presente dossier, convidando o leitor para a interlocução com diferentes aproximações teórico-metodológicas sobre o fenômeno migratório naquele contexto.

Abstract. This article aims to introduce aspects involved in studies on migratory dynamics in the Middle East and North Africa (MENA). In this sense, we present some historical dynamics for defining the territories of what is considered the MENA region, as well as highlighting the participation of these countries in the context of the migratory and humanitarian crises that have characterized the dynamics of mobility in and in the region. In such a context, we draw attention to the politicization of migratory phenomena and to the still sparse study and research initiatives that analyze the migratory dynamics of countries in the MENA region to the global south. Finally, the article introduces the discussions on migrations in the MENA region that are part of this dossier, inviting the reader to dialogue with different theoretical-methodological approaches on the migration phenomenon in that context.

Resumo Utilizamos os métodos de entrevista narrativa biográfica e reconstrução de caso biográfico para compreender e explicar as experiências de mobilidade de migrantes da África Ocidental no Brasil. O artigo está fundamentado na sociologia do conhecimento, na sociologia de orientação fenomenológica e na sociologia dos processos e figurações. Os resultados indicam a) a limitação de categorias restritivas para a compreensão do fenômeno, como a baseada em eixos geográficos; b) a necessidade de reconstrução dos deslocamentos anteriores e posteriores dos migrantes para explicar seus cursos migratórios; e c) a tradução dos pertencimentos étnico e religioso e de ativos pessoais e familiares em estratégias que impedem reduzir a explicação das motivações para migrar a determinantes estruturais.

Abstract We used the methods of biographical narrative interview and biographical case reconstruction to understand and explain the experiences of mobility of migrants from West Africa in Brazil. The article is theoretically grounded on the sociology of knowledge, the phenomenological sociology, and the sociology of figurations and processes. The results point out to a) the limitations of the use of restrictive categories for the understanding of the phenomenon, as the ones based on geographic axes; b) the importance of reconstructing the movements of migrants before and after their migration courses; and c) the transformation of ethnic and religious belongings and of personal and family assets in strategies that avoid reducing the causes for migration to structural constraints.

Abstract This work describes the synthesis and applications of amphiphilic polystyrene-block-poly(N-vinyl-2-pyrrolidone) (PS-b-PVP) copolymers as a silver and silica nanoparticle surface modification agent. The synthesis of PS-b-PVP was carried out using controlled/living radical polymerization techniques. The synthesis of the block copolymers was confirmed by gel permeation chromatography and hydrogen nuclear magnetic resonance, presenting a polydispersity index of around 1.4 and number average molecular weight ranging between 10,000-14,000 g mol-1. The PS-b-PVP copolymers were applied as a silver nanoparticle (AgNP) stabilizing agent. These nanoparticles were produced by a single step and presented an 11 ± 1 nm diameter. Furthermore, the PS-b-PVP copolymers were also applied as a silica nanoparticle (SiO2NP) surface modification agent. The SiO2NP were synthesized by the Stöber method presenting a 72 ± 9 nm diameter. The SiO2NP surface modification by adsorption of PS-b-PVP caused the formation of a 5 ± 1 nm thick polymeric layer, providing the SiO2NP with a hydrophobic surface character. The structural and chemical characteristics shown by PS-b-PVP copolymers highlights their versatility for several applications, such as: water-in-oil emulsifier, stabilizing or coupling agents between inorganic particles and polymeric matrices.

A new practical experiment involving silver and gold nanoparticle syntheses was introduced in an inorganic chemistry laboratory course for undergraduate students at the Institute of Chemistry, UNICAMP. The nanoparticles were synthesized by the reduction of silver nitrate and tetrachloroauric acid with sodium borohydride and sodium citrate in an aqueous medium. Stabilities of the suspensions were tested using several different reactants including sodium chloride, polyvinylpyrrolidone, polyvinyl alcohol and cistamine. Changes in optical properties were observed by electronic spectra and also by transmission electronic microscopy, which also yielded data for estimating particle size.

Neste trabalho apresentamos uma nova instrumentação instalada na linha de SAXS do LNLS. Este equipamento permite a realização de experimentos simultâneos e resolvidos no tempo de espalhamento de raios X a baixos e altos ângulos (SAXS/WAXD) e calorimetria diferencial de varredura (DSC). O dispositivo de DSC mostrou-se comparável a equipamentos convencionais, com taxas de variação de temperatura de até 60 °C/min e uma precisão de 0.1 °C. O uso de uma fonte de radiação síncrotron e de detetores de raios X sensíveis à posição permitiu a obtenção de dados com uma resolução temporal de 30 s. A aplicação deste arranjo experimental no estudo da cristalização isotérmica e da fusão em materiais poliméricos é mostrada para o caso da policaprolactona (PCL) e suas blendas com polietileno clorado (PCL/PECl). As experiências mostraram a formação simultânea da estrutura cristalina e da morfologia lamelar nos diferentes estágios da cristalização assim como mudanças na cinética do processo com o tratamento isotérmico e a composição da blenda. Finalmente cabe destacar que experimentos simultâneos de SAXS/WAXD/DSC permitem o estudo de distintos processos abrangendo não apenas os de cristalização, mas também a formação de colóides e géis ou as transições de fase estruturais em diversos materiais.

New instrumentation designed to perform simultaneous time-resolved X-ray scattering experiments at small and wide angles (SAXS/WAXD) as well as differential scanning calorimetry (DSC) has recently been installed at the SAXS beamline of the Laboratório Nacional de Luz Síncrotron. The DSC device proved to be comparable with conventional equipment, allowing temperature variation with rates of up to 60 °C/min with precision of 0.1 °C. The use of a synchrotron radiation source and position sensitive X-ray detectors allows data collection in real time with 30 s resolution. The application of this experimental set-up in the isothermal crystallization and fusion of polymeric materials is given as an example. We present results of experiments with polycaprolactone (PCL) and its blends with chlorinated polyethylene (PCL/PECl), in which the simultaneous appearance of a crystalline structure and lamellar formation can be observed and the rate of process change for different compositions and thermal treatments can be determined. As a concluding remark, we mention that the SAXS/WAXD/DSC simultaneous experiments can also be performed with great advantage in the study of colloids and gel formation, as well as phase transitions in a variety of samples.

An Al-5SiO2 (5 wt% of SiO2) aluminium matrix fiber composite was produced where the reinforcement consists of fossil silica fibers needles. After being heat-treated at 600 °C, the original fiber morphology was retained but its microstructure changed from solid silica to an interconnected (Al-Si)/Al2O3 interlaced structure named co-continuous composite. A technique of powder metallurgy, using commercial aluminium powder and the silica fibers as starting materials, followed by hot extrusion, was used to produce the composite. The co-continuous microstructure was obtained partially or totally on the fibers as a result of the reaction, which occurs during the heat treatment, first by solid diffusion and finally by the liquid Al-Si in local equilibrium, formed with the silicon released by reaction. The internal structure of the fibers was characterized using field emission electron microscope (FEG-SEM) and optical microscopy on polished and fractured samples.