Ambiguous boundaries between exclusion and inclusion. Experiences from the Meheba Refugee Camp (Zambia)

Refugee camps are often created and portrayed as places of exclusion where “supernumerary” (Bauman 2004), “undesired populations” (Agier 2011) are concentrated. And yet, experiences from the Meheba Refugee Settlement show that the reality is rather more complex, providing evidence of the ambiguous line between inclusion and exclusion involving refugees and the neighbouring population.info:eu-repo/semantics/publishedVersio

Depicting protracted refuge. Postcards from a refugee camp

This essay confronts the viewer with protracted refuge by looking at the Meheba Refugee Camp, Zambia. Created in 1971 and still running well beyond the moment of emergency at its origin, Meheba challenges the generic and generalized visual representation of refugees and refugee camps. This photo-essay seeks to depict how displaced populations forge a life in exile in spite of all the adversities, but also of how the spaces of refuge evolve, consolidate, and become part of the territory in which they are located.info:eu-repo/semantics/publishedVersio

Myelin figures: the buckling and flow of wet soap

Myelin figures are interfacial structures formed when certain surfactants swell in excess water. Here, I present data and model calculations suggesting myelin formation and growth is due to the fluid flow of surfactant, driven by the hydration gradient at the dry surfactant/water interface; a simple model based on this idea qualitatively reproduces the various myelin growth behaviors observed in different experiments. From a detailed experimental observation of how myelins develop from a planar precursor structure, I identify a mechanical instability that may underlie myelin formation. These results indicate the mixed mechanical character of the surfactant lamellar structure, where fluid and elastic properties coexist, is what enables the formation and growth of myelins.Comment: 11 pages, 10 figures, to appear in Phys. Rev. E. Corrected figures/typo

Seeing like a routier: routiers’ borderscapes between Southern Europe and West Africa

Routier is the self-designation employed by Senegalese men driving decades-old vehicles overloaded with mostly second-hand items from Southern Europe to be sold in West Africa. This activity involves navigating a constellation of overlapping politico-administrative, socio-economic, cultural and geographical borders. Building on the concept of borderscapes, whose plasticity and aesthetic qualities allows us to interrogate diverse border universes, this essay visually explores routiers border(ing) enactments and contingent meanings. By seeing like a routier, the piece seeks to feed an on-going debate not only on how to depict borders writ large but also on how certain groups of people embody, see and are seen by contemporary borders.info:eu-repo/semantics/publishedVersio

Manipulação de interações entre proteínas com tratamentos enzimáticos e alta pressão para alterar as propriedades dos alimentos

The demand for proteins is rising and alternatives to animal-based proteins are necessary, either for nutritional or environmental reasons. Plant-based proteins appear as an alternative, however, their techno-functional properties need improvement. High-pressure processing (HPP) is a non-thermal technology that allows modifying proteins’ structure hence allowing to change several of their properties. Enzymes, such as microbial transglutaminase (MTG), can also modify the techno-functional properties of proteins, however, many globular proteins show low susceptibility to the action of this enzyme. HPP, being able to change protein conformation, may be a useful tool to increase the accessibility of proteins to the action of MTG. Nevertheless, HPP conditions need to be carefully optimized to avoid the expected decrease in enzymatic activity when subjected to pressure. Pressure inactivation of MTG under different HPP conditions (200 – 600 MPa; 20 – 40 °C; 10 – 30 min) was evaluated at different pH values. At least 20 % of MTG was inactivated when low pressures (< 300 MPa) were used at pH 4 and 5, whereas a higher pressure (above 400 MPa) was needed to obtain a similar inactivation at pH 6 or 7. MTG pressure-inactivation followed first-order kinetics under all tested conditions. Inactivation rate constants decreased with increasing pressure at constant temperature and pH 4, with a positive activation volume, while the opposite was verified for the other pH values. Both activation energy and volume were dependent on pH. Overall, MTG can be considered relatively resistant to pressure, particularly near its optimal pH. The influence of HPP (200 – 600 MPa; 5 – 15 min) was also evaluated, applied individually or in combination with MTG (up to 30 U·g-1 ), on selected properties of pea (PPI) and soy (SPI) protein isolates with concentrations between 1 and 9 % (w/v). For a protein concentration of 1 % (w/v), HPP increased the protein solubility of both isolates when applied individually. This effect was more pronounced for SPI, particularly at pH 7 and 8. Similarly, the protein surface hydrophobicity also increased with HPP for proteins from both sources, increasing, in general, with increasing pressure and holding time. On the contrary, the content of free sulfhydryl groups decreased with HPP for proteins from both sources. The effects of HPP on the emulsifying properties of the protein isolates, considering both the whole and soluble protein fractions, were dependent on pH and HPP conditions (pressure, holding time). HPP appeared to have minimal effects on the surface tension of both proteins and the general absence of negative effects on emulsifying activity results from HPPinduced protein aggregation effects. On the other hand, MTG individual treatments had no significant effects on the studied properties. For the other protein concentrations studied, HPP increased the solubility of proteins when there were at low initial concentrations, decreasing it when they were in the higher concentration range analysed. Regardless of the concentration, HPP decreased the content of free sulfhydryl groups for pea proteins, however, had the contrary effect on soy proteins. Comparably to the solubility, the surface hydrophobicity increased in low protein concentrations and the contrary was verified in high protein concentrations. MTG decreased solubility and increased the content of free sulfhydryl groups of both proteins. The enzyme decreased the surface hydrophobicity of soy proteins and of the pea proteins, but only when these were within the higher concentration range analysed. When combined, HPP and MTG appear to have antagonistic effects on the solubility and content of free sulfhydryl groups and synergistic effects on viscosity. The obtained results indicate that simultaneous HPP and MTG treatments can be used to modify the proteins’ structure and consequently tailor their techno-functional properties.Verifica-se um crescente aumento da procura por proteínas para satisfazer as necessidades nutricionais da população a nível global, em particular de proteínas vegetais devido a preocupações nutricionais e ambientais. As proteínas de origem vegetal aparecem assim como uma alternativa vantajosa às proteínas de origem animal, no entanto, as suas propriedades tecno-funcionais precisam ser melhor conhecidas e otimizadas. O processamento de alta pressão (AP) é uma tecnologia não térmica que permite modificar a estrutura das proteínas, permitindo alterar várias das suas propriedades. Enzimas, como a transglutaminase microbiana (MTG), também podem modificar as propriedades tecno-funcionais das proteínas, no entanto, muitas proteínas globulares mostram baixa suscetibilidade à ação desta enzima. A AP, capaz de alterar a conformação de proteínas, pode ser uma ferramenta útil para aumentar a acessibilidade das proteínas à ação da MTG. No entanto, as condições de processamento precisam ser adequadamente otimizadas para evitar a diminuição da atividade enzimática quando sujeita a pressão. A inativação da MTG sob diferentes condições de pressão (200 – 600 MPa; 20 – 40 °C; 10 – 30 min) foi avaliada em diferentes valores de pH. Pelo menos 20% da MTG foi inativada quando foram usadas baixas pressões (< 300 MPa) a pH 4 e 5, enquanto foi necessária uma pressão acima de 400 MPa para obter uma inativação semelhante a pH 6 ou 7. A inativação por pressão da MTG seguiu uma cinética de primeira ordem em todas as condições testadas. As constantes cinéticas de inativação diminuíram com o aumento da pressão a uma temperatura constante a pH 4, com um volume de ativação positivo, enquanto o contrário foi verificado para os demais valores de pH. Tanto a energia de ativação quanto o volume de ativação foram dependentes do pH. No geral, a MTG pode ser considerada relativamente resistente à pressão, particularmente próximo do seu pH óptimo. Foi avaliada a influência da pressão (200 – 600 MPa; 5 – 15 min), aplicada individualmente ou em combinação com MTG (até 30 U·g-1 ), sobre propriedades selecionadas de proteínas de ervilha e soja com concentrações entre 1 e 9% (m/v). Para uma concentração de proteína de 1 % (m/v), a AP aumentou a solubilidade da proteína de ambos os isolados quando aplicada individualmente. Da mesma forma, a hidrofobicidade de superfície também aumentou com a AP nas proteínas de ambas as fontes, aumentando, em geral, com o aumento da pressão e do tempo. Pelo contrário, o conteúdo de grupos sulfidrilo livres diminuiu com a pressão nas proteínas de ambas as fontes. O efeito da AP nas propriedades emulsificantes das proteínas, considerando quer a fração total de proteína no isolado, quer a fração solúvel, foi dependente do pH e das condições de AP (pressão, tempo). A AP parece ter efeitos mínimos na tensão superficial de ambas as proteínas e a ausência geral de efeitos negativos na atividade emulsificante resulta dos efeitos de agregação de proteínas induzidas pela AP. Por outro lado, os tratamentos individuais de MTG não produziram efeitos sobre as propriedades estudadas. Para as demais concentrações de proteínas utilizadas, a AP aumentou a solubilidade de dispersões de baixa concentração, diminuindo-a nas mais altas. Independentemente da concentração, a AP diminuiu o conteúdo de grupos sulfidrilo livres para as proteínas de ervilha, no entanto, teve o efeito contrário para as proteínas de soja. Comparativamente à solubilidade, a hidrofobicidade de superfície aumentou para concentrações baixas de proteína e o contrário foi verificado para concentrações altas. A MTG diminuiu a solubilidade e aumentou o conteúdo de grupos sulfidrilo livres de ambas as as proteinas. A enzima diminuiu a hidrofobicidade de superfície de ambas as proteínas quando estas se encontravam em concentração relativamente elevada. Quando combinados, AP e MTG parecem ter efeitos antagonisticos na solubilidade e no conteúdo de grupos sulfidrilo livres e efeitos sinergisticos na viscosidade. Os resultados obtidos indicam que tratamentos simultâneos de AP e MTG podem ser usados para modificar a estrutura das proteínas e consequentemente adaptar suas propriedades tecno-funcionais.Programa Doutoral em Ciência e Tecnologia Alimentar e Nutriçã

Fixed-income arbitrage strategies: swap spread arbitrage and yield curve arbitrage

Abstract. There is a mythical question, well described by Duarte, Longstaff and Yu (2006), whether fixed-income arbitrage strategies are truly arbitrage or merely strategies that earn small positive returns most of the time, but occasionally experience dramatic losses. The question can be summarized in the anecdote “picking up nickels in front of a steamroller”. This master’s thesis studies two of these specific fixed-income arbitrage strategies: Swap Spread Arbitrage and Yield Curve Arbitrage. The methodology used in this master’s thesis is to apply these two arbitrage strategies through time from November 1988 to December 2011, using R language coding developed by the author of the master’s thesis, and to analyze their risk and return characteristics. The data used in this master’s thesis was gathered from different sources such as: Bloomberg™, Federal Reserve System (FED), Thompson Reuters Datastream™, Federal Reserve Bank of St. Louis, Kenneth French and Yahoo® Finance. The main hypothesis of this thesis is that the global financial crisis of 2008 had a big impact on these strategies return indexes. This proved to be wrong. These two fixed-income arbitrage strategies seem profitable on the long run even under financial crisis cycles, as they generate positive excess returns, and Yield Curve Arbitrage strategy even with significant α

Stability of Biaxial Nematic Phase for Systems with Variable Molecular Shape Anisotropy

We study the influence of fluctuations in molecular shape on the stability of the biaxial nematic phase by generalizing the mean field model of Mulder and Ruijgrok [Physica A {\bf 113}, 145 (1982)]. We limit ourselves to the case when the molecular shape anisotropy, represented by the alignment tensor, is a random variable of an annealed type. A prototype of such behavior can be found in lyotropic systems - a mixture of potassium laurate, 1-decanol, and $D_2O$, where distribution of the micellar shape adjusts to actual equilibrium conditions. Further examples of materials with the biaxial nematic phase, where molecular shape is subject to fluctuations, are thermotropic materials composed of flexible trimeric- or tetrapod-like molecular units. Our calculations show that the Gaussian equilibrium distribution of the variables describing molecular shape (dispersion force) anisotropy gives rise to new classes of the phase diagrams, absent in the original model. Depending on properties of the shape fluctuations, the stability of the biaxial nematic phase can be either enhanced or depressed, relative to the uniaxial nematic phases. In the former case the splitting of the Landau point into two triple points with a direct phase transition line from isotropic to biaxial phase is observed.Comment: 18 pages containing 6 figure

Enhancement of the nonlinear optical absorption of the E7 liquid crystal at the nematic-isotropic transition

We present an experimental study of the nonlinear optical absorption of the eutectic mixture E7 at the nematic-isotropic phase transition by the Z-scan technique, under a continuos wave excitation at 532 nm. In the nematic region, the effective nonlinear optical coefficient \beta for an extraordinary beam is negative and for an ordinary beam is positive, being null in the isotropic phase. The parameter S_{NL} defined in terms of the nonlinear absorption coefficients in a similar way than the optical order parameter from the linear dichoic ratio behavies like an order parameter with a critical exponent 0.22+-0.05, in good agreement with the tri-critical hipothesis of the N-I transition.Comment: 11 pages, 6 figures, to be published in the vol 42 of the Brazilian Jurnal of physic