Inégalités et (in)justices spatiales à Maputo

Cette thèse de doctorat porte sur la justice et l’injustice spatiales à Maputo, avec pour objet de recherche les inégalités d’accès aux services urbains (eau potable, collecte des déchets ménagers). Construite sur l’hypothèse d’un lien entre le degré de spatialisation des inégalités d’accès aux services urbains et la formation de sentiments d’injustice, la thèse se détourne toutefois d’un projet normatif sur ce que serait le juste et l’injuste par et dans la production de l’espace. L’enjeu pr..

Inégalités et (in)justices spatiales à Maputo

Cette thèse de doctorat porte sur la justice et l’injustice spatiales à Maputo, avec pour objet de recherche les inégalités d’accès aux services urbains (eau potable, collecte des déchets ménagers). Construite sur l’hypothèse d’un lien entre le degré de spatialisation des inégalités d’accès aux services urbains et la formation de sentiments d’injustice, la thèse se détourne toutefois d’un projet normatif sur ce que serait le juste et l’injuste par et dans la production de l’espace. L’enjeu pr..

Dehydration: coupling centrifuge drainage with microwave drying operation

In solid-liquid separation, the centrifugal drainage operation is an efficient and economic process for particulate suspensions which found main applications in the pharmaceutical, chemical and textile industries. It is often used before a thermal drying, and its interest relies on the elimination of most of the liquid at low energetic cost. Nevertheless, in many cases, the combination of mechanical and thermal operations in the same machine enables to optimize productivity, energy efficiency and safety aspects and to reduce cleaning fluids volumes and handling operations requirements. Microwave drying appears to be the most adapted technology to dry thick cakes in a centrifuge as basket rotation allows homogenizing electromagnetic fields leading to homogeneous heating. The heating is more efficient when the filtration cake is saturated but this process is expensive, so it is more interesting to mechanically dewater the cake and assist the process with microwave drying. Microwave heating should be brought in when mechanical dewatering sharply slows. The objective of this study is the optimization of coupling processes between mechanical dewatering and thermal drying by microwave. To reach this objective the development of a model with complete description of cake desaturation during centrifuge cycles is necessary, to implement thermal energy in order to assist the mechanical operation. To demonstrate the interest of the coupling process and the validity of the model, an instrumented pilot was developed and the first experiments were performed with model suspensions (talc, PVC) and industrial products (textile spool, Spath, etc.). Experimental results yielded to drainage curves during centrifuge cycle for these different products in various experimental conditions. The use of mathematical model allowed comparing experimental drainage curves with model predictions

Production and purification of staphylococcal nuclease in Lactococcus lactis using a new expression-secretion system and a pH-regulated mini-reactor

<p>Abstract</p> <p>Background</p> <p>Staphylococcal (or micrococcal) nuclease or thermonuclease (SNase or Nuc) is a naturally-secreted nucleic acid degrading enzyme that participates in <it>Staphylococcus aureus </it>spread in the infected host. Purified Nuc protein can be used as an exogenous reagent to clear cellular extracts and improve protein purification. Here, a recombinant form of Nuc was produced and secreted in a Gram-positive host, <it>Lactococcus lactis</it>, and purified from the culture medium.</p> <p>Results</p> <p>The gene segment corresponding to the <it>S. aureus </it>nuclease without its signal peptide was cloned in an expression-secretion vector. It was then fused to a lactococcal sequence encoding a signal peptide, and expressed under the control of a lactococcal promoter that is inducible by zinc starvation. An <it>L. lactis </it>subsp <it>cremoris </it>model strain (MG1363) transformed with the resulting plasmid was grown in either of two media (GM17v and CDM) that are free of animal compounds, allowing GMP (Good Manufacturing Practice) production. Induction conditions (concentration of the metal chelator EDTA and timing of addition) in small-scale pH-regulated fermentors were optimized using LacMF (Lactis Multi-Fermentor), a home-made parallel fermentation control system able to monitor 12 reactors simultaneously. Large amounts of recombinant Nuc (rNuc) were produced and secreted in both media, and rNuc was purified from GM17v medium in a single-step procedure.</p> <p>Conclusions</p> <p>In <it>L. lactis</it>, rNuc production and secretion were optimal after induction by 0.5 mM EDTA in small scale (200 mL) GM17v exponential phase cultures (at an OD₆₀₀of 2), leading to a maximal protein yield of 210 mg per L of culture medium. Purified rNuc was highly active, displaying a specific activity of 2000 U/mg.</p

Éditorial du comité de direction. Quoi de neuf après dix numéros ?

Pour le onzième numéro de la revue, l'équipe des Carnets de géographes a fait une pause dans l’élaboration de numéros spéciaux ciblant des domaines de recherches spécifiques et a lancé un appel à contributions pour un numéro non thématique (Varia). La préparation de ce 11ème numéro a également été un moment de réflexion sur la trajectoire de la revue depuis sa création et sur son positionnement dans le paysage éditorial et dans le champ de la géographie. Le comité de direction a souhaité ains..