Modeling of a solar dryer for fruit preservation in developing countries

About 25,3 % of the Mozambican population is suffering from undernourishment even though a sufficient amount of food and specifically fruits are produced. Post-harvest losses are estimated to 25 % to 40 % and part of the production is not even harvested due to a short season. A solution has to be found to improve fruit preservation and allow the population to consume what is harvested later. Drying fruits is a solution to preserve them. However, juicy fruits are harder to dry than other fruits since they contain more water. One small-scale solution is drying juicy fruits in a specific membrane which allows water vapour to escape from the fruit or the fruit juice to dry. Those membranes have been proven to provide more efficient drying when place in an airflow or wind. It is possible to couple these membranes with solar dryers technology to control the parameters (temperature, relative humidity, velocity) of such an airflow. Two types of solar dryers are tested : indirect and direct. Both solar dryers are modeled using a CFD tool (COMSOL Multiphysics) and the modeling work is based on former research to elaborate a mathematical model of the dryers physics. The simulations produced by COMSOL allow to study the influence of several parameters (geometry of the solar dryers, ambient conditions, solar dryers materials) and identify the parameters to consider in order to improve the design of the dryers. The results from the modeling are compared to on-site measurements, in Mozambique, in order to calibrate and validate the models

Core-substituted naphthalene diimides: influence of substituent conformation on strong visible absorption

Substitution of the aromatic core of naphthalene diimide (NDI) chromophores by morpholine leads to molecules with strong absorbance in the visible spectrum. The shift of absorption maxima to lower energy is determined not only by the degree of substitution but also by the relative conformation and orientation of the tertiary amine with respect to the plane of the NDI

A High-level Event System for Augmented Reality

3D graphics systems increasingly rely on sophisticated event systems derived from collision detection mechanisms, which support the discretisation of Physics as well as high-level programming and scripting. By contrast, Augmented Reality systems have not yet adopted this approach. We describe the development of a high-level event system on top of the ARToolkit environment incorporating the ODE Physics engine. We first define a typology of events encompassing interactions between virtual objects as well as interactions involving markers. We then describe how these events can be recognised in real-time from elementary collisions detected by the ODE Physics engine. We conclude by discussing examples of high-level event recognitions and how they can support the development of applications

Materials for depollution based on the model of manganese dioxygenase

La utilización intensiva de pesticidas ha traído consigo la presencia de una gran cantidad de moléculas contaminantes en aguas y suelos. Los tratamientos para degradar estas moléculas son caros, por lo que es de gran interés la búsqueda de soluciones más baratas. En el caso de los catecoles, existen enzimas, las catecol-dioxigenasas, que abren el ciclo aromático por oxidación con dioxígeno. Las condiciones suaves y la gran disponibilidad de este oxidante podrían ofrecer una solución para esos problemas de polución. El objetivo de este trabajo de tesis es mimetizar un tipo particular de dioxigenasa, la dioxigenasa de manganeso. Dado que tanto la primera esfera de coordinación como la segunda juegan un papel en la reacción enzimática, el modelo tiene que considerar estos dos aspectos. El sitio activo se modeliza mediante un complejo de manganeso(II) que imita el entorno directo del metal en la enzima. La segunda esfera de coordinación se mimetiza mediante la incorporación de los complejos en sílices mesoporosas funcionalizadas. Éstas recrean el confinamiento presente en la enzima, mientras que los sustituyentes pueden estabilizar los intermedios de la misma manera que los amino ácidos enzimáticos. Capitulo I Este capitulo describe la síntesis y la caracterización de los complejos de manganeso(II). En primer lugar, se han diseñado y caracterizado los ligandos para que no haya interferencias entre la complejación con el ion metálico y el anclaje en la sílice. A continuación, se procedió a la síntesis de los complejos. Los dos primeros cristales obtenidos nos hicieron investigar en dos direcciones: • La síntesis de complejos mononucleares, ya que éstos pueden ser mejores modelos del sitio activo que los dinucleares. • La síntesis de otros complejos dinucleares con objeto de estudiar la interacción entre los dos iones manganeso(II) bajo diferentes ligandos puente o ligandos terminales. En total, se han cristalizado cuatro complejos dinucleares, con cloruro, bromuro o azida. Los complejos con ligandos puente cloro presentan un comportamiento antiferromagnético a baja temperatura mientras que en el resto se observa acoplamiento ferromagnético. En el caso de los compuestos con ligando azida puente, se ha podido establecer, junto con otros valores del acoplamiento magnético J encontrados en la literatura, una relación entre este parámetro magnético y los parámetros estructurales. El estudio EPR del solido y de una disolución de complejos dinucleares nos permitió concluir que los puentes se destruyen al disolver el complejo. Capitulo II En este capítulo se compara la síntesis de sílices mesoporosas LUS clásicas con las sintetizadas con microondas. Hemos optimizado la síntesis con microondas para obtener un material mesoporoso de calidad en un tiempo de síntesis más corto. El tiempo de síntesis ha sido reducido desde un día hasta un par de horas. Más aún, la caracterización de estos materiales ha demostrado que las propiedades mesoporosas se mantienen, es decir, que el material final posee poros de dimensión (3-4 nm) y volumen (0.7-0.9 cm3.g-1) comparables, así como superficies porosas similares (900-1000 m2.g-1). Se puede alcanzar una temperatura máxima de 190 °C en la síntesis con microondas, mientras que esta temperatura degrada el tensoactivo en la síntesis clásica. Además, el aumento de temperatura muestra diferentes comportamientos: • En la síntesis clásica, los poros se agrandan con la temperatura, el volumen permanece constante y la superficie disminuye. • En la síntesis con microondas, el volumen de poro y la superficie siguen la misma tendencia: una disminución entre 130 y 170 °C seguido por un aumento hasta 180 °C y estabilización a 190 °C. Por lo tanto, el aumento de temperatura no tiene el mismo efecto que para la síntesis clásica. Esa diferencia de comportamiento fue interpretada por efectos térmicos y por cambios en la homogeneidad de la calefacción. Demostramos que la síntesis por microondas permite obtener sílices mesoporosas mucho más rápidamente y con una mejor homogeneidad del material. Los efectos de la agitación térmica son mucho menos importantes que los de la velocidad de condensación. Capitulo III En este último capítulo se detalla el diseño de materiales que soportarán los compuestos sintetizados en el primer capitulo. La sílice LUs mesoporosa sintetizada con microondas a 180 °C descrita en el capítulo II, se ha funcionalizado usando la estrategia de Molecular-Stencil Patterning (MSP). Esos materiales se dividen en dos familias: los que contienen una función de anclaje azida y una simple función espaciadora (trimetilsilano) y los que contienen una función de anclaje azida así como una función espaciadora coordinante (piridina). La difracción de rayos X en polvo nos permitió controlar la calidad de la estructura porosa. La cicloadición de Huisgen catalizada con cobre(I) ha sido adaptada para el anclaje de los complejos en las sílices funcionalizadas. Se ha utilizado CuBr(PPh3)3 como catalizador para esta última etapa de anclaje, obteniéndose materiales con un contenido medio en manganeso del 2 % en peso. El estudio EPR ha mostrado que en el material final estaban presentes especies aisladas de manganeso(II) y la adsorción de N2 que los compuestos de manganeso(II) estaban dentro de los poros y que el volumen poroso restante es suficiente para permitir la catálisis dentro del sólido mesoporoso. Las reacciones catalíticas se llevaron a cabo con complejos de manganeso(II) libres como catalizadores y con 4-ter-butilcatecol (4-TBC) así como 3,5-di-ter-butilcatecol (3,5-DTBC) como substratos. Los compuestos de manganeso(II) se comportan como oxidasas, al contrario que la actividad dioxigenasa del enzima: el substrato es oxidado desde alcohol hasta cetona sin incorporación de átomos de oxigeno del dioxígeno. Sin embargo, estos catalizadores son relativamente específicos comparados con otros encontrados en la literatura. La oxidación del 4-TBC con el complejo soportado produce la o-quinona sin otros subproductos como era el caso con los complejos libres.Intensive use of pesticides led to an excess of polluting molecules in water and soil. These molecules requires expensive treatments to be degraded, therefore cheaper alternative solutions are of interest. In the case of catechol derivatives, some enzymes called catechol dioxygenase perform an oxidative cleavage of the aromatic ring using O2 as oxidant. The mild conditions and the large availability of the oxidant make these enzymes a clever solution in such depollution issues. This work aims at providing mimics of a particular kind of dioxygenase enzymes, the manganese-dependent dioxygenases. Given that both first and second coordination spheres plays an important role in enzymes, our model must consider these two aspects. The active site is modelled by a manganese(II) complex that imitates the direct metal ion environment in the enzyme. The second coordination sphere is mimicked by incorporating these complexes inside a functionalized mesoporous silica. Then mesoporosity recreates the confinement present in the enzyme while side functions can play the role of the stabilizing enzymatic amino acids. Chapter I This chapter relates the synthesis and characterization of manganese(II) complexes. First, ligands were designed in such a way that complexation with metal ions and grafting on material would not interfere. Second, manganese(II) complexes were synthesized. The first two crystals we obtained with manganese(II) led us to investigate in two directions: • The synthesis of mononuclear species, which would be closer to the actual enzymatic site. • The synthesis of bridged dinuclear species, in order to study the evolution of the interaction between the two manganese(II) ions upon changes in the nature of the bridge or in the ligand. In total, four dinuclear complexes were obtained with chloride, bromide or azide bridges. Chloride-bridged complex exhibited a weak antiferromagnetic behaviour at low temperature, whereas a ferromagnetic coupling was observed in the three others. Comparing the value of coupling J in the azido-bridged species with other similar species described in the literature allowed us to link this magnetic parameter with structural ones such as the Mn-X-Mn angle (where X is the bridging atom) and the Mn-Mn distance. The EPR study in both solid and liquid states led us to conclude that although these complexes crystalize as a dinuclear unit, manganese centres do not interact anymore when dissolved. Chapter II This chapter compares two synthetic ways of LUS mesoporous silica with conventional and microwave ovens. Microwave synthesis is then optimized to provide mesoporous materials in a shorter time with a good porosity. The total synthesis time was reduced from one day to a couple of hours using the microwave irradiation. More important, characterizations of those materials showed that mesoporous properties are maintained through the process, i.e., the final materials possess similar pore sizes (between 3 and 4 nm), porous volumes (between 0.7 and 0.9 cm3.g-1) and specific surface areas (900 to 1000 m2.g-1). A maximal temperature of 190 °C, impossible to reach without damaging the surfactant in classical syntheses, was reached with microwave oven. Furthermore, increasing the temperature in both protocols enlightened different behaviours: • In the classical synthesis, the pores tend to enlarge upon such increase, the porous volume remains quasi-unchanged, and the specific surface area drops. • In microwave synthesis, porous volume and surface area follow the same trend: a decrease between 130 °C and 170 °C followed by an increase until 180 °C and stabilization at 190 °C. Hence increasing temperature has not the same effect than for classical syntheses which was interpreted by both purely thermal and heating homogeneity effects. We showed that microwave irradiation is a method that allows synthesis of mesoporous silica in much shorter time with a better homogeneity of the final material. The effects of thermal agitation become much less visible compared to the condensation speed ones. Chapter III This last chapter details the design of host materials to support the manganese(II) complexes synthesized in the first chapter. Mesoporous LUS silica synthesized at 180 °C using microwave irradiation described in chapter II were functionalized using the Molecular-Stencil Patterning (MSP) strategy. Host materials synthesized in this study were separated in two families, whether they contain a tethering azide function and a simple spacing function (trimethylsilyl) or a tethering azide function and a coordinating spacing function (pyridine). X-ray powder diffraction allowed controlling the integrity of the porous structure. Huisgen copper-catalyzed cycloaddition was adapted to the grating of complexes into the pores of these silica hosts. Tris(triphenylphosphine) copper bromide was employed as catalyst for this ultimate grafting step, providing solids with an average manganese content of 2 wt%.. EPR study showed that isolated manganese(II) species were indeed present in the final material, and nitrogen sorption isotherm demonstrated that the complexes were inside the pores and that there was enough remaining porous volume to allow catalytic reactions inside the mesopores of the solid. Catalytic reactions were then carried out using some free complexes as catalyst and 4-ter-butylcatechol (4-TBC) and 3,5-di-ter-butylcatechol (3,5-DTBC) as substrates. The complexes exhibit an oxidase activity, contrary to the dioxygenase one in the enzyme: the substrate is oxidized from alcohol to ketone without incorporation of oxygen atoms from dioxygen. However, these catalysts are thus relatively specific compared to other model catalysts described in literature. Oxidation of 4-TBC with supported complexes only provided the o-quinone. While the free catalysts also provided some by-products, this is no longer the case as supported complexes exclusively oxidize the catechol to its quinone form

Behavior and Impact of Zirconium in the Soil–Plant System: Plant Uptake and Phytotoxicity

Because of the large number of sites they pollute, toxic metals that contaminate terrestrial ecosystems are increasingly of environmental and sanitary concern (Uzu et al. 2010, 2011; Shahid et al. 2011a, b, 2012a). Among such metals is zirconium (Zr), which has the atomic number 40 and is a transition metal that resembles titanium in physical and chemical properties (Zaccone et al. 2008). Zr is widely used in many chemical industry processes and in nuclear reactors (Sandoval et al. 2011; Kamal et al. 2011), owing to its useful properties like hardness, corrosion-resistance and permeable to neutrons (Mushtaq 2012). Hence, the recent increased use of Zr by industry, and the occurrence of the Chernobyl and Fukashima catastrophe have enhanced environmental levels in soil and waters (Yirchenko and Agapkina 1993; Mosulishvili et al. 1994 ; Kruglov et al. 1996)

Is sweep-flocculation relevant to saponite aggregation?

International audienceSynthetic saponites with various Cationic Exchange Capacities were aggregated at pH 8.0 in a stirred vessel by hydrolyzed aluminum species. Floc growth was followed by Fraunhoffer laser diffraction and the efficiency of clarification was assessed from conventional residual turbidity and sediment volume measurements. We show that the aggregation mechanisms are layer-charge dependent and can not be described by the widely accepted sweep flocculation model

The role of extracellular polymers on Staphylococcus epidermidis biofilm biomass and metabolic activity

Staphylococcus epidermidis is now well established as being a major nosocomial pathogen, associated with indwelling medical devices. Its major virulence factor is related with the ability to adhere to indwelling medical devices, with consequent biofilm formation. The present study aimed to evaluate the role of polysaccharides and proteins on biofilm biomass and metabolic activity of five S. epidermidis clinical isolates. For this purpose, S. epidermis biofilms, formed on acrylic coupons, were characterized in terms of total biofilm biomass, determined through crystal violet assay, cell concentration, established by colony forming units (CFU) enumeration, and biofilm matrix composition, which was assessed for polysaccharides and proteins content. Biofilm metabolic activity was evaluated by two distinct methods: glucose uptake and XTT reduction assays. According to the results, S. epidermidis strains revealed different abilities for biofilm formation. In fact, some strains were able to form thicker biofilms than others and this is important because biofilm formation is considered one of the major virulence factors of S. epidermidis species. S. epidermidis 1457 was the strain that produced the larger amount of biofilm and strain LE7 was the lowest biofilm producer, and these were also the highest and the lowest polysaccharides producers, respectively. This suggests a certain degree of correlation between exopolysaccharides production and total amount of biomass formed. Besides, comparing the results obtained, in terms of exopolysaccharides production and biofilm cellular activity, it seems clear that a strong production of exopolysaccharides can lead to a decrease in the metabolic activity of cells, which was the case of S. epidermidis 1457. The protein concentration also varied among strains, with the biofilm matrix of S. epidermidis 9142 presenting a higher concentration of proteins comparing to the remaining strains. This fact indicates the different levels of importance that matrix proteins can have on biofilm composition among strains albeit overall, it is suggested that extracellular protein production it is not a determinant factor for biofilm total biomass, despite its qualitative value. In conclusion, this work provided a reliable approach for a better understanding of S. epidermidis biofilms composition and metabolic activity

Bdellovibrio bacteriovorus Inhibits Staphylococcus aureus Biofilm Formation and Invasion into Human Epithelial Cells

Bdellovibrio bacteriovorus HD100 is a predatory bacterium that attacks many Gram-negative human pathogens. A serious drawback of this strain, however, is its ineffectiveness against Gram-positive strains, such as the human pathogen Staphylococcus aureus. Here we demonstrate that the extracellular proteases produced by a host-independent B. bacteriovorus (HIB) effectively degrade/inhibit the formation of S. aureus biofilms and reduce its virulence. A 10% addition of HIB supernatant caused a 75% or greater reduction in S. aureus biofilm formation as well as 75% dispersal of pre-formed biofilms. LC-MS-MS analyses identified various B. bacteriovorus proteases within the supernatant, including the serine proteases Bd2269 and Bd2321. Tests with AEBSF confirmed that serine proteases were active in the supernatant and that they impacted S. aureus biofilm formation. The supernatant also possessed a slight DNAse activity. Furthermore, treatment of planktonic S. aureus with the supernatant diminished its ability to invade MCF-10a epithelial cells by 5-fold but did not affect the MCF-10a viability. In conclusion, this study illustrates the hitherto unknown ability of B. bacteriovorus to disperse Gram-positive pathogenic biofilms and mitigate their virulence.open6

Understanding Disruptive Monitoring Capabilities of Programmable Networks

International audienceThe design shift proposed by OpenFlow, with its simple stateless dataplane, initially contributed to the success of Software-Defined Networks. Its lack of state, however, prevents the implementation of many dataplane algorithms. Network applications must therefore offload stateful operations to the control plane, thereby increasing latency and limiting network scalability. Thus, recent research efforts centered on the addition of stateful properties to switches. In this paper, we discuss the impact of emerging programmable dataplane abstractions on network monitoring. In particular, we investigate the need for dataplane states in the design of scalable monitoring applications. We argue that these abstractions are ill-suited for software switches as they retain hardware-specific limitations. Furthermore, we analyse the impact of stateful dataplane designs on the control plane visibility of the network. Finally, we identify opportunities for improvement in the design of stateful software switches

An emotionally responsive AR art installation

In this paper, we describe a novel method of combining emotional input and an Augmented Reality (AR) tracking/display system to produce dynamic interactive art that responds to the perceived emotional content of viewer reactions and interactions. As part of the CALLAS project, our aim is to explore multimodal interaction in an Arts and Entertainment context. The approach we describe has been implemented as part of a prototype “showcase ” in collaboration with a digital artist designed to demonstrate how affective input from the audience of an interactive art installation can be used to enhance and enrich the aesthetic experience of the artistic work. We propose an affective model for combining emotionally-loaded participant input with aesthetic interpretations of interaction, together with a mapping which controls properties of dynamically generated digital art. 1