Human CD25+CD4+ T Suppressor Cell Clones Produce Transforming Growth Factor β, but not Interleukin 10, and Are Distinct from Type 1 T Regulatory Cells

T regulatory (Tr) cells are essential for the induction of peripheral tolerance. Several types of Tr cells exist, including CD4+ T cells which express CD25 constitutively and suppress immune responses via direct cell-to-cell interactions, and type 1 T regulatory (Tr1) cells, which function via secretion of interleukin (IL)-10 and transforming growth factor (TGF)-β. The relationship between CD25+CD4+ T cells and Tr1 cells remains unclear. Here, we demonstrate at the clonal level that Tr1 and CD25+CD4+ T cells are two distinct subsets of regulatory cells with different cytokine production profiles. Furthermore, CD25−CD4+ T cells can be rendered anergic by IL-10 and differentiated into Tr1 cells in the absence of CD25+CD4+ T cells. Cloned human CD25+CD4+ T cell populations are heterogeneous and only a subset of clones continues to express high levels of CD25 and is suppressive. The intensity of CD25, cytotoxic T lymphocyte antigen (CTLA)-4, and glucocorticoid-induced tumor necrosis factor (TNF) receptor expression correlates with the suppressive capacity of the T cell clones. None of the CD25+CD4+ T cell clones with suppressive function produce IL-10, but all produce TGF-β. Suppression mediated by CD25+CD4+ T cell clones is partially dependent on TGF-β, but not on constitutive high expression of CD25. Together these data indicate that naturally occurring human CD25+CD4+ T cells are distinct from IL-10–producing Tr1 cells

Water-Based Synthesis and Enhanced CO2 Capture Performance of Perfluorinated Cerium-Based Metal–Organic Frameworks with UiO-66 and MIL-140 Topology

Reaction of cerium ammonium nitrate and tetrafluoroterephthalic acid in water afforded two new metal–organic frameworks with UiO-66 [F4_UiO-66(Ce)] and MIL-140 [F4_MIL-140A(Ce)] topologies. The two compounds can be obtained in the same experimental conditions, just by varying the amount of acetic acid used as crystallization modulator in the synthesis. Both F4_UiO-66(Ce) and F4_MIL-140A(Ce) feature pores with size <8 Å, which classifies them as ultramicroporous. Combination of X-ray photoelectron spectroscopy and magnetic susceptibility measurements revealed that both compounds contain a small amount of Ce(III), which is preferentially accumulated near the surface of the crystallites. The CO2 sorption properties of F4_UiO-66(Ce) and F4_MIL-140A(Ce) were investigated, finding that they perform better than their Zr-based analogues. F4_MIL-140A(Ce) displays an unusual S-shaped isotherm with steep uptake increase at pressure <0.2 bar at 298 K. This makes F4_MIL-140A(Ce) exceptionally selective for CO2 over N2: the calculated selectivity, according to the ideal adsorbed solution theory for a 0.15:0.85 mixture at 1 bar and 293 K, is higher than 1900, among the highest ever reported for metal–organic frameworks. The calculated isosteric heat of CO2 adsorption is in the range of 38–40 kJ mol–1, indicating a strong physisorptive character

Furanic Humins from Biorefinery as Biobased Binder for Bitumen

To decrease the environmental impact of bitumen, more sustainable binders should be proposed. This study emphasizes how industrial humins co-produced during the biorefining of carbohydrates can be employed as a macromolecular binder for bitumen. Humins are heterogeneous polyfuranic compounds, and they were mixed at 50 wt% with bitumen. When the non-water-soluble fractions of humins were employed (Hns), no variation of the chemical structure was observed in FTIR spectra after the mixing. The DSC investigations showed that the crystallization of aromatic fractions in bitumen shifted to higher temperature for humins&rsquo; modified bitumen. The thermogravimetric data highlighted that the presence of humins or Hns in bitumen can lead to mass loss below 200 &deg;C. The rheological investigations highlighted some key advantages of using humins or Hns with bitumen. At high temperatures, the storage modulus of the modified bitumen is increased and shows lower susceptibility to variations in frequency. At low temperatures, the phase angle of Hns-modified bitumen is lower than that of bitumen, suggesting less temperature susceptibility as a consequence of a cross-linked network formation

Valorisation d'humines issues de biorafineries : vers le développement de thermodurcissables et de composites durables

The production of chemicals via acid-catalysed dehydration of sugars is inevitably related to the formation of co-products. Noteworthy, a black and viscous polymeric co-product called humins can be formed in significant quantities. Humins are heterogeneous and polydisperse macromolecules, mainly constituted by furanic rings and aldehydes, ketones and hydroxyls as main functional groups. For many years, scientists focused on finding a way to avoid humins formation during biorefinery processes but that appears to be almost inevitable. In current biorefinery process designs, humins are burnt to generate heat that can be integrated back into the process. However, the attention is now shifting towards ways to make high value-added products from humins, to further improve the process economics of biorefineries. An extensive analysis of the structure and pysico-chemical properties of humins was performed to support humins application research. Particular attention was paid to the identification of transitions and chemical reactions occurring in humins, by using advanced thermoanalytical techniques. It was demonstrated that it is possible to obtain a thermoset polymer with different properties, based on the treatment used. The cross-linking behaviour was then further elucidated by studying optimal initiators and through a deep investigation on the kinetics of cross-linking. Humin based thermosets were tested for different applications. The potential of all-humins-matrix in combination with natural fibres was investigated. Good interaction between organic matrix and natural fibres was observed, making humins very promising for the next generation of biobased thermoset materials. The use of humins as matrix is a sustainable solution to develop all "green" composites, with high hydrophobic properties and mechanical properties comparable with other biobased thermosets used in several commercial applications. Considering the very good affinity with lignocellulosic materials, a new process option was evaluated for fibre modification to enhance the interaction at the interface between cellulosic fibres and common polymeric matrices such as polypropylene. This study also allowed to get insights into the interactions between cellulose and humins. To further exploit these type of applications, wood modification with humin resin was studied. Dimension and weight stability of the modified wood after immersion in water confirmed improved hydrophobicity of the final material. Mechanical properties were studied by DMA. This study demonstrates that this new impregnation technique can improve the dimensional stability of wood, without compromising on the mechanical properties by valorising humins. Finally, the possibility to use humins as a binder to enhance bitumen’s rheological properties and decrease its environmental impact was investigated.La production de molécules plateformes via la déshydratation des sucres catalysée par un acide est inévitablement liée à la formation de sous-produits. Notamment, un sous-produit appelé humine peut être formé en quantités importantes. Les humines sont des macromolécules hétérogènes et polydisperses, constituées principalement de composés furaniques. Pendant nombreuses années, les scientifiques ont cherché à trouver un moyen d'éviter la formation d'humines au cours des processus de bioraffinage, mais cela semble presque inévitable. Les recherches actuelles se concentrent aujourd’hui sur les moyens de fabriquer des produits à haute valeur ajoutée à partir d'humines, afin d'améliorer la rentabilité des bioraffineries. Une analyse approfondie de la structure et des propriétés physico-chimiques des humines a été réalisée dans ce travail de thèse afin de développer de nouveaux axes de recherche sur les applications potentielles des humines, en particulier l'identification des transitions et des réactions chimiques se produisant dans les humines, en utilisant des techniques thermo-analytiques avancées. Il a été démontré qu'il est possible d'obtenir un polymère thermodurcissable avec différentes propriétés, en fonction du traitement utilisé. Les thermodurcissables à base d'humine ont été testés pour différentes applications. Le potentiel des humines comme matrice en combinaison avec des fibres naturelles afin de réaliser des composites 100 \% biosourcés a été étudié. Une bonne interaction entre la matrice organique et les fibres naturelles a été observée, rendant les humines très prometteuses pour la prochaine génération de matériaux et de composites thermodurcissables biosourcés. L'utilisation d'humines comme matrice est une solution durable pour développer des composites "verts", avec des propriétés hydrophobes et mécaniques élevées. Compte tenu de la très bonne affinité avec les matériaux lignocellulosiques, de nouvelles voies ont été proposées pour la modification des fibres afin de renforcer l’interaction entre les fibres cellulosiques et certaines matrices polymériques, telles que le polypropylène par exemple. Cette étude a également permis de mieux comprendre les interactions entre la cellulose et les humines. Pour exploiter ce type d’applications, la modification du bois avec des humines a été étudiée. La stabilité dans l’eau du bois modifié a confirmé l'amélioration de l'hydrophobicité du matériau final. Cette étude montre que cette nouvelle technique d'imprégnation peut améliorer la stabilité dimensionnelle du bois sans compromettre les propriétés mécaniques tout en valorisant les humines. Enfin, la possibilité d’utiliser des humines comme liant pour améliorer les propriétés rhéologiques du bitume et réduire son impact sur l’environnement a été étudiée

Carbon nanotubes morphology and dispersion in nanocomposites

The unique properties of carbon nanotubes (CNTs) offer great opportunities for nanocomposites with applications in many different sectors. Carbon nanotubes can be found in electronic devices, in application related with transportation, as well as energy and biotechnologies. Currently, the most popular use for carbon nanotubes is as reinforcement for polymer nanocomposites both for electrical and structural applications. CNTs are more efficient compared with other traditional fillers, primarily thanks to the large aspect ratio and surface area which increases the stress transfer and promote the formation of percolation network in the matrix. At the same time, the particular structure of the nanotubes also promotes the aggregation of the nanotubes due to strong Van der Waals attraction between the nanotubes, limiting the final properties of the nanocomposites. The ability to tailor electrical and mechanical properties and to totally employ the potential of CNTs widely depends on the ability to obtain a homogeneous dispersion of the fillers in the polymeric matrix. The influence of the morphology of the CNTs on the dispersion and on the rheological, electrical, mechanical and thermal properties of PC/CNTs and HDPE/CNTs were studied. Different synthesis conditions and different catalysts were tested in order to produce CNTs with different morphology. From the TEM analysis of the samples it was clear that particles produced at high temperature are characterized by larger diameters. Rheology measurements were performed on the samples in order to evaluate the level of dispersion of the nanotubes, showing significant differences between samples produced by different catalysts. Various nanocomposites were produced by micro compounding experiments in order to study the electrical properties of the samples and to discriminate the best ones. Finally, a study concerning the electrical and mechanical properties of specimens produced by injection molding was performed.Master [120] : ingénieur civil en chimie et science des matériaux, Université catholique de Louvain, 201

Valorisation of biorefinery-derived humins : towards the development of sustainable thermosets and composites

La production de molécules plateformes via la déshydratation des sucres catalysée par un acide est inévitablement liée à la formation de sous-produits. Notamment, un sous-produit appelé humine peut être formé en quantités importantes. Les humines sont des macromolécules hétérogènes et polydisperses, constituées principalement de composés furaniques. Pendant nombreuses années, les scientifiques ont cherché à trouver un moyen d'éviter la formation d'humines au cours des processus de bioraffinage, mais cela semble presque inévitable. Les recherches actuelles se concentrent aujourd’hui sur les moyens de fabriquer des produits à haute valeur ajoutée à partir d'humines, afin d'améliorer la rentabilité des bioraffineries. Une analyse approfondie de la structure et des propriétés physico-chimiques des humines a été réalisée dans ce travail de thèse afin de développer de nouveaux axes de recherche sur les applications potentielles des humines, en particulier l'identification des transitions et des réactions chimiques se produisant dans les humines, en utilisant des techniques thermo-analytiques avancées. Il a été démontré qu'il est possible d'obtenir un polymère thermodurcissable avec différentes propriétés, en fonction du traitement utilisé. Les thermodurcissables à base d'humine ont été testés pour différentes applications. Le potentiel des humines comme matrice en combinaison avec des fibres naturelles afin de réaliser des composites 100 \% biosourcés a été étudié. Une bonne interaction entre la matrice organique et les fibres naturelles a été observée, rendant les humines très prometteuses pour la prochaine génération de matériaux et de composites thermodurcissables biosourcés. L'utilisation d'humines comme matrice est une solution durable pour développer des composites "verts", avec des propriétés hydrophobes et mécaniques élevées. Compte tenu de la très bonne affinité avec les matériaux lignocellulosiques, de nouvelles voies ont été proposées pour la modification des fibres afin de renforcer l’interaction entre les fibres cellulosiques et certaines matrices polymériques, telles que le polypropylène par exemple. Cette étude a également permis de mieux comprendre les interactions entre la cellulose et les humines. Pour exploiter ce type d’applications, la modification du bois avec des humines a été étudiée. La stabilité dans l’eau du bois modifié a confirmé l'amélioration de l'hydrophobicité du matériau final. Cette étude montre que cette nouvelle technique d'imprégnation peut améliorer la stabilité dimensionnelle du bois sans compromettre les propriétés mécaniques tout en valorisant les humines. Enfin, la possibilité d’utiliser des humines comme liant pour améliorer les propriétés rhéologiques du bitume et réduire son impact sur l’environnement a été étudiée.The production of chemicals via acid-catalysed dehydration of sugars is inevitably related to the formation of co-products. Noteworthy, a black and viscous polymeric co-product called humins can be formed in significant quantities. Humins are heterogeneous and polydisperse macromolecules, mainly constituted by furanic rings and aldehydes, ketones and hydroxyls as main functional groups. For many years, scientists focused on finding a way to avoid humins formation during biorefinery processes but that appears to be almost inevitable. In current biorefinery process designs, humins are burnt to generate heat that can be integrated back into the process. However, the attention is now shifting towards ways to make high value-added products from humins, to further improve the process economics of biorefineries. An extensive analysis of the structure and pysico-chemical properties of humins was performed to support humins application research. Particular attention was paid to the identification of transitions and chemical reactions occurring in humins, by using advanced thermoanalytical techniques. It was demonstrated that it is possible to obtain a thermoset polymer with different properties, based on the treatment used. The cross-linking behaviour was then further elucidated by studying optimal initiators and through a deep investigation on the kinetics of cross-linking. Humin based thermosets were tested for different applications. The potential of all-humins-matrix in combination with natural fibres was investigated. Good interaction between organic matrix and natural fibres was observed, making humins very promising for the next generation of biobased thermoset materials. The use of humins as matrix is a sustainable solution to develop all "green" composites, with high hydrophobic properties and mechanical properties comparable with other biobased thermosets used in several commercial applications. Considering the very good affinity with lignocellulosic materials, a new process option was evaluated for fibre modification to enhance the interaction at the interface between cellulosic fibres and common polymeric matrices such as polypropylene. This study also allowed to get insights into the interactions between cellulose and humins. To further exploit these type of applications, wood modification with humin resin was studied. Dimension and weight stability of the modified wood after immersion in water confirmed improved hydrophobicity of the final material. Mechanical properties were studied by DMA. This study demonstrates that this new impregnation technique can improve the dimensional stability of wood, without compromising on the mechanical properties by valorising humins. Finally, the possibility to use humins as a binder to enhance bitumen’s rheological properties and decrease its environmental impact was investigated

Kinetics and Chemorheological Analysis of Cross-Linking Reactions in Humins

Humins is a biomass-derived material, co-product of the acid-catalyzed conversion of cellulose and hemicellulose to platform chemicals. This work presents a thorough study concerning the crosslinking kinetics of humins by chemorheological analysis and model-free kinetics under isothermal and non-isothermal curing. Humins can auto-crosslink under the effect of temperature, and the reaction can be fastener when adding an acidic initiator. Thus, the effect of P-Toluenesulfonic acid monohydrate (pTSA) on the crosslinking kinetics was also studied. The dependencies of the effective activation energy (E&alpha;-dependencies) were determined by an advanced isoconversional method and correlated with the variation of complex viscosity during curing. It is shown that humins curing involves multi-step complex reactions and that the use of an acidic initiator allows faster crosslinking at lower temperatures, involving lower E&alpha;. The shift from chemical to diffusion control was also estimated

Kinetics and chemorheological analysis of cross-linking reactions in humins

InvitationInternational audienc

Synthesis, sintering by Cool-SPS and characterization of A2Cu(CO3)2 (A = K, Na): evidence for multiferroic and magnetoelectric cupricarbonates

We report here the synthesis and densification of two magnetic materials in the system A2Cu(CO3)2 (A = Na, K). Based on literature data, the synthesis route has been modified to offer the possibility of gram-scale production with high powder purity. The cool spark plasma sintering (Cool-SPS) method has been used to obtain highly dense samples (>95% of theoretical density). Not only did the sintering method prove its efficiency for giving dense ceramics, but it also extended the stability domain of both compounds to higher temperatures. The case of Na2Cu(CO3)2 is highly instructive of the possibilities offered by the Cool-SPS technique, since the pure phase can be obtained during the sintering process, while it is impossible through conventional heat treatments in a furnace. Obtaining dense ceramics allowed the exploration of dielectric properties, leading to the observation of a step-like anomaly in K2Cu(CO3)2 similar to some multiferroic systems, while Na2Cu(CO3)2 exhibits an interesting magnetocapacitance evolution, probably linked to a magnetoelectric coupling