L’or vert du Gabon : une synthèse bibliographique de trente années de recherche sur l’okoumé (Aucoumea klaineana Pierre)

peer reviewedIntroduction. Aucoumea klaineana Pierre is the most harvested timber species in Central Africa and plays a key role in the economy of Gabon. This tree is considered “Vulnerable” for more than three decades by the IUCN because its population is assumed to have been reduced by at least 50% as a result of logging. The objective of this review is to synthesize recent and relevant knowledge in order to update this status. It focuses more specifically on ecology, population dynamics, silviculture and impacts of logging. Literature. Its natural range mainly covers Gabon. It is a light-demanding and gregarious species that forms root anastomoses. It principally establishes itself in abandoned fields and savannahs. In mature forest its regeneration is rare and limited to large gaps. Selective logging only allows significant regeneration along roads. However, at the scale of Gabon, the species is abundant and its renewal is ensured. Legal logging does not threaten the species. However, after decades of logging focusing on best shaped trees, a production of lower quality is feared. The implementation of a thoughtful silviculture could be a solution. Conclusions. Aucoumea klaineana is not vulnerable under IUCN A1 criterion. However, the maintenance of a high-quality production over the long term calls for the implementation of silviculture based on a thorough knowledge of the factors affecting stand dynamics, especially the role of the rhizosphere. Although long described, the functioning of root anastomoses has never been studied in depth.Introduction. Aucoumea klaineana Pierre est l’essence de production la plus exploitée d’Afrique centrale et elle joue un rôle fondamental dans l’économie du Gabon. Elle est considérée comme « Vulnérable » depuis plus de trois décennies par l’UICN car sa population est supposée avoir été réduite d’au moins 50 % à cause de l’exploitation forestière. L’objectif de cette revue est de synthétiser les connaissances récentes et pertinentes afin d’actualiser ce statut. Elle se concentre plus particulièrement sur l’écologie, la dynamique des populations, la sylviculture et les impacts de l’exploitation forestière. Littérature. Il s’agit d’une espèce quasi endémique au Gabon. Elle est héliophile, grégaire et forme des anastomoses racinaires. Elle se régénère principalement dans les champs abandonnés et les savanes. Sa régénération en forêt mature est rare et limitée aux trouées de grande dimension. L’exploitation forestière sélective ne permet une régénération significative que le long des routes. Toutefois, à l’échelle du Gabon, l’espèce est abondante et sa régénération assurée. L’exploitation forestière, si elle respecte les normes légales, ne menace pas l’espèce. Cependant, s’étant focalisée pendant des décennies sur les plus beaux pieds, une production de moindre qualité est redoutée. La mise en œuvre de plantations et d’autres méthodes de régénération pourraient y remédier. Conclusions. Aucoumea klaineana n’est pas une espèce vulnérable selon le critère A1 de l’UICN. Néanmoins, le maintien d’une production de qualité sur le long terme nécessite la mise en place d’une sylviculture basée sur une connaissance approfondie des facteurs affectant la dynamique des peuplements, notamment le rôle de la rhizosphère. Bien que des anastomoses racinaires aient été décrites depuis longtemps, leur fonctionnement n’a jamais été étudié

Gabon's green gold: a bibliographical review of thirty years of research on okoume (Aucoumea klaineana Pierre)

Introduction. Aucoumea klaineana Pierre is the most harvested timber species in Central Africa and plays a key role in the economy of Gabon. This tree is considered “Vulnerable” for more than three decades by the IUCN because its population is assumed to have been reduced by at least 50% as a result of logging. The objective of this review is to synthesize recent and relevant knowledge in order to update this status. It focuses more specifically on ecology, population dynamics, silviculture and impacts of logging. Literature. Its natural range mainly covers Gabon. It is a light-demanding and gregarious species that forms root anastomoses. It principally establishes itself in abandoned fields and savannahs. In mature forest its regeneration is rare and limited to large gaps. Selective logging only allows significant regeneration along roads. However, at the scale of Gabon, the species is abundant and its renewal is ensured. Legal logging does not threaten the species. However, after decades of logging focusing on best shaped trees, a production of lower quality is feared. The implementation of a thoughtful silviculture could be a solution. Conclusions. Aucoumea klaineana is not vulnerable under IUCN A1 criterion. However, the maintenance of a high-quality production over the long term calls for the implementation of silviculture based on a thorough knowledge of the factors affecting stand dynamics, especially the role of the rhizosphere. Although long described, the functioning of root anastomoses has never been studied in depth

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Co-valorization of sediments incorporating high and low organic matter with alkali-activated GGBS and hydraulic binder for use in road construction

International audienceThis study investigates the valorization of dredged sediments containing high and low organic matter (OM) content with alkali-activated ground granulated blast furnace slag (GGBS) and conventional hydraulic binders (HB). The objective is to develop a sustainable material with the necessary qualities for road construction. Research is conducted on dredged sediments from the French port of Cherbourg (CHER-ALL sediments) and the dam in the Maurienne Valley of France (MOR-ALL sediments), with high and low levels of OM content, respectively. After the determination of physico-chemical and mineralogical characteristics, high organic CHER-ALL sediments were first valorized using conventional HB and then co-valorized using low carbon footprint alkaline activated byproducts (AAB). The alkali activation of the byproduct (GGBS) was performed with a chemical activator named NeoliX. AAB and HB were utilized to treat the dredged sediments to compare their mechanical performances as well as environmental impacts. In terms of mechanical performance, the obtained results revealed that AAB outperformed traditional HB, and concerning the environmental impacts, byproducts have no carbon footprint except for their transportation. As a consequence, AAB has also been utilized to co-valorize the sediments from the Maurienne dam (MOR-ALL sediments) as well. AAB co-valorization of these two sediments (CHER-ALL and MOR-ALL) with varying degrees of OM content facilitates an understanding of the effects of OM concentration on mechanical properties. The high OM content of the CHER-ALL sediment (>17%), regardless of the proposed mixing with traditional HB, proved to impede the valorization, since the 28-day UCS did not exceed 1 MPa. The CBR as well as ultimate tensile strength (UTS) testing confirms the reported trends from the UCS experiments. In addition, the presence of a high OM concentration significantly decreased the mechanical properties of dredging sediments co-valorized with AAB. However, depending on the mass percentage of sediment (wt%) in the mix design, it was achievable to attain the required minimum strength value of 1 MPa with 30% and 70% of CHER-ALL and MOR-ALL sediments, respectively. Even if the OM content of sediments is high, alkaline activation can be employed to co-valorize them, as demonstrated by these encouraging results. The quantity of sediment to be co-valorized is depend upon their OM content

Valorization of a Highly Organic Sediment: From Conventional Binders to a Geopolymer Approach

International audienceThe objective of this research is to investigate the possible reuse of dredged sediments from the port of Cherbourg, France, as an alternative material in road engineering and as a backfill material. These dredged sediments contain high percentages of organic matter (OM), and the presence of OM in the sediment, even in small amounts, can affect the engineering properties of sediments. This research was carried out in two series: the sediment was treated with traditional hydraulic binders (ordinary Portland cement (OPC), calcium sulfo-aluminate (CSA) cement, quarry sand (QS), lime, and a combination of them) in the first series, and with pozzolanic binders in the second series (ground-granulated blast-furnace slag (GGBS) and fly ash (FA)), along with the introduction of an activator. According to French legislation, these two pozzolanic binders (GGBS and FA) have no carbon footprint as they are industrial by-products, and therefore, the second series of this research is considered to be highly eco-friendly and economical. Sediment treated with hydraulic binders yielded a maximum value of unconfined compressive strength (UCS) of 1 MPa at 28 days. Out of eight formulations made using traditional binders, only one formulation barely met the French criteria to be used in the sub-base layer of roads. The development of geopolymer using alkali-activated GGBS and then the incorporation of 30% sediments yielded a UCS value above 2 MPa at 28, 60, 90, and 180 days. Furthermore, the addition of 5% lime and 3% granular calcium carbonate in the same mixture (geopolymer + 30% sediments) increased the UCS by up to 60% and 90%, respectively

Decrease in the photosynthetic performance of temperate grassland species does not lead to a decline in the gross primary production of the ecosystem

Plants, under stressful conditions, can proceed to photosynthetic adjustments in order to acclimatize and alleviate the detrimental impacts on the photosynthetic apparatus. However, it is currently unclear how adjustment of photosynthetic processes under environmental constraints by plants influences CO2 gas exchange at the ecosystem-scale. Over a two-year period, photosynthetic performance of a temperate grassland ecosystem was characterized by conducting frequent chlorophyll fluorescence (ChlF) measurements on three primary grassland species (Lolium perenne L., Taraxacum sp., and Trifolium repens L.). Ecosystem photosynthetic performance was estimated from measurements performed on the three dominant grassland species weighed based on their relative abundance. In addition, monitoring CO2 fluxes was performed by eddy covariance. The highest decrease in photosynthetic performance was detected in summer, when environmental constraints were combined. Dicot species (Taraxacum sp. and T. repens) presented the strongest capacity to up-regulate PSI and exhibited the highest electron transport efficiency under stressful environmental conditions compared with L. perenne. The decline in ecosystem photosynthetic performance did not lead to a reduction in gross primary productivity, likely because increased light energy was available under these conditions. The carbon amounts fixed at light saturation were not influenced by alterations in photosynthetic processes, suggesting photosynthesis was not impaired. Decreased photosynthetic performance was associated with high respiration flux, but both were influenced by temperature. Our study revealed variation in photosynthetic performance of a grassland ecosystem responded to environmental constraints, but alterations in photosynthetic processes appeared to exhibit a negligible influence on ecosystem CO2 fluxes

Casein micelles as sticky colloidal microgel particles

Casein micelles, which make up to 80% of the protein content of milk, are one of the most common "association colloids". They are highly hydrated (~85% w/w of water) and roughly spherical particles of ~100 nm in diameter. In a variety of dairy processing operations (membrane filtration, spray-drying...), milk is concentrated leading to dense, and ultimately, solid dispersions of casein micelles. We recently performed osmotic pressure and rheological measurements in order to explore how the micelles behave and interact in such conditions and to understand the resulting phase (or "dynamical arrest") behavior.Our results indicate that strong analogies exist between casein micelles and some "model" colloidal systems. In conditions where the micelles are separated from each other, the dispersions have the exact properties of the polydisperse hard-sphere fluid; with viscosities and osmotic pressures that increase significantly approaching close packing (C » 180 g/L). As concentration is further increased, the micelles are pushed against each other and stick one to another. The dispersions turn into soft solids that strongly resist to osmotic compression. Remarkably, the variation in the elastic properties with C is then very similar to that observed with deformable colloids like nano-emulsions droplets or microgel particles

Casein micelles as sticky colloidal microgel particles

Casein micelles, which make up to 80% of the protein content of milk, are one of the most common "association colloids". They are highly hydrated (~85% w/w of water) and roughly spherical particles of ~100 nm in diameter. In a variety of dairy processing operations (membrane filtration, spray-drying...), milk is concentrated leading to dense, and ultimately, solid dispersions of casein micelles. We recently performed osmotic pressure and rheological measurements in order to explore how the micelles behave and interact in such conditions and to understand the resulting phase (or "dynamical arrest") behavior.Our results indicate that strong analogies exist between casein micelles and some "model" colloidal systems. In conditions where the micelles are separated from each other, the dispersions have the exact properties of the polydisperse hard-sphere fluid; with viscosities and osmotic pressures that increase significantly approaching close packing (C » 180 g/L). As concentration is further increased, the micelles are pushed against each other and stick one to another. The dispersions turn into soft solids that strongly resist to osmotic compression. Remarkably, the variation in the elastic properties with C is then very similar to that observed with deformable colloids like nano-emulsions droplets or microgel particles