An old erg covers the northern part of the Lake Chad basin. This dune landform allowed the formation of many interdune ponds of various sizes. Still present in certain zones where the groundwater level is high (e.g. K...An old erg covers the northern part of the Lake Chad basin. This dune landform allowed the formation of many interdune ponds of various sizes. Still present in certain zones where the groundwater level is high (e.g. Kanem, southern Manga), these ponds formed in the past a vast network of lacustrine microsystems, as shown by the nature and the distribution of their deposits. In the Manga, these interdune deposits represent the main sedimentary records of the Holocene environmental succession. Their paleobiological (pollens, diatoms, ostracods) and geochemical (δ18O, δ13C, Sr/Ca) contents are often the basis for paleoenvironmental reconstruction. On the other hand, their sedimentological characters are rarely exploited. This study of palustro-lacustrine deposits of the Holocene N’Guigmi lake (northern bank of the Lake Chad;Niger) is based on the relationships between the sedimentological features and the climato-hydrological fluctuations. The mineralogical parameters (e.g. calcium carbonate content, clay mineralogy) and the nature of autochthonous mineralization (i.e. amorphous silica, clays, calcium carbonates) can be interpreted using a straightforward hydro-sedimentary model. Established to explain the geochemical dynamics of Lake Chad, this model is based on a biogeochemical cycle of the main elements (i.e. silicium, calcium) directly controlled by the local hydrological balance (i.e. rainfall/evaporation ratio). All these results show that a detailed study of sedimentological features can provide important paleohydrological informations about the regional aridification since ca 6500 14C BP.展开更多
Dextran-covered poly(D,L-lactide) (PLA) nano-and microparticles were prepared using an emulsion/solvent evaporation (or diffusion) process for the encapsulation of alkyl gallates (AGs).In the first step,a solution of ...Dextran-covered poly(D,L-lactide) (PLA) nano-and microparticles were prepared using an emulsion/solvent evaporation (or diffusion) process for the encapsulation of alkyl gallates (AGs).In the first step,a solution of PLA and AG in ethyl acetate was emulsified to give an aqueous phase containing a hydrophobically modified dextran,which acted as a stabilizer.The second step involved solvent evaporation or diffusion.The emulsification conditions were varied,which allowed for the preparation of nanoand microparticle suspensions covering a wide range of surface-average particle diameters from 0.1 μm (sonication) to 500 μm (stirring with a magnetic bar),with narrow and reproducible size distributions.Continuous microfluidic emulsification in a flow-focusing system led to well-defined microparticles,in the 10-50 μm range.Particles loaded with octyl gallate (OG) and nonyl gallate (NG) were obtained using the three processes,and we showed that the encapsulation efficiency of OG and NG varied significantly depending on the emulsification process.The effect of particle size on the mechanism of in vitro release of encapsulated AGs was investigated.The kinetics of release were controlled either by Fickian diffusion within the solid core or swelling and hydrolytic degradation of the PLA matrix,depending on the pH of the external medium.展开更多
The history of Formula conferences was summarized with a particular focus on Formula I and Formula Ⅸ (the first and last conferences of the series).The foundation of formulation during the middle of the 1980s by peop...The history of Formula conferences was summarized with a particular focus on Formula I and Formula Ⅸ (the first and last conferences of the series).The foundation of formulation during the middle of the 1980s by people from academia and industry in the fields of chemistry and chemical engineering was briefly overviewed.The current trends in formulation as well as in product engineering were listed.展开更多
基金supported by the AIRD(Agence Inter-établissements de Recherche pour le Développement)through the CORUS2 project entitled“Impact de la pression anthropique et du Changement Global sur les flux sédimentaires en zone sahélienne”(Grant No.6116).
文摘An old erg covers the northern part of the Lake Chad basin. This dune landform allowed the formation of many interdune ponds of various sizes. Still present in certain zones where the groundwater level is high (e.g. Kanem, southern Manga), these ponds formed in the past a vast network of lacustrine microsystems, as shown by the nature and the distribution of their deposits. In the Manga, these interdune deposits represent the main sedimentary records of the Holocene environmental succession. Their paleobiological (pollens, diatoms, ostracods) and geochemical (δ18O, δ13C, Sr/Ca) contents are often the basis for paleoenvironmental reconstruction. On the other hand, their sedimentological characters are rarely exploited. This study of palustro-lacustrine deposits of the Holocene N’Guigmi lake (northern bank of the Lake Chad;Niger) is based on the relationships between the sedimentological features and the climato-hydrological fluctuations. The mineralogical parameters (e.g. calcium carbonate content, clay mineralogy) and the nature of autochthonous mineralization (i.e. amorphous silica, clays, calcium carbonates) can be interpreted using a straightforward hydro-sedimentary model. Established to explain the geochemical dynamics of Lake Chad, this model is based on a biogeochemical cycle of the main elements (i.e. silicium, calcium) directly controlled by the local hydrological balance (i.e. rainfall/evaporation ratio). All these results show that a detailed study of sedimentological features can provide important paleohydrological informations about the regional aridification since ca 6500 14C BP.
文摘Dextran-covered poly(D,L-lactide) (PLA) nano-and microparticles were prepared using an emulsion/solvent evaporation (or diffusion) process for the encapsulation of alkyl gallates (AGs).In the first step,a solution of PLA and AG in ethyl acetate was emulsified to give an aqueous phase containing a hydrophobically modified dextran,which acted as a stabilizer.The second step involved solvent evaporation or diffusion.The emulsification conditions were varied,which allowed for the preparation of nanoand microparticle suspensions covering a wide range of surface-average particle diameters from 0.1 μm (sonication) to 500 μm (stirring with a magnetic bar),with narrow and reproducible size distributions.Continuous microfluidic emulsification in a flow-focusing system led to well-defined microparticles,in the 10-50 μm range.Particles loaded with octyl gallate (OG) and nonyl gallate (NG) were obtained using the three processes,and we showed that the encapsulation efficiency of OG and NG varied significantly depending on the emulsification process.The effect of particle size on the mechanism of in vitro release of encapsulated AGs was investigated.The kinetics of release were controlled either by Fickian diffusion within the solid core or swelling and hydrolytic degradation of the PLA matrix,depending on the pH of the external medium.
文摘The history of Formula conferences was summarized with a particular focus on Formula I and Formula Ⅸ (the first and last conferences of the series).The foundation of formulation during the middle of the 1980s by people from academia and industry in the fields of chemistry and chemical engineering was briefly overviewed.The current trends in formulation as well as in product engineering were listed.
