European University of Brittany

About: European University of Brittany is a education organization based out in Rennes, France. It is known for research contribution in the topics: Population & Context (language use). The organization has 2855 authors who have published 3115 publications receiving 75994 citations.

Structural built-up of cement-based materials used for 3D-printing extrusion techniques

Abstract: Additive manufacturing and digital fabrication bring new horizons to concrete and cement-based material construction. 3D printing inspired construction techniques that have recently been developed at laboratory scale for cement-based materials. This study aims to investigate the role of the structural build-up properties of cement-based materials in such a layer by layer construction technique. As construction progresses, the cement-based materials become harder with time. The mechanical strength of the cement-based materials must be sufficient to sustain the weight of the layers subsequently deposited. It follows that the comparison of the mechanical strength, which evolves with time (i.e. structural build-up), with the loading due to layers subsequently deposited, can be expected to provide the optimal rate of layer by layer construction. A theoretical framework has been developed to propose a method of optimization of the building rate, which is experimentally validated in a layer-wise built column.

Chemical vectors for gene delivery: a current review on polymers, peptides and lipids containing histidine or imidazole as nucleic acids carriers

Abstract: DNA/cationic lipid (lipoplexes), DNA/cationic polymer (polyplexes) and DNA/cationic polymer/cationic lipid (lipopolyplexes) electrostatic complexes are proposed as non-viral nucleic acids delivery systems These DNA-nanoparticles are taken up by the cells through endocytosis processes, but the low capacity of DNA to escape from endosomes is regarded as the major limitations of their transfection efficiency Here, we present a current report on a particular class of carriers including the polymers, peptides and lipids, which is based on the exploitation of the imidazole ring as an endosome destabilization device to favour the nucleic acids delivery in the cytosol The imidazole ring of histidine is a weak base that has the ability to acquire a cationic charge when the pH of the environment drops bellow 6 As it has been demonstrated for poly(histidine), this phenomena can induce membrane fusion and/or membrane permeation in an acidic medium Moreover, the accumulation of histidine residues inside acidic vesicles can induce a proton sponge effect, which increases their osmolarity and their swelling The proof of concept has been shown with polylysine partially substituted with histidine residues that has caused a dramatic increase by 3-45 orders of magnitude of the transfection efficiency of DNA/polylysine polyplexes Then, several histidine-rich polymers and peptides as well as lipids with imidazole, imidazolinium or imidazolium polar head have been reported to be efficient carriers to deliver nucleic acids including genes, mRNA or SiRNA in vitro and in vivo More remarkable, histidylated carriers are often weakly cytotoxic, making them promising chemical vectors for nucleic acids delivery

Analysis of Multivalley and Multibandgap Absorption and Enhancement of Free Carriers Related to Exciton Screening in Hybrid Perovskites

Abstract: Solution-processable metal–halide perovskites recently opened a new route toward low-cost manufacture of photovoltaic cells. Converting sunlight into electrical energy depends on several factors among which a broad absorption across the solar spectrum and attractive charge transport properties are of primary importance. Hybrid perovskites meet such prerequisites, but despite foremost experimental research efforts, their understanding remains scanty. Here we show that in these materials the appropriate absorption and transport properties are afforded by the multibandgap and multivalley nature of their band structure. We also investigate the nature of the photoexcited species. Our analysis suggests exciton screening by collective orientational motion of the organic cations at room temperature, leading to almost free carriers. Molecular collective motion is also expected to couple to carrier diffusion at room temperature. In mixed halides, our interpretation indicates that doping might hinder collective mole...

Optical image compression and encryption methods

Abstract: Over the years extensive studies have been carried out to apply coherent optics methods in real-time communications and image transmission. This is especially true when a large amount of information needs to be processed, e.g., in high-resolution imaging. The recent progress in data-processing networks and communication systems has considerably increased the capacity of information exchange. However, the transmitted data can be intercepted by nonauthorized people. This explains why considerable effort is being devoted at the current time to data encryption and secure transmission. In addition, only a small part of the overall information is really useful for many applications. Consequently, applications can tolerate information compression that requires important processing when the transmission bit rate is taken into account. To enable efficient and secure information exchange, it is often necessary to reduce the amount of transmitted information. In this context, much work has been undertaken using the principle of coherent optics filtering for selecting relevant information and encrypting it. Compression and encryption operations are often carried out separately, although they are strongly related and can influence each other. Optical processing methodologies, based on filtering, are described that are applicable to transmission and/or data storage. Finally, the advantages and limitations of a set of optical compression and encryption methods are discussed.