Réalisation de micro-résonateurs organiques par procédés hybrides : Nouvelles perspectives en photonique intégrée

L’article consiste en une étude de micro-résonateurs (MRs) sphériques fabriqués à partir d’un matériau organique : le polymère NOA (Northland Optical Adhesive). Les auteurs présentent en un premier lieu le circuit micro fluidique spécialement adapté à la création de gouttes sphériques MRs.L’excitation des modes de galerie permet de déterminer les rayons des sphères. Dans une intégration photonique et pour un meilleur confinement, les sphères sont excitées en utilisant un guide d’onde réalisé par technique de « spin coating » à l’aide de polymère SU8 (bisphénol A d’éther glycide). Le couplage est réalisé à l’aide d’ondes évanescentes circulant du guide vers la sphère. La photographie des sphères excitées (pour deux configurations différentes all-pass ou add-drop) met en évidence les modes optiques situés à la surface des sphères synonymes de modes de galerie. L’analyse spectrale du signal à la sortie du guide met en évidence la présence de pics confirmant l’excitation de cette catégorie de modes au sein de la structure. Ces mesures, à l’aide de l’intervalle spectrale libre permettent de remonter aux diamètres des sphères. Les valeurs déterminées sont en bon accord avec celles mesurées à l’aide de la microscopie optique

An Extended Network of Genomic Maintenance in the Archaeon Pyrococcus abyssi Highlights Unexpected Associations between Eucaryotic Homologs.

In Archaea, the proteins involved in the genetic information processing pathways, including DNA replication, transcription, and translation, share strong similarities with those of eukaryotes. Characterizations of components of the eukaryotic-type replication machinery complex provided many interesting insights into DNA replication in both domains. In contrast, DNA repair processes of hyperthermophilic archaea are less well understood and very little is known about the intertwining between DNA synthesis, repair and recombination pathways. The development of genetic system in hyperthermophilic archaea is still at a modest stage hampering the use of complementary approaches of reverse genetics and biochemistry to elucidate the function of new candidate DNA repair gene. To gain insights into genomic maintenance processes in hyperthermophilic archaea, a protein-interaction network centred on informational processes of Pyrococcus abyssi was generated by affinity purification coupled with mass spectrometry. The network consists of 132 interactions linking 87 proteins. These interactions give insights into the connections of DNA replication with recombination and repair, leading to the discovery of new archaeal components and of associations between eucaryotic homologs. Although this approach did not allow us to clearly delineate new DNA pathways, it provided numerous clues towards the function of new molecular complexes with the potential to better understand genomic maintenance processes in hyperthermophilic archaea. Among others, we found new potential partners of the replication clamp and demonstrated that the single strand DNA binding protein, Replication Protein A, enhances the transcription rate, in vitro, of RNA polymerase. This interaction map provides a valuable tool to explore new aspects of genome integrity in Archaea and also potentially in Eucaryotes

Soil methane sink capacity response to a long-term wildfire chronosequence in Northern Sweden

Boreal forests occupy nearly one fifth of the terrestrial land surface and are recognised as globally important regulators of carbon (C) cycling and greenhouse gas emissions. Carbon sequestration processes in these forests include assimilation of CO2 into biomass and subsequently into soil organic matter, and soil microbial oxidation of methane (CH4). In this study we explored how ecosystem retrogression, which drives vegetation change, regulates the important process of soil CH4 oxidation in boreal forests. We measured soil CH4 oxidation processes on a group of 30 forested islands in northern Sweden differing greatly in fire history, and collectively representing a retrogressive chronosequence, spanning 5000 years. Across these islands the build-up of soil organic matter was observed to increase with time since fire disturbance, with a significant correlation between greater humus depth and increased net soil CH4 oxidation rates. We suggest that this increase in net CH4 oxidation rates, in the absence of disturbance, results as deeper humus stores accumulate and provide niches for methanotrophs to thrive. By using this gradient we have discovered important regulatory controls on the stability of soil CH4 oxidation processes that could not have not been explored through shorter-term experiments. Our findings indicate that in the absence of human interventions such as fire suppression, and with increased wildfire frequency, the globally important boreal CH4 sink could be diminished

Propagation monomode dans des nanotubes et nanofils organiques couplés à des microstructures sur puce de potonique intégrée

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