Infrared supercontinuum generated in concatenated InF3 and As2Se3 fibers

We report on infrared supercontinuum (SC) generation through subsequent nonlinear propagation in concatenated step-index fluoride and As2Se3 fiber. These fibers were pumped by an all-fiber laser source based on an erbium amplifier followed by a thulium power amplifier. ZBLAN and InF3 fibers were compared for the concatenated scheme. The broadest SC produced was achieved by optimizing the length of the InF3 fiber. This arrangement allowed the generation of 200 mW infrared SC with high spectral flatness and spanning from 1.4 μm to 6.4 μm

Wavelength-Tuning of Nanosecond Pulses in Er-Doped Fluoride Fibre Amplifier

We investigate the gain bandwidth and wavelength-tuning range of an erbium-doped fluoride fibre amplifier. The presented experimental setup consisted of a widely wavelength-tunable optical parametric oscillator (OPO), which was amplified in a single-stage Er-doped fluoride fibre amplifier. The OPO laser provided seed pulses with a pulse width of 5.2 ns and a repetition rate of 10 kHz. The fibre section consisted of 2.2 m of double-clad, single-mode fibre with a doping concentration of 7 mol%. Wavelength-tuning was analysed at gain values of up to 26 dB and amplified pulse energies of up to 37.4 μ J. Using this setup, we demonstrate continuous wavelength tuning of more than 100 nm, covering the wavelength range from 2712 nm to 2818 nm

Amplification of nanosecond pulses in a single-mode erbium-doped fluoride fibre amplifier

We investigate the amplification of nanosecond pulses in a single-mode Er-fluoride fibre amplifier. A PPLN-based optical parametric oscillator (OPO) with a Q-switched Nd:YAG pump laser was used to generate seed pulses at a wavelength of 2790 nm. The OPO system produced seed pulses with sub-10 ns pulse durations and pulse energies of 0.5 μJ at a repetition rate of 10 kHz. These seed pulses were amplified in a single-mode Erbium-fluoride fibre amplifier, consisting of 2.2 m of double-clad fibre with a doping concentration of 7 mol%. Using this setup, we demonstrate gain values of up to 20 dB, output pulse energies of 52.7 μJ, and peak powers of more than 8 kW

Predicting global distributions of eukaryotic plankton communities from satellite data

プランクトンを宇宙から観測する --衛星データを入力データとする海洋真核微生物群集予測モデルの開発--. 京都大学プレスリリース. 2023-10-19.Satellite remote sensing is a powerful tool to monitor the global dynamics of marine plankton. Previous research has focused on developing models to predict the size or taxonomic groups of phytoplankton. Here, we present an approach to identify community types from a global plankton network that includes phytoplankton and heterotrophic protists and to predict their biogeography using global satellite observations. Six plankton community types were identified from a co-occurrence network inferred using a novel rDNA 18 S V4 planetary-scale eukaryotic metabarcoding dataset. Machine learning techniques were then applied to construct a model that predicted these community types from satellite data. The model showed an overall 67% accuracy in the prediction of the community types. The prediction using 17 satellite-derived parameters showed better performance than that using only temperature and/or the concentration of chlorophyll a. The constructed model predicted the global spatiotemporal distribution of community types over 19 years. The predicted distributions exhibited strong seasonal changes in community types in the subarctic–subtropical boundary regions, which were consistent with previous field observations. The model also identified the long-term trends in the distribution of community types, which suggested responses to ocean warming

Amplification of GaSb-Based Diode Lasers in an Erbium-Doped Fluoride Fibre Amplifier

Building upon recent advances in GaSb-based diode lasers and Er-doped fluoride fibre technologies, this article demonstrates for the first time the fibre-based amplification of mid-infrared diode lasers in the wavelength range around 2.78 $\mu$m. The laser setup consists of a GaSb-based diode laser and a single-stage Er-doped fibre amplifier. Amplification is investigated for continuous wave (CW) and ns-pulsed input signals, generated by gain-modulation of the GaSb-based seed lasers. The experimental results include the demonstration of output powers up to 0.9 W, pulse durations as short as 20 ns, and pulse repetition rates up to 1 MHz. Additionally, the amplification of commercial and custom-made GaSb-based seed lasers is compared and the impact of different fibre end-cap materials on laser performance is analysed

Plankton networks driving carbon export in the oligotrophic ocean

The biological carbon pump is the process by which CO 2 is transformed to organic carbon via photosynthesis, exported through sinking particles, and finally sequestered in the deep ocean. While the intensity of the pump correlates with plankton community composition, the underlying ecosystem structure driving the process remains largely uncharacterized. Here we use environmental and metagenomic data gathered during the Tara Oceans expedition to improve our understanding of carbon export in the oligotrophic ocean. We show that specific plankton communities, from the surface and deep chlorophyll maximum, correlate with carbon export at 150 m and highlight unexpected taxa such as Radiolaria and alveolate parasites, as well as Synechococcus and their phages, as lineages most strongly associated with carbon export in the subtropical, nutrient-depleted, oligotrophic ocean. Additionally, we show that the relative abundance of a few bacterial and viral genes can predict a significant fraction of the variability in carbon export in these regions

Community-Level Responses to Iron Availability in Open Ocean Plankton Ecosystems

Predicting responses of plankton to variations in essential nutrients is hampered by limited in situ measurements, a poor understanding of community composition, and the lack of reference gene catalogs for key taxa. Iron is a key driver of plankton dynamics and, therefore, of global biogeochemical cycles and climate. To assess the impact of iron availability on plankton communities, we explored the comprehensive bio-oceanographic and bio-omics data sets from Tara Oceans in the context of the iron products from two state-of-the-art global scale biogeochemical models. We obtained novel information about adaptation and acclimation toward iron in a range of phytoplankton, including picocyanobacteria and diatoms, and identified whole subcommunities covarying with iron. Many of the observed global patterns were recapitulated in the Marquesas archipelago, where frequent plankton blooms are believed to be caused by natural iron fertilization, although they are not captured in large-scale biogeochemical models. This work provides a proof of concept that integrative analyses, spanning from genes to ecosystems and viruses to zooplankton, can disentangle the complexity of plankton communities and can lead to more accurate formulations of resource bioavailability in biogeochemical models, thus improving our understanding of plankton resilience in a changing environment

Apport de la chirurgie assistée par ordinateur dans l'arthroplastie totale du genou (à propos de 47 cas)

PARIS6-Bibl.Pitié-Salpêtrie (751132101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Splicing fluoride glass and silica optical fibers

Splicing fluoride glass fibers and silica fibers is a critical point for manufacturing all fibered laser modules. As these materials are extremely different, various problems must be considered: thermal, expansion, mechanical, chemical. Reliability and power handling make priority concerns. We report splices made on a 200/220 multimode silica fiber and a double clad 15/250/290 ZBLAN fiber. Splices are proof tested at 300 g tensile strength. No damage is observed after thermal cycling from -30 °C to 85 °C, at 40 % RH during 24 hours. Typical optical splice loss is about 0.2 dB. They withstand 220 W input power at 976 nm without any damage and drastic temperature increasing