Multiplexed two-photon microscopy of dynamic biological samples with shaped broadband pulses.

International audienceCoherent control can be used to selectively enhance or cancel concurrent multiphoton processes, and has been suggested as a means to achieve nonlinear microscopy of multiple signals. Here we report multiplexed two-photon imaging in vivo with fast pixel rates and micrometer resolution. We control broadband laser pulses with a shaping scheme combining diffraction on an optically-addressed spatial light modulator and a scanning mirror allowing to switch between programmable shapes at kiloHertz rates. Using coherent control of the two-photon excited fluorescence, it was possible to perform selective microscopy of GFP and endogenous fluorescence in developing Drosophila embryos. This study establishes that broadband pulse shaping is a viable means for achieving multiplexed nonlinear imaging of biological tissues

UV spectrophotometry for monitoring the performance of a yeast-based deoxygenation process to treat ships' ballast water

International audienceThis study assessed the usefulness of UV spectrophotometry for the monitoring of a yeast-based deoxygenation process proposed for ships' ballast water treatment to prevent the transfer of aquatic invasive species. Ten-day laboratory experiments using three treatment concentrations and different water types were conducted and resulted in complete oxygen depletion of treated waters. The treatment performance and quality of treated waters were determined by measuring the UV-visible absorbance spectra of water samples taken over time. Samples were also used for laboratory analysis of water quality properties. The UV absorbance spectra values were strongly correlated (r = 0.96) to yeast cell density in treated waters. The second-order derivative (D (2)) of the spectra varied greatly over time, and the spectrum profiles could be divided into two groups corresponding to the oxygenated and anoxic phases of the treatment. The D (2) value at 215 nm was strongly correlated (r = 0.94) to ammonia levels, which increased over time. The D (2) value at 225 nm was strongly correlated (r \textgreater 0.97) to DO concentration. Our results showed that UV spectrophotometry may provide a rapid assessment of the behavior and performance of the yeast bioreactor over time by quantifying (1) the density of yeast cells, (2) the time at which anoxic conditions were reached, and (3) a water quality index of the treated water related to the production of ammonia. We conclude that the rapidity of the technique confers a solid advantage over standard methods used for water quality analysis in laboratory and would permit the direct monitoring of the treatment performance on-board ship

Analysis of bypass transition process using large eddy simulations

International audienceThis paper describes the setup of a wall-resolved large eddy simulation (LES) of bypass transition on a realistic flat plate and the results obtained. This simulation is the first to compute a bypass transition flow on a flat plate from the receptivity stage to the laminar-turbulent transition onset. The key mechanisms of bypass transition are highlighted by the simulation: the shear-sheltering, the birth of Klebanoff-modes, their amplification, and destabilization

Analysis of bypass transition process using large eddy simulations

International audienceThis paper describes the setup of a wall-resolved large eddy simulation (LES) of bypass transition on a realistic flat plate and the results obtained. This simulation is the first to compute a bypass transition flow on a flat plate from the receptivity stage to the laminar-turbulent transition onset. The key mechanisms of bypass transition are highlighted by the simulation: the shear-sheltering, the birth of Klebanoff-modes, their amplification, and destabilization

Method and device for acquiring signals in laser scanning microscopy (extension internationale du brevet EP20100708273)

A method for acquiring signals in laser scanning microscopy, includes the steps of: moving a focused optical excitation beam relative to an object to be measured so that the focus point of the beam follows a predetermined path in the space of the object; and acquiring optical measurement signals along the path according to at least one acquisition parameter; characterised in that the path of the excitation beam is determined so as to substantially minimise the variations of the optical properties of at least one portion of the environments crossed by the excitation beam between consecutive acquisitions, and in that at least one acquisition parameter among the acquisition parameters is modulated during the movement of the excitation beam. A device for implementing the method is also described

Cell lineage reconstruction of early zebrafish embryos using label-free nonlinear microscopy

International audienceQuantifying cell behaviors in animal early embryogenesis remains a challenging issue requiring in toto imaging and automated image analysis. We designed a framework for imaging and reconstructing unstained whole zebrafish embryos for their first 10 cell division cycles and report measurements along the cell lineage with micrometer spatial resolution and minute temporal accuracy. Point-scanning multiphoton excitation optimized to preferentially probe the innermost regions of the embryo provided intrinsic signals highlighting all mitotic spindles and cell boundaries. Automated image analysis revealed the phenomenology of cell proliferation. Blastomeres continuously drift out of synchrony. After the 32-cell stage, the cell cycle lengthens according to cell radial position, leading to apparent division waves. Progressive amplification of this process is the rule, contrasting with classical descriptions of abrupt changes in the system dynamics

Donor Age and Non-Relapse Mortality: Study of Their Association after HLA-Matched Allogeneic Hematopoietic Cell Transplantation for Acute Myeloid Leukemia and Myelodysplastic Syndrome

The purpose of this retrospective study was to study the correlation between donor age (DA) and non-relapse mortality (NRM) and relapse incidence (RI) among patients treated with allogeneic hematopoietic cell transplantation (aHCT) for acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) in a single Canadian center. Data from 125 consecutive patients transplanted with a matched related or unrelated donor between 2015 and 2020 were analyzed using multivariable models. After a median follow-up of 2.8 years, the cumulative incidences of NRM and relapse were 19% and 35% at 5 years. Despite being independently associated with NRM and relapse-free survival (RFS), DA was not associated with RI. The independent determinants of NRM in addition to DA were patient age and hematopoietic cell transplantation comorbidity index (HCT-CI), independently of donor kinship. The effect of DA on NRM was found to be significantly increased over the age of 50 years. DA was not associated with incidence of acute graft-versus-host disease (aGVHD) but showed an association with the occurrence of chronic GVHD (cGVHD). In conclusion, younger donors should be favored to limit NRM and increase RFS in HLA-matched aHCT. The etiological mechanisms behind the association of DA with higher NRM remain to be elucidated

100-W-level single-mode ytterbium-free erbium fiber laser

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