Time-domain reflectance diffuse optical tomography with Mellin-Laplace transform for experimental detection and depth localization of a single absorbing inclusion.

International audienceWe show how to apply the Mellin-Laplace transform to process time-resolved reflectance measurements for diffuse optical tomography. We illustrate this method on simulated signals incorporating the main sources of experimental noise and suggest how to fine-tune the method in order to detect the deepest absorbing inclusions and optimize their localization in depth, depending on the dynamic range of the measurement. To finish, we apply this method to measurements acquired with a setup including a femtosecond laser, photomultipliers and a time-correlated single photon counting board. Simulations and experiments are illustrated for a probe featuring the interfiber distance of 1.5 cm and show the potential of time-resolved techniques for imaging absorption contrast in depth with this geometry

Toward noninvasive assessment of flap viability with time-resolved diffuse optical tomography: a preclinical test on rats

The noninvasive assessment of flap viability in autologous reconstruction surgery is still an unmet clinical need. To cope with this problem, we developed a proof-of-principle fully automatized setup for fast time-gated diffuse optical tomography exploiting Mellin–Laplace transform to obtain three-dimensional tomographic reconstructions of oxy- and deoxy-hemoglobin concentrations. We applied this method to perform preclinical tests on rats inducing total venous occlusion in the cutaneous abdominal flaps. Notwithstanding the use of just four source-detector couples, we could detect a spatially localized increase of deoxyhemoglobin following the occlusion (up to 550 μM in 54 min). Such capability to image spatio-temporal evolution of blood perfusion is a key issue for the noninvasive monitoring of flap viability

Maths Express au carrefour des cultures

International audienceCette brochure a été réalisée à l'occasion de la quinzième édition du Salon Culture et Jeux mathématiques. Elle a pour objectif de montrer que les mathématiques sont au coeur de toutes les activités humaines qu'elles soient sociales, techniques, scientifiques, artistiques ou ludiques. Elles sont nées et se sont développées au rythme des sociétés humaines

Reversible transitions between noradrenergic and mesenchymal tumor identities define cell plasticity in neuroblastoma

Noradrenergic and mesenchymal identities have been characterized in neuroblastoma cell lines according to their epigenetic landscapes and core regulatory circuitries. However, their relationship and relative contribution in patient tumors remain poorly defined. We now document spontaneous and reversible plasticity between the two identities, associated with epigenetic reprogramming, in several neuroblastoma models. Interestingly, xenografts with cells from each identity eventually harbor a noradrenergic phenotype suggesting that the microenvironment provides a powerful pressure towards this phenotype. Accordingly, such a noradrenergic cell identity is systematically observed in single-cell RNA-seq of 18 tumor biopsies and 15 PDX models. Yet, a subpopulation of these noradrenergic tumor cells presents with mesenchymal features that are shared with plasticity models, indicating that the plasticity described in these models has relevance in neuroblastoma patients. This work therefore emphasizes that intrinsic plasticity properties of neuroblastoma cells are dependent upon external cues of the environment to drive cell identity

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Knocking on Heaven's Door : Are Novel Invaders Necessarily Facing Naïve Native Species on Islands?

International audienceThe impact of alien predator species on insular native biota has often been attributed to island prey naïveté (i.e. lack of, or inefficient, anti-predator behavior). Only rarely, however, has the concept of island prey naïveté been tested, and then only a posteriori (i.e. hundreds or thousands of years after alien species introduction). The presence of native or anciently introduced predators or competitors may be crucial for the recognition and development of adaptive behavior toward unknown predators or competitors of the same archetype (i.e. a set of species that occupy a similar ecological niche and show similar morphological and behavioral traits when interacting with other species). Here, we tested whether two squa-mates endemic to New Caledonia, a skink, Caledoniscincus austrocaledonicus, and a gecko, Bavayia septuiclavis, recognized and responded to the odor of two major invaders introduced into the Pacific islands, but not yet into New Caledonia. We chose one predator, the small Indian mongoose Herpestes javanicus and one competitor, the cane toad Rhinella marina, which belong respectively to the same archetype as the following two species already introduced into New Caledonia in the nineteenth century: the feral cat Felis catus and the golden bell frog Litoria aurea. Our experiment reveals that geckos are naïve with respect to the odors of both an unknown predator and an unknown competitor, as well as to the odors of a predator and a competitor they have lived with for centuries. In contrast, skinks seem to have lost some naïveté regarding the odor of a predator they have lived with for centuries and seem " predisposed " to avoid the odor of an unknown potential competitor. These results indicate that insular species living in contact with invasive alien species for centuries may be, although not systematically, predisposed toward developing adaptive behavior with respect to species belonging to the same archetype and introduced into their native range

“It's dry, it has fewer charms!”: Do perceptions and values of intermittent rivers interact with their management?

International audienceIntermittent rivers, which do not flow all year round, have biophysical functioning specificities which need to be considered when defining management policies, even more so in the current context of global change. However, in Europe intermittent rivers benefit from the same regulations as permanent rivers, which undoubtedly leads to their degradation. This paper aims to identify (1) how perceptions and values of intermittent rivers interact with their management and (2) determine whether the prospect of climate change leads the stakeholders to questioning their perceptions and values of intermittent rivers and the way we should manage them. Semi-structured interviews and mental mapping exercises were conducted with 28 various stakeholders (elected officials, fishers, river managers, and residents), all of whom lived along the French intermittent Albarine River. Qualitative analysis of the discourses and maps confirms strong interactions between the perceptions and values related to intermittent rivers and their management. The results highlight social devaluation of the intermittent section in terms of aesthetics, recreation, and biological values. They also point to the role of power plays between river managers and fishers, in the prioritization of management actions that favor perennial sections to the detriment of intermittent ones. These dynamics of devaluing and discarding intermittent sections or rivers from management plans are all the more alarming as there is little propensity among river stakeholders to think about the future of these intermittent rivers and their value in the context of climate change, where the prevalence of intermittent rivers is likely to increase dramatically

Time-resolved measurements in diffuse reflectance: effects of the instrument response function of different detection systems on the depth sensitivity

International audienceWe demonstrate the loss of depth sensitivity induced by the instrument response function on reflectance time-resolved diffuse optical tomography through the comparison of 3 detection systems: on one hand a photomultiplier tube (PMT) and a hybrid PMT coupled with a time-correlated single-photon counting card and on the other hand a high rate intensified camera. We experimentally evaluate the depth sensitivity achieved for each detection module with an absorbing inclusion embedded in a turbid medium. The different interfiber distances of 5, 10 and 15 mm are considered. Finally, we determine a maximal depth reached for each detection system by using 3D tomographic reconstructions based on the Mellin-Laplace transform

Time-Resolved Reflectance Diffuse Optical Tomography by using Mellin-Laplace Transform

International audienceIn this paper, we show how the Mellin-Laplace Transform helps to obtain robust and relevant reconstructions of deep optical heterogeneity from time-resolved diffuse optical tomography measurements

Map of New Caledonia with interception points (international airport; Noumea harbor and Prony industrial site) for the small Indian mongoose (<i>Herpestes javanicus</i>) and the cane toad (<i>Rhinella marina</i>) and capture sites for the common litter skink (<i>Caledoniscincus austrocaledonicus</i>) (yellow star) and the pale striped Bavayia gecko (<i>Bavayia septuiclavis</i>) (orange star).

<p>Map of New Caledonia with interception points (international airport; Noumea harbor and Prony industrial site) for the small Indian mongoose (<i>Herpestes javanicus</i>) and the cane toad (<i>Rhinella marina</i>) and capture sites for the common litter skink (<i>Caledoniscincus austrocaledonicus</i>) (yellow star) and the pale striped Bavayia gecko (<i>Bavayia septuiclavis</i>) (orange star).</p