Applications des impulsions femtosecondes infrarouges : façonnage programmable et spectroscopie bidimensionnelle

Mid-infrared femtosecond lasers have recently provided a new tool to study complex ultrafast dynamics, especially in biological systems such as hemeproteins. Using these lasers, two kind of powerful experiments can be planned. The first type contains optimal control experiments, in which the principle is to find the optimal shape of a pulse in order to reach one desired final state. This approach requires a way to produce an arbitrary shape of pulses, so in a first part we have worked on a new kind of linear programmable acousto-optic pulse-shaper called Mid-infrared Dazzler, which is produced by the company FASLITE. For this sake, we have implemented a new method to measure weak mid-infrared pulses with complex shapes, based on the homodyne detection of a replica of the mid-infrared field into the visible domain. Then, we have produced and measured shaped pulses which exhibit complex shapes like pi-steps in the spectral phase. This demonstrates the ability of the Dazzler to be used in optimal control experiments with hemeproteins. The second type of experiments contain the multidimensional coherent spectroscopy experiments, which are powerful tools to probe ultrafast dynamics since the principle is to measure the complete non-linear response function, which permits to disentangle the different microscopic informations. We have finalized the building of an innovative two-dimensional spectrometer, which exhibits a simple geometry, an excellent spectral resolution in both axes, an iterative and very precise self-calibration method, and a simple and efficient trick to remove the signal from scattering. Our first measurements of the Frequency-frequency correlation function of the CO vibration bound to Hemoglobin shows a promising agreement with recent progress in the modelization of ultrafast fluctuations.La mise au point des lasers femtosecondes, en particulier dans le moyen-infrarouge, a ouvert une voie d’étude des systèmes biologiques, où les couplages et les fluctuations impliquent des déphasages ultra-rapides. Ce travail participe à l’élaboration d’outils pour l’étude de systèmes vibrationnels, ici la carboxy-hémoglobine HbCO. L’approche du contrôle optimal, d’une part, détermine empiriquement le profil optimal d’une impulsion en vue d’un objectif, nécessitant la programmation d’impulsions de formes arbitraires. Nous avons étudié un prototype d’une technologie acousto-optique de façonnage d’impulsions infrarouges, le Dazzler, conçu par la société FASTLITE. Pour cela, une méthode adaptée de mesure du champ, effectuant la mesure homodyne d’une réplique de l’impulsion dans le domaine visible, a été mise au point. Puis, la production et la mesure d’impulsions infrarouges de formes complexes comprenant un saut de phase spectrale, ont été réalisées, montrant l’adéquation du Dazzler pour des expériences de contrôle cohérent dans les hémoprotéines. D’autre part, la spectroscopie multidimensionnelle mesure la réponse non-linéaire d’un échantillon, constituant un outil puissant d’étude de la surface de potentiel. Un spectromètre bidimensionnel a donc été finalisé, qui combine une géométrie simplifiée, une excellente résolution, une procédure d’auto-calibration itérative et précise, et une solution simple pour éliminer la principale source de bruit. Des mesures de la fonction de corrélation à deux temps de la fréquence de résonance du CO ont enfin été comparées à des résultats préliminaires issus d’avancées théoriques récentes, montrant un accord prometteur pour leur validation

Impact of pulse polarization on coherent vibrational ladder climbing signals

International audienceWe report a theoretical study that elaborates the influence of the polarization state of both the pump and the probe pulse in ultrafast coherent vibrational ladder climbing experiments in the mid-infrared. Whereas a subensemble in a randomly oriented sample of molecules is excited by the pump pulse in this multiphoton process, further inhomogeneities such as the spatial profile of the laser beams, the longitudinal attenuation in the sample, and the probe beam polarization have to be taken into account. Analytical expressions for a density function describing the number of molecules that are exposed to an effective pump intensity are introduced, and the variation of the population distribution and the actual transient absorption signal in dependence on the polarization-state combinations for pump and probe pulse are discussed in detail. In simulations on the model system carboxy-hemoglobin, it is demonstrated that the polarization states play important roles both for exciting a certain population distribution and for actually observing it. In particular, it will be discussed under which conditions experimental data indicates a population inversion. Cop. 2011 American Chemical Society

Calibration of an adaptive microscope using phase diversity

International audienceAccurate control over the phase and amplitude modulation in an adaptive microscope is essential to the quality of aberration correction that can be achieved. In this paper we present a robust and compact method for characterising such amplitude and phase modulation in the pupil plane of the focussing objective. This method, based on phase diversity, permits calibrating the microscope as a whole and thus avoids errors in the alignment of the wavefront shaping device after calibration and the resulting imprecision in the induced modulation: by acquiring three 2D images of the point spread function at different distances from the focal plane, we show that the electric field distribution at the pupil plane can be retrieved using an iterative algorithm. We have applied this technique to the characterisation of the phase modulation induced by a deformable mirror when conjugated with the entrance pupil of different objectives, which permits accurate evaluation of the performance of the mirror for subsequent aberration correction. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE)

Management and outcomes of critically ill adult patients with convulsive status epilepticus and preadmission functional impairments

International audienceObjective: Functional status is among the criteria relevant to decisions about intensive care unit (ICU) admission and level of care. Our main objective was to describe the characteristics and outcomes of adult patients requiring ICU admission for Convulsive Status Epilepticus (CSE) according to whether their functional status was previously impaired. Methods: We retrospectively analyzed data from consecutive adults who were admitted to two French ICUs for CSE between 2005 and 2018 and then included them retrospectively in the Ictal Registry. Pre-existing functional impairment was defined as a Glasgow Outcome Scale (GOS) score of 3 before admission. The primary outcome measure was a loss of ≥1 GOS score point at 1 year. Multivariate analysis was used to identify factors associated with this measure. Results: The 206 women and 293 men had a median age of 59 years [47–70 years]. The preadmission GOS score was 3 in 56 (11.2%) patients and 4 or 5 in 443 patients. Compared to the GOS-4/5 group, the GOS-3 group was characterized by a higher frequency of treatment-limitation decisions (35.7% vs. 12%, P < 0.0001), similar ICU mortality (19.6 vs. 13.1, P = 0.22), higher 1-year mortality (39.3% vs. 25.6%, P < 0.01), and a similar proportion of patients with no worsening of the GOS score at 1 year (42.9 vs. 44.1, P = 0.89). By multivariate analysis, not achieving a favorable 1-year outcome was associated with age above 59 years (OR, 2.36; 95%CI, 1.55–3.58, P < 0.0001), preexisting ultimately fatal comorbidity (OR, 2.92; 95%CI, 1.71–4.98, P = 0.0001), refractory CSE (OR, 2.19; 95%CI, 1.43–3.36, P = 0.0004), cerebral insult as the cause of CSE (OR, 2.75; 95%CI, 1.75–4.27, P < 0.0001), and Logistic Organ Dysfunction score ≥ 3 at ICU admission (OR, 2.08; 95%CI, 1.37–3.15, P = 0.0006). A preadmission GOS score of 3 was not associated with a functional decline during the first year (OR, 0.61; 95%CI, 0.31–1.22, P = 0.17). Significance: Preadmission functional status in adult patients with CSE is not independently associated with a functional decline during the first postadmission year. This finding may help physicians make ICU admission decisions and adult patients write advance directives. Study Registration: #NCT03457831

Parallel, linear, and subnanometric 3D tracking of microparticles with Stereo Darkfield Interferometry

International audienceWhile crucial for force spectroscopists and microbiologists, three-dimensional (3D) particle tracking suffers from either poor precision, complex calibration, or the need of expensive hardware, preventing its massive adoption. We introduce a new technique, based on a simple piece of cardboard inserted in the objective focal plane, that enables simple 3D tracking of dilute microparticles while offering subnanometer frame-to-frame precision in all directions. Its linearity alleviates calibration procedures, while the interferometric pattern enhances precision. We illustrate its utility in single-molecule force spectroscopy and single-algae motility analysis. As with any technique based on back focal plane engineering, it may be directly embedded in a commercial objective, providing a means to convert any preexisting optical setup in a 3D tracking system. Thanks to its precision, its simplicity, and its versatility, we envision that the technique has the potential to enhance the spreading of high-precision and high-throughput 3D tracking

Magnetic Membranes for Cell Growth Under Curved and Reversible Deformations

International audienceMagnetic polymer composites are very versatile candidates to fabricate soft robots and actuators thanks to their unique properties such as flexibility and shape memory effect. Thus, the possibility to reproduce natural shapes provides new tools for bioengineering applications. The wide panel of deformations of magnetic polymer composites can be implemented to mimic the movements and curvatures of living tissue. Herein, magnetic polymer membranes are developed to explore cell growth under curved, reversible, and controlled deformations. NdFeB/polydimethylsiloxane composite membranes (86 μm and 46 μm thick) are obtained by soft lithography and magnetized in rolled position under 3 T. Once actuated by a low magnetic field (5–86 mT), the membranes are deformed in wavy shapes with a deformation height of maximum 1.4 and 1.7 mm and a curvature radius of minimum 1.8 and 0.6 mm (86 μm and 46 μm thick membranes, respectively), for a maximum magnetic field of 86 mT. Then, Caco‐2 cell viability is studied on deformed substrates under a static (106 mT) and varying (8–78 mT) magnetic field. No increase in cell death is observed, validating a well‐characterized and promising approach for a new generation of dynamic and curved substrates for cell culture

Detection of genetic variation and base modifications at base-pair resolution on both DNA and RNA

International audienceAccurate decoding of nucleic acid variation is critical to understand the complexity and regulation of genome function. Here we use a single-molecule magnetic tweezer (MT) platform to identify sequence variation and map a range of important epigenetic base modifications with high sensitivity, specificity, and precision in the same single molecules of DNA or RNA. We have also developed a highly specific amplification-free CRISPR-Cas enrichment strategy to isolate genomic regions from native DNA. We demonstrate enrichment of DNA from both E. coli and the FMR1 5'UTR coming from cells derived from a Fragile X carrier. From these kilobase-length enriched molecules we could characterize the differential levels of adenine and cytosine base modifications on E. coli, and the repeat expansion length and methylation status of FMR1. Together these results demonstrate that our platform can detect a variety of genetic, epigenetic, and base modification changes concomitantly within the same single molecules

Prediction of esophagogastroduodenoscopy therapeutic usefulness for in-ICU suspected upper gastrointestinal bleeding: the SUGIBI score study

International audienceBackground: Suspected upper gastrointestinal bleeding (SUGIB) is a common issue during ICU stay. In the absence of specific guidelines on the indication and timing of esophagogastroduodenoscopy (EGD), there is substantial variability in EGD indication depending on accessibility and clinical presentation. This study aimed to investigate factors associated with the need for per-EGD hemostatic therapy and to create a score predicting therapeutic benefit of emergency bedside EGD in ICU patients with SUGIB. Methods: We conducted a retrospective study in our ICU to identify factors associated with the need for hemostatic procedure during EGD performed for SUGIB. From this observational cohort, we derived a score predicting the need for hemostasis during EGD, the SUGIBI score. This score was subsequently validated in a retrospective multicenter cohort. Results: Two hundred fifty-five patients not primarily admitted for GI bleeding who underwent a bedside EGD for SUGIB during their ICU stay were analyzed. The preeminent EGD indication were anemia (79%), melena (19%), shock (14%), and hematemesis (13%). EGD was normal in 24.7% of cases, while primary lesions reported were ulcers (23.1%), esophagitis (18.8%), and gastritis (12.5%). Only 12.9% of patients underwent hemostatic endotherapy during EGD. A SUGIBI score Conclusions Our study shows that the therapeutic usefulness of bedside emergency EGD for SUGIB in critically ill patients is limited to a minority of patients. The SUGIBI score should help clinicians stratify the probability of a therapeutic EGD