Large second harmonic generation enhancement in SiN waveguides by all-optically induced quasi phase matching

Integrated waveguides exhibiting efficient second-order nonlinearities are crucial to obtain compact and low power optical signal processing devices. Silicon nitride (SiN) has shown second harmonic generation (SHG) capabilities in resonant structures and single-pass devices leveraging intermodal phase matching, which is defined by waveguide design. Lithium niobate allows compensating for the phase mismatch using periodically poled waveguides, however the latter are not reconfigurable and remain difficult to integrate with SiN or silicon (Si) circuits. Here we show the all-optical enhancement of SHG in SiN waveguides by more than 30 dB. We demonstrate that a Watt-level laser causes a periodic modification of the waveguide second-order susceptibility. The resulting second order nonlinear grating has a periodicity allowing for quasi phase matching (QPM) between the pump and SH mode. Moreover, changing the pump wavelength or polarization updates the period, relaxing phase matching constraints imposed by the waveguide geometry. We show that the grating is long term inscribed in the waveguides, and we estimate a second order nonlinearity of the order of 0.3 pm/V, while a maximum conversion efficiency (CE) of 1.8x10-6 W-1 cm-2 is reached

A new stochastic process to model Heart Rate series during exhaustive run and an estimator of its fractality parameter

International audienceIn order to interpret and explain the physiological signal behaviors, it can be interesting to find some constants among the fluctuations of these data during all the effort or during different stages of the race (which can be detected using a change points detection method). Several recent papers have proposed the long-range dependence (Hurst) parameter as such a constant. However, their results induce two main problems. Firstly, DFA method is usually applied for estimating this parameter. Clearly, such a method does not provide the most efficient estimator and moreover it is not at all robust even in the case of smooth trends. Secondly, this method often gives estimated Hurst parameters larger than $1$, which is the larger possible value for long memory stationary processes. In this article we propose solutions for both these problems and we define a new model allowing such estimated parameters

Versatile short-wave and mid-infrared sources based on wideband parametric conversion

The mid-infrared part of the optical spectrum is of high interest in a wide range of applications such as environmental gas monitoring, contaminant detection in the chemical, food or pharmaceutical industry, medical diagnosis, or defense and security. Relevant molecules can readily be identified through their mid-infrared absorption spectra, as the latter contains the fundamental resonances of a number of pollutant and toxic gases. Consequently, spectroscopic apparatus, light detection and ranging systems or free-space communication links all benefit from the progress accomplished by mid-infrared technologies over the last years. However some shortcomings in the light emitters capabilities are still to be addressed. In this research work, we aim at designing a mid-infrared laser as versatile as possible and based on nonlinear wavelength conversion. The conversion relies on third-order parametric effects in waveguides such as optical fibers made of various types of glass, or integrated semiconductor chips. The objective is to leverage mature communication-band components to generate and shape the seed optical signals, then mixed in the abovementioned waveguides to down-convert them towards midinfrared. The wavelength conversion is performed in two stages, and the first stage consists of a parametric source emitting in the short-wave infrared range. This thesis mostly focuses on the design and realization of this stage. As such, it is closely linked to the field of nonlinear fiber optics, where the use of silica is preponderant. We build on the research performed over the last years on parametric amplifiers, initially used for the re-amplification of communication signals, and we combine it with technologies dedicated to short-wave infrared fiber lasers. As such, we are able to build wavelength tunable and modulation-capable short-wave infrared sources, significantly more powerful and versatile than previous broadband parametric converter designs. The end of the dissertation is then dedicated to the solutions that are then envisioned to realize the second conversion stage, towards mid-infrared. Very promising numerical and experimental results indicate a successful outcome to the project, confirming the validity of the laser concept

Relations exposition-effets et pharmacogénétique du ganciclovir chez le patient transplanté

Cytomegalovirus infection is a major issue in transplant patients as it affects the graft survival and contributes to patients’ morbi-mortality. The implementation of ganciclovir prophylaxis has significantly decreased its incidence, however GCV frequently induces neutropenia. This adverse effect leads to a decrease in the ganciclovir dose or to a discontinuation of the therapy, thereby favoring viral resistance. Resistance to ganciclovir is a growing problem in solid organ transplantion because of the lack of proper data to support treatment decisions when it is encountered. In this context we aim at better understanding the factors involved in this toxicity. First we explored the intracellular metabolism of ganciclovir in patients’ white blood cells. We found that the active form of ganciclovir is associated with neutrophil toxicity at month 3 of treatment. Then we explored the effect of targeted polymorphisms among transporter genes in two cohorts of renal transplant patients. We found that a single nucleotide polymorphism is strongly associated with a decrease in the neutrophil count and in ganciclovir intracellular accumulation. This thesis provides relevant tools for a deeper exploration of ganciclovir intracellular metabolism and accumulation which might be useful for the prevention of ganciclovir induced neutropenia.Les infections par cytomégalovirus sont un problème majeur en transplantation rénale du fait de l’augmentation du risque de perte de greffon et de l’augmentation de la morbi-mortalité des patients. Toutefois la mise en place d’un traitement prophylactique par ganciclovir a significativement fait diminuer l’incidence de ces infections. Cette efficacité est toutefois limitée par une importante hématotoxicité notamment des neutropénies. La survenue de cet évènement indésirable conduit à une réduction des doses voire à un arrêt du traitement, favorisant ainsi l’émergence de résistances virales. Ces résistances sont un problème grandissant chez les personnes transplantées du fait du manque de protocole de prise en charge de celles-ci. Dans ce contexte notre objectif était de mieux comprendre la survenue et le mécanisme de cette toxicité. Dans un premier temps nous avons étudié le métabolisme intracellulaire du ganciclovir chez des patients. Nous avons remarqué qu’il y a une forte corrélation entre l’exposition à la forme active du ganciclovir et la diminution du nombre de neutrophiles au 3ème mois de traitement. Nous avons par la suite étudié l’impact de variations génétiques sur des transporteurs. Nous avons remarqué qu’un polymorphisme était fortement associé à une diminution du nombre de neutrophiles et qu’il entrainait également une augmentation de la concentration intracellulaire de ganciclovir à l’aide d’un modèle in vitro. Cette thèse fournit de nouveaux outils d’exploration du métabolisme et de l’accumulation intracellulaire du ganciclovir qui pourraient être utiles pour la prévention de la survenue de neutropénies sous ganciclovir

Prediction of Performance in a Short Trail Running Race: The Role of Body Composition

The aim of the present study was to examine the role of the classical physiological model of endurance running performance - maximal oxygen uptake (VO(2)max), %VO(2)max at ventilatory thresholds (VT), work economy, lactate levels, and body composition on the prediction of short trail running performance. Eleven male trail runners (age 36.1 +/- 6.5 years, sport experience 6.6 +/- 3.8 years, and mean +/- standard deviation) were examined for fat mass and skeletal muscle mass, and performed a graded exercise test to measure VO(2)max, vVO(2)max, and VT. Also, they participated in a short 27 km trail run with a positive elevation of +1750 m. Age, years of training and skeletal muscle mass did not correlate with race time (P > 0.05), and fat mass and body mass index (BMI) showed significant correlations with race time (P 0.05). Only vVO(2)max (P = 0.005) and VO(2)max (P = 0.007) is correlated to race time. Multiple regression models for VO(2)max accounted for 57% of the total variance. The vVO(2)max model variable accounted for 60% and the fat mass model for 59.5%. Finally, the combined VO(2)max and fat mass model explained 83.9% of the total variance (P < 0.05 in all models). The equation for this model is "race time (min) = 203.9956-1.9001 x VO(2)max + 10.2816 x Fat mass%" (R-2 = 0.839, SEE = 11.1 min, and P = 0.0007). The classical variable VO(2)max together with fat mass percent are two strong predictors for short trail running performance

Efficient broadband parametric conversion: reaching for the Mid IR

In this paper, we report recent results on the efficient generation of SWIR sources exploiting broadband wavelength conversion in silica fibers. Optimized cavity-less designs of fiber parametric amplifiers (FOPA) associated with Thulium amplification capable of high CW powers, wide tunability and modulation will be presented. We also present how parametric conversion can be extended deeper in the Mid-IR by engineering of non-silica mixing platforms

Two dechlorinated chlordecone derivatives formed by in situ chemical reduction are devoid of genotoxicity and mutagenicity and have lower proangiogenic properties compared to the parent compound

Chlordecone (CLD) is a chlorinated hydrocarbon insecticide, now classified as a persistent organic pollutant. Several studies have previously reported that chronic exposure to CLD leads to hepatotoxicity, neurotoxicity, raises early child development and pregnancy complications, and increases the risk of liver and prostate cancer. In situ chemical reduction (ISCR) has been identified as a possible way for the remediation of soils contaminated by CLD. In the present study, the objectives were (i) to evaluate the genotoxicity and the mutagenicity of two CLD metabolites formed by ISCR, CLD-5a-hydro, or CLD-5-hydro (5a- or 5- according to CAS nomenclature; CLD-1Cl) and tri-hydroCLD (CLD-3Cl), and (ii) to explore the angiogenic properties of these molecules. Mutagenicity and genotoxicity were investigated using the Ames\u27s technique on Salmonella typhimurium and the in vitro micronucleus micromethod with TK6 human lymphoblastoid cells. The proangiogenic properties were evaluated on the in vitro capillary network formation of human primary endothelial cells. Like CLD, the dechlorinated derivatives of CLD studied were devoid of genotoxic and mutagenic activity. In the assay targeting angiogenic properties, significantly lower microvessel lengths formed by endothelial cells were observed for the CLD-3Cl-treated cells compared to the CLD-treated cells for two of the three tested concentrations. These results suggest that dechlorinated CLD derivatives are devoid of mutagenicity and genotoxicity and have lower proangiogenic properties than CLD

Vers la détermination d'un profil d'humidité dans des matériaux biopolymères en utilisant une méthode de séparation de sources

Le but de ce travail est de déterminer de manière non destructive un profil d'humidité dans des matériaux biopolymères. Son originalité réside dans l'utilisation de deux capteurs pyroélectriques sans contact direct avec l'échantillon. Le capteur en face avant est transparent à la longueur d'onde utilisée. C'est le traitement du signal réalisé par une méthode de séparation de sources qui permet d'exploiter les possibilités de ce nouveau montage expérimental. La mise en oeuvre d'un tel dispositif n'a jamais été faite tant du point de vue expérimental que du point de vue traitement de l'information

Cardiac Output and Performance during a Marathon Race in Middle-Aged Recreational Runners

Purpose. Despite the increasing popularity of marathon running, there are no data on the responses of stroke volume (SV) and cardiac output (CO) to exercise in this context. We sought to establish whether marathon performance is associated with the ability to sustain high fractional use of maximal SV and CO (i.e, cardiac endurance) and/or CO, per meter (i.e., cardiac cost). Methods. We measured the SV, heart rate (HR), CO, and running speed of 14 recreational runners in an incremental, maximal laboratory test and then during a real marathon race (mean performance: 3 hr 30 min ± 45 min). Results. Our data revealed that HR, SV and CO were all in a high but submaximal steady state during the marathon (87.0 ± 1.6%, 77.2 ± 2.6%, and 68.7 ± 2.8% of maximal values, respectively). Marathon performance was inversely correlated with an upward drift in the CO/speed ratio (mL of CO × m−1) (r = −0.65, P < 0.01) and positively correlated with the runner's ability to complete the race at a high percentage of the speed at maximal SV (r = 0.83, P < 0.0002). Conclusion. Our results showed that marathon performance is inversely correlated with cardiac cost and positively correlated with cardiac endurance. The CO response could be a benchmark for race performance in recreational marathon runners

Wavelength Multicasting and Amplification of 5 Gb/s Data in the 2 Micron Band

We report wavelength multicasting to three 5Gb/s channels around 1950nm via broadband four-wave-mixing between RZ-OOK modulated pump and O-band signals. The thulium-assisted configuration enables high fidelity copying and output powers of 10’s of mW