Facing the challenge of predicting the standard formation enthalpies of n-butyl-phosphate species with ab initio methods

Tributyl-phosphate (TBP), a ligand used in the PUREX liquid-liquid separation process of spent nuclear fuel, can form explosive mixture in contact with nitric acid, that might lead to violent explosive thermal runaway. In the context of safety of a nuclear reprocessing plant facility, it is crucial to predict the stability of TBP at elevated temperatures. So far, only the enthalpies of formation of TBP is available in the literature with a rather large uncertainties, while those of its degradation products, di-(HDBP) and mono-(H$_2$MBP}) are unknown. In this goal, we have used state-of-the art quantum chemical methods to compute the formation enthalpies and entropies of TBP and its degradation products di-(HDBP), mono-(H$_2$MBP) in gas and liquid phases. Comparisons of levels of quantum chemical theory revealed that there are significant effects of correlation on their electronic structures, pushing for the need of not only high level of electronic correlation treatment, namely local coupled cluster with single and double excitation operators and perturbative treatment of triple excitations [LCCSD(T)], but also extrapolations to the complete basis to produce reliable and accurate thermodynamics data. Solvation enthalpies were computed with the conductor like screening model for real solvents [COSMO-RS], for which we observe errors not exceeding 22 kJ mol$^{-1}$. We thus propose with final uncertainty of about 20 kJ mol$^{-1}$ standard enthalpies of formation of TBP, HDBP, and H$_2$MBP which amounts to -1281.7$\pm$24.4, -1229.4$\pm$19.6 and -1176.7$\pm$14.8 kJ mol$^{-1}$, respectively, in the gas phase. In the liquid phase, the predicted values are -1367.3$\pm$24.4, -1348.7$\pm$19.6 and -1323.8$\pm$14.8 kJ mol$^{-1}$, to which we may add about -22 kJ mol$^{-1}$ error from the COSMO-RS solvent model. From these data, we predict the complete hydrolysis of TBP to be nearly thermoneutral

A three-level signature by graph for Reverse Engineering of mechanical assemblies

Several approaches exist to provide Reverse Engineering solutions on mechanical parts. Mechanical assemblies and the expertise information retrieved at the same time with the model geometry are not really taken into account in the literature. Thus, the main challenge of this contribution is to propose a methodology to retrieve the Digital Mock-Up of a mechanical assembly from its meshed data (from digitalization). The output DMU consists of expertise information and parameterized CAD models. The methodology proposed relies on a signature by a three-level graph. It enables to provide an adequate level of details by identifying the corresponding functional surfaces in meshed data. The first-level graph is a connectivity graph; the intermediate level is the same as the first with the geometric type of face added to each node (plane, cylinder and sphere) and the deepest level corresponds to a precedence graph. This one provides information such as functional surfaces and position between them (perpendicularity, coaxiality etc.). The solutions developed and the results are presented in this paper. The methodology is illustrated thanks to an industrial use-case with a scan of an assembly with a connecting rod and a piston. The conclusion and perspectives will complete this paper

Semiconductor laser Markov models in the micro-canonical, canonical and grand-canonical ensembles

International audienceWe are interested in semiconductor laser (SL) dynamics, namely its multimode stability. To that aim a microcanonical (MC) model was built and is very effective, but highly time-consuming to simulate [1]. We then question about the relevance of this statistical ensemble. The model represents a SL by a Markov chain. It is composed of photon reservoirs figuring optical modes, and a finite number of electrons sharing a set of evenly-spaced energy levels. These states are split in two energy bands. Each energy level is occupied by zero or one electron, following the Pauli exclusion principle without spin consideration [2]. The system reaches its steady-state regime when pumping compensates exactly photon exits. Electron repartitions are directed by the Boltzmann thermalisation within each band. This photon flux is the main output of the model since it contains the laser noise. Photon absorption and emissions take place only at the laser energy level pair, one per mode. Their intensities are dictated by electron presence at each laser level. The way the latter occupation is coped with is determined by which statistical ensemble is favored. The MC simulation takes into account the whole microstates, including electron thermalisation. It shows the laser multimode stability as expected and the possible occurrence of both the spectral hole burning and carrier heating [1]. Its main drawback is that one photonic event only occurs every 10 5 thermal ones. To speed up calculations, we shift to a canonical (C) frame for electron thermalisation because the number of electrons in a band does not change except when photonics events occur. The C occupancies of the laser levels are obtained analytically [3], which allows to get rid of thermal events. As a main disadvantage, spectral hole burning and carrier-heating are now ignored. However a possible addition to the Markov framework may solve the question owing to an extension of the event set. Finally, using the Fermi-Dirac distribution instead of the C ones is irrelevant for laser simulation purposes because carriers number fluctuations are ruled out. But it allows for a complete analytical description, which was shown to coincide with MC and C results for big systems. The differences between the three ensembles will be discussed in this communication.[l] L. Chusseau et al., Optics express 22, 5312 (2014).[2] J. Arnaud et al., Am. J. Phys. 67, 215 (1999).[3] F. Philippe et al., arXiv math-ph, 0211029 (2002)

Illustration du passage au seuil des nanolasers par une modélisation markovienne

National audienceNous présentons un modèle traitant du passage au seuil des nanolasers grâcè a une chaˆınechaˆıne de Markov simulée par Monte-Carlo. La quantification des variables traitées dans le modèle permet de mettre enévidenceen´enévidence les allumages et extinctions autour du seuil laser. La coexistence d'un régime pulsé avec un régime continu bruité lors du passage au seuil montre que celui-ci ne peut plusêtreplusˆplusêtre défini avec précision pour les nanolaser

Markov model of quantum fluctuations at the transition to lasing of semiconductor nanolasers

International audienceA Markov model of semiconductor nanolaser is constructed in order to describe finely the effects of quantum fluctuations in the dynamics of the laser, in particular by considering the transition to lasing. Nanolasers are expected to contain only a small number of emitters, whose semiconductor bands are simulated using true carrier energy states. The model takes into account carrier-carrier interactions in the conduction and valence bands, but the result is a huge Markov chain that is often too demanding for direct Monte-Carlo simulation. We introduce here a technique to split the whole chain into two subchains, one referring to thermalization events within the bands and the other to laser photonic events of interest. The model is applied to the analysis of laser transition and enlightens the coexistence of a pulse regime triggered by the quantum nature of the photon with the birth of the known coherent cw regime. This conclusion is highlighted by calculated time traces. We show that on the ultrasmall scale of nanolasers, we are unable to define perfectly the threshold

Induction of Phlorotannins and Gene Expression in the Brown Macroalga Fucus vesiculosus in Response to the Herbivore Littorina littorea

Mechanisms related to the induction of phlorotannin biosynthesis in marine brown algae remain poorly known. Several studies undertaken on fucoid species have shown that phlorotannins accumulate in the algae for several days or weeks after being exposed to grazing, and this is measured by direct quantification of soluble phenolic compounds. In order to investigate earlier inducible responses involved in phlorotannin metabolism, Fucus vesiculosus was studied between 6 and 72 h of grazing by the sea snail Littorina littorea. In this study, the quantification of soluble phenolic compounds was complemented by a Quantitative real-time PCR (qRT-PCR) approach applied on genes that are potentially involved in either the phlorotannin metabolism or stress responses. Soluble phlorotannin levels remained stable during the kinetics and increased significantly only after 12 h in the presence of grazers, compared to the control, before decreasing to the initial steady state for the rest of the kinetics. Under grazing conditions, the expression of vbpo, cyp450 and ast6 genes was upregulated, respectively, at 6 h, 12 h and 24 h, and cyp450 gene was downregulated after 72 h. Interestingly, the pksIII gene involved in the synthesis of phloroglucinol was overexpressed under grazing conditions after 24 h and 72 h. This study supports the hypothesis that phlorotannins are able to provide an inducible chemical defense under grazing activity, which is regulated at different stages of the stress response

A three-level signature by graph for Reverse Engineering of mechanical assemblies

Several approaches exist to provide Reverse Engineering solutions on mechanical parts. Mechanical assemblies and the expertise information retrieved at the same time with the model geometry are not really taken into account in the literature. Thus, the main challenge of this contribution is to propose a methodology to retrieve the Digital Mock-Up of a mechanical assembly from its meshed data (from digitalization). The output DMU consists of expertise information and parameterized CAD models. The methodology proposed relies on a signature by a three-level graph. It enables to provide an adequate level of details by identifying the corresponding functional surfaces in meshed data. The first-level graph is a connectivity graph; the intermediate level is the same as the first with the geometric type of face added to each node (plane, cylinder and sphere) and the deepest level corresponds to a precedence graph. This one provides information such as functional surfaces and position between them (perpendicularity, coaxiality etc.). The solutions developed and the results are presented in this paper. The methodology is illustrated thanks to an industrial use-case with a scan of an assembly with a connecting rod and a piston. The conclusion and perspectives will complete this paper

Extracorporeal life support for primary graft dysfunction after heart transplantation

OBJECTIVES Survival after heart transplantation is steadily improving but primary graft dysfunction (PGD) is still a leading cause of death. Medical management seems useful in mild or moderate PGD, whereas extracorporeal life support (ECLS) could be suggested for severe PGD refractory to conventional treatment. Our aim is to present the results of ECLS for PGD after heart transplantation at a single-centre experience. METHODS We performed an observational analysis of our local database. According to the International Society for Heart and Lung Transplantation classification, patients were divided into a left and biventricular failure (PGD-LV) or isolated right ventricular failure (PGD-RV) group. The primary end point was survival to hospital discharge. RESULTS Between January 2010 and December 2016, 38 patients presented with PGD (PGD-LV n = 22, 58%; PGD-RV n = 16, 42%) requiring ECLS support. The mean age was 50.8 ± 12.4 years and 79% were males. Baseline characteristics were comparable between the 2 groups. PGD-LV patients displayed a significantly higher mortality rate on ECLS support as opposed to PGD-RV patients (46% vs 13%, P = 0.033). The rate of complications during ECLS support was comparable between the 2 groups. Twenty-three (61%) patients were successfully weaned from ECLS (PGD-LV = 50% vs PGD-RV = 75%, P = 0.111) after a mean support of 9.0 ± 6.4 days. Seventeen (45%) patients survived to hospital discharge (PGD-LV = 41% vs PGD-RV = 50%, P = 0.410). CONCLUSIONS In case of severe PGD with various manifestations of ventricular failure refractory to conventional treatment, ECLS can be considered as a feasible option with satisfactory survival in this critically ill population

An integrated analysis of surface velocities induced by rainfall in the Séchilienne landslide (Western Alps, France)

International audienceAn integrated analysis on the relationship between rainfall and displacement in the most active area of the Séchilienne unstable slope was performed. This study combines several techniques and models to adequately reproduce the landslide movement induced by the rainfall. The analysis of available time series shows a long term trend and seasonal variations in the displacement, respectively independent and synchronous to precipitations. In particular wavelet analysis highlights that the movement is rather linked to groundwater recharge than to precipitation (rainfall + snowfall), involving then the importance of groundwater process in the area. A first and simple relationship between the water input and the fluctuations of displacements apart from the general trend is shown using a tank model. Moreover, a seasonal analysis of this relationship was performed, showing that displacement rate follows the behavior of the hydrological cycle. Two different models were applied to the long temporal series of extensometric and precipitation data: the FLAME model, from BRGM and the FORESEES model, from Univ. Lausanne. These tools are based on a combined statistical-mechanical approach to predict changes in landslide displacement rates from observed changes in precipitation amounts. The forecasting tool FLAME associates 1) a statistical impulse response (IR) model to simulate the changes in landslide rates by computing a transfer function between the rainfall and the displacements, and 2) a 1D mechanical (ME) model (e.g. visco-plastic rheology), in order to take into account changes in pore water pressures. The performance of different combinations of models was evaluated against observed displacement rates at the selected pilot study area. Our results indicate that both models are able to reproduce, with a high degree of accuracy, the observed displacement pattern in the general kinematic regime. Finally the variability of the results, depending in particular on the input data, is discussed