From bare interactions, low--energy constants and unitary gas to nuclear density functionals without free parameters: application to neutron matter

We further progress along the line of Ref. [Phys. Rev. {\bf A 94}, 043614 (2016)] where a functional for Fermi systems with anomalously large $s$-wave scattering length $a_s$ was proposed that has no free parameters. The functional is designed to correctly reproduce the unitary limit in Fermi gases together with the leading-order contributions in the s- and p-wave channels at low density. The functional is shown to be predictive up to densities $\sim0.01$ fm$^{-3}$ that is much higher densities compared to the Lee-Yang functional, valid for $\rho < 10^{-6}$ fm$^{-3}$. The form of the functional retained in this work is further motivated. It is shown that the new functional corresponds to an expansion of the energy in $(a_s k_F)$ and $(r_e k_F)$ to all orders, where $r_e$ is the effective range and $k_F$ is the Fermi momentum. One conclusion from the present work is that, except in the extremely low--density regime, nuclear systems can be treated perturbatively in $-(a_s k_F)^{-1}$ with respect to the unitary limit. Starting from the functional, we introduce density--dependent scales and show that scales associated to the bare interaction are strongly renormalized by medium effects. As a consequence, some of the scales at play around saturation are dominated by the unitary gas properties and not directly to low-energy constants. For instance, we show that the scale in the s-wave channel around saturation is proportional to the so-called Bertsch parameter $\xi_0$ and becomes independent of $a_s$. We also point out that these scales are of the same order of magnitude than those empirically obtained in the Skyrme energy density functional. We finally propose a slight modification of the functional such that it becomes accurate up to the saturation density $\rho\simeq 0.16$ fm$^{-3}$

Effect of dipolar interactions on cavity magnon-polaritons

The strong photon-magnon coupling between an electromagnetic cavity and two yttrium iron garnet (YIG) spheres has been investigated in the context of a strong mutual dipolar interaction between the spheres. A decrease in the coupling strength between the YIG spheres and the electromagnetic cavity is observed, along with an increase of the total magnetic losses, as the distance between the spheres is decreased. A model of inhomogeneous broadening of the ferromagnetic resonance linewidth, partly mitigated by the dipolar narrowing effect, reproduces the reduction in the coupling strength observed experimentally. These findings have important implications for the understanding of strongly coupled photon-magnon system involving densely packed magnetic objects, such as ferromagnetic nanowires arrays, in which the total coupling strength with an electromagnetic cavity might become limited due to mutual dipolar interactions.Comment: 5 pages, 5 figure

Évaluation des performances d'adsorption d'un système de captage direct du CO2 avec lits mobiles

Le réchauffement climatique est proportionnel aux émissions mondiales de dioxyde de carbone dans l’atmosphère. Si aucune action réelle n’est entreprise, ces émissions pourraient atteindre 72 gigatonnes par année d’ici 2060, soit 60 gigatonnes de plus que l’objectif fixé par l’Accord de Paris sur le climat. L’objectif en question est d’atteindre une carboneutralité d’ici 2070 afin de maintenir le réchauffement climatique sous la barre des 2 °C par rapport à l’époque préindustrielle. Pour l’atteindre, la réduction des émissions ne sera pas suffisante. Il faudra impérativement capter le CO2 directement de l’atmosphère, et ce, dès 2030. Ce projet de recherche repose sur le captage direct du CO2 par adsorption solide à basse température, phénomène de transfert de masse où un adsorbat gazeux se fixe à la surface d’un adsorbant solide. Cette méthode de captage est d’ailleurs la plus viable commercialement par rapport au captage direct par absorption, avantage non négligeable dans un monde où l’implantation de marchés et de taxes sur le carbone est de plus est plus répandue. Le but de cette maîtrise est d’appliquer cette méthode de captage à un procédé utilisant une configuration à lits mobiles. Cette configuration se base sur le mouvement de multiples cellules d’adsorbant en phase d’adsorption et optimise leur cycle de service dans un écoulement contenant du CO2. Cela permet à la fois de diminuer la quantité de matériau nécessaire et de créer un cycle d’adsorption continu. Le présent rapport est une présentation du travail complété permettant de répondre à la question de recherche suivante :Quel est le gain en performance d’adsorption de dioxyde de carbone d’un système d’adsorption, par cyclage de cellules mobiles d’un matériau adsorbant poreux solide à grande échelle, par rapport à un système d’adsorption par cyclage d’un lit fixe, pendant 24 heures d’opération continue ? Le matériau adsorbant en question est un gel de silice fonctionnalisé au polyéthylèneimine. Il a été choisi pour son faible coût d’acquisition et ses performances d’adsorption. Le gain maximal obtenu pour le système par cyclage de cellules mobiles évalué est de 2.57. Ce système aurait 8 cellules mobiles au total, dont 5 se trouveraient dans le réacteur d’adsorption en tout temps. La quantité de matériau adsorbant utilisée par cellule est équivalente au 1/32 de celle qui serait utilisée pour une seule cellule fixe. Pour une même quantité de CO2 capté, cela engendre une réduction de 61 % de la masse de matériau nécessaire avec le système à lits mobiles. Si aucune contrainte de conception et d’opération n’est considérée, un gain maximal est obtenu en utilisant 2 cellules contenant le moins de matériau possible avec un temps de cycle complet (adsorption et régénération, avec ou sans échange de chaleur) le plus court possible

High levels of circulating leukocyte microparticles are associated with better outcome in acute respiratory distress syndrome

International audienceINTRODUCTION: The current study has addressed the presence and the cellular origin of microparticles (MP) isolated from bronchoalveolar lavage (BAL) fluid and from blood samples from patients with acute respiratory distress syndrome (ARDS). Their prognostic interest was also investigated. METHODS: Fifty-two patients were included within the first 24 hours of ARDS. They were compared to spontaneous breathing (SB) and ventilated control (VC) groups. Bronchoalveolar lavage (BAL) and blood samples were obtained on Day 1 and Day 3 in an ARDS group. Leukocyte microparticles (LeuMP), neutrophil microparticles (NeuMP), endothelial microparticles (EMP), and platelet microparticles (PMP) were measured in arterial blood and in BAL samples by flow cytometry. Mortality from all causes was recorded at Day 28. RESULTS: All MP subpopulations were detected in BAL. However, only LeuMP and NeuMP were elevated in ARDS patients compared to the SB group (P = 0.002 for both). Among ARDS patients, higher levels of LeuMP were detected in blood (Day 1) and in BAL (Day 3) in survivors as compared with the non survivors. Circulating LeuMP >60 elements/microliter detectable on Day 1 of ARDS, was associated with a higher survival rate (odds ratio, 5.26; 95% confidence interval, 1.10 to 24.99; P = 0.037). CONCLUSIONS: The identification of the cellular origin of microparticles at the onset of ARDS has identified LeuMP as a biomarker of prognostic significance. The higher levels of LeuMP in survivors could be associated with a protective role of this MP subpopulation. This hypothesis needs further investigations

Aircraft Anti-Icing Fluids Endurance Under Natural and Artificial Snow: a Comparative Study

The usage of De-Icing and Anti-Icing fluids is the most common method recognized to protect aircraft on the ground from freezing and frozen contaminants. The snow endurance times, which means the duration that a fluid can protect the vehicle from snow accumulations, is currently determined outdoor under natural conditions. To replace this expensive and very impractical method, the Anti-Icing Materials International Laboratory developed snow machine was used to perform a comparative study. In this first study, three commercial fluids were tested at various snow intensity rates under artificial snow generated with the snow machine in a cold chamber to validate the testing procedure and investigate the way forward. The results obtained were then positively compared to natural snow endurance times. They were also compared with natural snow regression curves, showing similar trends. This study demonstrated the great potential of this method showing the necessity of pursuing this investigation

Intestinal permeability and gut microbiota interactions of pharmacologically active compounds in valerian and St. John’s wort

Phytomedicines such as valerian and St. John's wort are widely used for the treatment of sleeping disorders, anxiety and mild depression. They are perceived as safe alternatives to synthetic drugs, but limited information is available on the intestinal absorption and interaction with human intestinal microbiota of pharmacologically relevant constituents valerenic acid in valerian, and hyperforin and hypericin in St. John's wort. The intestinal permeability of these compounds and the antidepressant and anxiolytic drugs citalopram and diazepam was investigated in the Caco-2 cell model with bidirectional transport experiments. In addition, interaction of compounds and herbal extracts with intestinal microbiota was evaluated in artificial human gut microbiota. Microbiota-mediated metabolisation of compounds was assessed, and bacterial viability and short-chain fatty acids (SCFA) production were measured in the presence of compounds or herbal extracts. Valerenic acid and hyperforin were highly permeable in Caco-2 cell monolayers. Hypericin showed low-to-moderate permeability. An active transport process was potentially involved in the transfer of valerenic acid. Hyperforin and hypericin were mainly transported through passive transcellular diffusion. All compounds were not metabolized over 24 h in the artificial gut microbiota. Microbial SCFA production and bacterial viability was not substantially impaired nor promoted by exposure to the compounds or herbal extracts

Node configuration for the Aho-Corasick algorithm in intrusion detection systems

In this paper, we analyze the performance and cost trade-off from selecting two representations of nodes when implementing the Aho-Corasick algorithm. This algorithm can be used for pattern matching in network-based intrusion detection systems such as Snort. Our analysis uses the Snort 2.9.7 rules set, which contains almost 26k patterns. Our methodology consists of code profiling and analysis, followed by the selection of a parameter to maximize a metric that combines clock cycles count and memory usage. The parameter determines which of two types of nodes is selected for each trie node. We show that it is possible to select the parameter to optimize the metric, which results in an improvement by up to 12× compared with the single node-type case