Solving nonlinear Klein-Gordon equations on unbounded domains via the Finite Element Method

A large class of scalar-tensor theories of gravity exhibit a screening mechanism that dynamically suppresses fifth forces in the Solar system and local laboratory experiments. Technically, at the scalar field equation level, this usually translates into nonlinearities which strongly limit the scope of analytical approaches. This article presents $femtoscope$ $-$ a Python numerical tool based on the Finite Element Method (FEM) and Newton method for solving Klein-Gordon-like equations that arise in particular in the symmetron or chameleon models. Regarding the latter, the scalar field behavior is generally only known infinitely far away from the its sources. We thus investigate existing and new FEM-based techniques for dealing with asymptotic boundary conditions on finite-memory computers, whose convergence are assessed. Finally, $femtoscope$ is showcased with a study of the chameleon fifth force in Earth orbit.Comment: Correction of typography in Table I (p.7

What to expect from scalar-tensor space geodesy

Scalar-tensor theories with screening mechanisms come with non-linearities that make it difficult to study setups of complex geometry without resorting to numerical simulations. In this article, we use the $\textit{femtoscope}$ code that we introduced in a previous work in order to compute the fifth force arising in the chameleon model in the Earth orbit. We go beyond published works by introducing a departure from spherical symmetry \unicode{x2014} embodied by a mountain on an otherwise spherical Earth \unicode{x2014} as well as by implementing several atmospheric models, and quantify their combined effect on the chameleon field. Building on the numerical results thus obtained, we address the question of the detectability of a putative chameleon fifth force by means of space geodesy techniques and, for the first time, quantitatively assess the back-reaction created by the screening of a satellite itself. We find that although the fifth force has a supposedly measurable effect on the dynamics of an orbiting spacecraft, the imprecise knowledge of the mass distribution inside the Earth greatly curtails the constraining power of such space missions. Finally, we show how this degeneracy can be lifted when several measurements are performed at different altitudes.Comment: 32 pages, 19 figure

Higher COVID-19 pneumonia risk associated with anti-IFN-α than with anti-IFN-ω auto-Abs in children

We found that 19 (10.4%) of 183 unvaccinated children hospitalized for COVID-19 pneumonia had autoantibodies (auto-Abs) neutralizing type I IFNs (IFN-alpha 2 in 10 patients: IFN-alpha 2 only in three, IFN-alpha 2 plus IFN-omega in five, and IFN-alpha 2, IFN-omega plus IFN-beta in two; IFN-omega only in nine patients). Seven children (3.8%) had Abs neutralizing at least 10 ng/ml of one IFN, whereas the other 12 (6.6%) had Abs neutralizing only 100 pg/ml. The auto-Abs neutralized both unglycosylated and glycosylated IFNs. We also detected auto-Abs neutralizing 100 pg/ml IFN-alpha 2 in 4 of 2,267 uninfected children (0.2%) and auto-Abs neutralizing IFN-omega in 45 children (2%). The odds ratios (ORs) for life-threatening COVID-19 pneumonia were, therefore, higher for auto-Abs neutralizing IFN-alpha 2 only (OR [95% CI] = 67.6 [5.7-9,196.6]) than for auto-Abs neutralizing IFN-. only (OR [95% CI] = 2.6 [1.2-5.3]). ORs were also higher for auto-Abs neutralizing high concentrations (OR [95% CI] = 12.9 [4.6-35.9]) than for those neutralizing low concentrations (OR [95% CI] = 5.5 [3.1-9.6]) of IFN-omega and/or IFN-alpha 2

Qu'attendre de la géodésie spatiale sur les théories tenseur-scalaire

International audienceScalar-tensor theories with screening mechanisms come with non-linearities that make it difficult to study setups of complex geometry without resorting to numerical simulations. In this article, we use the $\textit{femtoscope}$ code that we introduced in a previous work in order to compute the fifth force arising in the chameleon model in the Earth orbit. We go beyond published works by introducing a departure from spherical symmetry \unicode{x2014} embodied by a mountain on an otherwise spherical Earth \unicode{x2014} as well as by implementing several atmospheric models, and quantify their combined effect on the chameleon field. Building on the numerical results thus obtained, we address the question of the detectability of a putative chameleon fifth force by means of space geodesy techniques and, for the first time, quantitatively assess the back-reaction created by the screening of a satellite itself. We find that although the fifth force has a supposedly measurable effect on the dynamics of an orbiting spacecraft, the imprecise knowledge of the mass distribution inside the Earth greatly curtails the constraining power of such space missions. Finally, we show how this degeneracy can be lifted when several measurements are performed at different altitudes.Les théories du tenseur-scalaire avec mécanismes d'écrantage présentent des non-linéarités qui rendent difficile l'étude de configurations à géométrie complexe sans recourir à des simulations numériques. Dans cet article, nous utilisons le code femtoscope que nous avons introduit dans un travail précédent afin de calculer la cinquième force apparaissant dans le modèle du caméléon en orbite terrestre. Nous allons au-delà des travaux publiés en introduisant un écart par rapport à la symétrie sphérique — incarné par une montagne sur une Terre par ailleurs sphérique — ainsi qu'en mettant en œuvre plusieurs modèles atmosphériques, et en quantifiant leur effet combiné sur le champ du caméléon. Sur la base des résultats numériques ainsi obtenus, nous abordons la question de la détectabilité d'une cinquième force caméléon supposée au moyen de techniques de géodésie spatiale et, pour la première fois, nous évaluons quantitativement la rétroaction créée par l'écrantage d'un satellite lui-même. Nous constatons que, bien que la cinquième force ait un effet supposément mesurable sur la dynamique d'un engin spatial en orbite, la connaissance imprécise de la distribution de la masse à l'intérieur de la Terre réduit considérablement le pouvoir contraignant de ces missions spatiales. Enfin, nous montrons comment cette dégénérescence peut être levée lorsque plusieurs mesures sont effectuées à différentes altitudes

Spheroplast formation from nine rapidly growing mycobacteria

International audienceCell-wall-deficient forms from nine rapidly growing mycobacteria were prepared by treating the cells during exponential growth with D-cycloserine, glycine, lysozyme, EDTA, and lithium chloride for the time corresponding to three cell divisions. The cell-wall-deficient forms were then converted to spheroplasts in the presence of lysozyme and EDTA. The spheroplasts were characterized by their susceptibility to lysis by 0.5% (wt/vol) sodium dodecyl sulfate (SDS), as well as by their response to eight biochemical tests commonly used for mycobacterial identification. Intact cells, on the other hand, could not be lysed even with 2.5% (wt/vol) SDS and, moreover, gave negative responses to certain biochemical tests that turned positive once the cell wall was removed. This implied an exclusion mechanism at the level of the mycobacterial wall. The present method of spheroplast formation was found applicable to various mycobacterial species

Résolution d'équations de Klein-Gordon non-linéaires sur des domaines non-bornés via la méthode des éléments finis

A large class of scalar-tensor theories of gravity exhibit a screening mechanism that dynamically suppresses fifth forces in the Solar system and local laboratory experiments. Technically, at the scalar field equation level, this usually translates into nonlinearities which strongly limit the scope of analytical approaches. This article presents femtoscope-a Python numerical tool based on the Finite Element Method (FEM) and Newton method for solving Klein-Gordon-like equations that arise in particular in the symmetron or chameleon models. Regarding the latter, the scalar field behavior is generally only known infinitely far away from the its sources. We thus investigate existing and new FEM-based techniques for dealing with asymptotic boundary conditions on finite-memory computers, whose convergence are assessed. Finally, femtoscope is showcased with a study of the chameleon fifth-force in Earth orbit

Solving nonlinear Klein-Gordon equations on unbounded domains via the Finite Element Method

A large class of scalar-tensor theories of gravity exhibit a screening mechanism that dynamically suppresses fifth forces in the Solar system and local laboratory experiments. Technically, at the scalar field equation level, this usually translates into nonlinearities which strongly limit the scope of analytical approaches. This article presents $femtoscope$$-$ a Python numerical tool based on the Finite Element Method (FEM) and Newton method for solving Klein-Gordon-like equations that arise in particular in the symmetron or chameleon models. Regarding the latter, the scalar field behavior is generally only known infinitely far away from the its sources. We thus investigate existing and new FEM-based techniques for dealing with asymptotic boundary conditions on finite-memory computers, whose convergence are assessed. Finally, $femtoscope$ is showcased with a study of the chameleon fifth force in Earth orbit

Reducing the Gap Between Formal and Informal Worlds in Automotive Safety-Critical Systems

Presented also at IEEE 5th Annual International System Conference, Montreal, April 2011.The upcoming ISO26262 standard, which deals with the functional safety of roadvehicles, will induce car manufacturers to adapt the way in which vehicle systems are usuallydeveloped. To achieve this, more rigorous development processes along with new tools andtechniques will most certainly be necessary. This paper presents an overview of currentinitiatives at Renault dealing with the improvement of development processes for mechatronicsystems to comply with ISO 26262. It focuses on introducing more formalization in thesystems engineering design process via the definition of an ontology to formalize the conceptsand knowledge of the systems engineering, functional safety and automotive specialty domains(e.g. braking, energy management). The ontology is at the heart of our improvement initiativessince it allows establishing logical consistency of the whole design process. A regenerativehybrid braking system integrated into a full electrical vehicle will serve as the case study for theevaluation of the improvements made possible by the approach

Positive expiratory pressure improves oxygenation in healthy subjects exposed to hypoxia.

INTRODUCTION: Positive end-expiratory pressure (PEEP) is commonly used in critical care medicine to improve gas exchange. Altitude sickness is associated with exaggerated reduction in arterial oxygenation. We assessed the effect of PEEP and pursed lips breathing (PLB) on arterial and tissue oxygenation under normobaric and hypobaric hypoxic conditions. METHODS: Sixteen healthy volunteers were exposed to acute normobaric hypoxia (Laboratory study, FiO₂=0.12). The protocol consisted in 3-min phases with PEEPs of 0, 5 or 10 cmH₂O, PLB or similar ventilation than with PEEP-10, interspaced with 3-min phases of free breathing. Arterial (pulse oximetry) and quadriceps (near-infrared spectroscopy) oxygenation, ventilation, cardiac function, esophageal and gastric pressures and subjects' subjective perceptions were recorded continuously. In addition, the effect of PEEP on arterial oxygenation was tested at 4,350 m of altitude in 9 volunteers breathing for 20 min with PEEP-10 (Field study). RESULTS: During the laboratory study, PEEP-10 increased arterial and quadriceps oxygenation (arterial oxygen saturation +5.6±5.0% and quadriceps oxyhemoglobin +58±73 µmol.cm compared to free breathing; p<0.05). Conversely, PLB did not increase oxygenation. Oxygenation improvement with PEEP-10 was accompanied by an increase in expiratory esophageal and gastric pressures (esophageal pressure swing +5.4±3.2 cmH₂O, p<0.05) but no change in minute ventilation, breathing pattern, end-tidal CO₂ or cardiac function (all p>0.05) compared to PEEP-0. During the field study, PEEP-10 increased arterial oxygen saturation by +6.7±6.0% after the 3(rd) minute with PEEP-10 without further significant increase until the 20(th) minute with PEEP-10. Subjects did not report any significant discomfort with PEEP. CONCLUSIONS: These data indicate that 10-cmH₂O PEEP significantly improves arterial and muscle oxygenation under both normobaric and hypobaric hypoxic conditions in healthy subjects. PEEP-10 could be an attractive non-pharmacological tool to limit blood oxygen desaturation and possibly symptoms at altitude