Non-linear normal modes, invariance, and modal dynamics approximations of non-linear systems

Non-linear systems are here tackled in a manner directly inherited from linear ones, that is, by using proper normal modes of motion. These are defined in terms of invariant manifolds in the system's phase space, on which the uncoupled system dynamics can be studied. Two different methodologies which were previously developed to derive the non-linear normal modes of continuous systems — one based on a purely continuous approach, and one based on a discretized approach to which the theory developed for discrete systems can be applied-are simultaneously applied to the same study case-an Euler-Bernoulli beam constrained by a non-linear spring-and compared as regards accuracy and reliability. Numerical simulations of pure non-linear modal motions are performed using these approaches, and compared to simulations of equations obtained by a classical projection onto the linear modes. The invariance properties of the non-linear normal modes are demonstrated, and it is also found that, for a pure non-linear modal motion, the invariant manifold approach achieves the same accuracy as that obtained using several linear normal modes, but with significantly reduced computational cost. This is mainly due to the possibility of obtaining high-order accuracy in the dynamics by solving only one non-linear ordinary differential equation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43333/1/11071_2004_Article_BF00045620.pd

Nonlinear Modal Analysis of Structural Systems Using Multi-Mode Invariant Manifolds

In this paper, an invariant manifold approach is introduced for the generationof reduced-order models for nonlinear vibrations of multi-degrees-of-freedomsystems. In particular, the invariant manifold approach for defining andconstructing nonlinear normal modes of vibration is extended to the case ofmulti-mode manifolds. The dynamic models obtained from this technique capture the essential coupling between modes of interest, while avoiding coupling fromother modes. Such an approach is useful for modeling complex systemresponses, and is essential when internal resonances exist between modes.The basic theory and a general, constructive methodology for the method arepresented. It is then applied to two example problems, one analytical andthe other finite-element based. Numerical simulation results are obtainedfor the full model and various types of reduced-order models, including theusual projection onto a set of linear modes, and the invariant manifoldapproach developed herein. The results show that the method is capable ofaccurately representing the nonlinear system dynamics with relatively fewdegrees of freedom over a range of vibration amplitudes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43322/1/11071_2004_Article_281266.pd

Vuorovaikutteisen suunnittelun haasteet ja mahdollisuudet metsätalouden vesiensuojelussa

Rapport de l'expertise scientifique collectiveLes animaux peuvent-ils éprouver des émotions, peuvent-ils penser, ont-ils une histoire de vie ? Depuis l’Antiquité, les philosophes ont proposé des réponses contrastées à ces questions. Du XIXème siècle à nos jours, la réflexion sur ce que sont les animaux s’est enrichie d’apports scientifiques : théorie de l’évolution, éthologie, neurophysiologie, sciences cognitives. Mais la conscience animale reste toujours l’objet de débats importants dans la communauté scientifique. Ainsi en 2012 un groupe de scientifiques de premier plan a éprouvé la nécessité de publier un manifeste intitulé « Déclaration de Cambridge sur la Conscience », qui énonce qu’«…une convergence de preuves indique que les animaux non humains disposent des substrats neuro-anatomiques, neurochimiques et neurophysiologiques des états conscients ainsi que la capacité d’exprimer des comportements intentionnels...».Les connaissances actuelles, dont cette expertise collective propose une synthèse, montrent que les animaux possèdent un large éventail de capacités cognitives associées à des comportements plus ou moins complexes. Les formes de conscience étudiées chez les humains supposent des capacités cognitives distinctes que l’on retrouve chez certains animaux. Peut-on en postuler que ceux-ci ont des formes de consciences équivalentes à celles de l’homme, sans être forcément identiques ?L’étude des niveaux et des contenus de la conscience chez les animaux est en passe de devenir un enjeu scientifique important en raison de la complexité du sujet et des controverses qu’il ne manquera pas de susciter. Enfin, les acquis scientifiques dans ce domaine invitent à reprendre les réflexions morales concernant les relations que les hommes entretiennent avec les animaux (et particulièrement avec les animaux domestiques

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Evolution des modalités de la pré-désinfection des instruments chirurgicaux en sortie de blocs opératoires (exemple du CHU de Rennes)

La pré-désinfection, première étape du processus de stérilisation des dispositifs médicaux stérilisables, est réalisée au niveau du service utilisateur. Elle consiste à immerger le matériel souillé dans une solution pré-désinfectante afin d'éliminer les matières organiques et les micro-organismes. Cependant, cette pratique présente de nombreux risques, tant pour le personnel (risques infectieux, chimiques...) que pour les dispositifs médicaux (corrosion). L'utilisation de laveurs-désinfecteurs en sortie de blocs opératoires représente une alternative intéressante améliorant les conditions de travail. L'instauration d'une traçabilité à ce niveau et la possibilité de réaliser une inactivation totale des agents transmissibles non conventionnels représentent également des avancées majeures. Suite à des restructurations au niveau du CHU de Rennes, il a été décidé en 2012 de faire l'acquisition de laveurs-désinfecteurs afin d'automatiser la pré-désinfection dans certaines unités opératoires.The pre-disinfection cleaning at point of use is the first step of the reusable medical device decontaminiation. This stage consists in an immersion of contaminated medical devices in a solution containing a pre-disinfectant agent, in order to remove soils and micro-organisms. However, this operation is not risk free for the nursing staff and for the medical devices integrity. The use of washer-disinfectors within surgical unit could be an alternative to reduce these risks. This could also contribute to improve working conditions. Besides, the implementation of a traceability system and the realisation of an inactivation of non-conventional transmissible agents can be up at this stage. In Rennes hospital (France), the purchase of washer-disinfectors in order to mechanize this stage in surgical unit has taken place in 2012.RENNES1-BU Santé (352382103) / SudocSudocFranceF

Development of a new OpenFOAM solver for plasma cutting modelling

International audienceA new OpenFOAM solver is presented, for the simulation of plasma cutting torches. The mathematical model that is introduced is based on the compressible Navier-Stokes equations coupled via source terms to the electric current conservation equation. Due to the conservative and hyperbolic nature of the model, a Godunov-type scheme is used for the first time in the context of plasma cutting simulation. The numerical method consists of a second-order Total Variation Diminishing (TVD) integration with flux Harten-Lax-van Leer-Contact (HLLC) Riemann solver for the flow conservation equations, coupled with a Laplace solver for the current conservation equation. An efficient formulation for the equation of state, accurately taking into account the plasma properties, is also presented. The solver is validated through a set of canonical test cases (shock tubes and 2D Riemann problems) and it is used to simulate a three-dimensional plasma cutting torch. Good agreement is found with the literature, with an improvement in the ability to deal with the shocks occurring during plasma cutting

Physicochemical stability of compounded midazolam capsules over a one-year storage period

In patients suffering from chronic liver disease, the hepatic metabolism of drugs is perturbed and the metabolic capacity is difficult to assess. Midazolam could be used as a phenotypical probe to predict the metabolic capacity of CYP3A to adjust dosages of drug substrates of this cytochrome. In this context, a prospective clinical trial is going to be conducted in our institution and a hospital preparation of midazolam capsules suitable for the clinical trial was developed. The objective of the present work was to assess the physicochemical stability of the formulation over 12 months to set shelf life

Magma crystallization and viscosity: A study of molten basalts from the Piton de la Fournaise volcano (La Réunion island)

International audienceThe viscosity of three molten basalts produced by fusion of lavas issued from different eruptions of the Piton de la Fournaise (La Réunion island) has been investigated above the liquidus and at high degrees of supercooling. For all basalts, crystallization took place rapidly above the glass transition range, which made static measurements problematic because of time-dependent, non-Newtonian rheology. By contrast, reproducible results were obtained in dynamic measurements made at a constant heating rate of 5 K/mn. Partial crystallization resulted in strong viscosity increases which were primarily due to the presence of solid inclusions. Comparisons with phase equilibria experiments performed for the same samples at higher temperatures show that crystallization takes place differently below the liquidus and at strong degrees of supercooling. As recently described for simpler systems, these differences in nucleation and growth are controlled by the relative mobilities of the cations diffusing within the melt to attach themselves to crystal–melt interfaces. A consequence is that the composition evolution of the residual melt differs in equilibrium and irreversible crystallization. In turn, this contrast induces opposite viscosity variations for the residual melt

Building and ornamental use of trachyte in the center of France during antiquity: Sources and criteria of identification

International audienceThe volcanic field of Chaîne des Puys (French Massif Central) includes six trachytic volcanoes, the lavas of which were more or less extensively exploited during antiquity and medieval ages as a raw material for construction, sculpture and fabrication of sarcophagi. Recent questioning on the origin of trachytes from the famous Mercury sanctuary (2nd centuries AD) built atop Puy de Dôme volcano motivated the launch of a program devoted to establish source identification criteria for trachytic artifacts based on petrography, geochemistry and mineralogy These analyses allowed to establish a list of very strong criteria allowing to distinguish each volcano. The nature of the minerals being discriminating in most cases, a small sample size is sufficient for the diagnosis.The possibilities offered by the new classification are illustrated by a reappraisal of trachyte supplying around Augustonemetum (Clermont-Ferrand) during the Gallo-Roman period. In the course of this program, we discovered a previously unknown major quarry of trachyte

Numerical assessment of Diffuse-Interface method for air-assisted liquid sheet simulation

International audienceThis study presents the implementation and validation of a second-order accurate solver for the 4-equation multi-fluid method in a cell-vertex context, to handle aeronautical air-assisted liquid sheet configurations. Validations include one and two-dimensional shock tube problems, Laplace tests, droplets oscillations, and a two-dimensional configuration reminiscent of an aeronautical airblast injector. Promising results are obtained in the last case, especially when the pressure is increased and the characteristic flow times decreased, a trend observed in recent aeronautical developments, but not necessary in classical academical benchmarks. Being fully compatible of the reactive flow formulation of the cell-vertex solver AVBP, this study paves the way to future monolithic simulations of airblast injectors for aeronautical combustion chambers, including both the multi-phase and the reactive regions