Continuous nonlinear eigenvalue solver with applications to the design of electro/magnetorheological sandwich structures

International audienceSmart sandwich structures comprising an electro-or a magnetorheo-logical material have the potential to attenuate vibration over a wide range of frequencies. The analysis of their vibration behaviour with respect to the continuous variation of the field intensity is thus a major challenge for research and industry to maximize damping treatments. The numerical higher order homotopy method we propose models the effects of a continuous variation of the field intensity on resonant frequencies and loss factors by means of Taylor expansions. Comparisons between our continuous approach and the classical incremental method are proposed for state of the art sandwich beams and plate structures comprising ER/MR fluids to highlight the benefits of our continuous methods in terms of maximal damping determination

Quantum nature of the critical points of substances

Thermodynamics of chemical elements, based on the two-component electron-nuclear plasma model shows that the critical parameters for the liquid-vapor transition are the quantum values for which the classical limit is absent.Comment: 4 pages, no figure

Simulation Application for the LHCb Experiment

We describe the LHCb detector simulation application (Gauss) based on the Geant4 toolkit. The application is built using the Gaudi software framework, which is used for all event-processing applications in the LHCb experiment. The existence of an underlying framework allows several common basic services such as persistency, interactivity, as well as detector geometry description or particle data to be shared between simulation, reconstruction and analysis applications. The main benefits of such common services are coherence between different event-processing stages as well as reduced development effort. The interfacing to Geant4 toolkit is realized through a facade (GiGa) which minimizes the coupling to the simulation engine and provides a set of abstract interfaces for configuration and event-by-event communication. The Gauss application is composed of three main blocks, i.e. event generation, detector response simulation and digitization which reflect the different stages performed during the simulation job. We describe the overall design as well as the details of Gauss application with a special emphasis on the configuration and control of the underlying simulation engine. We also briefly mention the validation strategy and the planing for the LHCb experiment simulation.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 6 pages, LaTeX, 9 eps figures. PSN TUMT00

Reducing the impact of radioactivity on quantum circuits in a deep-underground facility

As quantum coherence times of superconducting circuits have increased from nanoseconds to hundreds of microseconds, they are currently one of the leading platforms for quantum information processing. However, coherence needs to further improve by orders of magnitude to reduce the prohibitive hardware overhead of current error correction schemes. Reaching this goal hinges on reducing the density of broken Cooper pairs, so-called quasiparticles. Here, we show that environmental radioactivity is a significant source of nonequilibrium quasiparticles. Moreover, ionizing radiation introduces time-correlated quasiparticle bursts in resonators on the same chip, further complicating quantum error correction. Operating in a deep-underground lead-shielded cryostat decreases the quasiparticle burst rate by a factor fifty and reduces dissipation up to a factor four, showcasing the importance of radiation abatement in future solid-state quantum hardware

Earthworm management in tropical agroecosystems

In agrosystem field experiments, earthworm inoculation did not impede depletion of soil organic stocks in most cases, in spite of increased carbon inputs through enhanced primary production. Slight evidence of soil organic matter (SOM) protection was found in poorly structured soil, such as a yam plot in Ivory Coast (soil sieved before experimentation), and a pasture plot on Martinique. Aggregation inherited from past earthworm activities probably maintains SOM protection after earthworms have disappeared ; longer term experiments are necessary to observe C dynamics after the disappearance of inherited earthworm structures. In two experiments with maize in Ivory Coast and Peru, the activity of earthworms led to a small increase in the incorporation of organic matter from surface mulch in the SOM. Most of the C incorporated into the SOM originated from root material, and earthworm activities only slightly modified this pattern. Earthworm activity had significant effects on the distribution of C among particle size fractions. The general trend was a depletion of large (greater than 50 micrometers) particles and an accumulation of small (less than 2 micrometers) particles. Nutrient depletion in low-input cropping systems was not impeded by earthworm activities ; at Yurimaguas, some signs of a better conservation of K were noted after 3 years in the traditional rotation. (Résumé d'auteur

Ethoxyfagaronine, a synthetic analogue of fagaronine that inhibits vascular endothelial growth factor-1, as a new anti-angiogeneic agent

Angiogenesis plays a pivotal role in tumorigenesis and also contributes to the pathogenesis of hematologic malignancies. A number of plant compounds have shown efficacy in preclinical and clinical studies and some of them possess an anti-angiogenic activity. Our present findings report anti-angiogenic activities of ethoxyfagaronine (etxfag), a synthetic derivative of fagaronine. Once determined the non-cytotoxic concentration of etxfag, we showed that the drug inhibits VEGF-induced angiogenesis in a Matrigel™ plug assay and suppresses ex vivo sprouting from VEGF-treated aortic rings. Each feature leading to neovascularization was then investigated and results demonstrate that etxfag prevents VEGF-induced migration and tube formation in human umbilical vein endothelial cells (HUVEC). Moreover, etxfag also suppresses VEGF-induced VEGFR-2 phosphorylation and inhibits FAK phosphorylation at Y-861 as well as focal adhesion complex turnover. Beside these effects, etxfag modifies MT1-MMP localization at the endothelial cell membrane. Finally, immunoprecipitation assay revealed that etxfag decreases VEGF binding to VEGFR-2. As we previously reported that etxfag is able to prevent leukemic cell invasiveness and adhesion to fibronectin, all together our data collectively support the anti-angiogenic activities of etxfag which could represent an additional approach to current anti-cancer therapies

Thermal Diffusion of a Two Layer System

In this paper thermal conductivity and thermal diffusivity of a two layer system is examined from the theoretical point of view. We use the one dimensional heat diffusion equation with the appropriate solution in each layer and boundary conditions at the interfaces to calculate the heat transport in this bounded system. We also consider the heat flux at the surface of the samle as boundary condition instead of using a fixed tempertaure. From this, we obtain an expression for the efective thermal diffusivity of the composite sample in terms of the thermal diffusivity of its constituent materials whithout any approximations.Comment: 16 pages, 1 figure, RevTeX v. 3.0 macro packag

Surface Fatigue Behaviour of a WC/aC:H Thin-Film and the Tribochemical Impact of Zinc Dialkyldithiophosphate

In wind turbine gearboxes, (near-)surface initiated fatigue is attributed to be the primary failure mechanism. In this work, the surface fatigue of a hydrogenated tungsten carbide/amorphous carbon (WC/aC:H) thin-film was tested under severe cyclic tribo-contact using PolyAlphaOlefin (PAO) and PAO + Zinc DialkylDithioPhosphate (ZDDP) lubricants. The film was characterised in terms of its structure and chemistry using X-ray diffraction, analytical Transmission Electron Microscopy (TEM) including Electron Energy Loss Spectroscopy (EELS), as well as X-ray Photoelectron Spectroscopy (XPS). The multilayer carbon thin-film exhibited promising surface fatigue performance showing a slight change in the hybridization state of the aC:H matrix. Dehydrogenation of the thin-film and subsequent transformation of cleaved C-H bonds to non planar sp2 carbon rings were inferred from EELS and XPS results. Whilst tribo-induced changes to the aC:H matrix were not influenced by a nanometer-thick ZDDP reaction-film, the rate of oxidation of WC and its oxidation state were affected. Whilst accelerating surface fatigue on a steel surface, the ZDDP-tribofilm protected the WC/aC:H film from surface fatigue. In contrast to the formation of polyphosphates from ZDDP molecules on steel surfaces, it appeared that on the WC/aC:H thin film surface ZDDP molecules decompose to ZnO suppressing the oxidative degradation of WC

Intermediate Tail Dependence: A Review and Some New Results

The concept of intermediate tail dependence is useful if one wants to quantify the degree of positive dependence in the tails when there is no strong evidence of presence of the usual tail dependence. We first review existing studies on intermediate tail dependence, and then we report new results to supplement the review. Intermediate tail dependence for elliptical, extreme value and Archimedean copulas are reviewed and further studied, respectively. For Archimedean copulas, we not only consider the frailty model but also the recently studied scale mixture model; for the latter, conditions leading to upper intermediate tail dependence are presented, and it provides a useful way to simulate copulas with desirable intermediate tail dependence structures.Comment: 25 pages, 1 figur