4,422 research outputs found
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
Second-order Born approximation for the ionization of molecules by electron and positron impact
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
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