256 research outputs found

    Generalized D-Symmetric Operators I

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    2000 Mathematics Subject Classification: Primary: 47B47, 47B10; secondary 47A30.Let H be an infinite-dimensional complex Hilbert space and let A, B ∈ L(H), where L(H) is the algebra of operators on H into itself. Let ÎŽAB: L(H) → L(H) denote the generalized derivation ÎŽAB(X) = AX − XB. This note will initiate a study on the class of pairs (A,B) such that [‟(R(ÎŽAB))] = [‟(R(ÎŽB*A*))]; i.e. [‟(R(ÎŽAB))] is self-adjoint

    Single rooms may help to prevent nosocomial bloodstream infection and cross-transmission of methicillin-resistant Staphylococcus aureus in intensive care units

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    OBJECTIVE: Nosocomial infections remain a major problem in intensive care units. Several authorities have recommended housing patients in single rooms to prevent cross-transmission of potential pathogens, but this issue is currently debated. The aim of the present study was to compare the rate of nosocomial cross-contamination between patients hosted in single rooms versus bay rooms. DESIGN: Prospective observational data acquisition over 2.5 years. SETTING: A 14-bed medico-surgical ICU, composed of six single-bed rooms plus a six-bed and a two-bed bay room served by the same staff. PATIENTS AND PARTICIPANTS: All patients admitted from 1 July 2002 to 31 December 2004. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in admitted patients was 1.1% and acquisition rate 2.4%. The incidence density of MRSA acquisition was 4.1 [95% CI 2.7-6.3]/1,000 patient-days in bay rooms versus 1.3 [0.5-3.4]/1,000 patient-days in single rooms (p<0.001). Pseudomonas spp. acquisition rate was 3.9 [2.5-6.1]/1,000 patient-days in bay rooms versus 0.7 [0.2-2.4]/1,000 patient-days in single rooms (p<0.001), and Candida spp. colonization was 38.4 [33.3-44.1]/1,000 patient-days in bay rooms versus 13.8 [10.2-18.6]/1,000 patient-days (p<0.001). By multivariate analysis, the relative risk of MRSA, Pseudomonas aeruginosa and Candida spp. acquisition in single rooms or cubicles versus bay rooms was 0.65, 0.61 and 0.75 respectively. CONCLUSIONS: These data suggest that in an institution where MRSA is not hyperendemic, infection control measures may be more effective to prevent cross-transmission of microorganisms in patients housed in single rooms

    A context-aware user-driven strategy to exploit Offloading and sharing in ultra-dense deployments

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    This paper proposes a novel context-aware userdriven strategy to efficiently exploit all available bands and licensing regimes in ultra-dense deployments without prior knowledge about each combination. It relies first on fuzzy logic to estimate the suitability of each radio access technology (RAT) to support the requirements of various applications. Then, a fuzzy multiple attribute decision making (MADM) approach is developed to combine these estimates with the heterogeneous context components to assess the in-context suitability. Based on this metric, a spectrum management strategy is proposed to support interactive video sessions for a set of Bronze and Gold subscriptions. The results reveal that the proposed approach always assigns Gold users to the well-regulated licensed band, while switches Bronze users between licensed and unlicensed bands depending on the operating conditions. This results in a significant improvement of the quality-of-experience (QoE) compared to a baseline that exploits only licensed bands. Then, a comparative study is conducted between the available options to exploit unlicensed bands, namely Offloading and Sharing. The results show that the best option strongly depends on the existing load on WLAN. Therefore, a combined approach is proposed to efficiently switch between both options, which achieves the best QoE for all considered loads

    Evaporation of Electrolyte During SVET Measurements: The Scale of the Problem and the Solutions

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    The objective of this work is to investigate the scale of the effect of spontaneous solution evaporation during SVET (Scanning Vibrating Electrode Technique) measurements and demonstrate how it biases the final results. When SVET maps are continuously acquired for more than several hours, the measured currents are smaller than expected. This is attributed to solvent (typically water) evaporation which leads to an increase in solution conductivity over time. If this is not considered when converting the measured potential differences into the local current densities, the SVET results display currents smaller than the true ones. Here, this effect is studied with a platinum disk electrode as source of a constant current and a model corroding system consisting of the AA2024/CFRP galvanic couple. Corrective actions are proposed to mitigate the problem, either in the experimental set‐up or as numerical correction

    Uptake and distribution of heavy metals in agricultural production irrigated by raw wastewater

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    Une expérience au champ a été réalisée pour déterminer les concentrations en fer, cuivre, zinc, nickel, cadmium et plomb dans le sol du champ d’épandage d’eaux usées et dans les tissus de divers plantes de grande importance économique: fève (Aphis fabae L.), carotte (Daucus carota L.), petit pois (Pisum sativum L.), laitue (Lactuca sativa L.), blé tendre (Triticum vulgare L.) et avoine (Avena sativa L.). Les parcelles irriguées par les eaux usées présentent des taux de matière organique largement supérieurs à celui de la parcelle témoin. Les concentrations en métal (cuivre, zinc, plomb et cadmium) dans les parcelles irriguées par les eaux usées sont supérieures à celles de la parcelle témoin (Po) et des sols pollués par les métaux lourds. Dans les tissus des plantes irriguées par ces eaux usées, les teneurs en métaux sont élevées par rapport aux valeurs normales rencontrées chez les espèces végétales

    Tests d'adsorption des métaux lourds (Cd, Cu, Ni, Pb, Zn) sur des substrats organiques et minéraux de la ville d'Oujda

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    Des tests de lixiviation et d’adsorption de solutions des mĂ©taux lourds (Cd, Cu, Ni, Pb et Zn) sur quatre classes de sols de la ville d’Oujda, ainsi que sur trois substrats organiques Ă  base de compost d’ordures mĂ©nagĂšres et de tourbe, ont Ă©tĂ© effectuĂ©s pour modĂ©liser la rĂ©tention et l’adsorption de ces mĂ©taux au niveau des dĂ©charges d’ordures mĂ©nagĂšres. Ces essais ont montrĂ© en gĂ©nĂ©ral que les mĂ©taux prĂ©sentent une grande affinitĂ© vis-Ă -vis des quatre classes de sols. Les taux d’adsorption et de rĂ©tention sont trĂšs importants (80 Ă  100 %) Ă  diffĂ©rents pH. Les cinĂ©tiques d’adsorption du Cd, Cu et Zn sur les substrats organiques et minĂ©raux ont montrĂ© Ă©galement que ces matĂ©riaux ont presque le mĂȘme modĂšle d’adsorption. Ces matĂ©riaux sont de vĂ©ritables matrices de piĂ©geage de mĂ©taux lourds. Concernant les essais de percolation sur colonne, les taux de rĂ©tention, par un sol calcimagnĂ©sique (non contaminĂ©, issu de la dĂ©charge urbaine) du cadmium, cuivre, nickel et zinc, sont tous supĂ©rieurs Ă  80 %
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