256 research outputs found
Generalized D-Symmetric Operators I
2000 Mathematics Subject Classification: Primary: 47B47, 47B10; secondary 47A30.Let H be an infinite-dimensional complex Hilbert space and let A, B â L(H), where L(H) is the algebra of operators on H into itself. Let ÎŽAB: L(H) â L(H) denote the generalized derivation ÎŽAB(X) = AX â XB. This note will initiate a study on the class of pairs (A,B) such that [âŸ(R(ÎŽAB))] = [âŸ(R(ÎŽB*A*))]; i.e. [âŸ(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
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
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
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 setâup or as numerical correction
Uptake and distribution of heavy metals in agricultural production irrigated by raw wastewater
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
Des tests de lixiviation et dâadsorption de solutions des mĂ©taux lourds (Cd, Cu, Ni, Pb et Zn) sur quatre classes de sols de la ville dâOujda, ainsi que sur trois substrats organiques Ă base de compost dâordures mĂ©nagĂšres et de tourbe, ont Ă©tĂ© effectuĂ©s pour modĂ©liser la rĂ©tention et lâadsorption de ces mĂ©taux au niveau des dĂ©charges dâordures 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 dâadsorption et de rĂ©tention sont trĂšs importants (80 Ă 100 %) Ă diffĂ©rents pH. Les cinĂ©tiques dâadsorption 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 dâadsorption. 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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