1,558 research outputs found

    Fighting Novel Diseases amidst Humanitarian Crises

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    Humanitarian crises are becoming more prevalent and, frequently, more complex, in zones of mis-governance, lack of government presence, and even active conflict, marked by public mistrust and insecurity. The WHO and other health emergency responders lack the capacities and mandate to adequately respond. The current Ebola outbreak in an area of an active insurgency in the Democratic Republic of the Congo is just such a crisis. The State Department has banned U.S. personnel from the outbreak zone due to safety concerns, leaving the population feeling abandoned, potentially increasing the threat to the few brave health workers who remain. We need is to rethink health emergency response during complex crises and devise new strategies. We offer a blueprint for responding to health emergencies amidst complex humanitarian crises. This blueprint includes peacekeepers who have the mandate and modalities fit for the purpose of quelling a health emergency; “smart” diplomacy to negotiate with belligerents and community members to ensure health and humanitarian worker safety; and deploying all needed health, security, and diplomatic assets. We also call for international development assistance for health, including to support states in developing core public health capacities, creating inclusive health systems, and meeting other need like clean water and nutritious food. Political actors will need to assume their responsibilities if humanitarians and health workers are to carry out theirs

    Clustering in a precipitate free GeMn magnetic semiconductor

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    We present the first study relating structural parameters of precipitate free Ge0.95Mn0.05 films to magnetisation data. Nanometer sized clusters - areas with increased Mn content on substitutional lattice sites compared to the host matrix - are detected in transmission electron microscopy (TEM) analysis. The films show no overall spontaneous magnetisation at all down to 2K. The TEM and magnetisation results are interpreted in terms of an assembly of superparamagnetic moments developing in the dense distribution of clusters. Each cluster individually turns ferromagnetic below an ordering temperature which depends on its volume and Mn content.Comment: accepted for publication in Phys. Rev. Lett. (2006). High resolution images ibide

    Magnetic and structural properties of GeMn films: precipitation of intermetallic nanomagnets

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    We present a comprehensive study relating the nanostructure of Ge_0.95Mn_0.05 films to their magnetic properties. The formation of ferromagnetic nanometer sized inclusions in a defect free Ge matrix fabricated by low temperature molecular beam epitaxy is observed down to substrate temperatures T_S as low as 70 deg. Celsius. A combined transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) analysis of the films identifies the inclusions as precipitates of the ferromagnetic compound Mn_5Ge_3. The volume and amount of these precipitates decreases with decreasing T_S. Magnetometry of the films containing precipitates reveals distinct temperature ranges: Between the characteristic ferromagnetic transition temperature of Mn_5Ge_3 at approximately room temperature and a lower, T_S dependent blocking temperature T_B the magnetic properties are dominated by superparamagnetism of the Mn_5Ge_3 precipitates. Below T_B, the magnetic signature of ferromagnetic precipitates with blocked magnetic moments is observed. At the lowest temperatures, the films show features characteristic for a metastable state.Comment: accepted for publication in Phys. Rev. B 74 (01.12.2006). High resolution images ibide

    Phosphate bonded monolithics for reheating furnaces

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    Use of monolithic construction in reheating furnaces for roofs, hearths and burner blocks is gradually on the increase, Phosphate bonded sintered corundum and electro corundum have been reportedly used with considerable success in U. S. S. R. N. V. Pitak3 etal observed that such ramming mass for the bottoms of soaking pit furnaces offered high resistances to thermal shock and to action of ferrunginous 'slag at elevated temperature. According to S. R. Zamyatin4 etal phosphate bonded fireclay blocks could be recommended for use in blooming soaking pits

    The Role of Surface Area in Catalytic Gasification of Biomass

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    Gasification of biomass has the potential to provide a carbon-negative source of liquid fuels. The current limited use of gasification is due in part to the high temperatures necessary to achieve high conversion levels. These temperatures can be lowered by the use of catalysts, but the mechanisms by which catalysts affect the reaction rate are not fully understood. Here, the structural component of potassium carbonate’s role in the gasification process was examined. Samples of pinewood sawdust were impregnated with potassium carbonate, then pyrolyzed with N2 in a fixed bed reactor at 750°C (heater thermocouple reading). Half of the char was washed with deionized water twice to remove potassium ions. The char was ground to a 150 micron diameter. Gasification of the samples was performed using CO2 at 750°C and 900°C. Reaction rates over time were compared to the reaction rate of pure pinewood sawdust char. The pure char was then impregnated with K2CO3 and gasified, allowing a comparison to be made between the efficacy of impregnating the sawdust versus the char. Results show that after washing, the impregnated char shows similar or decreased reactivity compared to the pure char. Preliminary results do suggest that impregnation of the sawdust leads to greater reactivity over time than impregnation of the char. The results do not suggest a strong influence of surface area change during impregnation on the reactivity of the char

    Soot and Spectral Radiation Modeling for High-Pressure Turbulent Spray Flames

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    A transported probability density function (PDF) method and a photon Monte Carlo/line-by-line (PMC/LBL) spectral model are exercised to generate physical insight into soot processes and spectral radiation characteristics in transient high-pressure turbulent n-dodecane spray flames, under conditions that are relevant for compression-ignition piston engines. PDF model results are compared with experimental measurements and with results from a locally well-stirred reactor (WSR) model that neglects unresolved turbulent fluctuations in composition and temperature. Computed total soot mass and soot spatial distributions are highly sensitive to the modeling of unresolved turbulent fluctuations. To achieve reasonable agreement between model and experiment and to capture the highly intermittent nature of soot in the turbulent flame, it is necessary to accurately represent mixing and the low diffusivity of soot particles. This is accomplished in the PDF framework using a mixing model that enforces locality in the gas-phase composition space, while not mixing the transported soot variables. The results suggest that mixing is at least as important as kinetics in controlling soot formation and evolution in high-pressure turbulent flames. Regarding radiation, radiant fractions and global influences of radiation in these flames are relatively small. Nevertheless, an examination of spectral radiative heat transfer provides valuable insight into the nature and modeling of radiation in high-pressure turbulent combustion systems. There are complex spectral interactions that are revealed using PMC/LBL. CO2 dominates the total radiative emission and reabsorption, but most of the emitted CO2 radiation is reabsorbed before reaching the walls. On the other hand, most of the emitted soot radiation reaches the walls, but soot radiation is a small contribution overall; H2O dominates the radiation that reaches the walls. Global turbulence–radiation interactions (TRI) effects are small, but radiative emission from soot increases by approximately a factor two when TRI are considered. Radiative transfer contributes both to energy redistribution in the vessel and to wall heat losses. The results suggest that a simple model that considers soot radiation and the principal CO2 and H2O spectral bands might be sufficient to capture the key influences of radiation in engine CFD. It is expected that these findings will contribute to the development of truly predictive CFD models for engines and other high-pressure turbulent combustion systems
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