839 research outputs found

    He^2+ transport in the Martian upper atmosphere with an induced magnetic field

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    Solar wind helium may be a significant source of neutral helium in the Martian atmosphere. The precipitating particles also transfer mass, energy, and momentum. To investigate the transport of He^2+ in the upper atmosphere of Mars, we have applied the direct simulation Monte Carlo method to solve the kinetic equation. We calculate the upward He, He^+, and He^2+ fluxes, resulting from energy spectra of the downgoing He^2+ observed below 500 km altitude by the Analyzer of Space Plasmas and Energetic Atoms 3 instrument onboard Mars Express. The particle flux of the downward moving He^2+ ions was 1–2 × 10^6 cm^–2 s^–1, and the energy flux is equal to 9–10 × 10^–3 erg cm^–2 s^–1. The calculations of the upward flux have been made for the Martian atmosphere during solar minimum. It was found, that if the induced magnetic field is not introduced in the simulations the precipitating He^2+ ions are not backscattered at all by the Martian upper atmosphere. If we include a 20 nT horizontal magnetic field, a typical field measured by Mars Global Surveyor in the altitude range of 85–500 km, we find that up to 30%–40% of the energy flux of the precipitating He^2+ ions is backscattered depending on the velocity distribution of the precipitating particles. We thus conclude that the induced magnetic field plays a crucial role in the transport of charged particles in the upper atmosphere of Mars and, therefore, that it determines the energy deposition of the solar wind

    Governance of Incomes from the Inland Fishing Industry in the Republic of Congo: Analysis by the Catfish Value Chain, Clarias Gabonensis, from the Lac Télé Community Reserve

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    The results of this study conducted between July and November 2019 have identified that a Clarias gabonensis value chain in the North part of Congo is principally dominated by men with regards to fishing activities and women with regard to the marketing of fish products harvested from the Lac T l Community Reserve LTCR to the cities of Impfondo Pokola and Oyo Both the fishing and the marketing are practiced by all age groups in the reserve and others localities Among fishermen 20 40 are over 55 years old and 69 60 are between 18 and 54 years old 34 69 have no education 38 77 have a primary level of education and 26 53 have a secondary level of education In comparison wholesalers and retailers have mainly a basic educational level 30 of the workforce is over 50 and over 70 have more than 10 years of experience in the business The absence of institutional investment in this value chain is demonstrated by the importance of internal investment resulting in dependence between the actor

    New-onset diabetic ketoacidosis in a 13-months old african toddler: a case report

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    Type 1 diabetes mellitus is very rare in infants and toddlers and is usually associated with high mortality when complicated with diabetic ketoacidosis (DKA). Toddlers in DKA are often missed in our typical African setting where there is low index of suspicion. Usually, the classical symptoms are not usually at the forefront and many infants and toddlers who develop DKA are mistreated for infections. The case of a 13-months old toddler with new-onset type 1 diabetes mellitus, complicated with DKA at diagnosis is reported in view of its rarity and elevated mortality even when diagnosed in our African setting. She was subsequently treated with intravenous insulin and was passed over to subcutaneous insulin after the eradication of ketones in urine. She continues follow-up at the out-patient children diabetes clinic at the Bafoussam Regional Hospital.Key words: Diabetic ketoacidosis, children, Africa, diabetes complicatio

    Line shape diagnostics for solid density plasmas produced by ultra intense subpicosecond laser

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87325/2/158_1.pd

    Proton and hydrogen atoms transport in the Martian upper atmosphere with an induced magnetic field

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    We have applied the Direct Simulation Monte Carlo method to solve the kinetic equation for the H/H^+ transport in the upper Martian atmosphere. We calculate the upward H and H^+ fluxes, values that can be measured, and the altitude profile of the energy deposition to be used to understand the energy balance in the Martian atmosphere. The calculations of the upward flux have been made for the Martian atmosphere during solar minimum. We use an energy spectrum of the down moving protons in the altitude range 355–437 km adopted from the Mars Express Analyzer of Space Plasma and Energetic Atoms measurements in the range 700 eV–20 keV. The particle and energy fluxes of the downward moving protons were equal to 3.0 × 10^6 cm^−2 s^−1 and 1.4 × 10^−2 erg cm^−2 s^−1. It was found that 22% of particle flux and 12% of the energy flux of the precipitating protons is backscattered by the Martian upper atmosphere, if no induced magnetic field is taken into account in the simulations. If we include a 20 nT horizontal magnetic field, a typical field measured by Mars Global Surveyor in the altitude range of 85–500 km, we find that up to 40%–50% of the energy flux of the precipitating protons is backscattered depending on the velocity distribution of the precipitating protons. We thus conclude that the induced magnetic field plays a crucial role in the transport of charged particles in the upper atmosphere of Mars and, therefore, that it determines the energy deposition of the solar wind

    Spatially uniform enhancement of single quantum dot emission using plasmonic grating decoupler

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    International audience1 We demonstrate a spatially uniform enhancement of individual quantum dot (QD) fluorescence emission using plasmonic grating decouplers on thin gold or silver films. Individual QDs are deposited within the grating in a controlled way to investigate the position dependency on both the radiation pattern and emission enhancement. We also describe the optimization of the grating decoupler. We achieve a fluorescence enhancement ~3 times higher than using flat plasmon film, for any QD position in the grating. Future optical quantum devices require the development of photonic sources with control of light down to the single photon limit. Excellent examples of single photon emitters are the colloidal nanocrystal quantum dots (QDs) which are considered as the building blocks for future quantum devices such as quantum qubits and quantum cryptographic devices 1,2. The application area of quantum emitters is wide and these applications require control of their emission such as emission rate, polarization, spectral properties, collection efficiency etc. Integration of single molecule or nanocrystals into plasmonic structures has recently proved to be one of the most promising yet challenging ways to control the emission properties at the single photon level 3,
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