643 research outputs found

    Maximum a posteriori estimation through simulated annealing for binary asteroid orbit determination

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    This paper considers a new method for the binary asteroid orbit determination problem. The method is based on the Bayesian approach with a global optimisation algorithm. The orbital parameters to be determined are modelled through an a posteriori distribution made of a priori and likelihood terms. The first term constrains the parameters space and it allows the introduction of available knowledge about the orbit. The second term is based on given observations and it allows us to use and compare different observational error models. Once the a posteriori model is built, the estimator of the orbital parameters is computed using a global optimisation procedure: the simulated annealing algorithm. The maximum a posteriori (MAP) techniques are verified using simulated and real data. The obtained results validate the proposed method. The new approach guarantees independence of the initial parameters estimation and theoretical convergence towards the global optimisation solution. It is particularly useful in these situations, whenever a good initial orbit estimation is difficult to get, whenever observations are not well-sampled, and whenever the statistical behaviour of the observational errors cannot be stated Gaussian like.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Societ

    Dataset of total, oligomeric alpha-synuclein and hemoglobin levels in plasma in Parkinson׳s disease

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    AbstractThis data article presents a dataset of total, oligomeric alpha-synuclein and hemoglobin levels in plasma of drug-naïve PD patients and controls. This is the first attempt to assess the effect of hemolysis rate on oligomeric alpha-synuclein levels in peripheral plasma. The data are associated with the research article “Oligomeric alpha-synuclein and glucocerebrosidase activity levels in GBA-associated Parkinson׳s disease” (Pchelina et al., 2016) [1]

    Mechanisms of Microwave Absorption in Carbon Compounds from Shungite

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    According to SEM, X-ray phase analysis, Raman scattering data features of nanostructural changes in shungite carbon structure were found when processing shungite in 52 % hydrofluoric acid. It is found that conductivity increases up to the values of electrical graphite and absorption of microwave radiation also increases at frequencies up to 40 GHz, which, along with dielectric losses, is due to intense processes of both scattering at laminar carbon structures and absorption of electromagnetic energy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3365

    Surface-enhanced optical third-harmonic generation in Ag island films

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    Surface-enhanced optical third-harmonic generation (THG) is observed in silver island films. The THG intensity from Ag nanoparticles is enhanced by more than two orders of magnitude with respect to the THG intensity from a smooth and homogeneous silver surface. This enhancement is attributed to local plasmon excitation and resonance of the local field at the third-harmonic wavelength. The diffuse and depolarized component of the enhanced THG is associated with the third-order hyper-Rayleigh scattering in a 2-D random array of silver nanoparticles.Comment: 4 pages, 2 figure
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