23,571 research outputs found

    Gravitational Wave Emission and Mass Extraction from a Perturbed Schwarzschild Black Hole (continue)

    Full text link
    A relativistic model for the emission of gravitational waves from an initially unperturbed Schwarzschild black hole, or spherical collapsing configuration, is completely integrated. The model consists basically of gravitational perturbations of the Robinson-Trautman type on the Schwarzschild spacetime. In our scheme of perturbation, gravitational waves may extract mass from the collapsing configuration. Robinson-Trautmann perturbations also include another mode of emission of mass, which we denote shell emission mode: in the equatorial plane of the configuration, a timelike (1+2)(1+2) shell of matter may be present, whose stress-energy tensor is modelled by neutrinos and strings emitted radially on the shell; no gravitational waves are present in this mode. The invariant characterization of gravitational wave perturbations and of the gravitational wave zone is made through the analysis of the structure of the curvature tensor and the use of the Peeling Theorem.Comment: 26 pages, LaTex, no figure

    Mouse model of Schistosomiasis: infection with Schistosoma mansoni in CD-1 mice

    Get PDF
    Schistosomiasis is a parasitic disease that affects almost 240 million worldwide. CD1 mice were infected with cercariae of S. mansoni, after which infection developed for 8 weeks. Tissues were processed to immuno-histological techniques. It was performed H&E staining for overall analyses, Sirius Red for fibrosis and immunohistochemistry for inflammation biomarkers. The most infected organ was the liver, fibrosis decreased with egg development and Galectin-3 (Gal3) and Interleukin 6 (IL-6) were expressed inside granulomasThis work was also supported by FCT – Fundação para a Ciência e Tecnologia (REF UID/BIM/04293/2013) and by the project NORTE-01-0145-FEDER-000012 and by a scholarship to Carla Luís with the reference SAICT2016/FEDER/BIO4DIA/BTI under the supervision of Dr. Rúben Fernandes.N/

    The art of fitting p-mode spectra: Part II. Leakage and noise covariance matrices

    Full text link
    In Part I we have developed a theory for fitting p-mode Fourier spectra assuming that these spectra have a multi-normal distribution. We showed, using Monte-Carlo simulations, how one can obtain p-mode parameters using 'Maximum Likelihood Estimators'. In this article, hereafter Part II, we show how to use the theory developed in Part I for fitting real data. We introduce 4 new diagnostics in helioseismology: the (m,ν)(m,\nu) echelle diagramme, the cross echelle diagramme, the inter echelle diagramme, and the ratio cross spectrum. These diagnostics are extremely powerful to visualize and understand the covariance matrices of the Fourier spectra, and also to find bugs in the data analysis code. These diagrammes can also be used to derive quantitative information on the mode leakage and noise covariance matrices. Numerous examples using the LOI/SOHO and GONG data are given.Comment: 17 pages with tex and ps files, submitted to A&A, [email protected]

    The art of fitting p-mode spectra: Part I. Maximum Likelihood Estimation

    Full text link
    In this article we present our state of the art of fitting helioseismic p-mode spectra. We give a step by step recipe for fitting the spectra: statistics of the spectra both for spatially unresolved and resolved data, the use of Maximum Likelihood estimates, the statistics of the p-mode parameters, the use of Monte-Carlo simulation and the significance of fitted parameters. The recipe is applied to synthetic low-resolution data, similar to those of the LOI, using Monte-Carlo simulations. For such spatially resolved data, the statistics of the Fourier spectrum is assumed to be a multi-normal distribution; the statistics of the power spectrum is \emph{not} a χ2\chi^{2} with 2 degrees of freedom. Results for l=1l=1 shows that all parameters describing the p modes can be obtained without bias and with minimum variance provided that the leakage matrix is known. Systematic errors due to an imperfect knowledge of the leakage matrix are derived for all the p-mode parameters.Comment: 13 pages, ps file gzipped. Submitted to A&

    On the choice of parameters in solar structure inversion

    Get PDF
    The observed solar p-mode frequencies provide a powerful diagnostic of the internal structure of the Sun and permit us to test in considerable detail the physics used in the theory of stellar structure. Amongst the most commonly used techniques for inverting such helioseismic data are two implementations of the optimally localized averages (OLA) method, namely the Subtractive Optimally Localized Averages (SOLA) and Multiplicative Optimally Localized Averages (MOLA). Both are controlled by a number of parameters, the proper choice of which is very important for a reliable inference of the solar internal structure. Here we make a detailed analysis of the influence of each parameter on the solution and indicate how to arrive at an optimal set of parameters for a given data set.Comment: 14 pages, 15 figures. Accepted for publication on MNRA
    corecore