8,491 research outputs found

    Limb imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera

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    We investigated the Venus O2 visible nightglow with imagery from the Venus Monitoring Camera on Venus Express. Drawing from data collected between April 2007 and January 2011, we study the global distribution of this emission, discovered in the late 70s by the Venera 9 and 10 missions. The inferred limb-viewing intensities are on the order of 150 kiloRayleighs at the lower latitudes and seem to drop somewhat towards the poles. The emission is generally stable, although there are episodes when the intensities rise up to 500 kR. We compare a set of Venus Monitoring Camera observations with coincident measurements of the O2 nightglow at 1.27 {\mu}m made with the Visible and Infrared Thermal Imaging Spectrometer, also on Venus Express. From the evidence gathered in this and past works, we suggest a direct correlation between the instantaneous emissions from the two O2 nightglow systems. Possible implications regarding the uncertain origin of the atomic oxygen green line at 557.7 nm are noted.Comment: 7 pages, 3 figure

    The empirical process on Gaussian spherical harmonics

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    We establish weak convergence of the empirical process on the spherical harmonics of a Gaussian random field in the presence of an unknown angular power spectrum. This result suggests various Gaussianity tests with an asymptotic justification. The issue of testing for Gaussianity on isotropic spherical random fields has recently received strong empirical attention in the cosmological literature, in connection with the statistical analysis of cosmic microwave background radiation

    Optimal Scaling of Mala for Nonlinear Regression

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    We address the problem of simulating efficiently from the posterior distribution over the parameters of a particular class of nonlinear regression models using a Langevin-Metropolis sampler. It is shown that as the number N of parameters increases, the proposal variance must scale as N{-1/3} in order to converge to a diffusion. This generalizes previous results of Roberts and Rosenthal [J. R. Stat. Soc. Ser. B Stat. Methodol. 60 (1998) 255-268] for the i.i.d. case, showing the robustness of their analysis

    Book review: Pontrandolfo, G. y Piccioni, S (2022) Comunicación especializada y divulgación en la red: aproximaciones basadas en corpus

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    [ES] Comunicación especializada y divulgación en la red: aproximaciones basadas en corpus es el fruto de la amplia experiencia investigadora en el campo de la lingüística de corpus y de los discursos de especialidad en español y de una consolidada reflexión acerca de los temas objeto de análisis por parte de Sara Piccioni de la Universidad G. D Annunzio de Chieti-Pescara y de Gianluca Pontrandolfo de la Universidad de Trieste.[EN] Comunicación especializada y divulgación en la red: aproximaciones basadas en corpus is the appreciable result of the extensive research experience in the fields of corpus linguistics and of specialized discourse by Sara Piccioni (Università degli Studi "Gabriele D'Annunzio" Chieti-Pescara) and Gianluca Pontrandolfo (Università di Trieste).Colantonio, C. (2023). Reseña de Pontrandolfo G. Piccioni S. (2022) Comunicación especializada y divulgación en la red. Aproximaciones basadas en corpus. Revista de Lingüística y Lenguas Aplicadas. 18:163-166. https://doi.org/10.4995/rlyla.2023.184471631661

    The molecular chaperone Hsp90 is a component of the cap-binding complex and interacts with the translational repressor Cup during Drosophila oogenesis

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    In metazoa, the spatio-temporal translation of diverse mRNAs is essential to guarantee proper oocyte maturation and early embryogenesis. The eukaryotic translation initiation factor 4E (eIF4E), which binds the 5′ cap structure of eukaryotic mRNAs, associates with either stimulatory or inhibitory factors to modulate protein synthesis. In order to identify novel factors that might act at the translational level during Drosophila oogenesis, we have undertaken a functional proteomic approach and isolated the product of the Hsp83 gene, the evolutionarily conserved chaperone Hsp90, as a specific component of the cap-binding complex. Here we report that Hsp90 interacts in vitro with the translational repressor Cup. In addition, we show that Hsp83 and cup interact genetically, since lowering Hsp90 activity enhances the oogenesis alterations linked to diverse cup mutant alleles. Hsp90 and Cup co-localize in the cytoplasm of the developing germ-line cells within the germarium, thus suggesting a common function from the earliest stages of oogenesis. Taken together, our data start elucidating the role of Hsp90 during Drosophila female germ-line development and strengthen the idea that Cup has multiple essential functions during egg chamber development

    CCD-based observations of PG 0856+121 and a theoretical analysis of its oscillation modes

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    BVRI CCD-based and near-IR (J) imaging, together with unfiltered photometry of the hot subdwarf B star PG 0856+121 are reported. Two close, faint, red, point-like sources are resolved. They account for the previously reported IR excess observed in this hot subdwarf. In addition, the new unfiltered differential photometry of PG 0856+121 confirms its previously reported pulsational nature. A comparison with the oscillation modes of stellar models suggests the possible presence of g modes.Comment: Accepted for publication in A&A. Seven pages, four figures include

    Adaptive Continuous time Markov Chain Approximation Model to General Jump-Diffusions

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    We propose a non-equidistant Q rate matrix formula and an adaptive numerical algorithm for a continuous time Markov chain to approximate jump-diffusions with affine or non-affine functional specifications. Our approach also accommodates state-dependent jump intensity and jump distribution, a flexibility that is very hard to achieve with other numerical methods. The Kologorov-Smirnov test shows that the proposed Markov chain transition density converges to the one given by the likelihood expansion formula as in Ait-Sahalia (2008). We provide numerical examples for European stock option pricing in Black and Scholes (1973), Merton (1976) and Kou (2002)

    Tubal stump pregnancy in ART patients two cases of ectopic stump pregnancy after IVF-ET

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    Ectopic pregnancy (EP) is a complication of pregnancy in which the embryo attaches outside the uterus. The rate of ectopic pregnancy is about 1 and 2% that of live births, though it may be as high as 4% among those using assisted reproductive technology (ART). We present two cases of interstitial stump pregnancies in patients who previously underwent salpingectomy for ectopic pregnancies, and a review of the literature. One patient has been treated with methotrexate (MTX) before the removal of the tubal stump, while the second has gone directly to laparoscopic (LPS) surgery. Transvaginal ultrasound examination is essential for early and accurate management of this condition. It should be quickly performed to rule out a stump interstitial pregnancy in women who conceive by ART after bilateral salpingectomy. A correct attitude towards this condition is not yet internationally standardized and both medical and surgical options should be promptly considere
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