Practical Bayesian optimization in the presence of outliers

Inference in the presence of outliers is an important field of research as outliers are ubiquitous and may arise across a variety of problems and domains. Bayesian optimization is method that heavily relies on probabilistic inference. This allows outstanding sample efficiency because the probabilistic machinery provides a memory of the whole optimization process. However, that virtue becomes a disadvantage when the memory is populated with outliers, inducing bias in the estimation. In this paper, we present an empirical evaluation of Bayesian optimization methods in the presence of outliers. The empirical evidence shows that Bayesian optimization with robust regression often produces suboptimal results. We then propose a new algorithm which combines robust regression (a Gaussian process with Student-t likelihood) with outlier diagnostics to classify data points as outliers or inliers. By using an scheduler for the classification of outliers, our method is more efficient and has better convergence over the standard robust regression. Furthermore, we show that even in controlled situations with no expected outliers, our method is able to produce better results.Comment: 10 pages (2 of references), 6 figures, 1 algorith

Stellar populations in the center of barred spiral galaxies

We show observations obtained with the integral field spectrometer OASIS for the central regions of a sample of barred galaxies. The high spatial resolution of the instrument allows to distinguish various structures within these regions as defined by stellar populations of different ages and metallicities. From these data we obtain important clues about the star formation history. But we advise that, in order to obtain adequately the evolutionary sequence, a combination of chemical and synthesis models may be necessary.Comment: 4 pages, 2 figures, submitted to the IAU245 Symposium Formation and Evolution of Galaxy Bulge

Presence of atrial natriuretic factor prohormone in enterochromaffin cells of the human large intestine

Atrial natriuretic factor is a hormone intimately involved in water and salt homeostasis. The heart constitutes the major but not exclusive site of synthesis of this hormone. Among other functions, the gastrointestinal tract has endocrine functions, plays an important role in volume regulation of the body, and seems to be a target organ for atrial natriuretic factor. Therefore, the presence of atrial natriuretic factor was investigated in the human gut. Immunoreactive atrial natriuretic factor was found in intraoperatively obtained samples of normal human colon. Acidic extracts of human large intestine contained about 0.4 pmol/g wet wt of atrial natriuretic factor. Analysis of atrial natriuretic factor immunoreactivity by gel-filtration and reverse-phase high-performance liquid chromatography showed that about 65% of the immunoreactivity corresponded to the atrial natriuretic factor phohormone and about 35% corresponded to the C-terminal ANF99-126. Immunohistochemistry showed atrial natriuretic factor prohormone location in enterochromaffin cells of the colon mucosa. Altogether, these findings show the presence of atrial natriuretic factor prohormone in enterochromaffin cells of the human large intestine and may suggest this organ as a site of atrial natriuretic factor synthesis in humans

L’homme de Marx est-il un sujet individuel ou un être social? À propos de l’interprétation de Marx par Louis Dumont

Prenant le contre-pied de l'opinion généralement admise concernant l'anthropologie marxienne, Louis Dumont (dans son ouvrage Homo JEqualis. Genèse et épanouissement de l'idéologie économique} désigne celle-ci comme l'expression la plus achevée de l'idéologie individualiste moderne. Cet article examine les principaux arguments à l'appui de cette interprétation et s'interroge sur sa capacité à éclairer l'enjeu que recèle la conception marxienne de l'homme. Je me propose de montrer que l'opposition rigoureuse entre holisme et individualisme dans laquelle s'enferme la lecture dumontienne laisse échapper cet enjeu, que seule une juste appréhension du naturalisme marxien est, selon moi, en mesure de révéler. Le texte se divise en trois parties. La première expose les grandes lignes de la théorie dumontienne de l'idéologie moderne et attire l'attention sur les deux difficultés épistémologiques majeures auxquelles se heurte l'application de cette théorie à Marx. La seconde partie montre en quoi le naturalisme conséquent de Marx suppose le rejet et le dépassement de l'alternative holisme/individualisme. Dans la troisième partie, enfin, je m'efforce de poser quelques jalons en vue d'une recherche qui prendrait pour thème l'individualisme social de Marx.Challenging what is widely taught and believed to be the case about Marx's anthropology, Louis Dumont (in his book From Mandeville to Marx. The Genesis and Triumph of Economic Ideology} identifies it as the ultimate achievement of the modern individualist ideology. This paper looks at the main arguments of this interpretation and questions about its capacity of focusing on what is really at stake in the Marxian conception of man. I shall argue that Marx's naturalism invalidates the over-rigid opposition between holism and individualism within which Dumont imprisons Marx. The paper is divided into three parts. The first part deals with Dumont's theory of modern Ideology which supports and informs his interpretation of Marx; it focuses on two major epistemological difficulties inherent in the application of this theory to Marx. The second part shows how the naturalism of Marx makes the principle of an opposition between holism and individualism irrelevant. In the third part, I confine myself to a brief outline of a research to be done into Marx's social individualism