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International audience; After Mandelbrot’s seminal work, scale-free and multifractal temporal dynamics have been recognized as classical stylized facts for financial time series and massively documented. Multifractal analysis in finance has however mainly remained univariate (one time series at a time) when multivariate (or basket) properties are critical for financial applications. This is mostly due to a lack of theoretical foundations and practical tools for multivariate multifractal analysis. Expanding on a theoretically-grounded recently proposed multivariate multifractal formalism, the present work performs an original multivariate analysis for a basket of six Foreign Exchange rate time series. Beyond confirming multifractality for each component independently, the definition of cross-multifractalities amongst components is introduced, assessing cross-dependencies in temporal dynamics not already accounted for by cross-correlations. The key practical outcome is to show that, essentially, one same multifractal time governs jointly the temporal dynamics of all the Foreign Exchange time series studied here.

Fragestellung: Liegen der Sakrumdysmorphie anatomisch-betrachtet lumbosakrale Transitionalwirbel zugrunde? Lässt sich der iliosakrale Knochenkorridordurchmesser für auf Höhe von S1 und S2 durch eine in-out-in Platzierung der Schraube im dorsalen iliosakralen Recessus vergrößern?[zum vollständigen Text gelangen Sie über die oben angegebene URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2018)

Seit dem siebzehnten Jahrhundert war der weit ins Folgejahrhundert hineinreichende Streit über die kulturelle Überlegenheit der Antike oder der Moderne ein zentraler Topos intellektueller Debatten, zunächst in Frankreich, dann auch in anderen europäischen Ländern. Dieser Streit spiegelte sich in Positionen über die sich herausbildenden mathematischen Methoden in der Naturphilosophie wieder. Während nicht in Frage stand, dass es einen Wissensfortschritt bezüglich partikulärer Phänomene (z.B. dem Kompass) gegeben habe, war umstritten, inwiefern antike Methoden und Argumentationsformen für die moderne Wissenschaft nicht mehr verbindlich seien. Eine zentrale Innovation in der Methode der Mechanik des siebzehnten Jahrhunderts war die Verwendung der analytischen Geometrie (Übersetzung geometrischer Probleme in algebraische Gleichungen) und der Infinitesimalrechnung. In der Bewertung dieser Innovationen gab es große Differenzen: Newton berief sich explizit auf die Autorität der Euklidischen Geometrie als Begründung für die konservative Form der Beweise in den Principia Mathematica, in denen er so weit als möglich einen Rückgriff auf analytische Geometrie und Infinitesimalrechnung vermied. In Lagranges Mechanique analytique andererseits finden sich keinerlei geometrische Diagramme mehr und die Newtonsche Mechanik wird ausschließlich in Form algebraischer Gleichungen präsentiert. Der Aufsatz untersucht die Frage nach dem Verhältnis dieses radikalen Wandels in der theoretischen Methodologie der Mechanik zu den Vorstellungen der Akteure von antiker Wissenschaft und ihrer Autorität. Des weiteren verfolgt er die Entstehung eines Begriffs von antiker Wissenschaft als eines Anderen der modernen Wissenschaft und das Verhältnis dieses Begriffs zu einer Wissenschaftsgeschichte im modernen Sinne.

International audience; Change-point detection problems can be solved either by variational approaches based on total variation or by Bayesian procedures. The former class leads to small computational time but requires the choice of a regularization parameter that significantly impacts the achieved solution and whose automated selection remains a challenging problem. Bayesian strategies avoid this regularization parameter selection, at the price of high computational costs. In this contribution, we propose a hybrid Bayesian variational procedure that relies on the use of a hierarchical Bayesian model while preserving the computational efficiency of total variation optimization procedures. Behavior and performance of the proposed method compare favorably against those of a fully Bayesian approach, both in terms of accuracy and of computational time. Additionally, estimation performance are compared to the Stein unbiased risk estimate, for which the knowledge of the noise variance is needed.

International audience; Digital imaging and signal processing technologies offer new methods for inkjet and photographic media engineers and manufacturers, and those responsible for product quality control, to classify and characterize printing materials surface textures using new and more quantitative methods. This paper presents a collaborative project to systematically and semi-automatically characterize the surface texture of inkjet media. These methods have applications in product design and specification, and in manufacturing quality control. Surface texture is a critical feature in the manufacture, marketing and use of inkjet papers, especially those used for fine art printing. Raking light reveals texture through a stark rendering of highlights and shadows. Though raking light photomicrographs effectively document surface features of inkjet paper, the sheer number and diversity of textures prohibits efficient visual classification. This work provides evidence that automatic, computer-based classification of texture documented with raking light photomicrographs is feasible by demonstrating an encouraging degree of success sorting a set of 120 photomicrographs made from diverse samples of inkjet paper and canvas available in the market from 2000 through 2011. The samples used for this study were drawn from the Wilhelm Analog and Digital Color Print Materials Reference Collection. Using this dataset, four university teams applied different image processing strategies for automatic feature extraction and degree of similarity quantification. All four approaches were successful in detecting strong affinities among similarity groupings built into the dataset as well as identifying outliers. The creation and deployment of the algorithms was carried out by the teams without prior knowledge of the distributions of similarities and outliers. These results indicate that automatic classification of inkjet paper based on texture photomicrographs is feasible. To encourage the development of additional classification schemes, the 120 inkjet sample “training” dataset used in this work is available to other academic researchers at www.PaperTextureID.org.

Multifractal analysis, which mostly consists of estimating scaling exponents related to the power law behaviors of the moments of wavelet coefficients, is becoming a popular tool for empirical data analysis. However, little is known about the statistical performance of such procedures. Notably, despite their being of major practical importance, no confidence intervals are available. Here, we choose to replace wavelet coefficients with wavelet Leaders and to use a log-cumulant based multifractal analysis. We investigate the potential use of bootstrap to derive confidence intervals for wavelet Leaders log-cumulant multifractal estimation procedures. From numerical simulations involving well-known and well-controlled synthetic multifractal processes, we obtain two results of major importance for practical multifractal analysis : we demonstrate that the use of Leaders instead of wavelet coefficients brings significant improvements in log-cumulant based multifractal estimation, we show that accurate bootstrap designed confidence intervals can be obtained for a single finite length time series.