Archimedean Copulae and Positive Dependence.

In the first part of the paper we consider positive dependence properties of Archimedean copulae. Especially we characterize the Archimedean copulae that are multivariate totally positive of order 2 (MTP2) and conditionally increasing in sequence. In the second part we investigate conditions for binary sequences to admit an Archimedean copula.Conditionally increasing, MTP2, positive lower orthant dependent, exchangeability, binary sequences.

Some Counterexamples in Positive Dependence.

We provide some counterexamples showing that some concepts of positive dependence are strictly stronger than others. In particular we will settle two questions posed by Pemantle (2000) and Pellerey (2002) concerning respectively association versus weak association, weak association versus supermodular dependence, and supermodular dependence versus positive orthant dependence.Association, weak association, supermodular dependence, positive orthant dependence.

Archimedean Copulae and Positive Dependence

In the first part of the paper we consider positive dependence properties of Archimedean copulae. Especially we characterize the Archimedean copulae that are multivariate totally positive of order 2 (MTP2) and conditionally increasing in sequence. In the second part we investigate conditions for binary sequences to admit an Archimedean copula.In the first part of the paper we consider positive dependence properties of Archimedean copulae. Especially we characterize the Archimedean copulae that are multivariate totally positive of order 2 (MTP2) and conditionally increasing in sequence. In the second part we investigate conditions for binary sequences to admit an Archimedean copula.Refereed Working Papers / of international relevanc

Stochastic orders and risk measures: Consistency and bounds

We investigate the problem of consistency of risk measures with respect to usual stochastic order and convex order. It is shown that under weak regularity conditions risk measures are consistent with these stochastic orders. This result is used to derive bounds for risk measures of portfolios. As a by-product, we extend the characterization of Kusuoka (2001) of coherent, law-invariant risk measures with the Fatou property to unbounded random variables

Photoionization of astrophysically relevant atomic ions at PIPE

We review recent work on the photoionization of atomic ions of astrophysical interest that has been carried out at the photon-ion merged-beams setup PIPE, a permanently installed end station at the XUV beamline P04 of the PETRAIII synchrotron radiation source operated by DESY in Hamburg, Germany. Our results on single and multiple L-shell photoionization of Fe+, Fe2+, and Fe3+ ions and on single and multiple K-shell photoionization of C-, C+, C4+, Ne+, and Si2+ ions are discussed in astrophysical contexts. Moreover, these experimental results bear witness of the fact, that the implementation of the photon-ion merged-beams method at one of the world's brightest synchrotron light sources has led to a breakthrough for the experimental study of atomic inner-shell photoionization processes with ions.Comment: 18 pages, 7 figures, 1 table, 113 reference

Der Blaulicht-Photorezeptor Cryptochrom 2 aus Arabidopsis thaliana: Lichtabhängige Phosphorylierung und Interaktionspartner in der Signaltransduktion

Obwohl über die physiologische Bedeutung der pflanzlichen Cryptochrome bereits viel bekannt ist, und deren nahe Verwandte, die Photolyasen auch molekular sehr detailliert, einschließlich der Struktur auf atomarer Ebene, charakterisiert sind, sind die Mechanismen der Signalweiterleitung bei den Cryptochromen bis heute nur wenig erforscht. Dem Ziel folgend, diese molekularen Prozesse aufzuklären, wurde in dieser Arbeit Arabidopsis- Cryptochrom 2 untersucht. Es wurde dabei die lichtabhängige Phosphorylierung von cry2 entdeckt und näher untersucht. Das Aktionspektrum dieser Phosphorylierung ähnelt dabei stark einem Flavinspektrum. Versuche, die für diesen Prozess verantwortliche Kinase zu identifizieren, konnten nicht abgeschlossen werden. Eine Autophosphorylierungsaktivität wurde in Kooperation mit Margaret Ahmad (Paris) für cry1 gefunden, ist für cry2 bislang aber nicht gezeigt. In Hefe heterolog exprimiertes cry2 zeigt lichtabhängige Effekte, die auf mögliche Eigenschaften von cry2 als Transkriptionsaktivator schließen lassen. Zudem konnte eine DNA- Bindung für in vitro- transkribiertes und -translatiertes cry2 gezeigt werden. Untersuchungen zum Abbauweg von cry2 konnten unsere These eines proteasomalen Abbau von cry2 nicht bestätigen. Die subzelluläre Lokalisation zweier putativer Interaktionspartner von cry2 - At5g26280 und At2g02230 - wurde über konfokale Laserscan- Mikroskopie untersucht. At2g2230 konnte zudem als funktionelles F-Box Protein identifiziert werden

Longitudinal Shear Properties of European Larch Wood Related to Cell-Wall Structure

Using a new method to determine the longitudinal shear modulus (G) and shear strength (τ) of solid wood in a single test, the observed shear properties of normal (NW) and compression wood (CW) of larch samples were related to their microstructure, i.e., density, microfibril angle (MFA), and lignin content. To estimate the effective G of the solid cell wall, a semi-empirical model, which calculates G on the basis of porosity by extrapolation from experimental data, was used. For comparison, the effective G was derived from an analytical model, which considers the cell wall as a unidirectional laminate consisting of fiber and matrix material. The analytical model proved that the effect of increased MFA and higher lignin content on G in CW balance each other to a large degree. The effective G of the cell wall calculated by the analytical unidirectional laminate model was close to the estimate of the effective cell wall G performed by extrapolation from experimental data. Both models and mechanical test results demonstrated that effects of variability in cell-wall ultrastructure on G are minor, compared to effects of porosity and density, respectively. A multivariate regression model combining G and density showed that a good estimate of τ can be achieved using these input data

Altered structural connectivity of the left visual thalamus in developmental dyslexia

Developmental dyslexia is characterized by persistent reading and spelling deficits. Partly due to technical challenges with investigating subcortical sensory structures, current research on dyslexia in humans by-and-large focuses on the cerebral cortex. These studies found that dyslexia is typically associated with functional and structural alterations of a distributed left-hemispheric cerebral cortex network. However, findings from animal models and post-mortem studies in humans suggest that developmental dyslexia might also be associated with structural alterations in subcortical sensory pathways. Whether these alterations also exist in developmental dyslexia in-vivo and how they relate to dyslexia symptoms is currently unknown. Here we used ultra-high resolution structural magnetic resonance imaging (MRI), diffusion MRI and probabilistic tractography to investigate the structural connections of the visual sensory pathway in dyslexia in-vivo. We discovered that individuals with developmental dyslexia have reduced structural connections in the direct pathway between the left visual thalamus (LGN) and left middle temporal area V5/MT, but not between the left LGN and left primary visual cortex (V1). In addition, left V5/MT-LGN connectivity strength correlated with rapid naming abilities - a key deficit in dyslexia [14]. These findings provide the first evidence of specific structural alterations in the connections between the sensory thalamus and cortex in developmental dyslexia. The results challenge current standard models and provide novel evidence for the importance of cortico-thalamic interactions in explaining dyslexia.Comment: 31 pages, 5 figures, 2 table