Some critical remarks on Zhang's gamma test for independence

Zhang (2008) defines the quotient correlation coefficient to test for dependence and tail dependence of bivariate random samples. He shows that asymptotically the test statistics are gamma distributed. Therefore, he called the corresponding test gamma test. We want to investigate the speed of convergence by a simulation study. Zhang discusses a rank-based version of this gamma test that depends on random numbers drawn from a standard Frechet distribution. We propose an alternative that does not depend on random numbers. We compare the size and the power of this alternative with the well-known t-test, the van der Waerden and the Spearman rank test. Zhang proposes his gamma test also for situations where the dependence is neither strictly increasing nor strictly decreasing. In contrast to this, we show that the quotient correlation coefficient can only measure monotone patterns of dependence. --test on dependence,rank correlation test,Spearman's p,copula,Lehmann ordering

Extrinsic and intrinsic regulation of differentiation and selection events during lymphocyte development

The development of lymphocytes is a precise, stepwise process that is subject to multiple extrinsic as well as intrinsic molecular mechanisms that guide cell differentiation and selection. Two essential regulators of lymphopoiesis are environmental signal mediators in the form of cytokines and transcription factors. Both influence proliferation, survival, differentiation and cell fate decisions. In the present thesis, we investigated the role of the cytokines Flt3-ligand and IL-7 in lymphocyte development by the use of various mutant mouse strains. Our results unraveled crucial functions for both cytokines during lymphocyte differentiation. Flt3-ligand drives the proliferation of uncommitted progenitor populations such as CLP and EPLM, whereas IL-7 has a pro-survival effect on these cells. High levels of Flt3-ligand rescued the B-cell defect in IL-7-/- mice due to the tremendous expansion of the CLP and EPLM populations, surpassing the need for IL-7 as a survival factor. Thus, these observations clearly demonstrate that both, Flt3-ligand as well as IL-7, function in a permissive mode in the commitment process towards the B-cell lineage. Flt3 expression is suppressed upon commitment to the B-cell fate, but IL-7 has furthermore a proliferative function for committed CD19+ progenitor cells. Constitutive over-expression of both Flt3-ligand and IL-7 resulted in a lympho- and myelo-proliferative disease. The two cytokines had a synergistic effect on the development of B cells, resulting in the accumulation of progenitors also in peripheral lymphoid organs. Interestingly, even MPPs could be detected in lymph nodes of these mice and transplantation experiments confirmed the functionality of these progenitors, since they were capable of long-term multilineage reconstitution. Thus, Flt3-ligand and IL-7 act in concert during lymphocyte development. We further provided evidence that peripheral lymphoid organs have the capability to support extramedullary hematopoiesis in pathological situations. In a second study we focused on the molecular and transcriptional regulation of the first essential checkpoint of the antigen-receptor rearrangement in T-cell development, called β-selection. Even though almost half of the cells are eliminated at this checkpoint, only little is known about the underlying molecular mechanisms. Improvement of the current staging of thymocyte development by the addition of CD27 downregulation as a marker for cells that failed productive β-chain rearrangement at the DN3 stage allowed us to investigate this process in more detail than previously possible. Transcriptional analysis revealed a specific expression of the transcription factor Duxbl in cells prior to β-selection. Transgenic expression of Duxbl blocked the development of pre-T cells in vitro and in vivo due to increased apoptosis and cell cycle arrest. Further studies revealed the involvement of the Oas/RNaseL apoptosis pathway in this Duxbl-mediated developmental arrest. Additional expression of the pro-survival factor Bcl2 partially rescued the block and in vitro knockdown experiments of Duxbl reduced apoptosis induction within the DN3 compartment. Thus, the specific expression of Duxbl in conjunction with the gain- and loss-of-function phenotypes of increased and reduced apoptosis, respectively, provide clear evidence for a key role of Duxbl in the elimination of DN3 cells that are not able to recombine a functional β-chain. Overall, the results presented in this thesis, provide important new insights on the cell-extrinsic and -intrinsic regulation of differentiation and selection events in the development of lymphocytes. Furthermore, they highlight the validity of in vivo models for the investigation of immune cell development and function

Modellierung der Torsionstragfähigkeit segmentierter Betontürme auf Basis der Wölbtheorie dünnwandiger Stäbe

Dieser Beitrag beschäftigt sich mit der Modellierung der Torsionstragfähigkeit segmentierter Betontürme auf Basis der Wölbtheorie dünnwandiger Stäbe. Ziel ist die wirklichkeitsnahe Abbildung des Tragverhaltens und die Entwicklung eines Ingenieurmodells, das dem praktischen Anwender stets die Kontrolle über sein Handeln bewahrt und die Resultate ohne gesonderten Interpretationsbedarf als Bewertungsgrundlage ansetzt. Auf der Grundlage von mechanischen Modellvorstellungen und nichtlinearen numerischen Untersuchungen wird die sukzessive Entwicklung eines ingenieurmäßigen Ansatzes vorgestellt. Dieser dient als Grundlage der Validierung sorgfältig durchzuführender Versuche an Betonsegmenten

Simulations of an accretion disk surrounding a supermassive black hole and its interaction with a nuclear star cluster

We investigate the time evolution of an AD surrounding a SMBH in an active galactic nucleus (AGN) and its dynamical interactions with a the nuclear star cluster (NSC). The AD is important in these interactions because of its dissipative force acting on the NSC stars, resulting in an increased mass flow to the SMBH and asymmetries in the phase space distribution due to its rotation. As the StarDisk project (Just et al., Kennedy et al.) only treated a static AD, viscous hydrodynamical simulations including gravity and self-gravity are used in this thesis to take dissipative feedback and lifetime checks of the AD into account. These simulations were performed using the PLUTO code along with additional modules written by Rolf Kuiper and equilibrium initial condition similar to Shakura & Sunyayev. The results were a quasi-static state as well as the confirmation of the scale-height assumptions from Kennedy et al. and the estimation of the accretion rate reproducing the expected result from Shakura & Sunyayev. Furthermore, the obtained data was used to interpolate the dissipative forces in the direct N-body code NBODY6++GPU and carry out a first test. The inclusion of more physics into the hydrodynamics as well as the advancement of the NBODY6++GPU project to real applications are both tasks for future researc

Psychophysiologische Korrelate emotionaler Informationsverarbeitung bei Depression und bei Posttraumatischer Belastungsstörung im Jugendalter

Klein F. Psychophysiologische Korrelate emotionaler Informationsverarbeitung bei Depression und bei Posttraumatischer Belastungsstörung im Jugendalter. Bielefeld: Universität Bielefeld; 2019.In meiner Arbeit untersuche ich Besonderheiten in der emotionalen Informationsverarbeitung bei den Störungsbildern Depression und Posttraumatische Belastungsstörung (PTBS). Für beide Störungsbilder gibt es in der Literatur populäre Annahmen hinsichtlich bestimmter dysfunktionaler Aufmerksamkeitsprozesse. Ein zentraler Einflussfaktor, welcher das Risiko für PTBS oder Depression beziehungsweise die Entwicklung entsprechender Subtypen dieser Erkrankungen beeinflusst, scheinen frühe traumatische Lebensereignisse zu sein. Es wird in diesem Zusammenhang von schädlichen Einflüssen auf die Stress- und Informationsverarbeitung der Betroffenen ausgegangen. Das Ziel der vorliegenden Dissertation war es, Besonderheiten in der emotionalen Informationsverarbeitung beider Störungsbilder weiter zu erforschen. In allen drei Studien der Dissertation sollte hierbei die Rolle sozial bedrohlicher Stimuli bei der emotionalen Informationsverarbeitung beleuchtet werden, in den störungsbezogenen Studien sollte zudem übergreifend die Rolle früher traumatischer Kindheitserfahrungen auf verschiedene Stufen der emotionalen Informationsverarbeitung untersucht werden. Es zeigte sich in allen drei Studien, dass sozial bedrohliche Stimuli einen besonderen Einfluss auf die emotionale Informationsverarbeitung besitzen, da sie zu distinkten (verstärkten) Amplituden bei Gesunden und Depressiven/PTBS-Patienten führten. Des Weiteren weisen die Ergebnisse der ersten beiden Studien darauf hin, dass Selbstrelevanz einen wichtigen Faktor bei der Integration von Kontextinformationen darstellt, da selbstbezogene Stimuli in beiden Studien zu verstärkten Reaktionen auf die neutralen Gesichter führten. Bei der Untersuchung der depressiven Probanden in Studie 2 wiesen diese im Vergleich zur Kontrollgruppe eine generell verstärkte frühe Verarbeitung der neutralen Gesichtsausdrücke auf. In Bezug auf die Rolle traumatischer Kindheitserfahrungen auf mögliche Subtypen von Depression oder PTBS zeigte sich zum einen, dass physische Missbrauchserlebnisse bei depressiven Probanden mit verringerten Aufmerksamkeitsreaktionen zusammenhingen, während traumatische Kindheitserfahrungen bei Probanden der Kontrollgruppe zu verstärkten Aufmerksamkeitsreaktionen führten. Bei den Probanden der dritten Studie zeigte sich zum anderen eine verstärkte Verarbeitungsreaktion in späteren, bewussteren Bereichen der emotionalen Informationsverarbeitung. Dieses Ergebnis lässt vermuten, dass traumatische Kindheitserfahrungen bei einer adoleszenten PTBS-Patientengruppe möglicherweise zu einer distinkten Form der PTBS führen können, welche insbesondere mit einer intensivierten bewussten Verarbeitung emotionaler Stimuli zusammenhängt

Parametrised polyconvex hyperelasticity with physics-augmented neural networks

In the present work, neural networks are applied to formulate parametrised hyperelastic constitutive models. The models fulfill all common mechanical conditions of hyperelasticity by construction. In particular, partially input-convex neural network (pICNN) architectures are applied based on feed-forward neural networks. Receiving two different sets of input arguments, pICNNs are convex in one of them, while for the other, they represent arbitrary relationships which are not necessarily convex. In this way, the model can fulfill convexity conditions stemming from mechanical considerations without being too restrictive on the functional relationship in additional parameters, which may not necessarily be convex. Two different models are introduced, where one can represent arbitrary functional relationships in the additional parameters, while the other is monotonic in the additional parameters. As a first proof of concept, the model is calibrated to data generated with two differently parametrised analytical potentials, whereby three different pICNN architectures are investigated. In all cases, the proposed model shows excellent performance

Tricyanated Ferrocenes;Isolation, structure, electrochemistry and DFT calculations

1,2,3- Tricyanoferrocene and 1,3-dibromo-2,4,5-tricyanoferrocene have been synthesized via metallation and usage of dimethylmalononitrile (DMMN) as cyanating agent. They are the first compounds where three nitrile functions could be introduced into the ferrocene sceleton. Further studies on the electrophilic cyanation of lithiated haloferrocenes [Fe(C5HmX4-mLi)(C5H5)] (X=Cl, Br;m=0-3) show the formation of complex mixtures of cyano-halo-ferrocenes [Fe{C5HmX5-m-n(CN)(n)}(C5H5)] (m=0-3, n=0-3) most likely induced by halogen-dance reactions. The molecular and crystal structures of [Fe{C5H2(CN)(3)}(C5H5)] and [Fe(C5Cl4CN)(C5H5)] are discussed. Cyclic voltametric studies of both tricyanoferrocenes show irreversible oxidations at very high potentials (E-onset approximate to 845 mV and 945 mV, respectively, vs FcH/FcH(+))