Software Development for the Analysis of Exotic Beam Experiments and Study of the Neutron-Deficient Nuclei 98Cd and 98Ag

In this thesis, results of an experiment to study exotic nuclei in the 100Sn region are presented. 100Sn is the heaviest doubly-magic, self-conjugate nucleus. The nucleus and its neighbourhood are an important testing ground for the nuclear shell model, giving input on topics such as the single particle structure or the πν residual interaction. In addition, as the rapid proton capture (rp) process involves nuclei in the region, it is of interest for nuclear astrophysics. Recently, modern exotic beam facilities have made it possible to study nuclei very far from stability, such as the region around 100Sn. Thus, the questions from above can finally be addressed experimentally, and the evolution of nuclear structure can be tracked over a much larger region than previously possible. The experimental work for this thesis was performed at the FRS (FRagment Separator) instrument at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Exotic nuclei were produced by fragmentation of an 850 MeV/u 128Xe beam on a 9Be target. After being separated in the fragment separator they were brought to rest in an active stopper. The RISING high-purity germanium array with 15 Euroball cluster detectors was used to record ɣ rays and ɣɣ coincidences emitted by isomeric states in the fragmentation products and daughter nuclei from their subsequent β decay. For the daughter nuclei, the active stopper allowed identification via implantation-decay correlation. I present results for 98Cd and 98Ag. In 98Cd, a previously unknown excited state with an energy slightly below the known (12+) state was discovered, and assigned a tentative spin/parity of (10+). Previous theoretical calculations had predicted this state to lie above the (12+) state. Tentative explanations hint at either a reversal of the neutron νd5/2 and the νg7/2 single particle orbitals, or an increased proton strength. In 98Ag, evidence for a reversed ordering of the transitions from the two lowest-lying excited states was found. This would change energy and tentative spin assignment for the first (lowest-lying) excited state. In addition, the lifetime of the first excited state was determined. In both cases, reproducing the new results by theoretical calculations yields new insights into nuclear structure in this region

UCP-3 Uncoupling Protein Confers Hypoxia Resistance to Renal Epithelial Cells and is Upregulated in Renal Cell Carcinoma

Tumor cells can adapt to a hostile environment with reduced oxygen supply. The present study aimed to identify mechanisms that confer hypoxia resistance. Partially hypoxia/reoxygenation (H/R)-resistant proximal tubular (PT) cells were selected by exposing PT cultures to repetitive cycles of H/R. Thereafter, H/R-induced changes in mRNA and protein expression, inner mitochondrial membrane potential (Delta Psi m), formation of superoxide, and cell death were compared between H/R-adapted and control PT cultures. As a result, H/R-adapted PT cells exhibited lower H/R-induced hyperpolarization of Delta Psi m and produced less superoxide than the control cultures. As a consequence, H/R triggered Delta Psi m break-down and DNA degradation in a lower percentage of H/R-adapted than control PT cells. Moreover, H/R induced upregulation of mitochondrial uncoupling protein 3 (UCP-3) in H/R-adapted PT but not in control cultures. In addition, ionizing radiation killed a lower percentage of H/R-adapted compared to control cells suggestive of an H/R-radiation cross-resistance developed by the selection procedure. Knockdown of UCP-3 decreased H/R- and radioresistance of the H/R-adapted cells. Finally, UCP-3 protein abundance of PT-derived clear cell renal cell carcinoma and normal renal tissue was compared in human specimens indicating upregulation of UCP-3 during tumor development. Combined, our data suggest functional significance of UCP-3 for H/R resistance.Tumorzellen können sich an ein hypoxisches Milieu anpassen. Die vorliegende Studie untersucht Mechanismen, die zu einer Resistenz gegenüber Hypoxie beitragen können. Partiell gegenüber Hypoxie/Reoxigenierung (H/R) unempfindliche proximale Tubuluszellen (PT) wurden durch repetitive Zyklen von Hypoxie und Reoxigenierung aus ursprünglichen PT-Kulturen herausselektioniert. Im Anschluss erfolgte eine Untersuchung der H/R induzierten Veränderungen hinsichtlich der mRNA- und Proteinexpression, des mitochondrialen Membranpotentials, der Bildung freier O2-Radikale und des induzierten Zelltodes verglichen mit den unselektionierten Kontrollkulturen. H/R-angepasste Zellen zeigten eine geringere H/R bedingte Hyperpolarisierung des mitochondrialen Membranpotentials und eine geringere Bildung freier O2-Radikale. In der Folge verursachte H/R bei den angepassten Zellen in einem geringeren Prozentsatz einen Zusammenbruch des Membranpotentials und der DNA-Degradierung. Zudem wurde durch H/R in den selektionierten Zellen das Uncoupling Protein 3 (UCP-3) im Vergleich zu den Kontrollzellen stärker exprimiert. Des Weiteren hatte Bestrahlung in den selektionierten Zellen eine geringere Wirkung als in den Kontrollzellen, was auf eine Kreuzresistenz durch den Selektionierungsprozess hindeutet. Eine Herunterregulation der UCP-3 Expression führte zu einer Verringerung der Resistenz gegenüber H/R und Bestrahlung. Zuletzt erfolgte ein Vergleich der UCP-3 Expression in aus Tubuluszellen enstehenden klarzelligen Nierenzellkarzinomen und normalem Nierengewebe menschlichen Ursprungs. Zusammenfassend weisen die vorliegenden Daten auf die Bedeutung von UCP-3 für die H/R Resistenz hin

Recurrence flow measure of nonlinear dependence

Couplings in complex real-world systems are often nonlinear and scale dependent. In many cases, it is crucial to consider a multitude of interlinked variables and the strengths of their correlations to adequately fathom the dynamics of a high-dimensional nonlinear system. We propose a recurrence-based dependence measure that quantifies the relationship between multiple time series based on the predictability of their joint evolution. The statistical analysis of recurrence plots (RPs) is a powerful framework in nonlinear time series analysis that has proven to be effective in addressing many fundamental problems, e.g., regime shift detection and identification of couplings. The recurrence flow through an RP exploits artifacts in the formation of diagonal lines, a structure in RPs that reflects periods of predictable dynamics. Using time-delayed variables of a deterministic uni-/multivariate system, lagged dependencies with potentially many time scales can be captured by the recurrence flow measure. Given an RP, no parameters are required for its computation. We showcase the scope of the method for quantifying lagged nonlinear correlations and put a focus on the delay selection problem in time-delay embedding which is often used for attractor reconstruction. The recurrence flow measure of dependence helps to identify non-uniform delays and appears as a promising foundation for a recurrence-based state space reconstruction algorithm

Prototypical Components of Honeybee Homing Flight Behavior Depend on the Visual Appearance of Objects Surrounding the Goal

Honeybees use visual cues to relocate profitable food sources and their hive. What bees see while navigating, depends on the appearance of the cues, the bee’s current position, orientation, and movement relative to them. Here we analyze the detailed flight behavior during the localization of a goal surrounded by cylinders that are characterized either by a high contrast in luminance and texture or by mostly motion contrast relative to the background. By relating flight behavior to the nature of the information available from these landmarks, we aim to identify behavioral strategies that facilitate the processing of visual information during goal localization. We decompose flight behavior into prototypical movements using clustering algorithms in order to reduce the behavioral complexity. The determined prototypical movements reflect the honeybee’s saccadic flight pattern that largely separates rotational from translational movements. During phases of translational movements between fast saccadic rotations, the bees can gain information about the 3D layout of their environment from the translational optic flow. The prototypical movements reveal the prominent role of sideways and up- or downward movements, which can help bees to gather information about objects, particularly in the frontal visual field. We find that the occurrence of specific prototypes depends on the bees’ distance from the landmarks and the feeder and that changing the texture of the landmarks evokes different prototypical movements. The adaptive use of different behavioral prototypes shapes the visual input and can facilitate information processing in the bees’ visual system during local navigation

Detection of dynamical regime transitions with lacunarity as a multiscale recurrence quantification measure

We propose lacunarity as a novel recurrence quantification measure and illustrate its efficacy to detect dynamical regime transitions which are exhibited by many complex real-world systems. We carry out a recurrence plot-based analysis for different paradigmatic systems and nonlinear empirical data in order to demonstrate the ability of our method to detect dynamical transitions ranging across different temporal scales. It succeeds to distinguish states of varying dynamical complexity in the presence of noise and non-stationarity, even when the time series is of short length. In contrast to traditional recurrence quantifiers, no specification of minimal line lengths is required and geometric features beyond linear structures in the recurrence plot can be accounted for. This makes lacunarity more broadly applicable as a recurrence quantification measure. Lacunarity is usually interpreted as a measure of heterogeneity or translational invariance of an arbitrary spatial pattern. In application to recurrence plots, it quantifies the degree of heterogeneity in the temporal recurrence patterns at all relevant time scales. We demonstrate the potential of the proposed method when applied to empirical data, namely time series of acoustic pressure fluctuations from a turbulent combustor. Recurrence lacunarity captures both the rich variability in dynamical complexity of acoustic pressure fluctuations and shifting time scales encoded in the recurrence plots. Furthermore, it contributes to a better distinction between stable operation and near blowout states of combustors

Interdépendance du potentiel d'exploitation et la structure d'habitat dans la région de l'Atakora

Le département de l’Atakora est une région très contrastée et jusqu’à présent très peu explorée. Son élément le plus saillant est la Chaîne de l’Atakora, une des rares élévations montagneuses de cette partie de l’Afrique occidentale. Le haut-plateau de l’Atakora est caractérisé par une densité de la population relativement basse, comparée au reste de la région, et une végétation variée, qui est jusqu’à présent extrêmement mal connu. Il contraste fortement avec son piémont à l’ouest de la chaîne qui est très densément peuplé et exploité de manière intensive. Notre recherche a été consacrée à la question de savoir si ce sont des facteurs dépendant du géopotentiel ou plutôt des données socio-économiques qui sont responsables pour la disparité actuelle de ce paysage. Partant de l’hypothèse que non seulement les conditions socio-économiques mais aussi les conditions naturelles sont beaucoup plus favorables dans le piémont que sur le plateau, nous avons - par une approche interdisciplinaire - effectué une analyse et une évaluation de ces facteurs. Des méthodes de la télédétection, de la pédologie, de la botanique et de la géographie agraire ont été employées

Microdomain Ca2+ Activation during Exocytosis in Paramecium Cells. Superposition of Local Subplasmalemmal Calcium Store Activation by Local Ca2+ Influx

In Paramecium tetraurelia, polyamine-triggered exocytosis is accompanied by the activation of Ca2+-activated currents across the cell membrane (Erxleben, C., and H. Plattner. 1994. J. Cell Biol. 127:935– 945). We now show by voltage clamp and extracellular recordings that the product of current × time (As) closely parallels the number of exocytotic events. We suggest that Ca2+ mobilization from subplasmalemmal storage compartments, covering almost the entire cell surface, is a key event. In fact, after local stimulation, Ca2+ imaging with high time resolution reveals rapid, transient, local signals even when extracellular Ca2+ is quenched to or below resting intracellular Ca2+ concentration ([Ca2+]e ⩽ [Ca2+]i). Under these conditions, quenched-flow/freeze-fracture analysis shows that membrane fusion is only partially inhibited. Increasing [Ca2+]e alone, i.e., without secretagogue, causes rapid, strong cortical increase of [Ca2+]i but no exocytosis. In various cells, the ratio of maximal vs. minimal currents registered during maximal stimulation or single exocytotic events, respectively, correlate nicely with the number of Ca stores available. Since no quantal current steps could be observed, this is again compatible with the combined occurrence of Ca2+ mobilization from stores (providing close to threshold Ca2+ levels) and Ca2+ influx from the medium (which per se does not cause exocytosis). This implies that only the combination of Ca2+ flushes, primarily from internal and secondarily from external sources, can produce a signal triggering rapid, local exocytotic responses, as requested for Paramecium defense

Challenges and Pitfalls for Implementing Digital Health Solutions in Clinical Studies in Europe

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Evolution of progenitor stars of Type Ibc supernovae and long gamma-ray bursts

We discuss how rotation and binary interactions may be related to the diversity of type Ibc supernovae and long gamma-ray bursts. After presenting recent evolutionary models of massive single and binary stars including rotation, the Tayler-Spruit dynamo and binary interactions, we argue that the nature of SNe Ibc progenitors from binary systems may not significantly differ from that of single star progenitors in terms of rotation, and that most long GRB progenitors may be produced via the quasi-chemically homogeneous evolution at sub-solar metallicity. We also briefly discuss the possible role of magnetic fields generated in the convective core of a massive star for the transport of angular momentum, which is potentially important for future stellar evolution models of supernova and GRB progenitors.Comment: 6 pages, 4 figures, to appear in IAU Symp. 250, Massive Stars as Cosmic Engines, Kauai (HI), 12/2007, ed. F. Bresolin, P. Crowther, & J. Pul

Uncertainty Assessment of Ice Discharge Using GPR-Derived Ice Thickness from Gourdon Glacier, Antarctic Peninsula

Ice cliffs within a glacier represent a challenge for the continuity equations used in many glacier models by interrupting the validity of input parameters. In the case of Gourdon Glacier on James Ross Island, Antarctica, a ∼300–500 m high, almost vertical cliff, separates the outlet glacier from its main accumulation area on the plateau of the island. In 2017 and 2018 we conducted ice thickness measurements during two airborne ground penetrating radar campaigns in order to evaluate differences to older measurements from the 1990s. The observed differences are mostly smaller than the estimated error bars. In comparison to the in situ data, the published “consensus ice thickness estimate” strongly overestimates the ice thickness at the outlet. We analyse three different interpolation and ice thickness reconstruction methods. One approach additionally includes the mass input from the plateau. Differences between the interpolation methods have a minor impact on the ice discharge estimation if the used flux gates are in areas with a good coverage of in situ measurements. A much stronger influence was observed by uncertainties in the glacier velocities derived from remote sensing, especially in the direction of the velocity vector in proximity to the ice cliff. We conclude that the amount of in situ measurements should be increased for specific glacier types in order to detect biases in modeled ice thickness and ice discharge estimations