In Vivo Optical Projection Tomography in Biological Model Organisms

The term “tomography” is composed of the two Greek words “τόμος“, which can be translated as “cut” or “slice” and “γραφία” which is the Greek term for “picture”. The image that is produced by a tomograph is called a tomogram. In order to achieve information from a tomogram, one needs to reconstruct the data set by using a reconstruction algorithm, which then computes the tomographic slices of the object. These slices can be stacked together and form a 3D stack of the object of interest

Entwicklung von Methoden zur ereignisgesteuerten neurofunktionellen Kernspintomographie für die Messung der Gehirnaktivität bei der Schmerzverarbeitung

Die ereignisgesteuerte neurofunktionelle Magnetresonanz-Tomographie ermöglicht die Darstellung der aktiven Gehirnareale, indem sie die unterschiedlichen magnetischen Eigenschaften von oxygeniertem und desoxygeniertem Blut ausnutzt. Im Rahmen dieser Arbeit wurden vier ereignisgesteuerte FLASH-Meßsequenzen für die Untersuchung der Schmerzverarbeitung entwickelt und implementiert. Diese Methoden ermöglichen die Abbildung der Gehirnfunktion auf einen äußeren Reiz mit hoher zeitlicher und räumlicher Auflösung. In Messungen am Phantom und am Probanden wurden die Techniken mit ereignisgesteuerten EPI-Aufnahmen verglichen. Zur Lokalisation und Untersuchung der Dynamik der an der Schmerzverarbeitung beteiligten Areale wurden zwei Sequenzen bei phasischen und tonischen Reizen durch Thermoden- und CO2-Laserstimulation eingesetzt. Durch Implementierung eines randomisierten Stimulationsdesigns gelang die Evaluation der reizstärkenabhängigen Dynamik. Der Einfluß von Kopfbewegungen des Probanden während der Datenaufnahme wurde mit Hilfe von Simulationsrechnungen für zwei Sequenztypen ermittelt. Die im Rahmen dieser Arbeit entwickelten Methoden für die Ableitung eines EEGs im Tomographen erlauben eine Messung der Hirnströme auch während funktioneller MR-Messungen. Damit können die Vorteile der hohen zeitlichen Auflösung des EEGs mit der guten räumlichen Auflösung der MRT kombiniert werden. Mit Hilfe dieser Methoden gelingt es, die Prozesse der Schmerzverarbeitung zu untersuchen und der Neuropsychologie ein Werkzeug zur Erforschung der Mechanismen der Chronifizierung des Schmerzes zur Verfügung zu stellen

The changing meaning of left and right: supply- and demand-side effects on the perception of party positions

Political conflict is often described in terms of "left" and "right" even though societal conflicts stem from various sub-dimensions such as economic and cultural issues. We argue that individuals map parties’ left-right positions based on party positions on such underlying dimensions, though their impact depends on their importance for parties and citizens. To test this, we study the German Alternative für Deutschland (AfD) whose programmatic appeal has changed fundamentally in the last years, as have citizens’ issue concerns. Using longitudinal data from the German Longitudinal Election Study (GLES), we find that citizens' perceptions of the AfD's left-right position are more closely related to the party's position on specific issues (1) when these issues are prominent in the party's communication and (2) for citizens that care more about these issues. Moreover, how voters perceive left and right in comparison to parties' issue emphasis also affects vote choice. Our findings have important implications for the meaning of left and right, electoral behaviour, representation, and party competition

From the European debt crisis to a culture of closed borders: how issue salience changes the meaning of left and right for perceptions of the German AfD party

Political parties are traditionally described as being on a left-right spectrum according to their economic policies. However, socio-cultural dynamics also contribute to the public perception of parties. Looking at the case of Alternative für Deutschland, Heiko Giebler, Thomas M. Meyer and Markus Wagner show how shifting issue salience from one to the other both by the party and voters affects how the party is perceived in terms of left and right

Optical coherence tomography for laser transmission joining processes in polymers and semiconductors

Laser transmission welding applications become wide spread technology in joining transparent and turbid materials. The requirement of higher throughputs and lesser rejects support the need of alternative methods to commonly used machine vision or temperature measurements. Optical coherence tomography delivers the opportunity to qualitatively assess transmission welding seems and welding spots even in three dimensions. Fourier Domain Mode Lock Lasers (FDMLs) used in OCT enable high throughput by high sweep rates. Preliminary results of OCT used for qualitatively assessment of laser transmission welded polymers and fiber reinforced plastics are shown as well as first approaches of using OCT in a silicon chip bonding process

SERCA is critical to control the Bowditch effect in the heart

The Bowditch effect or staircase phenomenon is the increment or reduction of contractile force when heart rate increases, defined as either a positive or negative staircase. The healthy and failing human heart both show positive or negative staircase, respectively, but the causes of these distinct cardiac responses are unclear. Different experimental approaches indicate that while the level of Ca2+ in the sarcoplasmic reticulum is critical, the molecular mechanisms are unclear. Here, we demonstrate that Drosophila melanogaster shows a negative staircase which is associated to a slight but significant frequency-dependent acceleration of relaxation (FDAR) at the highest stimulation frequencies tested. We further showed that the type of staircase is oppositely modified by two distinct SERCA mutations. The dominant conditional mutation SERCAA617T induced positive staircase and arrhythmia, while SERCAE442K accentuated the negative staircase of wild type. At the stimulation frequencies tested, no significant FDAR could be appreciated in mutant flies. The present results provide evidence that two individual mutations directly modify the type of staircase occurring within the heart and suggest an important role of SERCA in regulating the Bowditch effect.Fil: Balcazar, Dario Emmanuel. Universidad Nacional de La Plata; ArgentinaFil: Regge, María Victoria. Universidad Nacional de La Plata; ArgentinaFil: Santalla, Manuela. Universidad Nacional de La Plata; ArgentinaFil: Behrensmeyer, Anna Kay. Universität Osnabrück;Fil: Achimón, Fernanda. Universität Osnabrück;Fil: Mattiazzi, Ramona Alicia. Universidad Nacional de La Plata; ArgentinaFil: Ferrero, Paola Viviana. Universidad Nacional de La Plata; Argentin

Time domain boundary elements for dynamic contact problems

This article considers a unilateral contact problem for the wave equation. The problem is reduced to a variational inequality for the Dirichlet-to-Neumann operator for the wave equation on the boundary, which is solved in a saddle point formulation using boundary elements in the time domain. As a model problem, also a variational inequality for the single layer operator is considered. A priori estimates are obtained for Galerkin approximations both to the variational inequality and the mixed formulation in the case of a flat contact area, where the existence of solutions to the continuous problem is known. Numerical experiments demonstrate the performance of the proposed mixed method. They indicate the stability and convergence beyond flat geometries.Comment: 38 pages, to appear in Computer Methods in Applied Mechanics and Engineerin

Pick, Pack, & Survive: Charging Robots in a Modern Warehouse based on Online Connected Dominating Sets

The modern warehouse is partially automated by robots. Instead of letting human workers walk into shelfs and pick up the required stock, big groups of autonomous mobile robots transport the inventory to the workers. Typically, these robots have an electric drive and need to recharge frequently during the day. When we scale this approach up, it is essential to place recharging stations strategically and as soon as needed so that all robots can survive. In this work, we represent a warehouse topology by a graph and address this challenge with the Online Connected Dominating Set problem (OCDS), an online variant of the classical Connected Dominating Set problem [Guha and Khuller, 1998]. We are given an undirected connected graph G = (V, E) and a sequence of subsets of V arriving over time. The goal is to grow a connected subgraph that dominates all arriving nodes and contains as few nodes as possible. We propose an O(log^2 n)-competitive randomized algorithm for OCDS in general graphs, where n is the number of nodes in the input graph. This is the best one can achieve due to Korman\u27s randomized lower bound of Omega(log n log m) [Korman, 2005] for the related Online Set Cover problem [Alon et al., 2003], where n is the number of elements and m is the number of subsets. We also run extensive simulations to show that our algorithm performs well in a simulated warehouse, where the topology of a warehouse is modeled as a randomly generated geometric graph

Boundary elements with mesh refinements for the wave equation

The solution of the wave equation in a polyhedral domain in $\mathbb{R}^3$ admits an asymptotic singular expansion in a neighborhood of the corners and edges. In this article we formulate boundary and screen problems for the wave equation as equivalent boundary integral equations in time domain, study the regularity properties of their solutions and the numerical approximation. Guided by the theory for elliptic equations, graded meshes are shown to recover the optimal approximation rates known for smooth solutions. Numerical experiments illustrate the theory for screen problems. In particular, we discuss the Dirichlet and Neumann problems, as well as the Dirichlet-to-Neumann operator and applications to the sound emission of tires.Comment: 45 pages, to appear in Numerische Mathemati

Taste, A New Incentive to Switch to (R)-Praziquantel in Schistosomiasis Treatment

Schistosomiasis, or Bilharzia, is a parasitic disease caused by flatworms, which affects about 200 million people worldwide. Praziquantel (PZQ) is the drug compound of choice in the control and treatment of this disease. Only half of the drug dose currently administered actually has activity against schistosomiasis, whereas the other half has no activity. Therefore, the WHO has assigned the low-cost preparation of the pure active component a key priority for future PZQ research and development. PZQ has two major administration drawbacks, the first being the high dose needed, the second its well documented bitter taste. Attempts of masking the unpleasant taste have not been successful. We hypothesized that the non-active component in PZQ would be the main contributor to the unpleasant taste of the drug. We determined the extent of bitterness for regular PZQ compared to the pure active component in a taste study in humans. We found that the pure active component alone is significantly less bitter than regular PZQ. This new finding should serve as an additional incentive for the PZQ research and development community to provide a low-cost, large-scale preparation route to the pure active component of PZQ