Counting Complexity for Reasoning in Abstract Argumentation

In this paper, we consider counting and projected model counting of extensions in abstract argumentation for various semantics. When asking for projected counts we are interested in counting the number of extensions of a given argumentation framework while multiple extensions that are identical when restricted to the projected arguments count as only one projected extension. We establish classical complexity results and parameterized complexity results when the problems are parameterized by treewidth of the undirected argumentation graph. To obtain upper bounds for counting projected extensions, we introduce novel algorithms that exploit small treewidth of the undirected argumentation graph of the input instance by dynamic programming (DP). Our algorithms run in time double or triple exponential in the treewidth depending on the considered semantics. Finally, we take the exponential time hypothesis (ETH) into account and establish lower bounds of bounded treewidth algorithms for counting extensions and projected extension.Comment: Extended version of a paper published at AAAI-1

Neuromorphic Learning towards Nano Second Precision

Temporal coding is one approach to representing information in spiking neural networks. An example of its application is the location of sounds by barn owls that requires especially precise temporal coding. Dependent upon the azimuthal angle, the arrival times of sound signals are shifted between both ears. In order to deter- mine these interaural time differences, the phase difference of the signals is measured. We implemented this biologically inspired network on a neuromorphic hardware system and demonstrate spike-timing dependent plasticity on an analog, highly accelerated hardware substrate. Our neuromorphic implementation enables the resolution of time differences of less than 50 ns. On-chip Hebbian learning mechanisms select inputs from a pool of neurons which code for the same sound frequency. Hence, noise caused by different synaptic delays across these inputs is reduced. Furthermore, learning compensates for variations on neuronal and synaptic parameters caused by device mismatch intrinsic to the neuromorphic substrate.Comment: 7 pages, 7 figures, presented at IJCNN 2013 in Dallas, TX, USA. IJCNN 2013. Corrected version with updated STDP curves IJCNN 201

Luminescent single and dual sensors for in vivo imaging of pH and pO2

This thesis describes the development and characterization of novel optical sensor materials for clinical in vivo applications. At first, biocompatible single- and dual sensors for the clinically important parameters pH and pO2 were realized using a time-resolved read-out. For the first time, spatial pH and/or pO2 distributions in cutaneous and chronic wounds of humans were visualized. Further, a novel read-out technique for Fluorescence Ratiometric Imaging (FRIM) is presented. Planar sensor membranes for photographing of oxygen-, pH-, or CO2 distributions were designed. Finally, a biocompatible in vivo sensor for simultaneous and continuous read-out of pH/pO2 based on the new technique is demonstrated. Chapter 1 gives a short introduction on the importance of pH and pO2 especially in dermatology. Further, a brief overview on measurement techniques for oxygen and pH, and optical sensor techniques is presented. Chapter 2 describes the instruments that are applied in this thesis. In chapter 3, a referenced luminescent sensor for 2D high-resolution imaging of pH in vivo is described. The time-resolved sensing scheme is based on time-domain luminescence imaging of FITC and using a ruthenium complex as reference. The biocompatibility of this sensor is warranted via a three step safety mechanism. First, the dyes were covalently bound to, or incorporated in microparticles. Second, the size of the microparticles hampers or at least slows down cellular uptake. Finally, the particles were immobilized in a hydrogel to prevent particle leakage. A set of in vitro experiments served to characterize the sensor. It covers the physiologically relevant range of pH 3 to pH 9. The biocompatibility of the sensor was tested by conducting experiments on cytotoxicity, cellular uptake, and singlet oxygen production. Several in vivo studies on human tissue pH comparing sensor and pH electrode signals served to validate the sensor. Next, spatial and temporal pH distributions during cutaneous wound healing were imaged via the sensor. The visualization of heterogenic pH distribution in a chronic ulcer demonstrates the potential of the sensor. An in vivo sensor to image physiological wound oxygenation is presented in chapter 4. The sensor is based on luminescence lifetime imaging of an oxygen sensitive palladium porphyrin. The dye was incorporated in a partially oxygen blocking polymer in order to extend the sensitivity matching the physiological range of 0 to 100 mmHg. Studies on split-skin harvest sites and the oxygen gradient of the stratum corneum were accomplished. The pH sensor particles of chapter 3 and the pO2 sensitive particles (chapter 4) were combined to form one dual sensor layer for simultaneous in vivo imaging of pH/pO2. The sensor is described in detail in chapter 5. The signals of the hybrid sensor were separated using different emission filter sets. The sensor served to visualize analyte distributions on split skin donor sites and chronic venous as well as vasculitc ulcers. Chapter 6 deals with a novel and straightforward concept for ratiometric imaging read-out referred to as RGB imaging or photographing. The technique relies on fluorescence ratiometric imaging and makes use of the fact that digital pictures are composed of three virtually independent (viz. a red, green, and blue) pictures that are separately stored in digital cameras. The camera serves as a rudimental "spectrometer" for wavelength separation. The imaging concept is illustrated with the help of a specially designed oxygen sensor membrane, and a sensor for intrinsically referenced imaging of CO2 with RGB read-out is described. Moreover, the proof of principle of a RGB pH sensor membrane is demonstrated. Finally, chapter 7 describes a referenced dual sensor for pO2/pH based on the RGB technique including its transfer from the lab bench to clinical application. The novel material uses all three color channels of the RGB camera. It comprises the utilization of an inert reference fluorophore in the blue channel, a pH dependent signal in the green channel, and an oxygen dependent signal in the red channel. The biocompatibility of the materials was studied and ensured. The sensor material was characterized in detail in vitro, and applied in vivo to simultaneously visualize pH and pO2 distributions in human tissue on intact skin and during cutaneous and chronic wound healing

SpinC quantization in odd dimensions

We define and discuss an extension of the SpinC quantization concept to odd-dimensional manifolds. After that we describe its relation to (the usual) even-dimensional SpinC quantization and how its famous properties like "Quantization commutes with reduction" can be regained in odd dimensions. At the end, we analyze the situation on 3-manifolds and give some examples.Comment: 9 page

Seismic wavefield visualizations with AlpArray and AdriaArray

The dense network of broadband seismometers in the alpine region is making it possible to resolve the seismic waves moving across the array in fine detail. These animations allow for an insight into the wave field dynamics, but processing the data poses several challenges, especially in bringing the amplitudes across the array into a range where they can be usefully shown alongside each other, and filtering the data to bring out the seismic phases visually from the shorter period noise. Here, we use a normalisation method based on the envelopes of the long-period lowpass filtered waveforms. The waveforms are then also band-pass filtered. The amplitudes are represented in color, with red being positive and blue being negative, as well as marker sizes in the animations for vertical component data. An estimate for the wave propagation of the most important seismic phases is performed via TauPy, and this estimate is drawn into the animation as coloured lines of theoretical wavefronts to facilitate the association of the visible wavefronts with them. The horizontal component is shown as well, but here the color is used to represent horizontal direction, while the marker size still corresponds to amplitude. The colour wheel encoding the directional information is shown in the top right, with white and black corresponding to radial polarisation and red and blue to transversal polarisation of the seismic waves. These animations can provide an intuitive, visual way to gain an understanding of seismic waves. They can also showcase the data quality, and might represent an early step in identifying specific problems at a glance over the whole array, like polarity errors or strong station noise level

Beitrag zur Geschichte der Naturwissenschaftlichen Forschung im Raum Osnabrück

Angeregt durch die sehr vielfältige Landschaft um Osnabrück haben Heimatkundler und Naturwissenschaftler in der ersten Hälfte des 19. Jahrhunderts begonnen, diese Region zu erforschen. Eine Ausnahme bildeten die Anregungen von Justus Möser (1750), eine "agronomisch-geologische Karte" anzufertigen und sein 1780 publizierter Vorschlag, die "natürliche Beschaffenheit des Landes" zu beschreiben; sie wurden aber von den "Osnabrückern" noch nicht verstanden. Die Arbeitsgebiete waren zunächst Erdgeschichte und Florenkunde. Dann, insbesondere nach der Gründung des Naturwissenschaftlichen Vereins Osnabrück am 1. Oktober 1870, kamen bald zur Geologie, Mineralogie und Botanik die folgenden Bereiche: Ornithologie und Entomologie, Meteorologie und Klimatologie, Natur- und Landschaftsschutz sowie später Hydrologie, Astronomie und Bodenkunde. In den Jahrbüchern des Naturwissenschaftlichen Vereins Osnabrück wurden seit 1872 in 48 Bänden zahlreiche Forschungsergebnisse veröffentlicht. Dies ist das Verdienst der Personen, die bei Gründung des Vereins in den Statuten die Aufgabe der regelmäßigen Veröffentlichung von Untersuchungsergebnissen zur "Förderung und Verbreitung der Kenntnis der Natur" beschlossen. Die Beiträge des Zeitraumes von 1872 bis heute zeigen ein strukturreiches Landschaftsbild vom Osnabrücker Raum. Zum oben angesprochenen Ziel der Förderung der Kenntnisse der Natur legten die Mitglieder mit ihren geologischen, botanischen und zoologischen Sammlungen eine wichtige Grundlage für ein umfangreiches und wertvolles Archiv, das die Voraussetzung für ein öffentliches Museum bot

The effect of heterogeneity on decorrelation mechanisms in spiking neural networks: a neuromorphic-hardware study

High-level brain function such as memory, classification or reasoning can be realized by means of recurrent networks of simplified model neurons. Analog neuromorphic hardware constitutes a fast and energy efficient substrate for the implementation of such neural computing architectures in technical applications and neuroscientific research. The functional performance of neural networks is often critically dependent on the level of correlations in the neural activity. In finite networks, correlations are typically inevitable due to shared presynaptic input. Recent theoretical studies have shown that inhibitory feedback, abundant in biological neural networks, can actively suppress these shared-input correlations and thereby enable neurons to fire nearly independently. For networks of spiking neurons, the decorrelating effect of inhibitory feedback has so far been explicitly demonstrated only for homogeneous networks of neurons with linear sub-threshold dynamics. Theory, however, suggests that the effect is a general phenomenon, present in any system with sufficient inhibitory feedback, irrespective of the details of the network structure or the neuronal and synaptic properties. Here, we investigate the effect of network heterogeneity on correlations in sparse, random networks of inhibitory neurons with non-linear, conductance-based synapses. Emulations of these networks on the analog neuromorphic hardware system Spikey allow us to test the efficiency of decorrelation by inhibitory feedback in the presence of hardware-specific heterogeneities. The configurability of the hardware substrate enables us to modulate the extent of heterogeneity in a systematic manner. We selectively study the effects of shared input and recurrent connections on correlations in membrane potentials and spike trains. Our results confirm ...Comment: 20 pages, 10 figures, supplement

Online Gaming and Personality: Explaining Gamers’ Cheating Intention

Cheating in online games poses a risk to game publishers, as it deters other gamers and reduces revenues. These facts make it essential for game publishers to understand ‘who’ in the sense of gamers with what personalities have cheating intentions. Building on psychology research, we draw on (a) the big five personality traits and (b) the dark triad personality traits to explain how these reflect gamers’ personalities and together lead to cheating intentions. Following a configurational approach (N=192), we reveal two configurations explaining high cheating intention and one explaining low cheating intention. We contribute to online gaming research by revealing that gamers with cheating intentions have specific personalities. We advance information systems (IS) personality research by combining broad and dark triad traits to explain divergent behavior like cheating