TY - THES A1 - Herok, Christoph T1 - Quantum Chemical Exploration of Potential Energy Surfaces: Reaction Cycles and Luminescence Phenomena T1 - Quantenchemische Erforschung von Energiehyperflächen: Reaktionszyklen und Lumineszenzphänomene N2 - This work aims at elucidating chemical processes involving homogeneous catalysis and photo–physical relaxation of excited molecules in the solid state. Furthermore, compounds with supposedly small singlet–triplet gaps and therefore biradicaloid character are investigated with respect to their electro–chemical behavior. The work on hydroboration catalysis via a reduced 9,10–diboraanthracene (DBA) was preformed in collaboration with the Wagner group in Frankfurt, more specifically Dr. Sven Prey, who performed all laboratory experiments. The investigation of delayed luminescence properties in arylboronic esters in their solid state was conducted in collaboration with the Marder group in Würzburg. The author of this work took part in the synthesis of the investigated compounds while being supervised by Dr. Zhu Wu. The final project was a collaboration with the group of Anukul Jana from Hyderabad, India who provided the experimental data. N2 - Ziel dieser Arbeit ist die Aufklärung chemischer Prozesse, die homogene Katalyse und photophysikalische Relaxation angeregter Moleküle im Festkörper beinhalten. Darüber hinaus werden Verbindungen mit vermeintlich kleinen Singulett-Triplett-Lücken und damit biradikaloidem Charakter auf ihr elektrochemisches Verhalten hin untersucht. Die Arbeiten zur Hydroborierungskatalyse mit einem reduzierten 9,10-Diboraanthracen (DBA) wurden in Zusammenarbeit mit der Wagner-Gruppe in Frankfurt durchgeführt, genauer gesagt mit Dr. Sven Prey, der alle Laborexperimente durchführte. Die Untersuchung der verzögerten Lumineszenzeigenschaften von Arylborsäureestern im Festkörper wurde in Zusammenarbeit mit der Marder Gruppe in Würzburg durchgeführt. Der Autor dieser Arbeit war an der Synthese der untersuchten Verbindungen beteiligt und wurde dabei von Dr. Zhu Wu betreut. Das abschließende Projekt war eine Zusammenarbeit mit der Gruppe von Anukul Jana aus Hyderabad, Indien, die die experimentellen Daten zur Verfügung stellte. KW - Simulation KW - Quantum Chemistry KW - Reaction Mechanism KW - Fluorescence KW - Phosphoresence KW - Chemie KW - Katalyse KW - Lumineszenz KW - chemistry KW - simulation KW - catalysis KW - mechanism KW - luminescence KW - Energiehyperfläche Y1 - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-352185 ER - TY - THES A1 - Geißler, Stefan T1 - Performance Evaluation of Next-Generation Data Plane Architectures and their Components T1 - Leistungsbewertung von Data Plane Architekturen der Nächsten Generation sowie ihrer Einzelkomponenten N2 - In this doctoral thesis we cover the performance evaluation of next generation data plane architectures, comprised of complex software as well as programmable hardware components that allow fine granular configuration. In the scope of the thesis we propose mechanisms to monitor the performance of singular components and model key performance indicators of software based packet processing solutions. We present novel approaches towards network abstraction that allow the integration of heterogeneous data plane technologies into a singular network while maintaining total transparency between control and data plane. Finally, we investigate a full, complex system consisting of multiple software-based solutions and perform a detailed performance analysis. We employ simulative approaches to investigate overload control mechanisms that allow efficient operation under adversary conditions. The contributions of this work build the foundation for future research in the areas of network softwarization and network function virtualization. N2 - Diese Doktorarbeit behandelt die Leistungsbewertung von Data Plane Architekturen der nächsten Generation, die aus komplexen Softwarelösungen sowie programmierbaren Hardwarekomponenten bestehen. Hierbei werden Mechanismen entwickelt, die es ermöglichen, die Leistungsfähigkeit einzelner Komponenten zu messen und zentrale Leistungsindikatoren softwarebasierter Systeme zur Verarbeitung von Datenpaketen zu modellieren. Es werden neuartige Ansätze zur Netzabstraktion entworfen, die eine vollständig transparente Integration heterogener Technologien im selben Netz ermöglichen. Schließlich wird eine umfassende Leistungsbewertung eines komplexen Systems, das aus einer Vielzahl softwarebasierter Netzfunktionen besteht, durchgeführt. Anhand simulativer Modelle werden Überlastkontrollmechanismen entwickelt, die es dem System erlauben auch unter Überlast effizient zu arbeiten. Die Beiträge dieser Arbeit bilden die Grundlage weiterer Forschungen im Bereich der Softwarisierung von Netzen sowie der Virtualisierung von Netzfunktionen. T3 - Würzburger Beiträge zur Leistungsbewertung Verteilter Systeme - 02/21 KW - Leistungsbewertung KW - Simulation KW - Zeitdiskretes System KW - Implementierung KW - performance evaluation KW - simulation KW - discrete-time analysis KW - network softwarization KW - mobile networks Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-260157 SN - 1432-8801 ER - TY - JOUR A1 - Kiesel, Matthias A1 - Beyers, Inga A1 - Kalisz, Adam A1 - Wöckel, Achim A1 - Löb, Sanja A1 - Schlaiss, Tanja A1 - Wulff, Christine A1 - Diessner, Joachim T1 - Evaluating a novel 3D printed model for simulating Large Loop Excision of the Transformation Zone (LLETZ) JF - 3D Printing in Medicine N2 - Background Electrosurgical excisions are common procedures for treating cervical dysplasia and are often seen as minor surgeries. Yet, thorough training of this intervention is required, as there are considerable consequences of inadequate resections, e.g. preterm birth, the risk of recurrence, injuries and many more. Unfortunately, there is a lack of sufficiently validated possibilities of simulating electrosurgeries, which focus on high fidelity and patient safety. Methods A novel 3D printed simulator for examination and electrosurgical treatment of dysplastic areas of the cervix was compared with a conventional simulator. Sixty medical students experienced a seminar about cervical dysplasia. Group A underwent the seminar with the conventional and Group B with the novel simulator. After a theoretical introduction, the students were randomly assigned by picking a ticket from a box and went on to perform the hands-on training with their respective simulator. Each student first obtained colposcopic examination training. Then he or she performed five electrosurgical excisions (each). This was assessed with a validated score, to visualize their learning curve. Furthermore, adequate and inadequate resections and contacts between electrosurgical loop and vagina or speculum were counted. Both groups also assessed the seminar and their simulator with 18 questions (Likert-scales, 1–10, 1 = strongly agree / very good, 10 = strongly disagree / very bad). Group B additionally assessed the novel simulator with four questions (similar Likert-scales, 1–10). Results Nine of 18 questions showed statistically significant differences favoring Group B (p < 0.05). Group B also achieved more adequate R0-resections and less contacts between electrosurgical loop and vagina or speculum. The learning curves of the performed resections favored the novel simulator of Group B without statistically significant differences. The four questions focusing on certain aspects of the novel simulator indicate high appreciation of the students with a mean score of 1.6 points. Conclusion The presented novel simulator shows several advantages compared to the existing model. Thus, novice gynecologists can be supported with a higher quality of simulation to improve their training and thereby patient safety. KW - 3D printing KW - simulation KW - gynecology KW - Loop electrosurgical excision procedure (LEEP) KW - Large loop excision of the transformation zone (LLETZ) KW - teaching KW - education KW - patient safety KW - cervical dysplasia Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-313356 VL - 8 ER - TY - JOUR A1 - Schlund, Jonas A1 - German, Reinhard A1 - Pruckner, Marco T1 - Synergy of unidirectional and bidirectional smart charging of electric vehicles for frequency containment reserve power provision JF - World Electric Vehicle Journal N2 - Besides the integration of renewable energies, electric vehicles pose an additional challenge to modern power grids. However, electric vehicles can also be a flexibility source and contribute to the power system stability. Today, the power system still heavily relies on conventional technologies to stay stable. In order to operate a future power system based on renewable energies only, we need to understand the flexibility potential of assets such as electric vehicles and become able to use their flexibility. In this paper, we analyzed how vast amounts of coordinated charging processes can be used to provide frequency containment reserve power, one of the most important ancillary services for system stability. Therefore, we used an extensive simulation model of a virtual power plant of millions of electric vehicles. The model considers not only technical components but also the stochastic behavior of electric vehicle drivers based on real data. Our results show that, in 2030, electric vehicles have the potential to serve the whole frequency containment reserve power market in Germany. We differentiate between using unidirectional and bidirectional chargers. Bidirectional chargers have a larger potential but also result in unwanted battery degradation. Unidirectional chargers are more constrained in terms of flexibility, but do not lead to additional battery degradation. We conclude that using a mix of both can combine the advantages of both worlds. Thereby, average private cars can provide the service without any notable additional battery degradation and achieve yearly earnings between EUR 200 and EUR 500, depending on the volatile market prices. Commercial vehicles have an even higher potential, as the results increase with vehicle utilization and consumption. KW - smart charging KW - electric vehicles KW - simulation KW - ancillary services KW - smart grid Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-288324 SN - 2032-6653 VL - 13 IS - 9 ER - TY - JOUR A1 - McIlroy, Benjamin A1 - Passfield, Louis A1 - Holmberg, Hans-Christer A1 - Sperlich, Billy T1 - Virtual training of endurance cycling – A summary of strengths, weaknesses, opportunities and threats JF - Frontiers in Sports and Active Living N2 - Virtual online training has emerged as one of the top 20 worldwide fitness trends for 2021 and continues to develop rapidly. Although this allows the cycling community to engage in virtual training and competition, critical evaluation of virtual training platforms is limited. Here, we discuss the strengths, weaknesses, opportunities and threats associated with virtual training technology and cycling in an attempt to enhance awareness of such aspects. Strengths include immersive worlds, innovative drafting mechanics, and versatility. Weaknesses include questionable data accuracy, inadequate strength and reliability of power-speed algorithms. Opportunities exist for expanding strategic partnerships with major cycling races, brands, and sponsors and improving user experience with the addition of video capture and “e-coaching.” Threats are present in the form of cheating during competition, and a lack of uptake and acceptance by a broader community. KW - algorithms KW - cycling KW - e-coach KW - e-health KW - ergometer KW - simulation KW - virtual training KW - SWOT Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258876 VL - 3 ER - TY - JOUR A1 - Sarukhanyan, Edita A1 - Shityakov, Sergey A1 - Dandekar, Thomas T1 - In silico designed Axl receptor blocking drug candidates against Zika virus infection JF - ACS Omega N2 - After a large outbreak in Brazil, novel drugs against Zika virus became extremely necessary. Evaluation of virus-based pharmacological strategies concerning essential host factors brought us to the idea that targeting the Axl receptor by blocking its dimerization function could be critical for virus entry. Starting from experimentally validated compounds, such as RU-301, RU-302, warfarin, and R428, we identified a novel compound 2′ (R428 derivative) to be the most potent for this task amongst a number of alternative compounds and leads. The improved affinity of compound 2′ was confirmed by molecular docking as well as molecular dynamics simulation techniques using implicit solvation models. The current study summarizes a new possibility for inhibition of the Axl function as a potential target for future antiviral therapies. KW - free energy KW - molecular docking KW - molecular dynamics KW - simulation KW - pharmacology KW - proteins KW - structure-activity relationship KW - viruses KW - Zika virus Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-176739 VL - 3 IS - 5 ER - TY - JOUR A1 - van Toor, Mariëlle L. A1 - Newman, Scott H. A1 - Takekawa, John Y. A1 - Wegmann, Martin A1 - Safi, Kamran T1 - Temporal segmentation of animal trajectories informed by habitat use JF - Ecosphere N2 - Most animals live in seasonal environments and experience very different conditions throughout the year. Behavioral strategies like migration, hibernation, and a life cycle adapted to the local seasonality help to cope with fluctuations in environmental conditions. Thus, how an individual utilizes the environment depends both on the current availability of habitat and the behavioral prerequisites of the individual at that time. While the increasing availability and richness of animal movement data has facilitated the development of algorithms that classify behavior by movement geometry, changes in the environmental correlates of animal movement have so far not been exploited for a behavioral annotation. Here, we suggest a method that uses these changes in individual–environment associations to divide animal location data into segments of higher ecological coherence, which we term niche segmentation. We use time series of random forest models to evaluate the transferability of habitat use over time to cluster observational data accordingly. We show that our method is able to identify relevant changes in habitat use corresponding to both changes in the availability of habitat and how it was used using simulated data, and apply our method to a tracking data set of common teal (Anas crecca). The niche segmentation proved to be robust, and segmented habitat suitability outperformed models neglecting the temporal dynamics of habitat use. Overall, we show that it is possible to classify animal trajectories based on changes of habitat use similar to geometric segmentation algorithms. We conclude that such an environmentally informed classification of animal trajectories can provide new insights into an individuals' behavior and enables us to make sensible predictions of how suitable areas might be connected by movement in space and time. KW - Anas crecca KW - animal movement KW - common teal KW - habitat use KW - life history KW - migration KW - niche dynamics KW - random forest models KW - segmentation KW - simulation KW - species distribution model KW - transferability Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164970 VL - 7 IS - 10 ER - TY - JOUR A1 - Grundgeiger, T. A1 - Albert, M. A1 - Reinhardt, D. A1 - Happel, O. A1 - Steinisch, A. A1 - Wurmb, T. T1 - Real-time tablet-based resuscitation documentation by the team leader: evaluating documentation quality and clinical performance JF - Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine N2 - Background Precise and complete documentation of in-hospital cardiopulmonary resuscitations is important but data quality can be poor. In the present study, we investigated the effect of a tablet-based application for real-time resuscitation documentation used by the emergency team leader on documentation quality and clinical performance of the emergency team. Methods Senior anaesthesiologists either used the tablet-based application during the simulated resuscitation for documentation and also used the application for the final documentation or conducted the full documentation at the end of the scenario using the local hospital information system. The latter procedure represents the current local documentation method. All scenarios were video recorded. To assess the documentation, we compared the precision of intervention delivery times, documentation completeness, and final documentation time. To assess clinical performance, we compared adherence to guidelines for defibrillation and adrenaline administration, the no-flow fraction, and the time to first defibrillation. Results The results showed significant benefits for the tablet-based application compared to the hospital information system for precision of the intervention delivery times, the final documentation time, and the no-flow fraction. We observed no differences between the groups for documentation completeness, adherence to guidelines for defibrillation and adrenaline administration, and the time to first defibrillation. Discussion In the presented study, we observed that a tablet-based application can improve documentation data quality. Furthermore, we demonstrated that a well-designed application can be used in real-time by a member of the emergency team with possible beneficial effects on clinical performance. Conclusion The present evaluation confirms the advantage of tablet-based documentation tools and also shows that the application can be used by an active member of an emergency team without compromising clinical performance. KW - cardiac arrest documentation KW - cardiopulmonary resuscitation KW - simulation KW - no-flow fraction Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-146582 VL - 24 IS - 51 ER - TY - THES A1 - Bolaños-Rosales, Alejandro T1 - Low Mach Number Simulations of Convective Boundary Mixing in Classical Novae T1 - Simulationen der konvektiven Mischung in Klassischen Novae im Strömungsbereich kleiner Machzahlen N2 - Classical novae are thermonuclear explosions occurring on the surface of white dwarfs. When co-existing in a binary system with a main sequence or more evolved star, mass accretion from the companion star to the white dwarf can take place if the companion overflows its Roche lobe. The envelope of hydrogen-rich matter which builds on top of the white dwarf eventually ignites under degenerate conditions, leading to a thermonuclear runaway and an explosion in the order of 1046 erg, while leaving the white dwarf intact. Spectral analyses from the debris indicate an abundance of isotopes that are tracers of nuclear burning via the hot CNO cycle, which in turn reveal some sort of mixing between the envelope and the white dwarf underneath. The exact mechanism is still a matter of debate. The convection and deflagration in novae develop in the low Mach number regime. We used the Seven League Hydro code (SLH ), which employs numerical schemes designed to correctly simulate low Mach number flows, to perform two and three- dimensional simulations of classical novae. Based on a spherically-symmetric model created with aid of a stellar evolution code, we developed our own nova model and tested it on a variety of numerical grids and boundary conditions for validation. We focused on the evolution of temperature, density and nuclear energy generation rate at the layers between white dwarf and envelope, where most of the energy is generated, to understand the structure of the transition region, and its effect on the nuclear burning. We analyzed the resulting dredge-up efficiency stemming from the convective motions in the envelope. Our models yield similar results to the literature, but seem to depend very strongly on the numerical resolution. We followed the evolution of the nuclear species involved in the CNO cycle and concluded that the thermonuclear reactions primarily taking place are those of the cold and not the hot CNO cycle. The reason behind this could be that under the conditions generally assumed for multi-dimensional simulations, the envelope is in fact not degenerate. We performed initial tests for 3D simulations and realized that alternative boundary conditions are needed. N2 - Klassische Novae sind thermonukleare Explosionen an der Oberfläche von Weißen Zwergen. Wenn ein solcher sich in einem Doppelsternsystem zusammen mit einem Hauptreihenstern oder einem späteren Stern befindet, kann Akkretion vom Begleiter zum Weißen Zwerg stattfinden, falls der Begleitstern seine Roche-Grenze überschre- itet. Die wasserstoffreiche Hülle, die sich auf der Oberfläche des Sterns bildet, zündet aufgrund des enormen Gravitationsdrucks in einer Deflagration. Aufgrund der Entar- tung des Gases führt das nukleare Brennen zu einem thermonuklearen Durchgehen (engl. runaway)und schließlich zu einer Explosion mit Energien in der Größenord- nung von 1046 erg. Der Weiße Zwerg bleibt dabei unberührt. Spektralanalysen der ausgestoßenen Gase deuten auf Isotope hin, die am heißen CNO-Zyklus beteiligt sind. Dies legt nahe, dass vor oder während der Brennphase eine Durchmischung von Materie zwischen der akkretierten Hülle und dem Weißen Zwerg stattfinden muss. Die Konvektion und Deflagration entwickeln sich im Strömungsbereich kleiner Machzahlen. Wir benutzten den Seven League Hydro code (SLH ), welcher ëber numerische Verfahren verfügt, die auf einen weiten Bereich von Machzahlen anwend- bar sind. Daraus errechneten wir Simulationen von Klassischen Novae in zwei und drei Dimensionen. Basierend auf einem sphärisch-symmetrischen Modell, das wir mit einem Sternentwicklungscode erstellten, entwickelten wir ein eigenes Nova-Modell. Wir testeten dies in Kombination mit eienr Reihe von Gittern und Randbedingun- gen. Anschließend analysierten wir im Detail das Verhalten von Temperatur, Dichte und nuklearer Energieerzeugungsrate in den Schichten zwischen Weißem Zwerg und Wasserstoffhülle, wo die Kernfusion hauptsächlich stattfindet, um die Struktur der Brennzone und deren Einfluss auf die Nukleosynthese zu verstehen. Wir analysierten die Effizienz der Konvektion, welche Elemente aus dem Weißen Zwerg nach oben in die Hülle transportiert. Die Ergebnisse entsprechen denen der Literatur, dennoch hängen sie stark von der numerischen Auflösung ab. Wir untersuchten die Isotopen- häufigkeit der im CNO-Zyklus beteiligten Elemente, und schloßen hieraus, dass das Brennen durch den weniger energetischen “kalten” CNO-Zyklus verläuft. Dies kann darauf zurückgeführt werden, dass unter den Bedingungen, die die Mehrzahl der multi- dimensionalen Modelle aus der Fachliteratur mit sich bringen, die Wasserstoffhülle tatsächlich nicht entartet ist. Abschließend simulierten wir testweise 3D-Modelle, aber neue Randbedingungen sind nötig, um mit den Berechnungen fortfahren zu können. KW - Nova KW - Weißer Zwerg KW - classical novae KW - convection KW - numerical hydrodynamics KW - nuclear reactions KW - stellar evolution KW - simulation KW - low Mach number flows KW - numerische Hydrodynamik KW - thermonukelare Reaktionen KW - Sternentwicklung Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-132863 ER - TY - JOUR A1 - Körner, Anita A1 - Topolinski, Sascha A1 - Strack, Fritz T1 - Routes to Embodiment JF - Frontiers of Psychology N2 - Research on embodiment is rich in impressive demonstrations but somewhat poor in comprehensive explanations. Although some moderators and driving mechanisms have been identified, a comprehensive conceptual account of how bodily states or dynamics influence behavior is still missing. Here, we attempt to integrate current knowledge by describing three basic psychological mechanisms: direct state induction, which influences how humans feel or process information, unmediated by any other cognitive mechanism; modal priming, which changes the accessibility of concepts associated with a bodily state; sensorimotor simulation, which affects the ease with which congruent and incongruent actions are performed. We argue that the joint impact of these mechanisms can account for most existing embodiment effects. Additionally, we summarize empirical tests for distinguishing these mechanisms and suggest a guideline for future research about the mechanisms underlying embodiment effects. KW - priming KW - simulation KW - grounded cognition KW - embodied cognition KW - metaphors Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125960 VL - 9 IS - 940 ER - TY - JOUR A1 - Heddergott, Niko A1 - Krüger, Timothy A1 - Babu, Sujin B. A1 - Wei, Ai A1 - Stellamanns, Erik A1 - Uppaluri, Sravanti A1 - Pfohl, Thomas A1 - Stark, Holger A1 - Engstler, Markus T1 - Trypanosome Motion Represents an Adaptation to the Crowded Environment of the Vertebrate Bloodstream JF - PLoS Pathogens N2 - Blood is a remarkable habitat: it is highly viscous, contains a dense packaging of cells and perpetually flows at velocities varying over three orders of magnitude. Only few pathogens endure the harsh physical conditions within the vertebrate bloodstream and prosper despite being constantly attacked by host antibodies. African trypanosomes are strictly extracellular blood parasites, which evade the immune response through a system of antigenic variation and incessant motility. How the flagellates actually swim in blood remains to be elucidated. Here, we show that the mode and dynamics of trypanosome locomotion are a trait of life within a crowded environment. Using high-speed fluorescence microscopy and ordered micro-pillar arrays we show that the parasites mode of motility is adapted to the density of cells in blood. Trypanosomes are pulled forward by the planar beat of the single flagellum. Hydrodynamic flow across the asymmetrically shaped cell body translates into its rotational movement. Importantly, the presence of particles with the shape, size and spacing of blood cells is required and sufficient for trypanosomes to reach maximum forward velocity. If the density of obstacles, however, is further increased to resemble collagen networks or tissue spaces, the parasites reverse their flagellar beat and consequently swim backwards, in this way avoiding getting trapped. In the absence of obstacles, this flagellar beat reversal occurs randomly resulting in irregular waveforms and apparent cell tumbling. Thus, the swimming behavior of trypanosomes is a surprising example of micro-adaptation to life at low Reynolds numbers. For a precise physical interpretation, we compare our high-resolution microscopic data to results from a simulation technique that combines the method of multi-particle collision dynamics with a triangulated surface model. The simulation produces a rotating cell body and a helical swimming path, providing a functioning simulation method for a microorganism with a complex swimming strategy. KW - simulation KW - multiparticle collision dynamics KW - propulsion KW - viscosity KW - flagellar KW - motility KW - solvent KW - model KW - hydrodynamics KW - spiroplasma Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134595 VL - 8 IS - 11 ER - TY - JOUR A1 - Egetemeir, Johanna A1 - Stenneken, Prisca A1 - Koehler, Saskia A1 - Fallgatter, Andreas J. A1 - Herrmann, Martin J. T1 - Exploring the neural basis of real-life joint action: measuring brain activation during joint table setting with functional near-infrared spectroscopy JF - FRONTIERS IN HUMAN NEUROSCIENCE N2 - Many every-day life situations require two or more individuals to execute actions together. Assessing brain activation during naturalistic tasks to uncover relevant processes underlying such real-life joint action situations has remained a methodological challenge. In the present study, we introduce a novel joint action paradigm that enables the assessment of brain activation during real-life joint action tasks using functional near-infrared spectroscopy (fNIRS). We monitored brain activation of participants who coordinated complex actions with a partner sitting opposite them. Participants performed table setting tasks, either alone (solo action) or in cooperation with a partner (joint action), or they observed the partner performing the task (action observation). Comparing joint action and solo action revealed stronger activation (higher [oxy-Hb]-concentration) during joint action in a number of areas. Among these were areas in the inferior parietal lobule (IPL) that additionally showed an overlap of activation during action observation and solo action. Areas with such a close link between action observation and action execution have been associated with action simulation processes. The magnitude of activation in these IPL areas also varied according to joint action type and its respective demand on action simulation. The results validate fNIRS as an imaging technique for exploring the functional correlates of interindividual action coordination in real-life settings and suggest that coordinating actions in real-life situations requires simulating the actions of the partner. KW - joint action KW - fNIRS KW - neuroimaging KW - social interaction KW - real-life interaction KW - simulation Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-137054 N1 - Copyright © 2011 Egetemeir, Stenneken, Koehler, Fallgatter and Herrmann.This is an open-access article subject to a non-exclusive license between the authors and Frontiers Media SA,which permits use, distribution and reproduction in other forums, provided the original authors and source are credited andother Frontiers conditions are complied with. VL - 5 IS - 9, Artikel 95 ER - TY - THES A1 - Klein, Alexander T1 - Performance Issues of MAC and Routing Protocols in Wireless Sensor Networks T1 - Leistungsbeschränkende Faktoren von MAC und Routingprotokollen in drahtlosen Sensornetzen N2 - The focus of this work lies on the communication issues of Medium Access Control (MAC) and routing protocols in the context of WSNs. The communication challenges in these networks mainly result from high node density, low bandwidth, low energy constraints and the hardware limitations in terms of memory, computational power and sensing capabilities of low-power transceivers. For this reason, the structure of WSNs is always kept as simple as possible to minimize the impact of communication issues. Thus, the majority of WSNs apply a simple one hop star topology since multi-hop communication has high demands on the routing protocol since it increases the bandwidth requirements of the network. Moreover, medium access becomes a challenging problem due to the fact that low-power transceivers are very limited in their sensing capabilities. The first contribution is represented by the Backoff Preamble-based MAC Protocol with Sequential Contention Resolution (BPS-MAC) which is designed to overcome the limitations of low-power transceivers. Two communication issues, namely the Clear Channel Assessment (CCA) delay and the turnaround time, are directly addressed by the protocol. The CCA delay represents the period of time which is required by the transceiver to detect a busy radio channel while the turnaround time specifies the period of time which is required to switch between receive and transmit mode. Standard Carrier Sense Multiple Access (CSMA) protocols do not achieve high performance in terms of packet loss if the traffic is highly correlated due to the fact that the transceiver is not able to sense the medium during the switching phase. Therefore, a node may start to transmit data while another node is already transmitting since it has sensed an idle medium right before it started to switch its transceiver from receive to transmit mode. The BPS-MAC protocol uses a new sequential preamble-based medium access strategy which can be adapted to the hardware capabilities of the transceivers. The protocol achieves a very low packet loss rate even in wireless networks with high node density and event-driven traffic without the need of synchronization. This makes the protocol attractive to applications such as structural health monitoring, where event suppression is not an option. Moreover, acknowledgments or complex retransmission strategies become almost unnecessary since the sequential preamble-based contention resolution mechanism minimizes the collision probability. However, packets can still be lost as a consequence of interference or other issues which affect signal propagation. The second contribution consists of a new routing protocol which is able to quickly detect topology changes without generating a large amount of overhead. The key characteristics of the Statistic-Based Routing (SBR) protocol are high end-to-end reliability (in fixed and mobile networks), load balancing capabilities, a smooth continuous routing metric, quick adaptation to changing network conditions, low processing and memory requirements, low overhead, support of unidirectional links and simplicity. The protocol can establish routes in a hybrid or a proactive mode and uses an adaptive continuous routing metric which makes it very flexible in terms of scalability while maintaining stable routes. The hybrid mode is optimized for low-power WSNs since routes are only established on demand. The difference of the hybrid mode to reactive routing strategies is that routing messages are periodically transmitted to maintain already established routes. However, the protocol stops the transmission of routing messages if no data packets are transmitted for a certain time period in order to minimize the routing overhead and the energy consumption. The proactive mode is designed for high data rate networks which have less energy constraints. In this mode, the protocol periodically transmits routing messages to establish routes in a proactive way even in the absence of data traffic. Thus, nodes in the network can immediately transmit data since the route to the destination is already established in advance. In addition, a new delay-based routing message forwarding strategy is introduced. The forwarding strategy is part of SBR but can also be applied to many routing protocols in order to modify the established topology. The strategy can be used, e.g. in mobile networks, to decrease the packet loss by deferring routing messages with respect to the neighbor change rate. Thus, nodes with a stable neighborhood forward messages faster than nodes within a fast changing neighborhood. As a result, routes are established through nodes with correlated movement which results in fewer topology changes due to higher link durations. N2 - Im Rahmen dieser Arbeit werden leistungsbeschränkende Faktoren von Medium Access Control (MAC) und Routingprotokollen im Kontext von drahtlosen Sensornetzen untersucht. Zunächst werden typische Probleme des Funkkanals diskutiert. Anschließend führen eine Einteilung von MAC Protokollen, sowie eine Gegenüberstellung relevanter Protokolle in die Thematik ein. Daraufhin werden hardwarelimitierende Faktoren und deren Auswirkung auf die Effizienz von Kanalzugriffsprotokollen untersucht. Des Weiteren wird das vom Autor entwickelte Backoff Preamble-based MAC Protokoll (BPS-MAC) vorgestellt, welches auf die limitierten Fähigkeiten sensortypischer Hardware eingeht und für dichte Sensornetze mit korreliertem Datenverkehr optimiert ist. Ein weiterer Schwerpunkt dieser Arbeit stellt das Thema Routing dar. Hier wird ebenfalls mit einer Einteilung der Protokolle in die Thematik eingeführt. Darüber hinaus werden die wichtigsten Aufgaben von Routingprotokollen vorgestellt. Ein Überblick über häufig verwendete Routingmetriken und Routingprotokolle schließen die Einführung in diesen Themenkomplex ab. Abschließend wird das im Rahmen der Dissertation entwickelte Statistic-Based-Routing (SBR) Protokoll vorgestellt, welches ebenfalls für drahtlose Sensornetze optimiert ist. Der letzte Schwerpunkt beschreibt die Problematik der Leistungsbewertung von Routingprotokollen hinsichtlich klassischer Leistungsparameter wie Paketverlust und Verzögerung. Ebenfalls werden weitere Leistungsparameter wie zum Beispiel die vom Nutzer wahrgenommene Netzqualität genauer untersucht. T3 - Würzburger Beiträge zur Leistungsbewertung Verteilter Systeme - 03/10 KW - Routing KW - Drahtloses Sensorsystem KW - Leistungsbewertung KW - Diskrete Simulation KW - MAC KW - Kanalzugriff KW - Medium KW - MAC KW - routing KW - sensor KW - networks KW - simulation Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-52870 ER -