TY - JOUR A1 - Grotendorst, Johannes T1 - IAS Winter School: Hierarchical Methods for Dynamics in Complex Molecular Systems JF - Innovatives Supercomputing in Deutschland : inSiDE. 10 (2012), H. 1 Y1 - 2012 SP - 104 PB - - ER - TY - JOUR A1 - Nomdedeu, Mar Monsonis A1 - Willen, Christine A1 - Schieffer, Andre A1 - Arndt, Hartmut T1 - Temperature-dependent ranges of coexistence in a model of a two-prey-one-predator microbial food web JF - Marine Biology N2 - The objective of our study was to analyze the effects of temperature on the population dynamics of a three-species food web consisting of two prey bacteria (Pedobacter sp. and Acinetobacter johnsonii) and a protozoan predator (Tetrahymena pyriformis) as model organisms. We assessed the effects of temperature on the growth rates of all three species with the objective of developing a model with four differential equations based on the experimental data. The following hypotheses were tested at a theoretical level: Firstly, temperature changes can affect the dynamic behavior of a system by temperature-dependent parameters and interactions and secondly, food web response to temperature cannot be derived from the single species temperature response. The main outcome of the study is that temperature changes affect the parameter range where coexistence is possible within all three species. This has significant consequences on our ideas regarding the evaluation of effects of global warming. Y1 - 2012 U6 - https://doi.org/10.1007/s00227-012-1966-x SN - 1432-1793 VL - 159 IS - 11 SP - 2423 EP - 2430 PB - Springer CY - Berlin ER - TY - THES A1 - Schieffer, Andre T1 - Studies on diversity and coexistence in an experimental microbial community N2 - Biodiversity and the coexistence of species have puzzled and fascinated biologists since decades and is a hotspot in todays’ natural sciences. Preserving this biodiversity is a great challenge as habitats and environments underlying tremendous changes like climate change and the loss of natural habitats, which are mainly due to anthropogenic influences. The coexistence of numerous species even in homogeneous environments is a stunning feature of natural communities and has been summarized under the term ‘paradox of plankton’. Up to now, there are several mechanisms discussed, which may contribute to local and global diversity of organisms. Several interspecific trade offs have been identified maintaining the coexistence of species like their abilities regarding competition and predator avoidance, their capability to disperse in space and time, and their ability to exploit variable resources. Further, micro-evolutionary dynamics supporting the coexistence of species have been added to our knowledge, and deriving from theoretical deterministic models, non-linear dynamics which describe the temporal fluctuation of abundances of organisms. Whereas competition and predation seem to be clue structural elements within interacting organisms, the intrinsic dynamic behavior – by means of temporal changes in abundance - plays an important role regarding coexistence within a community. The present work sheds light on different factors affecting the coexistence of species using experimental microbial model systems consisting of a bacterivorous ciliate as the predator and two bacteria strains as prey organism. Additionally, another experimental setup consisting of two up to five bacteria species competing for one limiting resource was investigated. Highly controllable chemostat systems were established to exclude extrinsic disturbances. According to theoretical analyses I was able to show - experimentally and theoretically - that phenotypic plasticity of one species within a microbial one-predator-two-prey food web enlarges the range of possible coexistence of all species under different dynamic conditions, compared to a food web without phenotypic plasticity. This was accompanied by non-linear (chaotic) population dynamics within all experimental systems showing phenotypic plasticity. The experiments on the interplay of competition, predation and invasion showed that all aspects have an influence on species coexistence. Under undisturbed controlled conditions all aspects were analyzed in detail and in combination. Populations showed oscillations which were shown by quasi-chaotic attractors in phase space diagrams. Competition experiments with two up to five bacteria species competing for one limiting resource showed that all organisms were able to coexist which was mediated by species oscillations entering a regime of chaos. Besides that fact it was found, that the productivity (biomass) as well as the total cell numbers – under the same nutrition supply – increased by an increasing number of species in the experimental systems. Up to now, the occurrence of non-linear dynamics in well controlled experimental studies has been recognized several times and this phenomenon seemed to be more common in natural systems than generally assumed. N2 - Biodiversität und die Koexistenz von Arten fasziniert und verblüfft Biologen seit Jahr-zehnten und stellen einen Schwerpunkt in der heutigen Umweltforschung dar. Der Schutz und die Konservierung dieser Mannigfaltigkeit stellen eine große Herausfor-derung dar, da die natürlichen Lebensräume sowie die Umwelt enormen Verände-rungen unterworfen sind, welche meist in einem anthropogenen Ursprung wurzeln. Die Koexistenz vieler Arten, auch in relativ homogenen Habitaten ist ein faszinieren-des Charakteristikum natürlicher Lebensgemeinschaften und wird als ‚Paradox des Planktons‘ bezeichnet. Gegenwärtig werden diverse Ursachen diskutiert, welche vermutlich zur lokalen und globalen Diversität von Organismen beitragen. Einige die-ser möglichen Ursachen, die zur Aufrechterhaltung der Koexistenz der Arten beitra-gen, wurden identifiziert: Das Vermögen der Konkurrenz- und Prädationsvermeidung, die Fähigkeit räumlicher sowie zeitlicher Verteilung, sowie das Vermögen variable Ressourcen zu nutzen. Des Weiteren wurden mikro-evolutionäre Phänomene und Dynamiken identifiziert, sowie, von theoretischen deterministischen Modellen ausge-hend, nichtlineare Dynamiken, welche die zeitlichen Schwankungen der Abundanzen von Organismen beschreiben. Diese Aspekte stellen die Schlüsselkomponenten zwi-schen interagierenden Organismen dar, wobei das intrinsiche, nicht lineare dynami-sche Verhalten in Form von zeitlichen Veränderungen in Abundanzen eine zusätzli-che entscheidende Rolle bezüglich der Koexistenz von Arten spielen kann. Einige dieser Aspekte wurden in der vorliegenden Arbeit untersucht. In Anlehnung an theoretische Analysen konnte experimentell sowie theoretisch gezeigt werden, dass phänotypische Plastizität in einer Bakterienart in einem mikrobiellen Ein-Räuber-zwei-Beute-Nahrungsgewebe den Bereich der möglichen Koexistenz unter sich än-dernden experimentellen Bedingungen (Änderungen der Durchflussraten der Chemostate) – im direkten Vergleich zu einem experimentellen Nahrungsgewebe ohne phänotypische Plastizität – erweitern kann. Dies wurde begleitet durch nicht lineare Abundanzschwankungen in den Populationen aller untersuchten Versuchs-ansätze. In weiteren Untersuchungen wurde das Zusammenspiel von Konkurrenz, Prädation und Invasion in einer experimentellen mikrobiellen Gemeinschaft untersucht. Unter kontrollierten Bedingungen konnten diese Aspekte detailliert untersucht werden und es konnten Aufschlüsse darüber gewonnen werden, welche Reaktionen (Interaktionen) innerhalb der untersuchten Gemeinschaften stattfinden. Im Versuchsverlauf wurden Veränderungen in den Abundanzen sowie chaotische Schwankungen der Zellzahlen festgestellt. In Konkurrenzexperimenten von zwei bis zu fünf um eine limitierende Ressource konkurrierende Bakterienarten konnte gezeigt werden, dass alle Arten – vermittelt durch chaotische Abundanzschwankungen – nebeneinander koexistieren konnten. Begleitend dazu wurde herausgefunden, dass die Produktivität (Biomasse) sowie die Gesamtzellzahl bei gleicher Nahrungsverfügbarkeit der experimentellen Systeme mit steigender Artenzahl zunehmen. Gegenwärtig ist das Auftreten von Chaos in gut kontrollierten experimentellen Studien vereinzelt beobachtet worden, wobei dieses Phänomen jedoch häufiger in der Natur aufzutreten scheint als generell vermutet. Y1 - 2012 N1 - Köln, Univ., Diss., 2012 ER - TY - CHAP A1 - Streun, M. A1 - Al-Kaddoum, R. A1 - Parl, C. A1 - Pietrzyk, U. A1 - Ziemons, Karl A1 - Waasen, S. van T1 - Simulation studies of optical photons in monolithic block scintillators T2 - 2011 IEEE Nuclear Science Symposium Conference Record (NSS/MIC) N2 - The interest in PET detectors with monolithic block scintillators is growing. In order to obtain high spatial resolutions dedicated positioning algorithms are required. But even an ideal algorithm can only deliver information which is provided by the detector. In this simulation study we investigated the light distribution on one surface of cuboid LSO scintillators of different size. Scintillators with a large aspect ratio (small footprint and large height) showed significant position information only for a minimum interaction depth of the gamma particle. The results allow a quantitative estimate for a useful aspect ratio. Y1 - 2012 SN - 978-1-4673-0120-6 (electronic ISBN) SN - 978-1-4673-0118-3 (print ISBN) U6 - https://doi.org/10.1109/NSSMIC.2011.6154621 SP - 1380 EP - 1382 PB - IEEE CY - New York ER - TY - JOUR A1 - Lustfeld, H. A1 - Pithan, C. A1 - Reißel, Martin T1 - Metallic electrolyte composites in the framework of the brick-layer model JF - Journal of the European Ceramic Society N2 - It is well known that the already large dielectric constants of some electrolytes like BaTiO₃ can be enhanced further by adding metallic (e.g. Ni, Cu or Ag) nanoparticles. The enhancement can be quite large, a factor of more than 1000 is possible. The consequences for the properties will be discussed in the present paper applying a brick-layer model (BLM) for calculating dc-resistivities of thin layers and a modified one (PBLM) that includes percolation for calculating dielectric properties of these materials. The PBLM results in an at least qualitative description and understanding of the physical phenomena: This model gives an explanation for the steep increase of the dielectric constant below the percolation threshold and why this increase is connected to a dramatic decrease of the breakdown voltage as well as the ability of storing electrical energy. We conclude that metallic electrolyte composites like BaTiO₃ are not appropriate for energy storage. Y1 - 2012 U6 - https://doi.org/10.1016/j.jeurceramsoc.2011.10.017 SN - 0955-2219 VL - 32 IS - 4 SP - 859 EP - 864 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Reisert, Steffen A1 - Geissler, H. A1 - Flörke, R. A1 - Weiler, C. A1 - Wagner, P. A1 - Schöning, Michael Josef ED - Abdelghani, Adnane ED - Schöning, Michael Josef T1 - Characterisation of aseptic sterilisation processes using an electronic nose T2 - Nanoscale Science and Technology (NS&T´12) : Proceedings Book Humboldt Kolleg ; Tunisia, 17-19 March, 2012 Y1 - 2012 SP - 45 EP - 45 ER - TY - CHAP A1 - Yoshinobu, Tatsuo A1 - Miyamoto, Ko-Ichiro A1 - Wagner, Torsten A1 - Schöning, Michael Josef ED - Yamaguchi, Takami T1 - Miniaturized and high-speed chemical imaging systems T2 - Nano-Biomedical Engineering 2012. Proceedings of the Tohoku University Global Centre of Excellence Programme, Sakura Hall, Tohoku University, Sendai Japan, 5 – 6 March 2012 Y1 - 2012 U6 - https://doi.org/10.1142/9781848169067_0045 SP - 386 EP - 395 PB - World Scientific CY - Singapur ER - TY - JOUR A1 - Grinsven, Bart van A1 - Bon, Natalie vanden A1 - Strauven, Hannelore A1 - Grieten, Lars A1 - Murib, Mohammed A1 - Jiménez Monroy, Kathia L. A1 - Janssens, Stoffel D. A1 - Haenen, Ken A1 - Schöning, Michael Josef A1 - Vermeeren, Veronique A1 - Ameloot, Marcel A1 - Michiels, Luc A1 - Thoelen, Ronald A1 - Ceuninck, Ward de A1 - Wagner, Patrick T1 - Heat-Transfer Resistance at Solid-Liquid Interfaces: A Tool for The Detection of Single Nucleotide Polymorphisms in DNA. JF - ACS Nano N2 - In this article, we report on the heat-transfer resistance at interfaces as a novel, denaturation-based method to detect single-nucleotide polymorphisms in DNA. We observed that a molecular brush of double-stranded DNA grafted onto synthetic diamond surfaces does not notably affect the heat-transfer resistance at the solid-to-liquid interface. In contrast to this, molecular brushes of single-stranded DNA cause, surprisingly, a substantially higher heat-transfer resistance and behave like a thermally insulating layer. This effect can be utilized to identify ds-DNA melting temperatures via the switching from low- to high heat-transfer resistance. The melting temperatures identified with this method for different DNA duplexes (29 base pairs without and with built-in mutations) correlate nicely with data calculated by modeling. The method is fast, label-free (without the need for fluorescent or radioactive markers), allows for repetitive measurements, and can also be extended toward array formats. Reference measurements by confocal fluorescence microscopy and impedance spectroscopy confirm that the switching of heat-transfer resistance upon denaturation is indeed related to the thermal on-chip denaturation of DNA. Y1 - 2012 U6 - https://doi.org/10.1021/nn300147e SN - 1936-086X VL - 6 IS - 3 SP - 2712 EP - 2721 PB - ACS Publications CY - Washington, DC ER - TY - CHAP A1 - Bohrn, U. A1 - Stütz, E. A1 - Fleischer, M. A1 - Schöning, Michael Josef A1 - Wagner, P. ED - Abdelghani, Adnane ED - Schöning, Michael Josef T1 - Towards a paradigm change – mammalian cells as sensitive biosensor layers for the detection of unexpected toxic substances in air T2 - Nanoscale Science and Technology (NS&T´12) : Proceedings Book Humboldt Kolleg ; Tunisia, 17-19 March, 2012 Y1 - 2012 SP - 44 EP - 44 ER - TY - JOUR A1 - Spelthahn, Heiko A1 - Kirsanov, Dmitry A1 - Legin, Andrey A1 - Osterrath, Thomas A1 - Schubert, Jürgen A1 - Zander, Willi A1 - Schöning, Michael Josef T1 - Development of a thin-film sensor array for analytical monitoring of heavy metals in aqueous solutions JF - Physica Status Solidi (a) N2 - In industrial processes there is a variety of heavy metals (e.g., copper, zinc, cadmium, and lead) in use for wires, coatings, paints, alloys, batteries, etc. Since the application of these transition metals for industry is inevitable, it is a vital task to develop proper analytical techniques for their monitoring at low activity levels, especially because most of these elements are acutely toxic for biological organisms. The determination of ions in solution by means of a simple and inexpensive sensor array is, therefore, a promising task. In this work, a sensor array with heavy metal-sensitive chalcogenide glass membranes for the simultaneous detection of the four ions Ag⁺, Cu2⁺, Cd2⁺, and Pb2⁺ in solution is realized. The results of the physical characterization by means of microscopy, profilometry, Rutherford backscattering spectroscopy (RBS), and scanning electron microscopy (SEM) as well as the electrochemical characterization by means of potentiometric measurements are presented. Additionally, the possibility to expand the sensor array by polymeric sensor membranes is discussed. Y1 - 2012 SN - 1862-6319 U6 - https://doi.org/10.1002/pssa.201100733 VL - 209 IS - 5 SP - 885 EP - 891 PB - Wiley-VCH CY - Weinheim ER -