@phdthesis{Glatzel2013, author = {Glatzel, Stefan}, title = {Cellulose based transition metal nano-composites : structuring and development}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-64678}, school = {Universit{\"a}t Potsdam}, year = {2013}, abstract = {Cellulose is the most abundant biopolymer on earth. In this work it has been used, in various forms ranging from wood to fully processed laboratory grade microcrystalline cellulose, to synthesise a variety of metal and metal carbide nanoparticles and to establish structuring and patterning methodologies that produce highly functional nano-hybrids. To achieve this, the mechanisms governing the catalytic processes that bring about graphitised carbons in the presence of iron have been investigated. It was found that, when infusing cellulose with an aqueous iron salt solution and heating this mixture under inert atmosphere to 640 °C and above, a liquid eutectic mixture of iron and carbon with an atom ratio of approximately 1:1 forms. The eutectic droplets were monitored with in-situ TEM at the reaction temperature where they could be seen dissolving amorphous carbon and leaving behind a trail of graphitised carbon sheets and subsequently iron carbide nanoparticles. These transformations turned ordinary cellulose into a conductive and porous matrix that is well suited for catalytic applications. Despite these significant changes on the nanometre scale the shape of the matrix as a whole was retained with remarkable precision. This was exemplified by folding a sheet of cellulose paper into origami cranes and converting them via the temperature treatment in to magnetic facsimiles of those cranes. The study showed that the catalytic mechanisms derived from controlled systems and described in the literature can be transferred to synthetic concepts beyond the lab without loss of generality. Once the processes determining the transformation of cellulose into functional materials were understood, the concept could be extended to other metals and metal-combinations. Firstly, the procedure was utilised to produce different ternary iron carbides in the form of MxFeyC (M = W, Mn). None of those ternary carbides have thus far been produced in a nanoparticle form. The next part of this work encompassed combinations of iron with cobalt, nickel, palladium and copper. All of those metals were also probed alone in combination with cellulose. This produced elemental metal and metal alloy particles of low polydispersity and high stability. Both features are something that is typically not associated with high temperature syntheses and enables to connect the good size control with a scalable process. Each of the probed reactions resulted in phase pure, single crystalline, stable materials. After showing that cellulose is a good stabilising and separating agent for all the investigated types of nanoparticles, the focus of the work at hand is shifted towards probing the limits of the structuring and pattering capabilities of cellulose. Moreover possible post-processing techniques to further broaden the applicability of the materials are evaluated. This showed that, by choosing an appropriate paper, products ranging from stiff, self-sustaining monoliths to ultra-thin and very flexible cloths can be obtained after high temperature treatment. Furthermore cellulose has been demonstrated to be a very good substrate for many structuring and patterning techniques from origami folding to ink-jet printing. The thereby resulting products have been employed as electrodes, which was exemplified by electrodepositing copper onto them. Via ink-jet printing they have additionally been patterned and the resulting electrodes have also been post functionalised by electro-deposition of copper onto the graphitised (printed) parts of the samples. Lastly in a preliminary test the possibility of printing several metals simultaneously and thereby producing finely tuneable gradients from one metal to another have successfully been made. Starting from these concepts future experiments were outlined. The last chapter of this thesis concerned itself with alternative synthesis methods of the iron-carbon composite, thereby testing the robustness of the devolved reactions. By performing the synthesis with partly dissolved scrap metal and pieces of raw, dry wood, some progress for further use of the general synthesis technique were made. For example by using wood instead of processed cellulose all the established shaping techniques available for wooden objects, such as CNC milling or 3D prototyping, become accessible for the synthesis path. Also by using wood its intrinsic well defined porosity and the fact that large monoliths are obtained help expanding the prospect of using the composite. It was also demonstrated in this chapter that the resulting material can be applied for the environmentally important issue of waste water cleansing. Additionally to being made from renewable resources and by a cheap and easy one-pot synthesis, the material is recyclable, since the pollutants can be recovered by washing with ethanol. Most importantly this chapter covered experiments where the reaction was performed in a crude, home-built glass vessel, fuelled - with the help of a Fresnel lens - only by direct concentrated sunlight irradiation. This concept carries the thus far presented synthetic procedures from being common laboratory syntheses to a real world application. Based on cellulose, transition metals and simple equipment, this work enabled the easy one-pot synthesis of nano-ceramic and metal nanoparticle composites otherwise not readily accessible. Furthermore were structuring and patterning techniques and synthesis routes involving only renewable resources and environmentally benign procedures established here. Thereby it has laid the foundation for a multitude of applications and pointed towards several future projects reaching from fundamental research, to application focussed research and even and industry relevant engineering project was envisioned.}, language = {en} } @phdthesis{Glatzel2012, author = {Glatzel, Stefan}, title = {Cellulose based transition metal nano-composites : structuring and development}, address = {Potsdam}, pages = {102, XXIII S.}, year = {2012}, language = {en} } @article{GlatzelNoackSchanzenbachetal.2020, author = {Glatzel, Julia and Noack, Sebastian and Schanzenbach, Dirk and Schlaad, Helmut}, title = {Anionic polymerization of dienes in 'green' solvents}, series = {Polymer international}, volume = {70}, journal = {Polymer international}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {0959-8103}, doi = {10.1002/pi.6152}, pages = {181 -- 184}, year = {2020}, abstract = {Isoprene and beta-myrcene were polymerized by anionic polymerization in bulk and in the 'green' ether solvents cyclopentyl methyl ether and 2-methyltetrahydrofuran and, for comparison, in cyclohexane and tetrahydrofuran. The polydienes produced in bulk and in cyclohexane contained high amounts of 1,4 units (>90\%) whereas those produced in ether solvents were rich in 1,2 and 3,4 units (36\%-86\%). Comparison of the microstructures and glass transition temperatures of the polydienes obtained in the various solvents suggests that conventionally used solvents can be substituted by environmentally more friendly alternatives.}, language = {en} } @article{GlattBuschKaiseretal.2006, author = {Glatt, Erik and Busch, Hauke and Kaiser, Friedemann and Zaikin, Alexei A.}, title = {Noise-memory induced excitability and pattern formation in oscillatory neural models}, issn = {1539-3755}, doi = {10.1103/Physreve.73.026216}, year = {2006}, abstract = {We report a noise-memory induced phase transition in an array of oscillatory neural systems, which leads to the suppression of synchronous oscillations and restoration of excitable dynamics. This phenomenon is caused by the systematic contributions of temporally correlated parametric noise, i.e., possessing a memory, which stabilizes a deterministically unstable fixed point. Changing the noise correlation time, a reentrant phase transition to noise- induced excitability is observed in a globally coupled array. Since noise-induced excitability implies the restoration of the ability to transmit information, associated spatiotemporal patterns are observed afterwards. Furthermore, an analytic approach to predict the systematic effects of exponentially correlated noise is presented and its results are compared with the simulations}, language = {en} } @misc{Glasze2004, author = {Glasze, Georg}, title = {Schmid, Heiko, Der Wiederaufbau des Beiruter Stadtzentrums : ein Beitrag zur handlungsorientierten politisch-geographischen Konfliktforschung / [rezensiert von] Georg Glasze}, series = {Geographische Revue: Zeitschrift f{\"u}r Literatur und Diskussion}, volume = {6}, journal = {Geographische Revue: Zeitschrift f{\"u}r Literatur und Diskussion}, number = {1}, issn = {1438-3039}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-30812}, pages = {55 -- 58}, year = {2004}, abstract = {Rezensiertes Werk: Schmid, Heiko: Der Wiederaufbau des Beiruter Stadtzentrums : ein Beitrag zur handlungsorientierten politisch-geographischen Konfliktforschung ; mit 6 Tabellen / von Heiko Schmid. Geographisches Institut der Universit{\"a}t Heidelberg. - Heidelberg : Geographisches Inst., 2002. - X, 284 S. : Ill., graph. Darst., Kt. - (Heidelberger geographische Arbeiten ; H. 114) Zugl.: Heidelberg, Univ., Diss., 2001 ISBN 3-88570-114-6}, language = {de} } @misc{GlassKliegl1983, author = {Glass, Gene V. and Kliegl, Reinhold}, title = {An apology for research integration in the study of psychotherapy}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-40233}, year = {1983}, abstract = {Criticisms of the integration of psychotherapy-outcome research performed by Smith, Glass, and Miller (1980) are reviewed and answered. An attempt is made to account for the conflicting points of view in this disagreement in terms of certain issues that have engaged philosophers of science in the 20th century. It is hoped that, in passing, something useful is learned about research of many types on psychotherapy.}, language = {en} } @inproceedings{Glashuettner2008, author = {Glash{\"u}ttner, Robert}, title = {The perception of video games : from visual power to immersive interaction}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-24578}, year = {2008}, abstract = {This paper highlights the different ways of perceiving video games and video game content, incorporating interactive and non-interactive methods. It examines varying cognitive and emotive reactions by persons who are used to play video games as well as persons who are unfamiliar with the aesthetics and the most basic game play rules incorporated within video games. Additionally, the principle of "Flow" serves as a theoretical and philosophical foundation. A small case-study featuring two games has been made to emphasize the numerous possible ways of perception of video games.}, language = {en} } @article{Glashuettner2009, author = {Glash{\"u}ttner, Robert}, title = {Computerspiele-Journalismus}, series = {DIGAREC Lectures 2008/09 : Vortr{\"a}ge am Zentrum f{\"u}r Computerspielforschung mit Wissenschaftsforum der Deutschen Gamestage ; Quo Vadis 2008 und 2009}, journal = {DIGAREC Lectures 2008/09 : Vortr{\"a}ge am Zentrum f{\"u}r Computerspielforschung mit Wissenschaftsforum der Deutschen Gamestage ; Quo Vadis 2008 und 2009}, number = {2}, publisher = {Universit{\"a}tsverlag Potsdam}, address = {Potsdam}, isbn = {978-3-86956-004-5}, issn = {1867-6219}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-33269}, pages = {128 -- 146}, year = {2009}, abstract = {Der vorliegende Aufsatz liefert eine Kurzanalyse zur Entstehung des Computer- und Videospielejournalismus in den 1980er Jahren und gliedert seine unterschiedlichen Erscheinungsformen hinsichtlich Format, kulturellem Selbstverst{\"a}ndnis und ideologischer Ausrichtung bis zu Publikationen der Gegenwart. Dabei wird verst{\"a}rkt auf textbasierte Medien aus dem deutschsprachigen Raum Bezug genommen (Print und Online).}, language = {de} } @article{GlaserPrengelKlika2004, author = {Glaser, Edith and Prengel, Annedore and Klika, Dorle}, title = {Einleitung}, isbn = {3-7815-1323-8}, year = {2004}, language = {de} } @article{GlaserPrengel2004, author = {Glaser, Edith and Prengel, Annedore}, title = {Lernwerkst{\"a}tten}, isbn = {3-7815-1172-3}, year = {2004}, language = {de} } @article{GlaserPrengel2004, author = {Glaser, Edith and Prengel, Annedore}, title = {M{\"a}dchenbildung}, isbn = {3-7815-1172-3}, year = {2004}, language = {de} } @phdthesis{Glaser2004, author = {Glaser, Cornelia}, title = {F{\"o}rderung der Schreibkompetenz bei Grundsch{\"u}lern : Effekte einer integrierten Vermittlung kognitiver Schreibstrategien und selbstregulatorischer Fertigkeiten}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001933}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {In Anlehnung an das Self-Regulated-Strategy-Development-Modell von Harris und Graham (1996) wurde das Selbstregulatorische Aufsatztraining (SAT) zur F{\"o}rderung der Schreibkompetenz bei Grundsch{\"u}lern der 4. und 5. Klasse entwickelt. SAT integriert die Vermittlung von Schreibstrategien (hier: „Erz{\"a}hlendes Schreiben") mit Merkmalen selbstgesteuerten Lernens (Zielsetzung, strategisches Planen, Selbstbewertung und Selbstkorrektur). Die Wirksamkeit des Trainings wurde in drei Studien untersucht: 1. Eine Pilotstudie diente der {\"U}berpr{\"u}fung der prinzipiellen Eignung von SAT zur F{\"o}rderung von Schreibleistungen bei Grundsch{\"u}lern der 5. Klassen (N = 42) und der Optimierung seiner Teilkomponenten und Vorgehensweisen. 2. In der Hauptuntersuchung wurden die Effektivit{\"a}t und Nachhaltigkeit des SAT-Programms bei Sch{\"u}lern der 4. Klasse (N = 154) im Vergleich zu zwei Bedingungen getestet: (a) der isolierten Ein{\"u}bung von Schreibstrategien (Aufsatztraining) und (b) konventionellem Aufsatzunterricht (Unterrichtskontrollgruppe). 3. In einer weiteren Studie wurde die Wirksamkeit des Trainings speziell bei Sch{\"u}lern mit ung{\"u}nstigen Lernvoraussetzungen {\"u}berpr{\"u}ft; die Studie diente zudem der Illustration des dabei gew{\"a}hlten Vorgehens am Einzelfall (N = 6). Die ermittelten Befunde sprechen {\"u}bereinstimmend daf{\"u}r, dass die Kombination aus strategischem plus selbstregulatorischem Training (SAT) die st{\"a}rksten und nachhaltigsten Effekte auf die Schreibleistung erzielt. Der Trainingseffekt generalisiert zudem auf die Erinnerungsleistung bei der freien Wiedergabe einer Kurzgeschichte. Sch{\"u}ler mit schwachen Aufsatzleistungen und ung{\"u}nstigen Lernvoraussetzungen profitieren von dem SAT-Programm in besonderem Maße. In der Diskussion werden Aufgaben f{\"u}r die zuk{\"u}nftige Forschung er{\"o}rtert. Forschungsbedarf besteht u.a. hinsichtlich (a) einer st{\"a}rkeren Verkn{\"u}pfung von Schreibtrainings mit der kognitionspsychologischen Forschung; (b) der Dekomposition und gezielten {\"U}berpr{\"u}fung der einzelnen Trainingskomponenten; (c) der Ausweitung des SAT-Programms auf andere Textgenre; (d) der Integration verfeinerter Revisionsstrategien in das F{\"o}rderprogramm; und (e) dessen Implementierung in den Regelunterricht.}, language = {de} } @inproceedings{GlaschkeGronauBender2016, author = {Glaschke, Christian and Gronau, Norbert and Bender, Benedict}, title = {Cross-System Process Mining using RFID Technology}, series = {Proceedings of the Sixth International Symposium on Business Modeling and Software Design - BMSD}, booktitle = {Proceedings of the Sixth International Symposium on Business Modeling and Software Design - BMSD}, publisher = {SCITEPRESS - Science and Technology Publications}, address = {Set{\´u}bal}, isbn = {978-989-758-190-8}, doi = {10.5220/0006223501790186}, pages = {179 -- 186}, year = {2016}, abstract = {In times of digitalization, the collection and modeling of business processes is still a challenge for companies. The demand for trustworthy process models that reflect the actual execution steps therefore increases. The respective kinds of processes significantly determine both, business process analysis and the conception of future target processes and they are the starting point for any kind of change initiatives. Existing approaches to model as-is processes, like process mining, are exclusively focused on reconstruction. Therefore, transactional protocols and limited data from a single application system are used. Heterogeneous application landscapes and business processes that are executed across multiple application systems, on the contrary, are one of the main challenges in process mining research. Using RFID technology is hence one approach to close the existing gap between different application systems. This paper focuses on methods for data collection from real world objects via RFID technology and possible combinations with application data (process mining) in order to realize a cross system mining approach.}, language = {en} } @article{Glaschke2017, author = {Glaschke, Christian}, title = {Auswahl und Einf{\"u}hrung von ERP-Systemen}, series = {Die Rolle von ERP-Systemen im Zeitalter der Digitalisierung}, journal = {Die Rolle von ERP-Systemen im Zeitalter der Digitalisierung}, publisher = {Gito}, address = {Berlin}, isbn = {978-3-95545-197-4}, pages = {197 -- 210}, year = {2017}, language = {de} } @article{GlanemannWillnerLevermann2020, author = {Glanemann, Nicole and Willner, Sven N. and Levermann, Anders}, title = {Paris Climate Agreement passes the cost-benefit test}, series = {Nature Communications}, volume = {11}, journal = {Nature Communications}, number = {1}, publisher = {Nature Publishing Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/s41467-019-13961-1}, pages = {11}, year = {2020}, abstract = {The Paris Climate Agreement aims to keep temperature rise well below 2 degrees C. This implies mitigation costs as well as avoided climate damages. Here we show that independent of the normative assumptions of inequality aversion and time preferences, the agreement constitutes the economically optimal policy pathway for the century. To this end we consistently incorporate a damage-cost curve reproducing the observed relation between temperature and economic growth into the integrated assessment model DICE. We thus provide an intertemporally optimizing cost-benefit analysis of this century's climate problem. We account for uncertainties regarding the damage curve, climate sensitivity, socioeconomic future, and mitigation costs. The resulting optimal temperature is robust as can be understood from the generic temperature-dependence of the mitigation costs and the level of damages inferred from the observed temperature-growth relationship. Our results show that the politically motivated Paris Climate Agreement also represents the economically favourable pathway, if carried out properly.}, language = {en} } @article{GlanderDoellner2009, author = {Glander, Tassilo and D{\"o}llner, J{\"u}rgen Roland Friedrich}, title = {Abstract representations for interactive visualization of virtual 3D city models}, issn = {0198-9715}, doi = {10.1016/j.compenvurbsys.2009.07.003}, year = {2009}, abstract = {Virtual 3D city models increasingly cover whole city areas; hence, the perception of complex urban structures becomes increasingly difficult. Using abstract visualization, complexity of these models can be hidden where its visibility is unnecessary, while important features are maintained and highlighted for better comprehension and communication. We present a technique to automatically generalize a given virtual 3D city model consisting of building models, an infrastructure network and optional land coverage data; this technique creates several representations of increasing levels of abstraction. Using the infrastructure network, our technique groups building models and replaces them with cell blocks, while preserving local landmarks. By computing a landmark hierarchy, we reduce the set of initial landmarks in a spatially balanced manner for use in higher levels of abstraction. In four application examples, we demonstrate smooth visualization of transitions between precomputed representations; dynamic landmark highlighting according to virtual camera distance; an implementation of a cognitively enhanced route representation, and generalization lenses to combine precomputed representations in focus + context visualization.}, language = {en} } @phdthesis{Glander2012, author = {Glander, Tassilo}, title = {Multi-scale representations of virtual 3D city models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-64117}, school = {Universit{\"a}t Potsdam}, year = {2012}, abstract = {Virtual 3D city and landscape models are the main subject investigated in this thesis. They digitally represent urban space and have many applications in different domains, e.g., simulation, cadastral management, and city planning. Visualization is an elementary component of these applications. Photo-realistic visualization with an increasingly high degree of detail leads to fundamental problems for comprehensible visualization. A large number of highly detailed and textured objects within a virtual 3D city model may create visual noise and overload the users with information. Objects are subject to perspective foreshortening and may be occluded or not displayed in a meaningful way, as they are too small. In this thesis we present abstraction techniques that automatically process virtual 3D city and landscape models to derive abstracted representations. These have a reduced degree of detail, while essential characteristics are preserved. After introducing definitions for model, scale, and multi-scale representations, we discuss the fundamentals of map generalization as well as techniques for 3D generalization. The first presented technique is a cell-based generalization of virtual 3D city models. It creates abstract representations that have a highly reduced level of detail while maintaining essential structures, e.g., the infrastructure network, landmark buildings, and free spaces. The technique automatically partitions the input virtual 3D city model into cells based on the infrastructure network. The single building models contained in each cell are aggregated to abstracted cell blocks. Using weighted infrastructure elements, cell blocks can be computed on different hierarchical levels, storing the hierarchy relation between the cell blocks. Furthermore, we identify initial landmark buildings within a cell by comparing the properties of individual buildings with the aggregated properties of the cell. For each block, the identified landmark building models are subtracted using Boolean operations and integrated in a photo-realistic way. Finally, for the interactive 3D visualization we discuss the creation of the virtual 3D geometry and their appearance styling through colors, labeling, and transparency. We demonstrate the technique with example data sets. Additionally, we discuss applications of generalization lenses and transitions between abstract representations. The second technique is a real-time-rendering technique for geometric enhancement of landmark objects within a virtual 3D city model. Depending on the virtual camera distance, landmark objects are scaled to ensure their visibility within a specific distance interval while deforming their environment. First, in a preprocessing step a landmark hierarchy is computed, this is then used to derive distance intervals for the interactive rendering. At runtime, using the virtual camera distance, a scaling factor is computed and applied to each landmark. The scaling factor is interpolated smoothly at the interval boundaries using cubic B{\´e}zier splines. Non-landmark geometry that is near landmark objects is deformed with respect to a limited number of landmarks. We demonstrate the technique by applying it to a highly detailed virtual 3D city model and a generalized 3D city model. In addition we discuss an adaptation of the technique for non-linear projections and mobile devices. The third technique is a real-time rendering technique to create abstract 3D isocontour visualization of virtual 3D terrain models. The virtual 3D terrain model is visualized as a layered or stepped relief. The technique works without preprocessing and, as it is implemented using programmable graphics hardware, can be integrated with minimal changes into common terrain rendering techniques. Consequently, the computation is done in the rendering pipeline for each vertex, primitive, i.e., triangle, and fragment. For each vertex, the height is quantized to the nearest isovalue. For each triangle, the vertex configuration with respect to their isovalues is determined first. Using the configuration, the triangle is then subdivided. The subdivision forms a partial step geometry aligned with the triangle. For each fragment, the surface appearance is determined, e.g., depending on the surface texture, shading, and height-color-mapping. Flexible usage of the technique is demonstrated with applications from focus+context visualization, out-of-core terrain rendering, and information visualization. This thesis presents components for the creation of abstract representations of virtual 3D city and landscape models. Re-using visual language from cartography, the techniques enable users to build on their experience with maps when interpreting these representations. Simultaneously, characteristics of 3D geovirtual environments are taken into account by addressing and discussing, e.g., continuous scale, interaction, and perspective.}, language = {en} } @book{GlanderTreutler2017, author = {Glander, Johannes and Treutler, Gerd-Christian Th.}, title = {Kurm{\"a}rkische M{\"u}hlensachen-Generalia}, series = {Genealogische Quellen Brandenburgs ; Band 6 ; Einzelver{\"o}ffentlichung des Brandenburgischen Landeshauptarchivs ; Band 17}, journal = {Genealogische Quellen Brandenburgs ; Band 6 ; Einzelver{\"o}ffentlichung des Brandenburgischen Landeshauptarchivs ; Band 17}, publisher = {BGG-Verlag}, address = {Falkensee}, isbn = {978-3-945402-07-8}, publisher = {Universit{\"a}t Potsdam}, pages = {XXXI, 296}, year = {2017}, language = {de} } @misc{GlaesmerKleinPichottka2001, author = {Glaesmer, Janny and Klein, Armin and Pichottka, Maria}, title = {Portal = Internationalisierung: Wie weit ist die Universit{\"a}t Potsdam}, number = {01/2001}, organization = {Universit{\"a}t Potsdam, Referat f{\"u}r Presse- und {\"O}ffentlichkeitsarbeit}, issn = {1618-6893}, doi = {10.25932/publishup-43934}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-439343}, pages = {34}, year = {2001}, abstract = {Aus dem Inhalt: - Titel: Internationalisierung: Wie weit ist die Universit{\"a}t Potsdam? - Forschung: Quarz wird weich wie Kaugummi - Der neue AStA und seine Aufgaben - Personalia: Zum Tod von Hans-J{\"u}rgen Bachorski - Vermischtes: Lust an Kunst: Iris Unger}, language = {de} } @article{GlaeserBerghoffStratmannetal.2014, author = {Glaeser, Stefanie P. and Berghoff, Bork A. and Stratmann, Verena and Grossart, Hans-Peter and Glaeser, Jens}, title = {Contrasting effects of singlet oxygen and hydrogen peroxide on bacterial community composition in a humic lake}, series = {PLoS one}, volume = {9}, journal = {PLoS one}, number = {3}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0092518}, pages = {19}, year = {2014}, abstract = {Light excitation of humic matter generates reactive oxygen species (ROS) in surface waters of aquatic ecosystems. Abundant ROS generated in humic matter rich lakes include singlet oxygen (O-1(2)) and hydrogen peroxide (H2O2). Because these ROS differ in half-life time and toxicity, we compared their effects on microbial activity (C-14-Leucine incorporation) and bacterial community composition (BCC) in surface waters of humic Lake Grosse Fuchskuhle (North-eastern Germany). For this purpose, experiments with water samples collected from the lake were conducted in July 2006, September 2008 and August 2009. Artificially increased O-1(2) and H2O2 concentrations inhibited microbial activity in water samples to a similar extent, but the effect of the respective ROS on BCC varied strongly. BCC analysis by 16S rRNA gene clone libraries and RT-PCR DGGE revealed ROS specific changes in relative abundance and activity of major bacterial groups and composition of dominating phylotypes. These changes were consistent in the three experiments performed in different years. The relative abundance of Polynucleobacter necessarius, Limnohabitans-related phylotypes (Betaproteobacteria), and Novosphingobium acidiphilum (Alphaproteobacteria) increased or was not affected by photo-sensitized O-1(2) exposure, but decreased after H2O2 exposure. The opposite pattern was found for Actinobacteria of the freshwater AcI-B cluster which were highly sensitive to O-1(2) but not to H2O2 exposure. Furthermore, group-specific RT-PCR DGGE analysis revealed that particle-attached P. necessarius and Limnohabitans-related phylotypes exhibit higher resistance to O-1(2) exposure compared to free-living populations. These results imply that O-1(2) acts as a factor in niche separation of closely affiliated Polynucleobacter and Limnohabitans-related phylotypes. Consequently, oxidative stress caused by photochemical ROS generation should be regarded as an environmental variable determining abundance, activity, and phylotype composition of environmentally relevant bacterial groups, in particular in illuminated and humic matter rich waters.}, language = {en} }