@phdthesis{RodriguezCubillos2018,
  author    = {Rodriguez Cubillos, Andres Eduardo},
  title     = {Understanding the impact of heterozygosity on metabolism, growth and hybrid necrosis within a local Arabidopsis thaliana collection site},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-416758},
  school      = {Universit{\"a}t Potsdam},
  pages     = {106},
  year      = {2018},
  abstract  = {Plants are unable to move away from unwanted environments and therefore have to locally adapt to changing conditions. Arabidopsis thaliana (Arabidopsis), a model organism in plant biology, has been able to rapidly colonize a wide spectrum of environments with different biotic and abiotic challenges. In recent years, natural variation in Arabidopsis has shown to be an excellent resource to study genes underlying adaptive traits and hybridization's impact on natural diversity. Studies on Arabidopsis hybrids have provided information on the genetic basis of hybrid incompatibilities and heterosis, as well as inheritance patterns in hybrids. However, previous studies have focused mainly on global accessions and yet much remains to be known about variation happening within a local growth habitat. In my PhD, I investigated the impact of heterozygosity at a local collection site of Arabidopsis and its role in local adaptation. I focused on two different projects, both including hybrids among Arabidopsis individuals collected around T{\"u}bingen in Southern Germany. The first project sought to understand the impact of hybridization on metabolism and growth within a local Arabidopsis collection site. For this, the inheritance patterns in primary and secondary metabolism, together with rosette size of full diallel crosses among seven parents originating from Southern Germany were analyzed. In comparison to primary metabolites, compounds from secondary metabolism were more variable and showed pronounced non-additive inheritance patterns. In addition, defense metabolites, mainly glucosinolates, displayed the highest degree of variation from the midparent values and were positively correlated with a proxy for plant size. In the second project, the role of ACCELERATED CELL DEATH 6 (ACD6) in the defense response pathway of Arabidopsis necrotic hybrids was further characterized. Allelic interactions of ACD6 have been previously linked to hybrid necrosis, both among global and local Arabidopsis accessions. Hence, I characterized the early metabolic and ionic changes induced by ACD6, together with marker gene expression assays of physiological responses linked to its activation. An upregulation of simple sugars and metabolites linked to non-enzymatic antioxidants and the TCA cycle were detected, together with putrescine and acids linked to abiotic stress responses. Senescence was found to be induced earlier in necrotic hybrids and cytoplasmic calcium signaling was unaffected in response to temperature. In parallel, GFP-tagged constructs of ACD6 were developed. This work therefore gave novel insights on the role of heterozygosity in natural variation and adaptation and expanded our current knowledge on the physiological and molecular responses associated with ACD6 activation.},
  language  = {en}
}
@phdthesis{Ullmann2018,
  author    = {Ullmann, Wiebke},
  title     = {Understanding animal movement behaviour in dynamic agricultural landscapes},
  doi       = {10.25932/publishup-42715},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-427153},
  school      = {Universit{\"a}t Potsdam},
  pages     = {vii, 183},
  year      = {2018},
  abstract  = {The movement of organisms has formed our planet like few other processes. Movements shape populations, communities, entire ecosystems, and guarantee fundamental ecosystem functions and services, like seed dispersal and pollination. Global, regional and local anthropogenic impacts influence animal movements across ecosystems all around the world. In particular, land-use modification, like habitat loss and fragmentation disrupt movements between habitats with profound consequences, from increased disease transmissions to reduced species richness and abundance. However, neither the influence of anthropogenic change on animal movement processes nor the resulting effects on ecosystems are well understood. Therefore, we need a coherent understanding of organismal movement processes and their underlying mechanisms to predict and prevent altered animal movements and their consequences for ecosystem functions. In this thesis I aim at understanding the influence of anthropogenically caused land-use change on animal movement processes and their underlying mechanisms. In particular, I am interested in the synergistic influence of large-scale landscape structure and fine-scale habitat features on basic-level movement behaviours (e.g. the daily amount of time spend running, foraging, and resting) and their emerging higher-level movements (home range formation). Based on my findings, I identify the likely consequences of altered animal movements that lead to the loss of species richness and abundances. The study system of my thesis are hares in agricultural landscapes. European brown hares (Lepus europaeus) are perfectly suited to study animal movements in agricultural landscapes, as hares are hermerophiles and prefer open habitats. They have historically thrived in agricultural landscapes, but their numbers are in decline. Agricultural areas are undergoing strong land-use changes due to increasing food demand and fast developing agricultural technologies. They are already the largest land-use class, covering 38\% of the world's terrestrial surface. To consider the relevance of a given landscape structure for animal movement behaviour I selected two differently structured agricultural landscapes - a simple landscape in Northern Germany with large fields and few landscape elements (e.g. hedges and tree stands), and a complex landscape in Southern Germany with small fields and many landscape elements. I applied GPS devices (hourly fixes) with internal high-resolution accelerometers (4 min samples) to track hares, receiving an almost continuous observation of the animals' behaviours via acceleration analyses. I used the spatial and behavioural information in combination with remote sensing data (normalized difference vegetation index, or NDVI, a proxy for resource availability), generating an almost complete idea of what the animal was doing when, why and where. Apart from landscape structure (represented by the two differently structured study areas), I specifically tested whether the following fine-scale habitat features influence animal movements: resource, agricultural management events, habitat diversity, and habitat structure. My results show that, irrespective of the movement process or mechanism and the type of fine-scale habitat features, landscape structure was the overarching variable influencing hare movement behaviour. High resource variability forces hares to enlarge their home ranges, but only in the simple and not in the complex landscape. Agricultural management events result in home range shifts in both landscapes, but force hares to increase their home ranges only in the simple landscape. Also the preference of habitat patches with low vegetation and the avoidance of high vegetation, was stronger in the simple landscape. High and dense crop fields restricted hare movements temporarily to very local and small habitat patch remnants. Such insuperable barriers can separate habitat patches that were previously connected by mobile links. Hence, the transport of nutrients and genetic material is temporarily disrupted. This mechanism is also working on a global scale, as human induced changes from habitat loss and fragmentation to expanding monocultures cause a reduction in animal movements worldwide. The mechanisms behind those findings show that higher-level movements, like increasing home ranges, emerge from underlying basic-level movements, like the behavioural modes. An increasing landscape simplicity first acts on the behavioural modes, i.e. hares run and forage more, but have less time to rest. Hence, the emergence of increased home range sizes in simple landscapes is based on an increased proportion of time running and foraging, largely due to longer travelling times between distant habitats and scarce resource items in the landscape. This relationship was especially strong during the reproductive phase, demonstrating the importance of high-quality habitat for reproduction and the need to keep up self-maintenance first, in low quality areas. These changes in movement behaviour may release a cascade of processes that start with more time being allocated to running and foraging, resulting into an increased energy expenditure and may lead to a decline in individual fitness. A decrease in individual fitness and reproductive output will ultimately affect population viability leading to local extinctions. In conclusion, I show that landscape structure has one of the most important effects on hare movement behaviour. Synergistic effects of landscape structure, and fine-scale habitat features, first affect and modify basic-level movement behaviours, that can scales up to altered higher-level movements and may even lead to the decline of species richness and abundances, and the disruption of ecosystem functions. Understanding the connection between movement mechanisms and processes can help to predict and prevent anthropogenically induced changes in movement behaviour. With regard to the paramount importance of landscape structure, I strongly recommend to decrease the size of agricultural fields and increase crop diversity. On the small-scale, conservation policies should assure the year round provision of areas with low vegetation height and high quality forage. This could be done by generating wildflower strips and additional (semi-) natural habitat patches. This will not only help to increase the populations of European brown hares and other farmland species, but also ensure and protects the continuity of mobile links and their intrinsic value for sustaining important ecosystem functions and services.},
  language  = {en}
}
@phdthesis{Koc2018,
  author    = {Ko{\c{c}}, Azize},
  title     = {Ultrafast x-ray studies on the non-equilibrium of the magnetic and phononic system in heavy rare-earths},
  doi       = {10.25932/publishup-42328},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-423282},
  school      = {Universit{\"a}t Potsdam},
  pages     = {ii, 117},
  year      = {2018},
  abstract  = {In this dissertation the lattice and the magnetic recovery dynamics of the two heavy rare-earth metals Dy and Gd after femtosecond photoexcitation are described. For the investigations, thin films of Dy and Gd were measured at low temperatures in the antiferromagnetic phase of Dy and close to room temperature in the ferromagnetic phase of Gd. Two different optical pump-x-ray probe techniques were employed: Ultrafast x-ray diffraction with hard x-rays (UXRD) yields the structural response of heavy rare-earth metals and resonant soft (elastic) x-ray diffraction (RSXD), which allows measuring directly changes in the helical antiferromagnetic order of Dy. The combination of both techniques enables to study the complex interaction between the magnetic and the phononic subsystems.},
  language  = {en}
}
@phdthesis{Sander2018,
  author    = {Sander, Mathias},
  title     = {Ultrafast tailored strain fields in nanostructures},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-417863},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xvii, 119},
  year      = {2018},
  abstract  = {This publication based thesis, which consists of seven published articles, summarizes my contributions to the research field of laser excited ultrafast structural dynamics. The coherent and incoherent lattice dynamics on microscopic length scales are detected by ultrashort optical and X-ray pulses. The understanding of the complex physical processes is essential for future improvements of technological applications. For this purpose, tabletop soruces and large scale facilities, e.g. synchrotrons, are employed to study structural dynamics of longitudinal acoustic strain waves and heat transport. The investigated effects cover timescales from hundreds of femtoseconds up to several microseconds. The main part of this thesis is dedicated to the investigation of tailored phonon wave packets propagating in perovskite nanostructures. Tailoring is achieved either by laser excitation of nanostructured bilayer samples or by a temporal series of laser pulses. Due to the propagation of longitudinal acoustic phonons, the out-of-plane lattice spacing of a thin film insulator-metal bilayer sample is modulated on an ultrafast timescale. This leads to an ultrafast modulation of the X-ray diffraction efficiency which is employed as a phonon Bragg switch to shorten hard X-ray pulses emitted from a 3rd generation synchrotron. In addition, we have observed nonlinear mixing of high amplitude phonon wave packets which originates from an anharmonic interatomic potential. A chirped optical pulse sequence excites a narrow band phonon wave packet with specific momentum and energy. The second harmonic generation of these phonon wave packets is followed by ultrafast X-ray diffraction. Phonon upconversion takes place because the high amplitude phonon wave packet modulates the acoustic properties of the crystal which leads to self steepening and to the successive generation of higher harmonics of the phonon wave packet. Furthermore, we have demonstrated ultrafast strain in direction parallel to the sample surface. Two consecutive so-called transient grating excitations displaced in space and time are used to coherently control thermal gradients and surface acoustic modes. The amplitude of the coherent and incoherent surface excursion is disentangled by time resolved X-ray reflectivity measurements. We calibrate the absolute amplitude of thermal and acoustic surface excursion with measurements of longitudinal phonon propagation. In addition, we develop a diffraction model which allows for measuring the surface excursion on an absolute length scale with sub-{\"A}angstr{\"o}m precision. Finally, I demonstrate full coherent control of an excited surface deformation by amplifying and suppressing thermal and coherent excitations at the surface of a laser-excited Yttrium-manganite sample.},
  language  = {en}
}
@phdthesis{Aktan2018,
  author    = {Aktan, Oktay},
  title     = {Turkish football clubs in Berlin},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-413616},
  school      = {Universit{\"a}t Potsdam},
  pages     = {221},
  year      = {2018},
  abstract  = {Es gibt in Berlin eine einzigartige Vereinslandschaft im Amateur - und semiprofessionellen Fußballsport, in der einst von t{\"u}rkischen Migranten gegr{\"u}ndete Vereine einen festen Platz einnehmen. Fußballsport bietet einen sozialen Raum f{\"u}r Jugendliche verschiedener kultureller, ethnischer und religi{\"o}ser Herkunft, in dem Gruppen gebildet werden, um gegen einander zu konkurrieren. Ebenso er{\"o}ffnet Fußball dem Einzelnen die M{\"o}glichkeit, die G{\"u}ltigkeit und Relevanz von Vorurteilen und von g{\"a}ngigen Stereotypisierungen anderer Gruppen im Spielalltag einer st{\"a}ndigen Pr{\"u}fung zu unterziehen. Fußballspieler k{\"o}nnen sich sowohl zwischen multi-kulturellen als auch mono-ethnischen Gruppenkonstellationen, in einigen F{\"a}llen auch in transnationalen Konstellationen bewegen, womit sie dabei wesentlich an der Sinngebung ihrer eigenen sozialen Zugeh{\"o}rigkeit mitwirken, die sich aus dem Spannungsfeld von Selbst- und Fremdwahrnehmungsmustern ergibt. In Folge dessen werden in diesem Raum Anerkennungsmechanismen konstituiert. Die vorliegende Dissertation befasst sich mit dem allt{\"a}glichen Leben von t{\"u}rkisch-st{\"a}mmigen, jugendlichen Amateur- und semiprofessionellen Fußballspielern (delikanli), sowie von anderen sozialen Akteuren der t{\"u}rkischen Fußballwelt, wie zum Beispiel „{\"a}ltere" Fußballspieler (agbi) und Fußballtrainer (hoca). Hauptanliegen der Arbeit war die Rekonstruktion kollektiver Wahrnehmungs-, Deutungs - und Handlungsmuster von Mitgliedern t{\"u}rkischer Fußballvereine im allgemeinen und ihrer Selbstdarstellung aber auch ihrer Wahrnehmung der „Anderen" im besonderen. Mittels dieser Studie sollte nachvollzogen werden, ob und inwiefern sich traditionelle soziale Verhaltensmuster der gew{\"a}hlten Gruppe im technisch regulierten und stark Konkurrenz-orientierten Handlungsraum widerspiegeln und die reziproken Beziehungen zwischen dem „Selbst" und den „Anderen" regulieren. Dabei wurde die Relevanz von herkunftsbezogenen Stereotypisierungen und Vorurteilen in der kollektiven Konstitution von Selbstwahrnehmungen und Fremdverstehen im partikularen sozialen Feld (Bourdieu, 2001) des Fußballs rekonstruiert. In dieser Arbeit wurde dar{\"u}ber hinaus beleuchtet, welche Rolle t{\"u}rkische Fußballvereine auf der einen Seite bei der Entstehung sozialer Raumzugeh{\"o}rigkeit zu den Stadtquartieren in Berlin einnehmen und welche Art von Mechanismen der sozialen Integration sie in diesen Vereinen herstellen. Auf der anderen Seite wurde hinterfragt, inwiefern sie zur sozialen Koh{\"a}sion zwischen diversen Kulturen beitragen. Daher wurde gepr{\"u}ft, ob und inwiefern die negativ konnotierte ethnozentrische Wahrnehmung von „Differenz" (Bielefeld, 1998), die als soziales Konstrukt zwischen autochthonen und allochthonen Gruppen hergestellt wird, durch das Engagement der Vereinsakteure einen konstruktiven Wandel erf{\"a}hrt. {\"U}bergeordnetes Ziel all dieser Forschungsfragen war es, ein fundiertes Verst{\"a}ndnis {\"u}ber die Rolle von t{\"u}rkischen Fußballvereinen als soziale Mechanismen zu erlangen und deren Funktionsweise bei der Konstitution von Anpassungsstrategien in diesem sozialen Feld untersuchen. Detailliert wurde diese Rolle unter der Konzeptualisierung von sozialen Positionierungsmuster betrachtet, die als Gef{\"u}ge von Deutungen des Allt{\"a}glichen verstanden werden, das individuelle und kollektive Handlungsmuster und implizit Muster des Fremdverstehens sowie des othering im Migrationskontext reguliert. Eine Rekonstruktion der sozialen Positionierungsmuster bietet eine eingehende soziologische Untersuchung dieser Teilnehmergruppe, die zudem Aufschluss {\"u}ber die Bedeutung und das Verst{\"a}ndnis von ethnischer Zugeh{\"o}rigkeit f{\"u}r letztere gibt. Neben umfangreicher Feldbeobachtung wurden in dieser qualitativen Studie mit Spielern verschiedener Vereine insgesamt zehn Gruppendiskussionen (Bohnsack, 2004) innerhalb ihrer Mannschaften zu gemeinsamen allt{\"a}glichen Erlebnissen und Erfahrungen durchgef{\"u}hrt, aufgezeichnet und mittels sozialwissenschaftlichem hermeneutischem Verfahren (Soeffner, 2004) interpretiert. Auch mit anderen Vereinsmitgliedern, d. h. mit Trainern bzw. hoca, Vorsitzenden, Managern und Sponsoren wurden jeweils zehn narrative und sieben biographische Einzelinterviews sowie sieben Experteninterviews durchgef{\"u}hrt. Deren Analyse erlaubt es, die Rolle dieser Mitglieder sowie wirkende Autorit{\"a}tsmechanismen und kollektiv konstituierte Verhaltensmuster innerhalb der gesamten Vereinsgruppe zu rekonstruieren. Dabei wurde bezweckt, die Gesamtheit des sozialen Netzwerkes bzw. die Beziehungsschemata innerhalb der t{\"u}rkischen Fußballvereine Berlins zu verdeutlichen. In der Arbeit werden zwei Standpunkte der theoretischen Auseinandersetzung verwendet. Auf der einen Seite wird die Lebensweltanalyse (Sch{\"u}tz und Luckmann, 1979, 1990) angewendet, um das soziale Erbe der in der Vergangenheit gesellschaftlich konstituierten Titulierung „Menschen mit Migrationshintergrund" zu rekonstruieren, bzw. den Einfluss dieser sozialen Reproduktion auf die Wahrnehmungs-, Deutungs- und Handlungsmuster der Akteure zu untersuchen. Auf der anderen Seite wird die soziale Wirkung der tats{\"a}chlichen, allt{\"a}glichen Erfahrungsschemata im sozialen Feld des Fußballs auf die Selbstpositionierungen der Akteure mittels Goffmanscher Rahmenanalyse (Goffman, 1980) herausgearbeitet.},
  language  = {en}
}
@phdthesis{Zakarias2018,
  author    = {Zakari{\´a}s, Lilla},
  title     = {Transfer effects after working memory training in post-stroke aphasia},
  doi       = {10.25932/publishup-42360},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-423600},
  school      = {Universit{\"a}t Potsdam},
  pages     = {178},
  year      = {2018},
  abstract  = {Background: Individuals with aphasia after stroke (IWA) often present with working memory (WM) deficits. Research investigating the relationship between WM and language abilities has led to the promising hypothesis that treatments of WM could lead to improvements in language, a phenomenon known as transfer. Although recent treatment protocols have been successful in improving WM, the evidence to date is scarce and the extent to which improvements in trained tasks of WM transfer to untrained memory tasks, spoken sentence comprehension, and functional communication is yet poorly understood. Aims: We aimed at (a) investigating whether WM can be improved through an adaptive n-back training in IWA (Study 1-3); (b) testing whether WM training leads to near transfer to unpracticed WM tasks (Study 1-3), and far transfer to spoken sentence comprehension (Study 1-3), functional communication (Study 2-3), and memory in daily life in IWA (Study 2-3); and (c) evaluating the methodological quality of existing WM treatments in IWA (Study 3). To address these goals, we conducted two empirical studies - a case-controls study with Hungarian speaking IWA (Study 1) and a multiple baseline study with German speaking IWA (Study 2) - and a systematic review (Study 3). Methods: In Study 1 and 2 participants with chronic, post-stroke aphasia performed an adaptive, computerized n-back training. 'Adaptivity' was implemented by adjusting the tasks' difficulty level according to the participants' performance, ensuring that they always practiced at an optimal level of difficulty. To assess the specificity of transfer effects and to better understand the underlying mechanisms of transfer on spoken sentence comprehension, we included an outcome measure testing specific syntactic structures that have been proposed to involve WM processes (e.g., non-canonical structures with varying complexity). Results: We detected a mixed pattern of training and transfer effects across individuals: five participants out of six significantly improved in the n-back training. Our most important finding is that all six participants improved significantly in spoken sentence comprehension (i.e., far transfer effects). In addition, we also found far transfer to functional communication (in two participants out of three in Study 2) and everyday memory functioning (in all three participants in Study 2), and near transfer to unpracticed n-back tasks (in four participants out of six). Pooled data analysis of Study 1 and 2 showed a significant negative relationship between initial spoken sentence comprehension and the amount of improvement in this ability, suggesting that the more severe the participants' spoken sentence comprehension deficit was at the beginning of training, the more they improved after training. Taken together, we detected both near far and transfer effects in our studies, but the effects varied across participants. The systematic review evaluating the methodological quality of existing WM treatments in stroke IWA (Study 3) showed poor internal and external validity across the included 17 studies. Poor internal validity was mainly due to use of inappropriate design, lack of randomization of study phases, lack of blinding of participants and/or assessors, and insufficient sampling. Low external validity was mainly related to incomplete information on the setting, lack of use of appropriate analysis or justification for the suitability of the analysis procedure used, and lack of replication across participants and/or behaviors. Results in terms of WM, spoken sentence comprehension, and reading are promising, but further studies with more rigorous methodology and stronger experimental control are needed to determine the beneficial effects of WM intervention. Conclusions: Results of the empirical studies suggest that WM can be improved with a computerized and adaptive WM training, and improvements can lead to transfer effects to spoken sentence comprehension and functional communication in some individuals with chronic post-stroke aphasia. The fact that improvements were not specific to certain syntactic structures (i.e., non-canonical complex sentences) in spoken sentence comprehension suggest that WM is not involved in the online, automatic processing of syntactic information (i.e., parsing and interpretation), but plays a more general role in the later stage of spoken sentence comprehension (i.e., post-interpretive comprehension). The individual differences in treatment outcomes call for future research to clarify how far these results are generalizable to the population level of IWA. Future studies are needed to identify a few mechanisms that may generalize to at least a subpopulation of IWA as well as to investigate baseline non-linguistic cognitive and language abilities that may play a role in transfer effects and the maintenance of such effects. These may require larger yet homogenous samples.},
  language  = {en}
}
@phdthesis{Bergholz2018,
  author    = {Bergholz, Kolja},
  title     = {Trait-based understanding of plant species distributions along environmental gradients},
  doi       = {10.25932/publishup-42634},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-426341},
  school      = {Universit{\"a}t Potsdam},
  pages     = {128},
  year      = {2018},
  abstract  = {For more than two centuries, plant ecologists have aimed to understand how environmental gradients and biotic interactions shape the distribution and co-occurrence of plant species. In recent years, functional trait-based approaches have been increasingly used to predict patterns of species co-occurrence and species distributions along environmental gradients (trait-environment relationships). Functional traits are measurable properties at the individual level that correlate well with important processes. Thus, they allow us to identify general patterns by synthesizing studies across specific taxonomic compositions, thereby fostering our understanding of the underlying processes of species assembly. However, the importance of specific processes have been shown to be highly dependent on the spatial scale under consideration. In particular, it remains uncertain which mechanisms drive species assembly and allow for plant species coexistence at smaller, more local spatial scales. Furthermore, there is still no consensus on how particular environmental gradients affect the trait composition of plant communities. For example, increasing drought because of climate change is predicted to be a main threat to plant diversity, although it remains unclear which traits of species respond to increasing aridity. Similarly, there is conflicting evidence of how soil fertilization affects the traits related to establishment ability (e.g., seed mass). In this cumulative dissertation, I present three empirical trait-based studies that investigate specific research questions in order to improve our understanding of species distributions along environmental gradients. In the first case study, I analyze how annual species assemble at the local scale and how environmental heterogeneity affects different facets of biodiversity—i.e. taxonomic, functional, and phylogenetic diversity—at different spatial scales. The study was conducted in a semi-arid environment at the transition zone between desert and Mediterranean ecosystems that features a sharp precipitation gradient (Israel). Different null model analyses revealed strong support for environmentally driven species assembly at the local scale, since species with similar traits tended to co-occur and shared high abundances within microsites (trait convergence). A phylogenetic approach, which assumes that closely related species are functionally more similar to each other than distantly related ones, partly supported these results. However, I observed that species abundances within microsites were, surprisingly, more evenly distributed across the phylogenetic tree than expected (phylogenetic overdispersion). Furthermore, I showed that environmental heterogeneity has a positive effect on diversity, which was higher on functional than on taxonomic diversity and increased with spatial scale. The results of this case study indicate that environmental heterogeneity may act as a stabilizing factor to maintain species diversity at local scales, since it influenced species distribution according to their traits and positively influenced diversity. All results were constant along the precipitation gradient. In the second case study (same study system as case study one), I explore the trait responses of two Mediterranean annuals (Geropogon hybridus and Crupina crupinastrum) along a precipitation gradient that is comparable to the maximum changes in precipitation predicted to occur by the end of this century (i.e., -30\%). The heterocarpic G. hybridus showed strong trends in seed traits, suggesting that dispersal ability increased with aridity. By contrast, the homocarpic C. crupinastrum showed only a decrease in plant height as aridity increased, while leaf traits of both species showed no consistent pattern along the precipitation gradient. Furthermore, variance decomposition of traits revealed that most of the trait variation observed in the study system was actually found within populations. I conclude that trait responses towards aridity are highly species-specific and that the amount of precipitation is not the most striking environmental factor at this particular scale. In the third case study, I assess how soil fertilization mediates—directly by increased nutrient addition and indirectly by increased competition—the effect of seed mass on establishment ability. For this experiment, I used 22 species differing in seed mass from dry grasslands in northeastern Germany and analyzed the interacting effects of seed mass with nutrient availability and competition on four key components of seedling establishment: seedling emergence, time of seedling emergence, seedling survival, and seedling growth. (Time of) seedling emergence was not affected by seed mass. However, I observed that the positive effect of seed mass on seedling survival is lowered under conditions of high nutrient availability, whereas the positive effect of seed mass on seedling growth was only reduced by competition. Based on these findings, I developed a conceptual model of how seed mass should change along a soil fertility gradient in order to reconcile conflicting findings from the literature. In this model, seed mass shows a U-shaped pattern along the soil fertility gradient as a result of changing nutrient availability and competition. Overall, the three case studies highlight the role of environmental factors on species distribution and co-occurrence. Moreover, the findings of this thesis indicate that spatial heterogeneity at local scales may act as a stabilizing factor that allows species with different traits to coexist. In the concluding discussion, I critically debate intraspecific trait variability in plant community ecology, the use of phylogenetic relationships and easily measured key functional traits as a proxy for species' niches. Finally, I offer my outlook for the future of functional plant community research.},
  language  = {en}
}
@phdthesis{Lee2018,
  author    = {Lee, Hui-Chun},
  title     = {Toward ultimate control of polymerization and catalytic property},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-414973},
  school      = {Universit{\"a}t Potsdam},
  pages     = {vii, iii, 150},
  year      = {2018},
  abstract  = {Reversible-deactivation radical polymerization (RDRP) is without any doubt one of the most prevalent and powerful strategies for polymer synthesis, by which well-defined living polymers with targeted molecular weight (MW), low molar dispersity (Ɖ) and diverse morphologies can be prepared in a controlled fashion. Atom transfer radical polymerization (ATRP) as one of the most extensive studied types of RDRP has been particularly emphasized due to the high accessibility to hybrid materials, multifunctional copolymers and diverse end group functionalities via commercially available precursors. However, due to catalyst-induced side reactions and chain-chain coupling termination in bulk environment, synthesis of high MW polymers with uniform chain length (low Ɖ) and highly-preserved chain-end fidelity is usually challenging. Besides, owing to the inherited radical nature, the control of microstructure, namely tacticity control, is another laborious task. Considering the applied catalysts, the utilization of large amounts of non-reusable transition metal ions which lead to cumbersome purification process, product contamination and complicated reaction procedures all delimit the scope ATRP techniques. Metal-organic frameworks (MOFs) are an emerging type of porous materials combing the properties of both organic polymers and inorganic crystals, characterized with well-defined crystalline framework, high specific surface area, tunable porous structure and versatile nanochannel functionalities. These promising properties of MOFs have thoroughly revolutionized academic research and applications in tremendous aspects, including gas processing, sensing, photoluminescence, catalysis and compartmentalized polymerization. Through functionalization, the microenvironment of MOF nanochannel can be precisely devised and tailored with specified functional groups for individual host-guest interactions. Furthermore, properties of high transition metal density, accessible catalytic sites and crystalline particles all indicate MOFs as prominent heterogeneous catalysts which open a new avenue towards unprecedented catalytic performance. Although beneficial properties in catalysis, high agglomeration and poor dispersibility restrain the potential catalytic capacity to certain degree. Due to thriving development of MOF sciences, fundamental polymer science is undergoing a significant transformation, and the advanced polymerization strategy can eventually refine the intrinsic drawbacks of MOF solids reversely. Therefore, in the present thesis, a combination of low-dimensional polymers with crystalline MOFs is demonstrated as a robust and comprehensive approach to gain the bilateral advantages from polymers (flexibility, dispersibility) and MOFs (stability, crystallinity). The utilization of MOFs for in-situ polymerizations and catalytic purposes can be realized to synthesize intriguing polymers in a facile and universal process to expand the applicability of conventional ATRP methodology. On the other hand, through the formation of MOF/polymer composites by surface functionalization, the MOF particles with environment-adjustable dispersibility and high catalytic property can be as-prepared. In the present thesis, an approach via combination of confined porous textures from MOFs and controlled radical polymerization is proposed to advance synthetic polymer chemistry. Zn2(bdc)2(dabco) (Znbdc) and the initiator-functionalized Zn MOFs, ZnBrbdc, are utilized as a reaction environment for in-situ polymerization of various size-dependent methacrylate monomers (i.e. methyl, ethyl, benzyl and isobornyl methacrylate) through (surface-initiated) activators regenerated by electron transfer (ARGET/SI-ARGET) ATRP, resulting in polymers with control over dispersity, end functionalities and tacticity with respect to distinct molecular size. While the functionalized MOFs are applied, due to the strengthened compartmentalization effect, the accommodated polymers with molecular weight up to 392,000 can be achieved. Moreover, a significant improvement in end-group fidelity and stereocontrol can be observed. The results highlight a combination of MOFs and ATRP is a promising and universal methodology to synthesize versatile well-defined polymers with high molecular weight, increment in isotactic trial and the preserved chain-end functionality. More than being a host only, MOFs can act as heterogeneous catalysts for metal-catalyzed polymerizations. A Cu(II)-based MOF, Cu2(bdc)2(dabco), is demonstrated as a heterogeneous, universal catalyst for both thermal or visible light-triggered ARGET ATRP with expanded monomer range. The accessible catalytic metal sites enable the Cu(II) MOF to polymerize various monomers, including benzyl methacrylate (BzMA), styrene, methyl methacrylate (MMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA) in the fashion of ARGET ATRP. Furthermore, due to the robust frameworks, surpassing the conventional homogeneous catalyst, the Cu(II) MOF can tolerate strongly coordinating monomers and polymerize challenging monomers (i.e. 4-vinyl pyridine, 2-vinyl pyridine and isoprene), in a well-controlled fashion. Therefore, a synthetic procedure can be significantly simplified, and catalyst-resulted chelation can be avoided as well. Like other heterogeneous catalysts, the Cu(II) MOF catalytic complexes can be easily collected by centrifugation and recycled for an arbitrary amount of times. The Cu(II) MOF, composed of photostimulable metal sites, is further used to catalyze controlled photopolymerization under visible light and requires no external photoinitiator, dye sensitizer or ligand. A simple light trigger allows the photoreduction of Cu(II) to the active Cu(I) state, enabling controlled polymerization in the form of ARGET ATRP. More than polymerization application, the synergic effect between MOF frameworks and incorporated nucleophilic monomers/molecules is also observed, where the formation of associating complexes is able to adjust the photochemical and electrochemical properties of the Cu(II) MOF, altering the band gap and light harvesting behavior. Owing to the tunable photoabsorption property resulting from the coordinating guests, photoinduced Reversible-deactivation radical polymerization (PRDRP) can be achieved to further simplify and fasten the polymerization. More than the adjustable photoabsorption ability, the synergistic strategy via a combination of controlled/living polymerization technique and crystalline MOFs can be again evidenced as demonstrated in the MOF-based heterogeneous catalysts with enhanced dispersibility in solution. Through introducing hollow pollen pivots with surface immobilized environment-responsive polymer, PDMAEMA, highly dispersed MOF nanocrystals can be prepared after associating on polymer brushes via the intrinsic amine functionality in each DMAEMA monomer. Intriguingly, the pollen-PDMAEMA composite can serve as a "smart" anchor to trap nanoMOF particles with improved dispersibility, and thus to significantly enhance liquid-phase photocatalytic performance. Furthermore, the catalytic activity can be switched on and off via stimulable coil-to-globule transition of the PDMAEMA chains exposing or burying MOF catalytic sites, respectively.},
  language  = {en}
}
@phdthesis{Weiss2018,
  author    = {Weiß, Katharina},
  title     = {Three Essays on EFRAG},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-415355},
  school      = {Universit{\"a}t Potsdam},
  pages     = {II, 180},
  year      = {2018},
  abstract  = {This cumulative doctoral thesis consists of three papers that deal with the role of one specific European accounting player in the international accounting standard-setting, namely the European Financial Reporting Advisory Group (EFRAG). The first paper examines whether and how EFRAG generally fulfills its role in articulating Europe's interests toward the International Accounting Standards Board (IASB). The qualitative data from the conducted interviews reveal that EFRAG influences the IASB's decision making at a very early stage, long before other constituents are officially asked to comment on the IASB's proposals. The second paper uses quantitative data and investigates the formal participation behavior of European constituents that seek to determine EFRAG's voice. More precisely, this paper analyzes the nature of the constituents' participation in EFRAG's due process in terms of representation (constituent groups and geographical distribution) and the drivers of their participation behavior. EFRAG's official decision making process is dominated by some specific constituent groups (such as preparers and the accounting profession) and by constituents from some specific countries (e.g. those with effective enforcement regimes). The third paper investigates in a first step who of the European constituents choose which lobbying channel (participation only at IASB, only at EFRAG, or at both institutions) and unveils in a second step possible reasons for their lobbying choices. The paper comprises quantitative and qualitative data. It reveals that English skills, time issues, the size of the constituent, and the country of origin are factors that can explain why the majority participates only in the IASB's due process.},
  language  = {en}
}
@phdthesis{Nizardo2018,
  author    = {Nizardo, Noverra Mardhatillah},
  title     = {Thermoresponsive block copolymers with UCST-behavior aimed at biomedical environments},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-412217},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xiii, 134},
  year      = {2018},
  abstract  = {Thermoresponsive block copolymers of presumably highly biocompatible character exhibiting upper critical solution temperature (UCST) type phase behavior were developed. In particular, these polymers were designed to exhibit UCST-type cloud points (Tcp) in physiological saline solution (9 g/L) within the physiologically interesting window of 30-50°C. Further, their use as carrier for controlled release purposes was explored. Polyzwitterion-based block copolymers were synthesized by atom transfer radical polymerization (ATRP) via a macroinitiator approach with varied molar masses and co-monomer contents. These block copolymers can self-assemble in the amphiphilic state to form micelles, when the thermoresponsive block experiences a coil-to-globule transition upon cooling. Poly(ethylene glycol) methyl ether (mPEG) was used as the permanently hydrophilic block to stabilize the colloids formed, and polyzwitterions as the thermoresponsive block to promote the temperature-triggered assembly-disassembly of the micellear aggregates at low temperature. Three zwitterionic monomers were used for this studies, namely 3-((2-(methacryloyloxy)ethyl)dimethylammonio)propane-1-sulfonate (SPE), 4-((2-(methacryloyl- oxy)ethyl)dimethylammonio)butane-1-sulfonate (SBE), and 3-((2-(methacryloyloxy)ethyl)- dimethylammonio)propane-1-sulfate) (ZPE). Their (co)polymers were characterized with respect to their molecular structure by proton nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC). Their phase behaviors in pure water as well as in physiological saline were studied by turbidimetry and dynamic light scattering (DLS). These (co)polymers are thermoresponsive with UCST-type phase behavior in aqueous solution. Their phase transition temperatures depend strongly on the molar masses and the incorporation of co-monomers: phase transition temperatures increased with increasing molar masses and content of poorly water-soluble co-monomer. In addition, the presence of salt influenced the phase transition dramatically. The phase transition temperature decreased with increasing salt content in the solution. While the PSPE homopolymers show a phase transition only in pure water, the PZPE homopolymers are able to exhibit a phase transition only in high salinity, as in physiological saline. Although both polyzwitterions have similar chemical structures that differ only in the anionic group (sulfonate group in SPE and sulfate group in ZPE), the water solubility is very different. Therefore, the phase transition temperatures of targeted block copolymers were modulated by using statistical copolymer of SPE and ZPE as thermoresponsive block, and varying the ratio of SPE to ZPE. Indeed, the statistical copolymers of P(SPE-co-ZPE) show phase transitions both in pure water as well as in physiological saline. Surprisingly, it was found that mPEG-b-PSBE block copolymer can display "schizophrenic" behavior in pure water, with the UCST-type cloud point occurring at lower temperature than the LCST-type one. The block copolymer, which satisfied best the boundary conditions, is block copolymer mPEG114-b-P(SPE43-co-ZPE39) with a cloud point of 45°C in physiological saline. Therefore, it was chosen for solubilization studies of several solvatochromic dyes as models of active agents, using the thermoresponsive block copolymer as "smart" carrier. The uptake and release of the dyes were explored by UV-Vis and fluorescence spectroscopy, following the shift of the wavelength of the absorbance or emission maxima at low and high temperature. These are representative for the loaded and released state, respectively. However, no UCST-transition triggered uptake and release of these dyes could be observed. Possibly, the poor affinity of the polybetaines to the dyes in aqueous environtments may be related to the widely reported antifouling properties of zwitterionic polymers.},
  language  = {en}
}