Refine
Has Fulltext
- no (3966) (remove)
Year of publication
- 2024 (21)
- 2023 (94)
- 2022 (93)
- 2021 (111)
- 2020 (112)
- 2019 (127)
- 2018 (144)
- 2017 (168)
- 2016 (186)
- 2015 (180)
- 2014 (113)
- 2013 (174)
- 2012 (187)
- 2011 (179)
- 2010 (165)
- 2009 (169)
- 2008 (181)
- 2007 (148)
- 2006 (126)
- 2005 (112)
- 2004 (98)
- 2003 (131)
- 2002 (115)
- 2001 (132)
- 2000 (128)
- 1999 (148)
- 1998 (108)
- 1997 (87)
- 1996 (62)
- 1995 (36)
- 1994 (25)
- 1993 (27)
- 1992 (37)
- 1991 (7)
Document Type
- Doctoral Thesis (3966) (remove)
Keywords
- Deutschland (7)
- photosynthesis (5)
- Arabidopsis thaliana (4)
- Klimawandel (4)
- migration (4)
- Bundeswehr (3)
- Kunstgeschichte (3)
- Migration (3)
- Photosynthese (3)
- Politik (3)
Institute
- Institut für Biochemie und Biologie (655)
- Institut für Physik und Astronomie (376)
- Institut für Chemie (375)
- Wirtschaftswissenschaften (310)
- Öffentliches Recht (238)
- Bürgerliches Recht (217)
- Historisches Institut (194)
- Institut für Geowissenschaften (179)
- Institut für Ernährungswissenschaft (176)
- Institut für Informatik und Computational Science (121)
Answer Set Programming (ASP) allows us to address knowledge-intensive search and optimization problems in a declarative way due to its integrated modeling, grounding, and solving workflow. A problem is modeled using a rule based language and then grounded and solved. Solving results in a set of stable models that correspond to solutions of the modeled problem. In this thesis, we present the design and implementation of the clingo system---perhaps, the most
widely used ASP system. It features a rich modeling language originating from the field of knowledge representation and reasoning, efficient grounding algorithms based on database evaluation techniques, and high performance solving algorithms based on Boolean satisfiability (SAT) solving technology.
The contributions of this thesis lie in the design of the modeling language, the design and implementation of the grounding algorithms, and the design and implementation of an Application Programmable Interface (API) facilitating the use of ASP in real world applications and the implementation of complex forms of reasoning beyond the traditional ASP workflow.
In jüngerer Vergangenheit häuften sich Fälle, in denen die Verwaltung Entscheidungen von Verwaltungsgerichten bewusst nicht umsetzte. Der Autor nimmt diese Entwicklung zum Anlass und befasst sich mit der Frage, welchen Anteil die Vollstreckungsregeln der Verwaltungsgerichtsordnung an dieser Entwicklung haben. Dabei erfasst er sowohl die staatsrechtliche als auch die grundrechtliche Perspektive. Er überprüft insbesondere, ob die Vorschriften, die die Vollstreckung aus verwaltungsgerichtlichen Entscheidungen gegen den Staat regeln, verfassungsgemäß sind. Nach ausführlicher Diskussion denkbarer Lösungsansätze kommt der Autor zu dem Ergebnis, dass eine Änderung der Vollstreckungsvorschriften dringend geboten ist.
Hegels Phantasie
(2023)
Als »Zwischenreich«, »Drittes« oder »Mitte« bezeichnet, kommt der Imagination seit ihren Anfängen in der Antike die Rolle eines Mediums zu. Gleichzeitig bleibt ihr medialer Aspekt durchgehend ambivalent und prekär. Es ist Georg Wilhelm Friedrich Hegel, der die Imagination nicht mehr als subjektives Vermögen versteht, sondern als Kraft der »Entäußerung« und sie somit medial denkt. In einer bislang wenig beachteten Passage aus Hegels dritter Enzyklopädie von 1830 legt Ekaterina Vassilevski nicht nur die implizite Medialität der Imagination frei, sondern auch den in Hegels Denken verborgenen Begriff des Medialen.
»European Environmental Law and its Influence on Grandfathering – a Limiting Factor?«: How to deal with conflicts that arise between legally permitted activities and nature despite prior comprehensive environmental assessments? The author examines this question regarding EU species, habitat protection and environmental damage law. The material EU environmental law requirements for the use of permits are outlined, as well as the administrative instruments for their enforcement. A differentiation is made between permits under the Federal Immission Control Act and plan approvals.
This book provides empirical evidence that all States have a universally binding obligation to adopt national laws and international treaties to protect the marine environment, including the designation of Marine Protected Areas. Chapter by chapter this obligation is detailed, providing the foundation for holding States responsible for fulfilling this obligation. The fundamentals are analysed in a preliminary chapter, which examines the legally binding sources of the Law of the Sea as well as its historical development to help readers understand the key principles at hand.
The Law of the Sea provides more than 1000 instruments and more than 300 regulations concerning marine protection. While the scope of most treaties is limited either regarding species, regions or activities, one regulation addresses States in all waters: the obligation to protect and preserve the marine environment as stipulated under Art. 192 of the 1982 United Nations Convention on the Law of the Sea (UNCLOS). As this ‘Constitution of the Ocean’ not only contains conventional laws but also very broadly reflects pre-existing rules of customary international law, an extensive analysis of all statements made by States in the UN General Assembly, their practices, national laws and regulations as well as other public testimonials demonstrates that Art. 192 UNCLOS indeed binds the whole community of States as a rule of customary international law with an erga omnes effect. Due to the lack of any objections and its fundamental value for humankind, this regulation can also be considered a new peremptory norm of international law (ius cogens).
While the sovereign equality of States recognises States’ freedom to decide if and how to enter into a given obligation, States can also waive this freedom. If States accepted a legally binding obligation, they are thus bound to it. Concerning the specific content of Art. 192 UNCLOS, a methodical interpretation concludes that only the adoption of legislative measures (national laws and international agreements) suffices to comply with the obligation to protect and preserve the marine environment, which is confirmed by the States’ practices and relevant jurisprudence. When applied to a specific geographical area, legislative measures to protect the marine environment concur with the definition of Marine Protected Areas. Nonetheless, as the obligation applies to all waters, the Grotian principle of the freedom of the sea dictates that the restriction of activities through the designation of Marine Protected Areas, on the one hand, must be weighed against the freedoms of other States on the other. To anticipate the result: while all other rights under the UNCLOS are subject to and contingent on other regulations of the UNCLOS and international law, only the obligation to protect and preserve the marine environment is granted absolutely – and thus outweighs all other interests
Als eine der großen Veteranenorganisationen und rechte Sammlungsbewegung war der "Stahlhelm – Bund der Frontsoldaten" ein bedeutender politischer Akteur der Weimarer Republik. Er stand in einem äußerst ambivalenten Verhältnis zum aufstrebenden Nationalsozialismus. Einerseits konkurrierten sie um die Vorherrschaft innerhalb des nationalen Lagers, andererseits erkannten beide Seiten den Nutzen einer Kooperation. Insbesondere den einfachen Stahlhelm-Mitgliedern erschien die NS-Bewegung als attraktive Alternative, die ihre Ziele zu erreichen schien. Die Konkurrenz steigerte sich 1931/32 zur erbitterten Feindschaft. Nach der Eingliederung eines Großteils der Bundesmitglieder in die SA im Jahr 1933 sah sich der Rest-Bund immer heftigeren Repressalien ausgesetzt, bevor er 1935 aufgelöst wurde. 1951 neu gegründet, konnte er nicht an seine früheren Erfolge anknüpfen. Mehrere Spaltungen beschleunigten den Niedergang der Organisation.
Negative Ambientalität
(2023)
Functional characterization of ROS-responsive genes, ANAC085 and ATR7, in Arabidopsis thaliana
(2023)
Biostimulant SuperFifty based molecular priming to increase plant strength and stress tolerance
(2023)
In times of ongoing biodiversity loss, understanding how communities are structured and what mechanisms and local adaptations underlie the patterns we observe in nature is crucial for predicting how future ecological and anthropogenic changes might affect local and regional biodiversity. Aquatic zooplankton are a group of primary consumers that represent a critical link in the food chain, providing nutrients for the entire food web. Thus, understanding the adaptability and structure of zooplankton communities is essential. In this work, the genetic basis for the different temperature adaptations of two seasonally shifted (i.e., temperature-dependent) occurring freshwater rotifers of a formerly cryptic species complex (Brachionus calyciflorus) was investigated to understand the overall genetic diversity and evolutionary scenario for putative adaptations to different temperature regimes. Furthermore, this work aimed to clarify to what extent the different temperature adaptations may represent a niche partitioning process thus enabling co-existence. The findings were then embedded in a metacommunity context to understand how zooplankton communities assemble in a kettle hole metacommunity located in the northeastern German "Uckermark" and which underlying processes contribute to the biodiversity patterns we observe. Using a combined approach of newly generated mitochondrial resources (genomes/cds) and the analysis of a candidate gene (Heat Shock Protein 40kDa) for temperature adaptation, I showed that the global representatives of B. calyciflorus s.s.. are genetically more similar than B. fernandoi (average pairwise nucleotide diversity: 0.079 intraspecific vs. 0.257 interspecific) indicating that both species carry different standing genetic variation. In addition to differential expression in the thermotolerant B. calyciflorus s.s. and thermosensitive B. fernandoi, the HSP 40kDa also showed structural variation with eleven fixed and six positively selected sites, some of which are located in functional areas of the protein. The estimated divergence time of ~ 25-29 Myr combined with the fixed sites and a prevalence of ancestral amino acids in B. calyciflorus s.s. indicate that B. calyciflorus s.s. remained in the ancestral niche, while B. fernandoi partitioned into a new niche. The comparison of mitochondrial and nuclear markers (HPS 40kDa, ITS1, COI) revealed a hybridisation event between the two species. However, as hybridisation between the two species is rare, it can be concluded that the temporally isolated niches (i.e., seasonal-shifted occurrence) they inhabit based on their different temperature preferences most likely represent a pre-zygotic isolation mechanism that allows sympatric occurrence while maintaining species boundaries. To determine the processes underlying zooplankton community assembly, a zooplankton metacommunity comprising 24 kettle holes was sampled over a two-year period. Active (i.e., water samples) and dormant communities (i.e., dormant eggs hatched from sediment) were identified using a two-fragment DNA metabarcoding approach (COI and 18S). Species richness and diversity as well as community composition were analysed considering spatial, temporal and environmental parameters. The analysis revealed that environmental filtering based on parameters such as pH, size and location of the habitat patch (i.e., kettle hole) and surrounding field crops largely determined zooplankton community composition (explained variance: Bray-Curtis dissimilarities: 10.5%; Jaccard dissimilarities: 12.9%), indicating that adaptation to a particular habitat is a key feature of zooplankton species in this system. While the spatial configuration of the kettle holes played a minor role (explained variance: Bray-Curtis dissimilarities: 2.8% and Jaccard dissimilarities: 5.5%), the individual kettle hole sites had a significant influence on the community composition. This suggests monopolisation/priority effects (i.e., dormant communities) of certain species in individual kettle holes. As environmental filtering is the dominating process structuring zooplankton communities, this system could be significantly influenced by future land-use change, pollution and climate change.
Obwohl sieben der neun Menschenrechtsverträge auf Ebene der Vereinten Nationen die Möglichkeit eines Staatenbeschwerdeverfahrens eröffnen, kam dieser Verfahrensart über Jahrzehnte hinweg keinerlei praktische Bedeutung zu. Im Frühjahr 2018 erreichten den CERD-Ausschuss dann jedoch gleich drei verschiedene Staatenmitteilungen. Die erstmalige Aktivierung des Verfahrens fast 50 Jahre nach Inkrafttreten des Internationalen Übereinkommens zur Beseitigung jeder Form von Rassendiskriminierung (CERD) kann dabei als eine historische Entwicklung bezeichnet werden.
Vor diesem Hintergrund bietet dieses Buch erstmals eine umfassende Auseinandersetzung mit dem Staatenbeschwerdeverfahren nach Art. 11-13 CERD und den sich daraus ergebenden völkerrechtlichen Fragen. Unter Auswertung der jüngsten Praxis des CERD-Ausschusses und der ad hoc Vergleichskommission wird die Funktionsweise des Verfahrens detailliert dargestellt, wobei immer wieder Parallelen zu den Mechanismen anderer Vertragsregime gezogen werden. Auf diese Weise soll die Arbeit auch zu dem Verständnis vergleichbarer Staatenbeschwerdeverfahren anderer Menschenrechtsverträge beitragen und zugleich die Bedeutung des Phänomens zwischenstaatlicher Streitbeilegung in Menschenrechtsfragen stärker in den Vordergrund rücken.
Juana Borrero
(2023)
Juana Borrero y Pierra (1877–1896) war eine der wichtigsten Vertreterinnen des inselkubanischen Modernismo. Gleichwohl ist das Schaffen der schon zu Lebzeiten zum Wunderkind stilisierten Autorin, Dichterin und Malerin wissenschaftlich kaum eingehender untersucht worden. Die Werkstudie schlägt einen umfassenden, konsequent ästhetischen Blick auf das aus Gedichten, poetischer Prosa, literarischen Liebesbriefen, Zeichnungen und Malereien bestehende Gesamtwerk Borreros vor, das im Kern ein Streben nach Ganzheit von Kunst und Leben offenlegt. Dabei werden die Text- und Bildstrategien der Künstlerin mit den ästhetischen, soziohistorischen und biografischen Kontexten verzahnt, wodurch Juana Borreros Stimme als exemplarische Stimme der kubanischen Spätmoderne sowie einer bewegten kubanischen Literatur les- und sichtbar wird.
Zwischen Modellierung und Stakeholderbeteiligung - Wissensproduktion in der Energiewendeforschung
(2023)
Die Dekarbonisierung des Energiesystems ist Teil der international im Rahmen des Pariser Klimaabkommens beschlossenen CO2-Minderungsstrategie zur Bekämpfung des Klimawandels. Nach den Verhandlungen und Beschlüssen der Klimaziele stehen politische Entscheider weltweit nun vor der Frage, wie sie diese erreichen können. Dies produziert eine hohe politische Nachfrage nach Wissen um die direkten und indirekten Effekte verschiedener Instrumente und potentiellen Entwicklungspfade einer Energiewende. Dieser gesellschaftliche Bedarf an wissenschaftlichen Antworten zu Lösungsoptionen wurde im Rahmen einer Klimafolgenforschung, genauer einer Klimapolitikfolgenforschung, aufgenommen. Der relativ neue Zweig einer Energiewendeforschung hat sich weltweit entwickelt, steht dabei allerdings vor der doppelten Herausforderung: Erstens befindet sich das Objekt der Forschung nicht im luftleeren Raum, sondern innerhalb ökonomischer, sozialer und politischer Zusammenhänge, hier gesellschaftliche Einbettung genannt. Denn die Frage, wie die Energiewende erreicht werden kann, wird auch außerhalb der Wissenschaft debattiert und stellt damit ein Aushandlungsfeld unterschiedlicher Interessen und Narrative dar. Zweitens befindet sich das zu untersuchende Objekt in der Zukunft, hier unter dem Terminus des strukturellen Nicht-Wissens zusammengefasst. Diese beiden Bedingungen führen dazu, dass konventionelle Methoden der empirischen Sozialforschung nicht greifen und eine Öffnung und Transformation der Wissenschaft in Hinblick auf neue Methoden vonnöten ist (Nowotny 2001, Ravetz 2006, Schneidewind 2013). In dieser Arbeit untersuche ich zwei Möglichkeiten, wie mit der Herausforderung, Wissen unter der Bedingung des strukturellen Nicht-Wissens und der gesellschaftlichen Einbettung zu produzieren, in der Energiewendeforschung umgegangen wird. Einerseits wird dies durch die Einbeziehung von Stakeholdern, also nicht-wissenschaftlicher Akteure, in den Forschungsprozess getan. Andererseits ist die Nutzung von komplexen ökonometrischen Modellen zur Berechnung von Implikationen und energiewirtschaftlichen Entwicklungspfaden zu einem zentralen Mittel der Wissensgenerierung in der Energiewendeforschung avanciert. Damit wird der als Problem verstandenen strukturellen Bedingung des Nicht-Wissens insofern begegnet, als dass die Ergebnisse von Stakeholder-Involvement und von Modellierungsarbeiten zweifelsohne neues Wissen zur Verfügung stellen. Uneinigkeit besteht jedoch darin, worüber dieses Wissen etwas aussagt: Sind es Interessen oder legitime Perspektiven, die Stakeholder in den Forschungsprozess einbringen und sind Modelle vereinfachte Darstellungen der Welt oder sind sie Ausdruck der Vorstellung des Modellierers?
Für die Sondernutzung des gemeindlichen Verkehrsraumes durch die Verlegung und den Betrieb von Leitungen kann die Gemeinde vom Wasserversorger eine Konzessionsabgabe erheben. Gleichwohl kleine Regie- und Eigenbetriebe den größten Teil der Wasserversorger ausmachen, ein Großteil der Abnehmerbeziehungen über Gebühren ausgestaltet ist, und Konzessionsabgaben einen beachtlichen Faktor in den kommunalen Haushalten darstellen, ist die Frage, ob von einem Eigenbetrieb gezahlte Konzessionsabgaben in die Gebührenkalkulation eingestellt werden können, umstritten. Mehrere Oberverwaltungsgerichte verneinen dies. Die Verfasserin untersucht die zugrundeliegende Thematik aus zahlreichen rechtlichen Perspektiven und widerspricht der Rechtsprechung.
Heat stress (HS) is one of the major abiotic stresses which adversely affects the survival and growth of plants due to their sessile nature. To combat the detrimental effects of HS and develop thermotolerance, plants have evolved several defense mechanisms. Thermomemory is one such molecular mechanism whereby plants that have been acclimated (or primed/P) by a moderate HS can respond more efficiently and continue their growth after exposure to a severe or lethal HS (called triggering/T), while unprimed plants cannot survive. Thermomemory is known to be regulated by several transcription factors (TFs), epigenetic changes, chromatin remodellers, post-transcriptional changes and it also involves protein stability control and primary metabolism adjustment. Recent research has suggested that the shoot apical meristem (SAM) in Arabidopsis thaliana has a distinct transcriptional thermomemory which is possibly regulated by eight TFs called HEAT SHOCK FACTORS (HSFs). The main objective of this PhD thesis is to investigate the role of HSFA7b (one of the eight HSFs), in regulating thermomemory at the SAM by identifying the molecular networks it regulates. HSFA7a, a close homolog of HSFA7b, is also one of the eight HSFs that are involved in regulating thermomemory at the SAM. Thermomemory was found to be defective in the hsfa7b and hsfa7a hsfa7b mutants; the percentage survival of these seedlings was significantly lower than in wild-type (WT) seedlings after the priming and triggering (PT) treatment. Transcriptome and ChIP analyses were performed to identify the molecular networks controlled by HSFA7b and its close homolog HSFA7a, in regulating thermomemory at the SAM. The chromatin regulator SPLAYED (SYD) was found to be regulated by both HSFA7a and HSFA7b at the SAM during thermomemory. SYD is directly involved in SAM maintenance by directly regulating WUSCHEL (WUS), a master regulator of stem cell maintenance. WUS expression was down-regulated at the SAM of PT treated hsfa7a/b mutants compared to WT-Col-0 seedlings. HSFA7a and HSFA7b also jointly regulate the expression of orphan gene QUA QUINE STARCH (QQS) during thermomemory. Starch accumulation negatively correlates with QQS expression and this trend was observed in WT plants in response to thermopriming. The remobilization of starch was affected in the hsfa7a/b mutants compared to WT plants during the recovery period after T treatment. These findings indicate that defects in SAM maintenance and starch remobilization could possibly contribute to the reduced thermomemory in the hsfa7a/b mutants. Moreover, transcriptome and ChIP analysis indicate that ethylene signaling genes are directly regulated by HSFA7b during thermomemory. Transcriptome analysis of the HSFA7b-IOE line indicates that HSFA7b positively regulates the expression of HEAT STRESS ASSOCIATED 32 (HSA32), an important thermomemory gene, and HSFA7b strongly suppresses the expression of the reactive oxygen species (ROS) responsive REDOX RESPONSIVE TRANSCRIPTION FACTOR 1 (RRTF1) gene, which is also a repressed target of SYD. In Arabidopsis, the HSFA7b transcript undergoes alternative splicing at high temperatures to form two splice variants: one correctly/constitutively spliced variant which is functional and codes for the HSFA7b protein and one intron retained splice variant. Higher accumulation of the functional HSFA7b splice variant was found at the SAM compared to other tissues. Moreover, accumulation of the functional splice variant was higher in P and PT plants compared to control plants, whereas higher levels of the intron retained splice variant is found in plants subjected directly to the T treatment. The intron retained HSFA7b splice variant is degraded by the non-sense mediated decay (NMD) pathway as a means of regulating transcript level essential for protein synthesis at high temperatures. Importantly, HSFA7b protein accumulation was observed in plants subjected to PT treatment that survive and continue growth, but not in plants subjected directly to T treatment that do not survive, indicating that constitutive/ correct splicing of the HSFA7b transcript is a component of thermomemory. Taken together, these findings suggest that HSFA7a and HSFA7b jointly regulate SAM maintenance via the chromatin remodeller SYD and starch remobilization via QQS. In addition to them, HSFA7b also regulates the expression of ethylene signaling genes, heat responsive genes and the ROS responsive RRTF1. Furthermore, constitutive/correct splicing in the HSFA7b transcript is also an essential component of thermomemory.
Functional materials, also called "Smart Materials", are described by their ability to fulfill a desired task through targeted interaction with its environment. Due to this functional integration, such materials are of increased interest, especially in areas where the increasing micronization of components is required. Modern manufacturing processes (e.g. microfluidics) and the availability of a wide variety of functional materials (e.g. shape memory materials) now enable the production of particle-based switching components. This category includes micropumps and microvalves, whose basic function is the active control of liquid flows. One approach in realizing those microcomponents as pursued by this work, enables variable size-switching of water-filled microballoons by implementing a stimulus-sensitive switching motif in the capsule's membrane shell, while being under the influence of a constant driving force. The switching motif with its gatekeeper function has a critical influence on one or more material parameters, which modulate the capsule's resistance against the driving force in microballoon expansion process. The advantage of this concept is that even non-variable analyte conditions, such as concentration levels of ions, can be capitalized to generate external force fields that, under the control of the membrane, cause an inflation of the microballoon by an osmotically driven water influx. In case of osmotic pressure gradients as the driving force for the capsule expansion, material parameters associated with the gatekeeper function are specifically the permeability and the mechanical stiffness of the shell material. While a modulation of the shell permeability could be utilized to kinetically impede the water influx on large time scales, a modulation of the shell's mechanical stiffness even might be utilized to completely prevent the capsule inflation due to a possible non-deformability beneath a certain threshold pressure. In polymer networks, which are a suitable material class for the demanded capsule shell because of their excellent elasticity, both the permeability and the mechanical properties are strongly influenced by the crystallinity of the material. Since the permeability is effectively reduced with increasing crystallinity, while the mechanical stiffness is simultaneously greatly increased, both effects point in the same direction in terms of their functional relationship. For this reason and due to a reversible and contactless modulation of the membrane crystallinity by heat input, crystallites may be suitable switching motifs for controlling the capsule expansion. As second design element of reversible expandable microballoons, the capsule geometry, defined by an aqueous core enveloped by the temperature-sensitive polymer network membrane, should allow an osmotic pressure gradient across the membrane layer. The strength of the inflation pressure and the associated inflation velocity upon membrane melting should be controlled by the salt concentration within the aqueous core, while a turn in the osmotic gradient should furthermore allow the reversible process of capsule deflation. Therefore, it should be possible to build either microvalves and micropumps, while their intended action of either pumping or valving is determined by their state of expansion and the direction of the osmotic pressure gradient.. Microballoons of approximately 300 µm in diameter were formed via droplet-based microfluidics from double-emulsion templates (w/o/w). The elastomeric capsule membrane was formed by photo-crosslinking of methacrylate (MA) functionalized oligo(ε-caprolactone) precursors (≈ 3.8 MA-arms, Mn ≈ 12000 g mol-1) within the organic medium layer (o) via UV-exposure after droplet-formation. After removal of the toluene/chloroform mixture by slow extraction via the continuous aqueous phase, the capsules solidified under the development of a characteristic "mushroom"-like shape at specific experimental conditions (e.g. λ = 308 nm, 57 mJ·s-1·cm-2, 16 min). It could be furthermore shown that in dependency to the process parameters: oligomer concentration and curing-time also spherical capsules were accessible. Long curing-times and high oligomer concentrations at a fixed light-intensity favored the formation of "mushroom"-like capsules, whereas the contrary led to spherical shaped capsules. A comparative study on thin polymer network films of same composition and equal treatment proved a correlation between the film's crosslink density and their contraction capability, while stronger crosslinked polymer networks showed a stronger contraction after solvent removal. In combination with observations during capsule solidification via light-microscopy, where a continuous shaping from almost spherical crosslinked templates to "mushroom"-shaped and solidified capsules was stated, the following mechanism was proposed. In case of low oligomer contents and short curing-times, the contraction of the capsule shell during solvent removal is strongly diminished due to a low degree of crosslinking. Therefore, the solidifying shell could freely collapse onto the aqueous core. In the other case, high oligomer concentrations and long curing-times will favor the formation of highly crosslinked capsule membranes with a strong contraction capability. Due to an observed decentered location of the aqueous core within the swollen polymer network, an uneven radial stress along the capsule's circumference is exerted to the incompressible core. This lead to an uneven contraction during solvent removal and a directed flow of the core fluid into the direction of the minimal stress vector. In consequence, the initially thicker spherical cap contracts, whereas the opposing thinner spherical cap get stretched. The "mushroom"-shape over some advantages over their spherical shaped counterparts, why they were selected for the further experiments. Besides the necessity of a high density of crosslinking for the purpose of extraordinary elasticity and toughness, the form-anisotropy promotes a faster microballoon expandability due to a partial reduction of the membrane thickness. Additionally, pre-stretched regions of thin thickness might provide a better resistance against inflation pressure than spherical but non-stretched capsules of equal membrane thickness. The resulting "mushroom"-shaped microcapsules exhibited a melting point of Tm ≈ 50 - 60 °C and a degree of crystallinity of Xc ≈ 29 - 38 % depending on the membrane thickness and internal salt content, which is slightly lower than for the non-crosslinked oligomer and reasoned by a limited chain mobility upon crosslinking. Nonetheless, the melting transition of the polymer network was associated with a strong drop in its mechanical stiffness, which was shown to have a strong influence on the osmotic driven expansion of the microcapsules. Capsules that were subjected to osmotic pressures between 1.5 and 4.7 MPa did not expand if the temperature was well below the melting point of the capsule's membrane, i.e. at room temperature. In contrast, a continuous expansion, while approaching asymptotically to a final capsule size, was observed if the temperature exceeded the melting point, i.e. 60 °C. Microballoons, which were kept for 56 days at ∆Π = 1.5 MPa and room temperature, did not change significantly in diameter, why the impact of the mechanical stiffness on the expansion behavior is considered to be the greater than the influence of the shell permeability. The time-resolved expansion behavior of the microballoons above their Tm was subsequently modeled, using difusion equations that were corrected for shape anisotropy and elastic restoring forces. A shape-related and expansion dependent pre-factor was used to dynamically address the influence of the shell thickness differences along the circumference on the inflation velocity, whereas the microballoon's elastic contraction upon inflation was rendered by the inclusion of a hyperelastic constitutive model. An important finding resulting from this model was the pronounced increase in inflation velocity compared to hypothetical capsules with a homogeneous shell thickness, which stresses the benefit of employing shape anisotropic balloon-like capsules in this study. Furthermore, the model was able to predict the finite expandability on basis of entropy-elastic recovery forces and strain-hardening effects. A comparison of six different microballoons with different shell thicknesses and internal salt contents showed the linear relationship between the volumetric expansion, the shell thickness and the applied osmotic pressure, as represented by the model. As the proposed model facilitates the prediction of the expansion kinetics depending on the membranes mechanical and diffusional characteristics, it might be a screening tool for future material selections. In course of the microballoon expansion process, capsules of intermediate diameters could be isolated by recrystallization of the membrane, which is mainly caused by a restoration of the membrane's mechanical stiffness and is otherwise difficult to achieve with other stimuli-sensitive systems. The capsule's crystallinity of intermediate expansion states was nearly unchanged, whereas the lamellar crystal size tends to decreased with the expansion ratio. Therefore, it was assumed that the elastic modulus was only minimally altered and might increased due to the networks segment-chain extension. In addition to the volume increase achieved by inflation, a turn in the osmotic gradient also facilitated the reversible deflation, which was shown in inflation/deflation cycles. These both characteristics of the introduced microballoons are important parameter regarding the realization of micropumps and microvalves. The fixation of expanded microcapsules via recrystallization enabled the storage of entropy-elastic strain-energy, which could be utilized for pumping actions in non-aqueous media. Here, the pumping velocity depended on both, the type of surrounding medium and the applied temperature. Surrounding media that supported the fast transport of pumped liquid showed an accelerated deflation, while high temperatures further accelerate the pumping velocity. Very fast rejection of the incorporated payload was furthermore realized with pierced expanded microballoons, which were subjected to temperatures above their Tm. The possible fixation of intermediate particle sizes provide opportunities for vent constructions that allowed the precise adjustment of specific flow-rates and multiple valve openings and closings. A valve construction was realized by the insertion of a single or multiple microballoons in a microfluidic channel. A complete and a partial closing of the microballoon-valves was demonstrated as a function of the heating period. In this context, a difference between the inflation and deflation velocity was stated, summarizing slower expansion kinetics. Overall, microballoons, which presented both on-demand pumping and reversible valving by a temperature-triggered change in the capsule's volume, might be suitable components that help to design fully integrated LOC devices, due to the implementation of the control switch and controllable inflation/deflation kinetics. In comparison to other state of the art stimuli-sensitive materials, one has to highlight the microballoons capability of stabilizing almost continuously intermediate capsule sizes by simple recrystallization of the microballoon's membrane.
The increasing global population has led to a growing demand for cost-effective and eco-friendly methods of water purification. This demand has reached a peak due to the increasing presence of impurities and pollutants in water and a growing awareness of waterborne diseases. Advanced oxidation processes (AOPs) are effective methods to address these challenges, due to the generation of highly reactive radicals, such as sulfate radical (SO4•-), hydroxyl radical (•OH), and/or superoxide radical (•O2-) in oxidation reactions. Relative to conventional hydrogen peroxide (H2O2)-based AOPs for wastewater treatment, the persulfate-related AOPs are receiving increasing attention over the past decades, due to their stronger oxidizing capability and a wider pH working window. Further deployment of the seemingly plausible technology as an alternative for the well-established one in industry, however, necessitates a careful evaluation of compounding factors, such as water matrix effects, toxicological consequences, costs, and engineering challenges, etc. To this end, rational design of efficient and environmentally friendly catalysts constitutes an indispensable pathway to advance persulfate activation efficacy and to elucidate the mechanisms in AOPs, the combined endeavors are expected to provide insightful understanding and guidelines for future studies in wastewater treatment. A dozens of transition metal-based catalysts have been developed for persulfate-related AOPs, while the undesirable metal leaching and poor stability in acidic conditions have been identified as major obstacles. Comparatively, the carbonaceous materials are emerging as alternative candidates, which are characterized by metal-free nature, wide availability, and exceptional resistance to acid and alkali, as well as tunable physicochemical and electronic properties, the combined merits make them an attractive option to overcome the aforementioned limitations in metal-based catalytic systems. This dissertation aims at developing novel carbonaceous materials to boost the activity in peroxymonosulfate (PMS) activation processes. Functionalized carbon materials with metal particles or heteroatoms were constructed and further evaluated in terms of their ability to activate PMS for AOPs. The main contents of this thesis are summarized as follows: (1) Iron oxide-loaded biochar: improving stability and alleviating metal leakage Metal leaching constitutes one of the main drawbacks in using transition metals as PMS activators, which is accompanied by the generation of metal-containing sludge, potentially leading to secondary pollution. Meanwhile, the metal nanoparticles are prone to aggregate, causing rapid decay of catalytic performance. The use of carbons as supports for transition metals could mitigate these deficiencies, because the interaction between metals and carbons could in turn disperse and stabilize metal nanoparticles, thus suppressing the metal leaching. In this work, the environmentally benign lignin with its abundant phenolic groups, which is well known to serve as carbon source with high yields and flexibility, was utilized to load Fe ions. The facile low-temperature pre-treatment pyrolytic strategy was employed to construct a green catalyst with iron oxides embedded in Kraft-lignin-derived biochar (termed as γ-Fe2O3@KC). The γ-Fe2O3@KC was capable of activating PMS to generate stable non-radical species (1O2 and Fe (V)=O) and to enhance electron transfer efficiency. A surface-bound reactive complex (catalyst-PMS*) was identified by electrochemical characterizations and discussed with primary surface-bound radical pairs to explain the contradictions between quenching and EPR detection results. The system also showed encouraging reusability for at least 5 times and high stability at pH 3-9. The low concentration of iron in γ-Fe2O3@KC/PMS system implied that the carbon scaffold of biochar substantially alleviated metal leakage. (2) MOF-derived nanocarbon: new carbon crystals Traditional carbon materials are of rather moderate performance in activation PMS, due to the poor electron transfer capacity within the amorphous structure and limited active sites for PMS adsorption. Herein, we established crystalline nanocarbon materials via a simple NaCl-templated strategy using the monoclinic zeolitic imidazolate framework-8 (ZIF-8) sealed with NaCl crystals as the precursors. Specifically, NaCl captured dual advantages in serving as structure-directing agent during hydrolysis and protective salt reactor to facilitate phase transformation during carbonization. The structure-directing agent NaCl provided a protective and confined space for the evolution of MOF upon carbonization, which led to high doping amounts of nitrogen (N) and oxygen elements (O) in carbon framework (N: 14.16 wt%, O: 9.6 wt%) after calcination at a high temperature of 950 oC. We found that N-O co-doping can activate the chemically inert carbon network and the nearby sp2-hybridized carbon atoms served as active sites for adsorption and activation. Besides, the highly crystallized structure with well-established carbon channels around activated carbon atoms could significantly accelerate electron transfer process after initial adsorption of PMS. As such, this crystalline nanocarbon exhibited excellent catalytic kinetics for various pollutants. (3) MOF-derived 2D carbon layers: enhanced mass/electron transfer The two-dimensional (2D) configuration of carbon-based nanosheets with inherent nanochannels and abundant active sites residing on the layer edges or in between the layers, allowed the accessible interaction and close contact between the substrates and reactants, as well as the dramatically improved electron- and mass-transfer kinetics. In this regard, we developed dual-templating strategy to afford 2D assembly of the crystalline carbons, which found efficiency in reinforcing the interactions between the catalyst surface and foreign pollutants. Specifically, we found that the ice crystals and NaCl promoted the evolution of MOF in a 2D fashion during the freezing casting stage, while the later further allowed the formation of a graphitic surface at high calcination temperature, by virtue of the templating effect of molten salt. Due to the highly retained co-doping amounts, N and O heteroatoms created abundant active sites for PMS activation, the 2D configuration of carbon-based nanosheets enable efficient interaction of PMS and pollutants on the surface, which further boosted the kinetics of degradation.
In der vorliegenden Arbeit liegt der Fokus auf jungen russischsprachigen Jüdinnen und Juden, deren Eltern in den 90er Jahren des 20 Jahrhunderts nach Deutschland eingewandert sind. Im Rahmen dieser Studie wird der Bildungsweg dieser MigrantInnengruppe und deren Erfahrungen in Deutschland aus der biographischen Perspektive nachvollzogen. Der Fokus wird insbesondere auf die biographischen Lebenserfahrungen gelegt, d.h. die allgemeinen Lebensumstände, Hürden und Schwierigkeiten, die die jungen russischsprachigen Jüdinnen und Juden in Deutschland überwinden mussten, um auf ihrem Bildungsweg an ihr Ziel zu kommen. Des Weiteren werden die Rolle des sozialen Umfelds auf die Auswahl ihres Bildungsweges sowie ihre Zugehörigkeit und ihr Beitrag zur deutschen Gesellschaft beleuchtet. Ein weiteres Hauptaugenmerk dieser Arbeit liegt auf den gesellschaftlichen, politischen und familiären Rahmenbedingungen, die den BiographInnen den Zugang zum Bildungsweg ermöglichten.
Die in der Arbeit formulierten Forschungsfragen wurden mithilfe der interpretativen Sozialforschung, genauer, der fallrekonstruktiven Auswertung nach Gabriele Rosenthal beantwortet.
Über den biographischen Verlauf der Lebensgeschichte der jungen russischsprachigen Jüdinnen und Juden wurde deutlich, dass die BiographInnen in die säkulare Gesellschaft gehen müssen, um ihren Bildungsweg erfolgreich zu gestalten. Dort erfahren sie einen sehr starken Antisemitismus und sind diesem schutzlos ausgeliefert. Bei allen drei Interviewten wurde diese Erfahrung in der Schule gemacht, an einem Ort, an dem sie Schutz erfahren sollten. Diesen Anfeindungen begegneten sie auf unterschiedliche Weise und sie entwickelten verschiedene Handlungsstrategien. Einige BiographInnen setzen sich auf der intellektuellen Ebene bewusst damit auseinander, andere wiederum versuchen, nicht hinzuschauen und es zu ignorieren.
Des Weiteren wurde als Resultat der Untersuchung in einigen Fällen ein übereinstimmendes, in anderen ein nicht übereinstimmendes Passungsverhältnis zwischen elterlichen Vorstellungen und den Bildungswegen der jungen russischsprachigen Jüdinnen und Juden gefunden.
The development of seeds in angiosperms starts with a complex process of double fertilization, involving the fusion of the maternal egg cell and central cell with two paternal sperm cells. This gives rise to the embryo and the nourishing endosperm, which are then enclosed by the seed coat, derived from the maternal integuments. The growth of the seed coat in Arabidopsis thaliana (Arabidopsis) is actively inhibited before fertilization by epigenetic regulators known as Polycomb Group (PcG) proteins. These proteins deposit a repressive histone mark called H3K27me3, which must be removed to enable seed coat formation. In this thesis, I explored the mechanism of removal of H3K27me3 marks from the integument cells following fertilization, which allows for seed coat formation. We hypothesized that this removal should be primarily facilitated by histone demethylases from the JMJ family and potentially influenced by the plant hormones Brassinosteroids (BRs). This hypothesis was supported by the expression patterns of the JMJ protein REF6 and of BR related genes, which are specifically expressed in the integuments and in the seed coat. Moreover, mutations in both these pathways lead to developmental defects, such as reduced ovule viability and delayed seed coat growth. Our research provides evidence suggesting that BR signalling is likely involved in recruiting JMJ-type histone demethylases to target loci responsible for seed coat growth. Moreover, we have discovered an additional pathway through which BRs regulate seed coat development, independent of their influence on H3K27me3 marks. This finding emphasizes the diverse roles of BRs in coordinating seed development, extending beyond their well-known involvement in plant growth and development. Furthermore, I explored the role of another epigenetic mark, DNA methylation, in fertilization-independent (or autonomous) seed formation in Arabidopsis. For this, we utilized epigenetic Recombinant Inbred Lines (epiRILs) and thus identified an epigenetic Quantitative Trait Locus (epiQTL) on chromosome II, potentially responsible for the larger autonomous seed size observed in DNA methylation mutants. Overall, this thesis significantly enhances our comprehension of the intricate relationship between epigenetic modifications, hormonal signaling, and plant reproductive processes. It offers valuable insights into the genetic mechanisms governing both sexual and asexual seed formation, while also presenting potential avenues for the engineer of advantageous traits in agricultural crops.
Interested in the ideological workings of fiction, I study how major avant-garde tropes promote the potential of permanent renewal as white America’s property. Renewal ties to the capacities to create, progress, transcend, and simply be. From Black critique we know that, within dominant discourse, all these capacities have been denied to Black bodies ever since colonization. Black work has been fetishized, appropriated, stolen, and dismissed in and by dominant culture, while Black being is construed as negativity and barred on the level of ontology. It follows then that racialization operates on multiple levels in the conceptual frame of renewal. I study this conceptualization by re-reading the works of and criticism on progressive white authors. I examine how images of renewal enable the claim on futurity, transformative potential, and movement forward as exclusively white properties. Premised on oppositions between positive capacities and a state of complete incapacitation, these images are often viewed as separate constructions. This project shows that, deriving from white ideology, such representations are symbiotic and simultaneous - the "good" story of white renewal rests on the continual transgression towards Black being.
Biofilms are heterogeneous structures made of microorganisms embedded in a self-secreted extracellular matrix. Recently, biofilms have been studied as sustainable living materials with a focus on the tuning of their mechanical properties. One way of doing so is to use metal ions. In particular biofilms have been shown to stiffen in presence of some metal cations and to soften in presence of others. However, the specificity and the determinants of those interactions vary between species. While Escherichia coli is a widely studied model organism, little is known concerning the response of its biofilms to metal ions. In this work, we aimed at tuning the mechanics of E. coli biofilms by acting on the interplay between matrix composition and metal cations. To do so, we worked with E. coli strains producing a matrix composed of curli amyloid fibres or phosphoethanolamine-cellulose (pEtN-cellulose) fibres or both. The viscoelastic behaviour of the resulting biofilms was investigated with rheology after incubation with one of the following metal ion solutions: FeCl3, AlCl3, ZnCl2 and CaCl2 or ultrapure water. We observed that the strain producing both fibres stiffen by a factor of two when exposed to the trivalent metal cations Al(III) and Fe(III) while no such response is observed for the bivalent cations Zn(II) and Ca(II). Strains producing only one matrix component did not show any stiffening in response to either cation, but even a small softening. In order to investigate further the contribution of each matrix component to the mechanical properties, we introduced additional bacterial strains producing curli fibres in combination with non-modified cellulose, non-modified cellulose only or neither component. We measured biofilms produced by those different strains with rheology and without any solution. Since rheology does not preserve the architecture of the matrix, we compared those results to the mechanical properties of biofilms probed with the non-destructive microindentation. The microindentation results showed that biofilm stiffness is mainly determined by the presence of curli amyloid fibres in the matrix. However, this clear distinction between biofilm matrices containing or not containing curli is absent from the rheology results, i.e. following partial destruction of the matrix architecture. In addition, rheology also indicated a negative impact of curli on biofilm yield stress and flow stress. This suggests that curli fibres are more brittle and therefore more affected by the mechanical treatments. Finally, to examine the molecular interactions between the biofilms and the metal cations, we used Attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR) to study the three E.coli strains producing a matrix composed of curli amyloid fibres, pEtN-cellulose fibres or both. We measured biofilms produced by those strains in presence of each of the aforementioned metal cation solutions or ultrapure water. We showed that the three strains cannot be distinguished based on their FTIR spectra and that metal cations seem to have a non-specific effect on bacterial membranes in absence of pEtN-cellulose. We subsequently conducted similar experiments on purified curli or pEtN-cellulose fibres. The spectra of the pEtN-cellulose fibres revealed a non-valence-specific interaction between metal cations and the phosphate of the pEtN-modification. Altogether, these results demonstrate that the mechanical properties of E. coli biofilms can be tuned via incubation with metal ions. While the mechanism involving curli fibres remains to be determined, metal cations seem to adsorb onto pEtN-cellulose and this is not valence-specific. This work also underlines the importance of matrix architecture to biofilm mechanics and emphasises the specificity of each matrix composition.
Zielsetzung und leitendes Erkenntnisinteresse Als Arbeitsgrundlage soll folgende Definition der Bühnengesellschaft als Ausgangspunkt dienen: Die Bühnengesellschaft wird durch die Gesamtzahl der handelnden Personen einer Posse gebildet, die in einem sozialen, psychologischen und mentalen Beziehungsverhältnis zueinanderstehen. Ihr Umfang ist sowohl von gattungsspezifischen als auch von theaterpraktischen Faktoren abhängig. Die Bühnengesellschaft bildet die Schnittstelle zwischen der fiktionalen Welt der Posse und der Lebenswirklichkeit der Zuschauer. Sie verbindet Spielwelt und Wirklichkeit. Durch diese Brückenfunktion werden beide Elemente aufeinander bezogen. Der so umrissene Blick muss bei der Analyse der Bühnengesellschaft von Nestroys Possen folgende unterschiedlich gewichtete und akzentuierte Schwerpunkte enthalten: 1. Figurenkonzeption Die Konzeption der Figuren der Nestroyschen Bühnengesellschaften wird sowohl im Kontext der historischen Wirklichkeit und den herrschenden kulturellen Konzepten als auch in Bezug zur Gattungstradition analysiert unter der erkenntnisleitenden Fragestellung, wie Zeitwirklichkeit („das konfliktreiche Welttheater“) erfahrbar wird. Der Analyse der „komischen Zentralfigur“ kommt in diesem Zusammenhang eine besondere Bedeutung zu. 2. Bühnengesellschaftliche Beziehungen Eine Analyse der Figurenkonstellation, des Verhältnisses von Haupt- und Nebenfiguren sowie der Bildung von Gruppierungen erhellt ihre dramaturgische Funktion im Kontext der satirischen Intention. 3. Bühnengesellschaft und Theater Der theaterwissenschaftliche Aspekt wird dadurch akzentuiert, dass Theaterorganisation, Bühne und die männlich-weibliche Zusammensetzung des Ensembles in den Blick genommen werden, um die Abhängigkeit des Umfangs und der Zusammensetzung der Bühnengesellschaft von den realen Gegebenheiten des Volkstheaterbetriebs aufzuzeigen. Auf der Grundlage der genannten Schwerpunkte wird für die Untersuchung folgendes leitendes Erkenntnisinteresse formuliert: Die Bühnengesellschaft besitzt eine Schnittstellenfunktion zwischen der fiktionalen Spielwelt der Posse und der Lebenswirklichkeit der Zuschauerschaft. Durch die Analyse der personellen und strukturellen Gestaltung der Bühnengesellschaft wird ihre Brückenfunktion für die ‚Wirksamkeit‘ der satirischen und parodistischen Intention erhellt.
Teacher self-efficacy is highly relevant for effective teaching, student academic development, and teachers’ wellbeing, as theoretical work (Bandura, 1997; Tschannen-Moran et al., 1998) and empirical studies (i.e., Burić & Kim, 2020; Klassen & Chiu, 2010; van Uden et al., 2013) have shown associations with effective classroom management, student support, student motivation, and teachers’ job satisfaction. Given the importance of teacher self-efficacy for teaching and learning, it is interesting to note that existing research is limited in several aspects – first, longitudinal studies on the relations between teacher self-efficacy and student academic outcomes are widely missing; second, empirical studies often assess teacher self-efficacy as a one-dimensional construct, neglecting its multidimensional character; third, studies often only focus on either the students’ or the teachers’ perspective on teaching and thus do not include simultaneously multiple sources of information on teaching practices as a consequence of teacher self-efficacy; fourth, research often does not systematically consider the effects of teacher self-efficacy on students’ academic outcomes at both the group and individual level. Against this backdrop, this dissertation presents three longitudinal studies that aim to contribute to a more detailed perspective on teacher self-efficacy by examining systematically and longitudinally the relations between multiple dimensions of teacher self-efficacy and theoretically aligned teaching quality facets as perceived by teachers and students, as well as their relations to students’ motivational-affective outcomes – more concretely, their relations to students’ interest, enjoyment, and self-efficacy in a multi-level analysis approach. Study 1 examines the longitudinal relations between teacher self-efficacy for classroom management and student-perceived monitoring and social relatedness, and investigates whether the two student-reported teaching dimensions explain the relations between teacher self-efficacy for classroom management and student enjoyment using multi-level analyses. Study 2 examines longitudinally how teacher self-efficacy for student engagement relates to student interest through student- and teacher-perceived emotional support. Also, including student and teacher perspectives on teaching, Study 3 examines the longitudinal relations between specific facets of teacher self-efficacy for classroom management and classroom discipline, teacher self-efficacy for instructional strategies and cognitive activation, teacher self-efficacy for student engagement and competence support, teacher self-efficacy for emotional support and social relatedness, as well as teacher self-efficacy for student-oriented teaching and learning goal-oriented instruction with students’ enjoyment and self-efficacy. Furthermore, in Studies 2 and 3 the cross-level mediation effects of longitudinal relations with teacher self-efficacy on student motivational-affective characteristics via teaching practices are examined in order to address the lack of empirical studies disentangling the relations for specifically individual- vs. group-level effects. The limitations and implications are discussed in terms of their theoretical and practical relevance for school practice, teacher education, and teacher training.
Mechanosensation is a fundamental biological process that provides the basis for sensing touch and pain as well as for hearing and proprioception. A special class of ion-channel proteins known as mechanosensitive proteins convert the mechanical stimuli into electrochemical signals to mediate this process. Mechanosensitive proteins undergo conformational changes in response to mechanical force, which eventually leads to the opening of the proteins' ion channel. Mammalian mechanosensitive proteins remained a long sought-after mystery until 2010 when a family of two proteins - Piezo1 and Piezo2 - was identifed as mechanosensors [1]. The cryo-EM structures of Piezo1 and Piezo2 protein were resolved in the last years and reveal a propeller-shaped homotrimer with 114 transmembrane helices [2, 3, 4, 5]. The protein structures are curved and have been suggested to deform the surrounding membrane into a nano-dome, which mechanically responds to membrane tension resulting from external forces [2]. In this thesis, the conformations of membrane-embedded Piezo1 and Piezo2 proteins and their tension-induced conformational changes are investigated using molecular dynamics simulations. Our coarse-grained molecular dynamics simulations show that the Piezo proteins induce curvature in the surrounding membrane and form a stable protein-membrane nano-dome in the tensionless membrane. These membrane-embedded Piezo proteins, however, adopt substantially less curved conformations in our simulations compared to the cryo-EM structures solved in detergent micelles, which agrees with recent experimental investigations of the overall Piezo nano-dome shape in membrane vesicles [6, 7, 8]. At high membrane tension, the Piezo proteins attain nearly planar conformations in our simulations. Our systematic investigation of Piezo proteins under different membrane tensions indicates a half-maximal conformational response at membrane tension values rather close to the experimentally suggested values of Piezo activation [9, 10]. In addition, our simulations indicate a widening of the Piezo1 ion channel at high membrane tension, which agrees with the channel widening observed in recent nearly flattened cryo-EM structures of Piezo1 in small membrane vesicles [11]. In contrast, the Piezo2 ion channel does not respond to membrane tension in our simulations. These different responses of the Piezo1 and Piezo2 ion channels in our simulations are in line with patch-clamp experiments, in which Piezo1, but not Piezo2, was shown to be activated by membrane tension alone [12].
Vereine als Gefahr
(2023)
Die von kriminellen oder extremistischen Gruppen ausgehende Gefahr erhöht sich entsprechend ihres Organisationsgrades. Eine Zustandsanalyse des Vereinsrechts zeigt, dass Vereins- und Kennzeichenverbote wirkmächtige präemptive Maßnahmen gegen neue dezentrale oder mehrstufige Vereinigungen bleiben. Bei ihrer Weiterentwicklung lenkt Sandra Lukosek den Blick auf die Auslegung und wechselseitige Zurechnung verbotsrelevanten Verhaltens einzelner Mitglieder zum Verein und der Erstreckung auf gleichrangige Schwestervereine. Anhand des Waffenrechts arbeitet sie umgekehrt die Vereinszugehörigkeit als taugliches Wesensmerkmal der Mitglieder heraus. Sie betrachtet verschiedene Vereinstypen mit zu differenzierenden vereinigungsfreiheitlichen Schutzbereichen. Ein Verbot religiöser islamistisch-extremistischer Vereine unterscheidet sich vom Verbot eines Rocker- oder Reichsbürgervereins. Die Autorin lässt sich auf sicherheitsbehördliche Herausforderungen ein und findet praktikable Reformansätze zur Fortentwicklung des Vereinsrechts.
This dissertation focuses on the understanding of the optical manipulation of microgels dispersed in aqueous solution of azobenzene containing surfactant. The work consists of three parts where each part is a systematic investigation of the (1) photo-isomerization kinetics of the surfactant in complex with the microgel polymer matrix, (2) light driven diffusiosmosis (LDDO) in microgels and (3) photo-responsivity of microgel on complexation with spiropyran.
The first part comprises three publications where the first one [P1] investigates the photo-isomerization kinetics and corresponding isomer composition at a photo-stationary state of the photo-sensitive surfactant conjugated with charged polymers or micro sized polymer networks to understand the structural response of such photo-sensitive complexes. We report that the photo-isomerization of the azobenzene-containing cationic surfactant is slower in a polymer complex compared to being purely dissolved in an aqueous solution. The surfactant aggregates near the polyelectrolyte chains at concentrations much lower than the bulk critical micelle concentration. This, along with the inhibition of the photo-isomerization kinetics due to steric hindrance within the densely packed aggregates, pushes the isomer-ratio to a higher trans-isomer concentration for all irradiation wavelengths.
The second publication [P2] combines experimental results and non-adiabatic dynamic simulations for the same surfactant molecules embedded in the micelles with absorption spectroscopy measurements of micellar solutions to uncover the reasons responsible for the slowdown in photo induced trans → cis azobenzene isomerization at concentrations higher than the critical micelle concentration (CMC). The simulations reveal a decrease of isomerization quantum yields for molecules inside the micelles and observes a reduction of extinction coefficients upon micellization. These findings explain the deceleration of the trans → cis switching in micelles of the azobenzene-containing surfactants.
Finally, the third publication [P3] focusses on the kinetics of adsorption and desorption of the same surfactant within anionic microgels in the dark and under continuous irradiation. Experimental data demonstrate, that microgels can serve as a selective absorber of the trans isomers. The interaction of the isomers with the gel matrix induces a remotely controllable collapse or swelling on appropriate irradiation wavelengths. Measuring the kinetics of the microgel size response and knowing the exact isomer composition under light exposure, we calculate the adsorption rate of the trans-isomers.
The second part comprises two publications. The first publication [P4] reports on the phenomenon of light-driven diffusioosmotic (DO) long-range attractive and repulsive interactions between micro-sized objects, whose range extends several times the size of microparticles and can be adjusted to point towards or away from the particle by varying irradiation parameters such as intensity or wavelength of light. The phenomenon is fueled by the aforementioned photosensitive surfactant. The complex interaction of dynamic exchange of isomers and photo-isomerization rate yields to relative concentrations gradients of the isomers in the vicinity of micro-sized object inducing a local diffusioosmotic (DO) flow thereby making a surface act as a micropump.
The second publication [P5] exclusively aims the visualization and investigation of the DO flows generated from microgels by using small tracer particles. Similar to micro sized objects, the flow is able to push adjacent tracers over distances several times larger than microgel size. Here we report that the direction and the strength of the l-LDDO depends on the intensity, irradiation wavelength and the amount of surfactant adsorbed by the microgel. For example, the flow pattern around a microgel is directed radially outward and can be maintained quasi-indefinitely under exposure at 455 nm when the trans:cis ratio is 2:1, whereas irradiation at 365 nm, generates a radially transient flow pattern, which inverts at lower intensities.
Lastly, the third part consists of one publication [P6] which, unlike the previous works, reports on the study of the kinetics of photo- and thermo-switching of a new surfactant namely, spiropyran, upon exposure with light of different wavelengths and its interaction with p(NIPAM-AA) microgels. The surfactant being an amphiphile, switches between its ring closed spiropyran (SP) form and ring open merocyanine (MC) form which results in a change in the hydrophilic–hydrophobic balance of the surfactant as MC being a zwitterionic form along with the charged head group, generates three charges on the molecule. Therefore, the MC form of the surfactant is more hydrophilic than in the case of the neutral SP state. Here, we investigate the initial shrinkage of the gel particles via charge compensation on first exposure to SP molecules which results from the complex formation of the molecules with the gel matrix, triggering them to become photo responsive. The size and VPTT of the microgels during irradiation is shown to be a combination of heating up of the solution during light absorption by the surfactant (more pronounced in the case of UV irradiation) and the change in the hydrophobicity of the surfactant.
Dieses Buch geht der Frage nach, aus welchen Gründen im Berlin des Jahres 1845 mit der »Genossenschaft für Reform im Judenthum« die womöglich bis heute radikalste Ausprägung jüdischer Reform entstand. Dazu werden die Hauptwerke Sigismund Sterns (1812–1867), des Gründers der Bewegung, erstmals systematisch dargestellt und zeitgeschichtlich eingeordnet. Die Studie macht deutlich, dass die Gründung der Genossenschaft nur im Kontext der vielfältigen, gesamtgesellschaftlichen und innerjüdischen, religiösen und politischen Umwälzungen im Vormärz und deren theoretisch-diskursivem Unterbau verstanden werden kann. Das Aufkommen der Bewegung und das jähe Verklingen ihrer Vitalität nach 1848 erweisen sich dabei als Spiegel der komplexen Verflechtungszusammenhänge deutsch-jüdischen philosophisch-theologischen Denkens im 19. Jahrhundert.
In nature, plants often encounter biotic and abiotic stresses, which can cause reduced crop yield and quality, and threaten the nutrition of a growing human population. As heat stress (HS) is one of the main abiotic stresses, and is projected to increase due to global warming, it is necessary to better understand how plants respond and survive under HS. In Arabidopsis thaliana, plants can survive under severe HS if primed by a non-lethal HS, a process called acquisition of thermotolerance. This primed stated can be maintained for several days, and the ability of plants to maintain the primed state is called maintenance of acquired thermotolerance (mATT) or HS memory. According to current research, two Heat shock factors (HSFs) HSFA2 and HSFA3 are known to account for the majority of mATT capability, and there are other HSFs e.g. HSFA1b and HSFA6b in HSF complexes containing HSFA2 and/or HSFA3, however, the roles of these HSFs in HS memory is not clearly understood. Moreover, the mechanism of these HSFs in regulating HS memory is unclear, whether transcriptional machinery e.g. the Mediator complex contributes to transcriptional memory. This work investigates the role of HSFs and Mediator subunits in HS memory in A. thaliana. For the role of HSFs, the interaction between HSFA1b and HSFA2 during HS memory phase was confirmed by in vivo co- immunoprecipitation (Co-IP). HSFA1b, HSFA2, HSFA3 and HSFA6b targeted HS memory-related genes according to DNA affinity purification sequencing (DAP-seq) data, and targets of HSFA1b were confirmed in vivo by chromatin immunoprecipitation qPCR (ChIP-qPCR). The mutant of hsfa6b showed an HS memory deficiency phenotype in mATT survival assay. These data confirmed the role for HSFA2 and HSFA3 in HS memory, and suggest that HSFA1b and HSFA6b also function in HS memory. The Mediator complex functions as an RNA Polymerase II (RNA Pol II) co-regulator, and includes Head, Middle, Tail and Kinase modules. Both MED23 and MED32 belong to the Tail module, and they have a positive role in HS memory. MED23 interacted with HSFA3, as determined by yeast two hybrid (Y2H) and in vivo Co-IP assays. The med23 mutant showed a decreased HS memory phenotype, reduced expression of Type I (sustained expression) memory genes following HS, and reduced accumulation of the memory-associated Tri-methylation of histone H3 lysine 4 (H3K4me3)histone modification at HS memory-related gene loci after HS. MED23 was recruited to HS-inducible memory and non-memory genes after HS, as determined by ChIP-qPCR. The med32
mutant showed a reduced HS memory phenotype, decreased expression of Type I and Type II (hyper-induction) memory genes, and lower accumulation of H3K4me3 at memory gene lociafter HS. However, MED32 did not show interaction with any tested HSF in Y2H or in vivo Co-IP. MED32 regulated the recruitment of RNA Pol II at HS-inducible genes after HS, but was not itself recruited to HS memory genes after HS. These results provided more evidence
that the Mediator subunits MED23 and MED32 regulate HS memory on transcriptional and epigenetic levels. In general, this work provides a better insight into the molecular mechanism of how HSFs and Mediator subunits regulate HS memory in plants and will provide new perspectives to breed crops with improved thermotolerance.
Starch is an essential biopolymer produced by plants. Starch can be made inside source tissue (such as leaves) and sink tissue (such as fruits and tubers). Nevertheless, understanding how starch metabolism is regulated in source and sink tissues is fundamental for improving crop production.
Despite recent advances in the understanding of starch and its metabolism, there is still a knowledge gap in the source and sink metabolism. Therefore, this study aimed to summarize the state of the art regarding starch structure and metabolism inside plants. In addition, this study aimed to elucidate the regulation of starch metabolism in the source tissue using the leaves of a model organism, Arabidopsis thaliana, and the sink tissue of oil palm (Elaeis guineensis) fruit as a commercial crop.
The research regarding the source tissue will focus on the effect of the blockage of starch degradation on the starch parameter in leaves, especially in those of A. thaliana, which lack both disproportionating enzyme 2 (DPE2) and plastidial glucan phosphorylase 1 (PHS1) (dpe2/phs1). The additional elimination of phosphoglucan water dikinase (PWD), starch excess 4 (SEX4), isoamylase 3 (ISA3), and disproportionating enzyme 1 (DPE1) in the dpe2/phs1 mutant background demonstrates the alteration of starch granule number per chloroplast. This study provides insights into the control mechanism of granule number regulation in the chloroplast.
The research regarding the sink tissue will emphasize the relationship between starch metabolism and the lipid metabolism pathway in oil palm fruits. This study was conducted to observe the alteration of starch parameters, metabolite abundance, and gene expression during oil palm fruit development with different oil yields. This study shows that starch and sucrose can be used as biomarkers for oil yield in oil palms. In addition, it is revealed that the enzyme isoforms related to starch metabolism influence the oil production in oil palm fruit.
Overall, this thesis presents novel information regarding starch metabolism in the source tissue of A.thaliana and the sink tissue of E.guineensis. The results shown in this thesis can be applied to many applications, such as modifying the starch parameter in other plants for specific needs.
"Il Gattopardo" nella DDR
(2023)
Sulla base di materiale d'archivio inedito si ripercorre l'avvincente storia della prima edizione del Gattopardo nella DDR (1961). È qui analizzata la corsa ad ostacoli del romanzo tra congruenze ed eccezioni che assume i tratti di un giallo letterario. L'opera di un principe defunto scavalca il Muro grazie ad Alfred Kurella, potente funzionario della SED. Nella sua postfazione Il Gattopardo non è canto della decadenza, ma preannuncio di una nuova epoca, manifesto dello Stato in procinto di entrare nell'era socialista. La chiave di lettura è un unicum con una marcata impronta ideologica che ne determina prima la fortuna e poi l'isolamento. Al Gattopardo nella Germania Est Bernardina Rago dà per la prima volta voce.
Ausgehend von Überlegungen des anthropologisch orientierten Psychiaters Erwin Straus geht dieses Buch der Frage nach, welche Bedingungen vorliegen, wenn bestimmte Ereignisse von Personen als bedeutsam erlebt werden. Des Weiteren wird ausführlich erörtert, wie sich Personalität im Menschen ausbildet und inwieweit sie von der gelingenden Integration bedeutungsvoller Ersterlebnisse abhängt. Das dabei zugrundeliegende Person-Konzept stellt einen eigenständigen Syntheseversuch der vier Konzepte von Erwin Straus, Viktor Emil von Gebsattel, Helmuth Plessner und Max Scheler dar. Der Autor arbeitet in oberärztlicher Funktion am Klinikum Schloss Lütgenhof in Dassow, einer Akutklinik für Personale Medizin, integrierte Psychosomatik, Innere Medizin und Psychotherapie
Seasonal forecasts are of great interest in many areas. Knowing the amount of precipitation for the upcoming season in regions of water scarcity would facilitate a better water management. If farmers knew the weather conditions of the upcoming summer at sowing time, they could select those cereal species that are best adapted to these conditions. This would allow farmers to improve the harvest and potentially even reduce the amount of pesticides used. However, the undoubted advantages of seasonal forecasts are often opposed by their high degree of uncertainty. The great challenge of generating seasonal forecasts with lead times of several months mainly originates from the chaotic nature of the earth system. In a chaotic system, even tiny differences in the initial conditions can lead to strong deviations in the system’s state in the long run.
In this dissertation we propose an emergent machine learning approach for seasonal forecasting, called the AnlgModel. The AnlgModel combines the analogue method with myopic feature selection and bootstrapping. To benchmark the abilities of the AnlgModel we apply it to seasonal cyclone activity forecasts in the North Atlantic and Northwest Pacific. The AnlgModel demonstrates competitive hindcast skills with two operational forecasts and even outperforms these for long lead times.
In the second chapter we comprehend the forecasting strategy of the Anlg-Model. We thereby analyse the analogue selection process for the 2017 North Atlantic and the 2018 Northwest Pacific seasonal cyclone activity. The analysis shows that those climate indices which are known to influence the seasonal cyclone activity, such as the Niño 3.4 SST, are correctly represented among the selected analogues. Furthermore the selected analogues reflect large-scale climate patterns that were identified by expert reports as being determinative for these particular seasons.
In the third chapter we analyse the features that are used by the AnlgModel for its predictions. We therefore inspect the feature relevance (FR). The FR patterns learned by the AnlgModel show a high congruence with the predictor regions used by the operational forecasts. However, the AnlgModel also discovered new features, such as the SST anomaly in the Gulf of Guinea during November. This SST pattern exhibits a remarkably high predictive potential for the upcoming Atlantic hurricane activity.
In the final chapter we investigate potential mechanisms, that link two of these regions with high feature relevance to the Atlantic hurricane activity. We mainly focus on ocean surface transport. The ocean surface flow paths are calculated using Lagrangian particle analysis. We demonstrate that the FR patterns in the region of the Canary islands do not correspond with ocean surface transport. It is instead likely that these FR patterns fingerprint a wind transport of latent heat. The second region to be studied is situated in the Gulf of Guinea. Our analysis shows that the FR patterns seen there do fingerprint ocean surface transport. However, our simulations also show that at least one other mechanism is involved in linking the Gulf of Guinea SST anomaly in November to the hurricane activity of the upcoming season.
In this work the AnlgModel does not only demonstrate its outstanding forecast skills but also shows its capabilities as research tool for detecting oceanic and atmospheric mechanisms.
Nowadays, innovative and entrepreneurial activities and their actors are embedded in interdependent systems to drive joint value creation. Innovation ecosystems and entrepreneurial ecosystems have become established system-level concepts in management research to explain how value transpires between different actors and institutions in distinct contexts. Despite the popularity of the concepts, researchers have critiqued their theoretical depth, conceptual distinctiveness, as well as operationalization and measurement (Autio & Thomas, 2022; Klimas & Czakon, 2022). Furthermore, in light of current-day challenges, research has yet to address how context impacts innovation and entrepreneurial ecosystems and their actors and elements (Wurth et al., 2022).
The aim of this cumulative thesis is to provide a deeper understanding of the conceptualization, operationalization, and measurement of innovation and entrepreneurial ecosystems and investigate how contextual factors can influence the overall ecosystem and its key actors. To this end, bibliometric and empirical-qualitative methods, as well as narrative and systematic literature reviews, are employed. After introducing the research scope and key concepts in Chapter 1, a systematic literature review to operationalize and measure the concept of innovation ecosystems is conducted, and an integrative framework of its composition is introduced in Chapter 2. In Chapter 3, the innovation journal network is outlined by means of science mapping to determine current and emerging research areas characterizing innovation studies. In Chapters 4 and 5, the interplay between the temporal context of the Covid-19 pandemic and the spatial context of entrepreneurial ecosystems is assessed by focusing on the role of organizational resilience and affordances. The findings shed new light on the dynamics and boundaries of entrepreneurial ecosystems as they move between the spatial and digital realm. Building on this, an integrative framework of digital entrepreneurial ecosystems is presented in Chapter 6. The concluding Chapter 7 summarizes my thesis’s conceptual, theoretical, and empirical insights, highlighting implications, limitations, and promising future research avenues.
The findings of this cumulative thesis contribute to the theoretical and conceptual advancement of ecosystems in innovation and entrepreneurship by providing insights into the measurement and operationalization of its elements. Furthermore, the results show that contextual factors, such as crisis events or institutional circumstances, influence innovation and entrepreneurial ecosystems and their actors, calling for a more nuanced consideration of ecosystem configurations and dynamics. By drawing from the theory of affordances, the elements that actually afford value to the actors and how they shift between the physical and digital realm are portrayed. Based on these findings, this thesis introduces novel frameworks and conceptual advancements of the configurations and boundaries of innovation and (digital) entrepreneurial ecosystems, laying the foundation for a renewed understanding of how to design, orchestrate, and evaluate ecosystems today and in the future.