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Since 1980 Iraq passed through various wars and conflicts including Iraq-Iran war, Saddam Hussein’s the Anfals and Halabja campaigns against the Kurds and the killing campaigns against Shiite in 1986, Saddam Hussein’s invasion of Kuwait in August 1990, the Gulf war in 1990, Iraq war in 2003 and the fall of Saddam, the conflicts and chaos in the transmission of power after the death of Saddam, and the war against ISIS . All these wars left severe impacts in most households in Iraq; on women and children in particular.
The consequences of such long wars could be observed in all sectors including economic, social, cultural and religious sectors. The social structure, norms and attitudes are intensely affected. Many women specifically divorced women found them-selves in challenging different difficulties such as social as well as economic situations. Thus the divorced women in Iraqi Kurdistan are the focus of this research.
Considering the fact that there is very few empirical researches on this topic, a constructivist grounded theory methodology (CGT) is viewed as reliable in order to come up with a comprehensive picture about the everyday life of divorced women in Iraqi Kurdistan. Data collected in Sulaimani city in Iraqi Kurdistan. The work of Kathy Charmaz was chosen to be the main methodological context of the research and the main data collection method was individual intensive narrative interviews with divorced women.
Women generally and divorced women specifically in Iraqi Kurdistan are living in a patriarchal society that passing through many changes due to the above mentioned wars among many other factors. This research is trying to study the everyday life of divorced women in such situations and the forms of social insecurity they are experiencing. The social institutions starting from the family as a very significant institution for women to the governmental and non-governmental institutions that are working to support women, and the copying strategies, are in focus in this research. The main research argument is that the family is playing ambivalent roles in divorced women’s life. For instance, on one side families are revealed to be an essential source of security to most respondents, on the other side families posed also many threats and restrictions on those women. This argument supported by what called by Suad joseph "the paradox of support and suppression" . Another important finding is that the stat institution(laws , constitutions ,Offices of combating violence against woman and family) are supporting women somehow and offering them protection from the insecurities but it is clear that the existence of the laws does not stop the violence against women in Iraqi Kurdistan, As explained by Pateman because the laws /the contract is a sexual-social contract that upholds the sex rights of males and grants them more privileges than females. The political instability, Tribal social norms also play a major role in influencing the rule of law.
It is noteworthy to refer that analyzing the interviews in this research showed that in spite that divorced women living in insecurities and facing difficulties but most of the respondents try to find a coping strategies to tackle difficult situations and to deal with the violence they face; these strategies are bargaining, sometimes compromising or resisting …etc. Different theories used to explain these coping strategies such as bargaining with patriarchy. Kandiyoti who stated that women living under certain restraints struggle to find way and strategies to enhance their situations. The research finding also revealed that the western liberal feminist view of agency is limited this is agree with Saba Mahmood and what she explained about Muslim women agency. For my respondents, who are divorced women, their agency reveals itself in different ways, in resisting or compromising with or even obeying the power of male relatives, and the normative system in the society. Agency is also explained the behavior of women contacting formal state institutions in cases of violence like the police or Offices of combating violence against woman and family.
Plasmonic metal nanostructures can be tuned to efficiently interact with light, converting the photons into energetic charge carriers and heat. Therefore, the plasmonic nanoparticles such as gold and silver nanoparticles act as nano-reactors, where the molecules attached to their surfaces benefit from the enhanced electromagnetic field along with the generated energetic charge carriers and heat for possible chemical transformations. Hence, plasmonic chemistry presents metal nanoparticles as a unique playground for chemical reactions on the nanoscale remotely controlled by light. However, defining the elementary concepts behind these reactions represents the main challenge for understanding their mechanism in the context of the plasmonically assisted chemistry.
Surface-enhanced Raman scattering (SERS) is a powerful technique employing the plasmon-enhanced electromagnetic field, which can be used for probing the vibrational modes of molecules adsorbed on plasmonic nanoparticles. In this cumulative dissertation, I use SERS to probe the dimerization reaction of 4-nitrothiophenol (4-NTP) as a model example of plasmonic chemistry. I first demonstrate that plasmonic nanostructures such as gold nanotriangles and nanoflowers have a high SERS efficiency, as evidenced by probing the vibrations of the rhodamine dye R6G and the 4-nitrothiophenol 4-NTP. The high signal enhancement enabled the measurements of SERS spectra with a short acquisition time, which allows monitoring the kinetics of chemical reactions in real time.
To get insight into the reaction mechanism, several time-dependent SERS measurements of the 4-NTP have been performed under different laser and temperature conditions. Analysis of the results within a mechanistic framework has shown that the plasmonic heating significantly enhances the reaction rate, while the reaction is probably initiated by the energetic electrons. The reaction was shown to be intensity-dependent, where a certain light intensity is required to drive the reaction. Finally, first attempts to scale up the plasmonic catalysis have been performed showing the necessity to achieve the reaction threshold intensity. Meanwhile, the induced heat needs to quickly dissipate from the reaction substrate, since otherwise the reactants and the reaction platform melt. This study might open the way for further work seeking the possibilities to quickly dissipate the plasmonic heat generated during the reaction and therefore, scaling up the plasmonic catalysis.
The goal of this thesis is to broaden the empirical basis for a better, comprehensive understanding
of massive star evolution, star formation and feedback at low metallicity. Low metallicity massive stars are a key to understand the early universe. Quantitative information on metal-poor massive stars was sparse before. The quantitative spectroscopic studies of massive star populations associated with large-scale ISM structures were not performed at low metallicity before, but are important to investigate star-formation histories and feedback in detail. Much of this work relies on spectroscopic observations with VLT-FLAMES of ~500 OB stars in the Magellanic Clouds. When available, the optical spectroscopy was complemented by UV spectra from the HST, IUE, and FUSE archives. The two representative young stellar populations that have been studied are associated with the superbubble N 206 in the Large Magellanic Cloud (LMC) and with the supergiant shell SMC-SGS 1 in the Wing of the Small Magellanic Cloud (SMC), respectively. We performed spectroscopic analyses of the massive stars using the nonLTE Potsdam Wolf-Rayet (PoWR) model atmosphere code. We estimated the stellar, wind, and feedback parameters of the individual massive stars and established their statistical distributions.
The mass-loss rates of N206 OB stars are consistent with theoretical expectations for LMC metallicity. The most massive and youngest stars show nitrogen enrichment at their surface and are found to be slower rotators than the rest of the sample. The N 206 complex has undergone star formation episodes since more than 30 Myr, with a current star formation rate higher than average in the LMC. The spatial age distribution of stars across the complex possibly indicates triggered star formation due to the expansion of the superbubble. Three very massive, young Of stars in the region dominate the ionizing and mechanical feedback among hundreds of other OB stars in the sample. The current stellar wind feedback rate from the two WR stars in the complex is comparable to that released by the whole OB sample. We see only a minor fraction of this stellar wind feedback converted into X-ray emission. In this LMC complex, stellar winds and supernovae equally contribute to the total energy feedback, which eventually powered the central superbubble. However, the total energy input accumulated over the time scale of the superbubble significantly exceeds the observed energy content of the complex. The lack of energy along with the morphology of the complex suggests a leakage of hot gas from the superbubble.
With a detailed spectroscopic study of massive stars in SMC-SGS 1, we provide the stellar and wind parameters of a large sample of OB stars at low metallicity, including those in the lower mass-range. The stellar rotation velocities show a broad, tentatively bimodal distribution, with Be stars being among the fastest. A few very luminous O stars are found close to the main sequence, while all other, slightly evolved stars obey a strict luminosity limit. Considering additional massive stars in evolved stages, with published parameters and located all over the SMC, essentially confirms this picture. The comparison with single-star evolutionary tracks suggests a dichotomy in the fate of massive stars in the SMC. Only stars with an initial mass below 30 solar masses seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, more massive stars appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We measured the key parameters of stellar feedback and established the links between the rates of star formation and supernovae. Our study demonstrates that in metal-poor environments stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. We found indications of the stochastic mode of star formation, where the resulting stellar population is fully capable of producing large-scale structures such as the supergiant shell SMC-SGS 1 in the Wing. The low level of feedback in metal-poor stellar populations allows star formation episodes to persist over long timescales.
Our study showcases the importance of quantitative spectroscopy of massive stars with adequate stellar-atmosphere models in order to understand star-formation, evolution, and feedback. The stellar population analyses in the LMC and SMC make us understand that massive stars and their impact can be very different depending on their environment. Obviously, due to their different metallicity, the massive stars in the LMC and the SMC follow different evolutionary paths. Their winds differ significantly, and the key feedback agents are different. As a consequence, the star formation can proceed in different modes.
Objeto de esta investigación es el auge y caída de una legitimación teológica de la poesía que tuvo lugar en el virreinato del Perú entre fines del siglo XVI y la segunda mitad del siglo XVII. Su punto cúlmine está marcado por el surgimiento de una “Academia Antártica” en las primeras décadas del siglo XVII, mientras que su fin, se aprecia a fines del mismo siglo, cuando eruditos de las órdenes religiosas, especialmente Juan de Espinosa y Medrano en sus textos en defensa de la poesía y las ciencias, negaron a la poesía cualquier estatuto teológico, sirviéndose sin embargo de ella para escribir sus sermones y textos. A partir del auge y caída de esta legitimación teológica en el virreinato del Perú, este estudio muestra la existencia de dos movimientos que forman un quiasmo entre una teologización de la poesía y una poetización de la teología, en cuyo centro velado se encuentra en disputa el saber teórico y práctico de la poesía. Lo que está en disputa en este sentido no es la poesía, entendida como una cumbre de las bellas letras, sino la posesión legítima de un modo de lectura analógico y tipológico del orden del universo, fundado en las Sagradas Escrituras y en la historia de la salvación, y un modo poético para doctrinar a todos los miembros de la sociedad virreinal en concordancia con aquel modo de lectura.
In den letzten Jahrzehnten fand auch in der Beschichtungsindustrie ein Umdenken hin zu umweltfreundlicheren Farben und Lacken statt. Allerdings basieren auch neue Lösungen meist nicht auf Biopolymeren und in einem noch geringeren Anteil auf wasserbasierten Beschichtungssystemen aus nachwachsenden Rohstoffen. Dies stellt den Anknüpfungspunkt dieser Arbeit dar, in der untersucht wurde, ob das Biopolymer Stärke das Potenzial zum wasserbasierten Filmbildner für Farben und Lacke besitzt. Dabei müssen angelehnt an etablierte synthetische Marktprodukte die folgenden Kriterien erfüllt werden: Die wässrige Dispersion muss mindestens einen 30%igen Feststoffgehalt haben, bei Raumtemperatur verarbeitet werden können und Viskositäten zwischen 10^2-10^3 mPa·s aufweisen. Die finale Beschichtung muss einen geschlossenen Film bilden und sehr gute Haftfestigkeiten zu einer spezifischen Oberfläche, in dieser Arbeit Glas, besitzen. Als Grundlage für die Modifizierung der Stärke wurde eine Kombination von molekularem Abbau und chemischer Funktionalisierung ausgewählt. Da nicht bekannt war, welchen Einfluss die Stärkeart, die gewählte Abbaureaktion als auch verschiedene Substituenten auf die Dispersionsherstellung und deren Eigenschaften sowie die Beschichtungseigenschaften ausüben könnten, wurden die strukturellen Parameter getrennt voneinander untersucht.
Das erste Themengebiet beinhaltete den oxidativen Abbau von Kartoffel- und Palerbsenstärke mittels des Hypochlorit-Abbaus (OCl-) und des ManOx-Abbaus (H2O2, KMnO4). Mit beiden Abbaureaktionen konnten vergleichbare gewichtsmittlere Molmassen (Mw) von 2·10^5-10^6 g/mol (GPC-MALS) hergestellt werden. Allerdings führten die gewählten Reaktionsbedingungen beim ManOx-Abbau zur Bildung von Gelpartikeln. Diese lagen im µm-Bereich (DLS und Kryo-REM-Messungen) und hatten zur Folge, dass die ManOx-Proben deutlich erhöhte Viskositäten (c: 7,5 %; 9-260 mPa·s) im Vergleich zu den OCl--Proben (4-10 mPa·s) bei scherverdünnendem Verhalten besaßen und die Eigenschaften von viskoelastischen Gelen (G‘ > G‘‘) zeigten. Des Weiteren wiesen sie reduzierte Heißwasserlöslichkeiten (95 °C, vorrangig: 70-99 %) auf. Der OCl--Abbau führte zu hydrophileren (Carboxylgruppengehalt bis zu 6,1 %; ManOx: bis zu 3,1 %), nach 95 °C-Behandlung vollständig wasserlöslichen abgebauten Stärken, die ein Newtonsches Fließverhalten mit Eigenschaften einer viskoelastischen Flüssigkeit (G‘‘ > G‘) hatten. Die OCl--Proben konnten im Vergleich zu den ManOx-Produkten (10-20 %) zu konzentrierteren Dispersionen (20-40 %) verarbeitet werden, die gleichzeitig die Einschränkung von anwendungsrelevanten Mw auf < 7·10^5 g/mol zuließen (Konzentration sollte > 30 % sein). Außerdem führten nur die OCl--Proben der Kartoffelstärke zu transparenten (alle anderen waren opak) geschlossenen Beschichtungsfilmen. Somit hebt sich die Kombination von OCl--Abbau und Kartoffelstärke mit Hinblick auf die Endanwendung ab.
Das zweite Themengebiet umfasste Untersuchungen zum Einfluss von Ester- und Hydroxyalkylether-Substituenten auf Basis einer industriell abgebauten Kartoffelstärke (Mw: 1,2·10^5 g/mol) vor allem auf die Dispersionsherstellung, die rheologischen Eigenschaften der Dispersionen und die Beschichtungseigenschaften in Kombination mit Glassubstraten. Dazu wurden Ester und Ether mit DS/MS-Werten von 0,07-0,91 synthetisiert. Die Derivate konnten zu wasserbasierten Dispersionen mit Konzentrationen von 30-45 % verarbeitet werden, wobei bei hydrophoberen Modifikaten ein Co-Lösemittel, Diethylenglycolmonobutylether (DEGBE), eingesetzt werden musste. Die Feststoffgehalte sanken dabei für beide Derivatklassen vor allem mit zunehmender Alkylkettenlänge. Die anwendungsrelevanten Viskositäten (323-1240 mPa·s) stiegen auf Grund von Wechselwirkungen tendenziell mit DS/MS und Alkylkettenlänge an. Hinsichtlich der Beschichtungseigenschaften erwiesen sich die Ester vergleichend zu den Ethern als die bevorzugte Substituentenklasse, da nur die Ester geschlossene, defektfreie und mehrheitlich transparente Beschichtungsfilme bildeten, die exzellente bis sehr gute Haftfestigkeiten (ISO Klasse: 0 und 1) auf Glas besaßen. Die Ether bildeten mehrheitlich brüchige Filme. Basierend auf der Kombination der Ergebnisse aus Lösemittelaustausch, den rheologischen Untersuchungen und zusätzlichen Oberflächenspannungsmessungen (30-61 mN/m) konnte geschlossen werden, dass wahrscheinlich fehlende oder schlechte Haftfestigkeiten vorrangig akkumuliertem Wasser in den Beschichtungsfilmen (visuell: trüb oder weiß) geschuldet sind, während die Brüchigkeit vermutlich auf Wechselwirkungen (H-Brücken Wechselwirkungen, hydrophobe Wechselwirkungen) zwischen den Polymeren zurückgeführt werden kann.
Insgesamt scheint die Kombination aus Kartoffelstärke basierend auf dem OCl--Abbau mit Mw < 7·10^5 g/mol und einem Estersubstituenten eine gute Wahl für wasserbasierte Dispersionen mit hohen Feststoffkonzentrationen (> 30 %), guter Filmbildung und exzellenten Haftungen auf Glas zu sein.
Ficción herética
(2019)
La metáfora de la «isla» en la narrativa cubana contemporánea engloba toda una serie de complejidades simbólicas dependientes de la vivencia del espacio y el tiempo. Su potencial visual se manifiesta u oculta las propias vivencias insulares de los escritores cubanos. En los últimos 30 años en Cuba, los fenómenos políticos económicos y sociales han modificado categóricamente la percepción y la configuración del plano social e individual frente a las exigencias globales (Fornet 2006, Rojas 1999, 2002, 2006). Se ha confirmado una sensación de acinesia e ingravidez (Casamayor 2013) y se ha presentado una actitud «herética» por parte de los narradores cubanos, quienes se confrontan con las ideas de la postmodernidad, lo postsoviético o postutópico, reafirmando así una sensibilidad presentista (Guerrero 2016). Estos autores presentan resonancias y reivindicaciones de los imaginarios insulares de autores y de tradiciones estéticas dentro y fuera de la isla como José Lezama Lima, Virgilio Piñera, Guillermo Cabrera Infante, Reinaldo Arenas y Severo Sarduy). El análisis de las écfrasis insulares permite examinar las dinámicas de representación y de sentido: disimulación: la disimulación, la anamorfosis y la trompe l’oeil (Sarduy 1981). La novela Tuyo es el reino (1998) de Abilio Estévez es un modelo desde el que se localizará las relaciones de sentido entre canon literario y los referentes socioculturales de las variaciones somatopológicas de la isla en la narrativa cubana actual: Ena Lucía Portela, Atilio Caballero, Antonio José Ponte, Daniel Díaz Mantilla, Emerio Medina, Orlando Luis Pardo, Anisley Negrin y Ahmel Echeverría, entre otros.
The current thesis examined how second language (L2) speakers of German predict upcoming input during language processing. Early research has shown that the predictive abilities of L2 speakers relative to L1 speakers are limited, resulting in the proposal of the Reduced Ability to Generate Expectations (RAGE) hypothesis. Considering that prediction is assumed to facilitate language processing in L1 speakers and probably plays a role in language learning, the assumption that L1/L2 differences can be explained in terms of different processing mechanisms is a particularly interesting approach. However, results from more recent studies on the predictive processing abilities of L2 speakers have indicated that the claim of the RAGE hypothesis is too broad and that prediction in L2 speakers could be selectively limited. In the current thesis, the RAGE hypothesis was systematically put to the test.
In this thesis, German L1 and highly proficient late L2 learners of German with Russian as L1 were tested on their predictive use of one or more information sources that exist as cues to sentence interpretation in both languages, to test for selective limits. The results showed that, in line with previous findings, L2 speakers can use the lexical-semantics of verbs to predict the upcoming noun. Here the level of prediction was more systematically controlled for than in previous studies by using verbs that restrict the selection of upcoming nouns to the semantic category animate or inanimate. Hence, prediction in L2 processing is possible. At the same time, this experiment showed that the L2 group was slower/less certain than the L1 group. Unlike previous studies, the experiment on case marking demonstrated that L2 speakers can use this morphosyntactic cue for prediction. Here, the use of case marking was tested by manipulating the word order (Dat > Acc vs. Acc > Dat) in double object constructions after a ditransitive verb. Both the L1 and the L2 group showed a difference between the two word order conditions that emerged within the critical time window for an anticipatory effect, indicating their sensitivity towards case. However, the results for the post-critical time window pointed to a higher uncertainty in the L2 group, who needed more time to integrate incoming information and were more affected by the word order variation than the L1 group, indicating that they relied more on surface-level information. A different cue weighting was also found in the experiment testing whether participants predict upcoming reference based on implicit causality information. Here, an additional child L1 group was tested, who had a lower memory capacity than the adult L2 group, as confirmed by a digit span task conducted with both learner groups. Whereas the children were only slightly delayed compared to the adult L1 group and showed the same effect of condition, the L2 speakers showed an over-reliance on surface-level information (first-mention/subjecthood). Hence, the pattern observed resulted more likely from L1/L2 differences than from resource deficits.
The reviewed studies and the experiments conducted show that L2 prediction is affected by a range of factors. While some of the factors can be attributed to more individual differences (e.g., language similarity, slower processing) and can be interpreted by L2 processing accounts assuming that L1 and L2 processing are basically the same, certain limits are better explained by accounts that assume more substantial L1/L2 differences. Crucially, the experimental results demonstrate that the RAGE hypothesis should be refined: Although prediction as a fast-operating mechanism is likely to be affected in L2 speakers, there is no indication that prediction is the dominant source of L1/L2 differences. The results rather demonstrate that L2 speakers show a different weighting of cues and rely more on semantic and surface-level information to predict as well as to integrate incoming information.
Binaries play an important role in observational and theoretical astrophysics. Since the mass and the chemical composition are key ingredients for stellar evolution, high-resolution spectroscopy is an important and necessary tool to derive those parameters to high confidence in binaries. This involves carefully measured orbital motion by the determination of radial velocity (RV) shifts and sophisticated techniques to derive the abundances of elements within the stellar atmosphere.
A technique superior to conventional cross-correlation methods to determine RV shifts in known as spectral disentangling. Hence, a major task of this thesis was the design of a sophisticated software package for this approach. In order to investigate secondary effects, such as flux and line-profile variations, imprinting changes on the spectrum the behavior of spectral disentangling on such variability is a key to understand the derived values, to improve them, and to get information about the variability itself. Therefore, the spectral disentangling code presented in this thesis and available to the community combines multiple advantages: separation of the spectra for detailed chemical analysis, derivation of orbital elements, derivation of individual RVs in order to investigate distorted systems (either by third body interaction or relativistic effects), the suppression of telluric contaminations, the derivation of variability, and the possibility to apply the technique to eclipsing binaries (important for orbital inclination) or in general to systems that undergo flux-variations.
This code in combination with the spectral synthesis codes MOOG and SME was used in order to derive the carbon 12C/13C isotope ratio (CIR) of the benchmark binary Capella. The observational result will be set into context with theoretical evolution by the use of MESA models and resolves the discrepancy of theory and observations existing since the first measurement of Capella's CIR in 1976.
The spectral disentangling code has been made available to the community and its applicability to completely different behaving systems, Wolf-Rayet stars, have also been investigated and resulted in a published article.
Additionally, since this technique relies strongly on data quality, continues development of scientific instruments to achieve best observational data is of great importance in observational astrophysics. That is the reason why there has also been effort in astronomical instrumentation during the work on this thesis.
Light-switchable proteins are being used increasingly to understand and manipulate complex molecular systems. The success of this approach has fueled the development of tailored photo-switchable proteins, to enable targeted molecular events to be studied using light. The development of novel photo-switchable tools has to date largely relied on rational design. Complementing this approach with directed evolution would be expected to facilitate these efforts. Directed evolution, however, has been relatively infrequently used to develop photo-switchable proteins due to the challenge presented by high-throughput evaluation of switchable protein activity. This thesis describes the development of two genetic circuits that can be used to evaluate libraries of switchable proteins, enabling optimization of both the on- and off-states. A screening system is described, which permits detection of DNA-binding activity based on conditional expression of a fluorescent protein. In addition, a tunable selection system is presented, which allows for the targeted selection of protein-protein interactions of a desired affinity range. This thesis additionally describes the development and characterization of a synthetic protein that was designed to investigate chromophore reconstitution in photoactive yellow protein (PYP), a promising scaffold for engineering photo-controlled protein tools.
Vom Monomer zum Glykopolymer
(2019)
Glykopolymere sind synthetische und natürlich vorkommende Polymere, die eine Glykaneinheit in der Seitenkette des Polymers tragen. Glykane sind durch die Glykan-Protein-Wechselwirkung verantwortlich für viele biologische Prozesse. Die Beteiligung der Glykanen in diesen biologischen Prozessen ermöglicht das Imitieren und Analysieren der Wechselwirkungen durch geeignete Modellverbindungen, z.B. der Glykopolymere. Dieses System der Glykan-Protein-Wechselwirkung soll durch die Glykopolymere untersucht und studiert werden, um die spezifische und selektive Bindung der Proteine an die Glykopolymere nachzuweisen. Die Proteine, die in der Lage sind, Kohlenhydratstrukturen selektiv zu binden, werden Lektine genannt.
In dieser Dissertationsarbeit wurden verschiedene Glykopolymere synthetisiert. Dabei sollte auf einen effizienten und kostengünstigen Syntheseweg geachtet werden.
Verschiedene Glykopolymere wurden durch funktionalisierte Monomere mit verschiedenen Zuckern, wie z.B. Mannose, Laktose, Galaktose oder N-Acetyl-Glukosamin als funktionelle Gruppe, hergestellt. Aus diesen funktionalisierten Glykomonomeren wurden über ATRP und RAFT-Polymerisation Glykopolymere synthetisiert.
Die erhaltenen Glykopolymere wurden in Diblockcopolymeren als hydrophiler Block angewendet und die Selbstassemblierung in wässriger Lösung untersucht. Die Polymere formten in wässriger Lösung Mizellen, bei denen der Zuckerblock an der Oberfläche der Mizellen sitzt. Die Mizellen wurden mit einem hydrophoben Fluoreszenzfarbstoff beladen, wodurch die CMC der Mizellenbildung bestimmt werden konnte.
Außerdem wurden die Glykopolymere als Oberflächenbeschichtung über „Grafting from“ mit SI-ATRP oder über „Grafting to“ auf verschiedene Oberflächen gebunden. Durch die glykopolymerbschichteten Oberflächen konnte die Glykan Protein Wechselwirkung über spektroskopische Messmethoden, wie SPR- und Mikroring Resonatoren untersucht werden. Hierbei wurde die spezifische und selektive Bindung der Lektine an die Glykopolymere nachgewiesen und die Bindungsstärke untersucht.
Die synthetisierten Glykopolymere könnten durch Austausch der Glykaneinheit für andere Lektine adressierbar werden und damit ein weites Feld an anderen Proteinen erschließen. Die bioverträglichen Glykopolymere wären alternativen für den Einsatz in biologischen Prozessen als Transporter von Medikamenten oder Farbstoffe in den Körper. Außerdem könnten die funktionalisierten Oberflächen in der Diagnostik zum Erkennen von Lektinen eingesetzt werden. Die Glykane, die keine selektive und spezifische Bindung zu Proteinen eingehen, könnten als antiadsorptive Oberflächenbeschichtung z.B. in der Zellbiologie eingesetzt werden.
Sinkholes and depressions are typical landforms of karst regions. They pose a considerable natural hazard to infrastructure, agriculture, economy and human life in affected areas worldwide. The physio-chemical processes of sinkholes and depression formation are manifold, ranging from dissolution and material erosion in the subsurface to mechanical subsidence/failure of the overburden. This thesis addresses the mechanisms leading to the development of sinkholes and depressions by using complementary methods: remote sensing, distinct element modelling and near-surface geophysics.
In the first part, detailed information about the (hydro)-geological background, ground structures, morphologies and spatio-temporal development of sinkholes and depressions at a very active karst area at the Dead Sea are derived from satellite image analysis, photogrammetry and geologic field surveys. There, clusters of an increasing number of sinkholes have been developing since the 1980s within large-scale depressions and are distributed over different kinds of surface materials: clayey mud, sandy-gravel alluvium and lacustrine evaporites (salt). The morphology of sinkholes differs depending in which material they form: Sinkholes in sandy-gravel alluvium and salt are generally deeper and narrower than sinkholes in the interbedded evaporite and mud deposits. From repeated aerial surveys, collapse precursory features like small-scale subsidence, individual holes and cracks are identified in all materials. The analysis sheds light on the ongoing hazardous subsidence process, which is driven by the base-level fall of the Dead Sea and by the dynamic formation of subsurface water channels.
In the second part of this thesis, a novel, 2D distinct element geomechanical modelling approach with the software PFC2D-V5 to simulating individual and multiple cavity growth and sinkhole and large-scale depression development is presented. The approach involves a stepwise material removal technique in void spaces of arbitrarily shaped geometries and is benchmarked by analytical and boundary element method solutions for circular cavities. Simulated compression and tension tests are used to calibrate model parameters with bulk rock properties for the materials of the field site. The simulations show that cavity and sinkhole evolution is controlled by material strength of both overburden and cavity host material, the depth and relative speed of the cavity growth and the developed stress pattern in the subsurface. Major findings are: (1) A progressively deepening differential subrosion with variable growth speed yields a more fragmented stress pattern with stress interaction between the cavities. It favours multiple sinkhole collapses and nesting within large-scale depressions. (2) Low-strength materials do not support large cavities in the material removal zone, and subsidence is mainly characterised by gradual sagging into the material removal zone with synclinal bending. (3) High-strength materials support large cavity formation, leading to sinkhole formation by sudden collapse of the overburden. (4) Large-scale depression formation happens either by coalescence of collapsing holes, block-wise brittle failure, or gradual sagging and lateral widening.
The distinct element based approach is compared to results from remote sensing and geophysics at the field site. The numerical simulation outcomes are generally in good agreement with derived morphometrics, documented surface and subsurface structures as well as seismic velocities. Complementary findings on the subrosion process are provided from electric and seismic measurements in the area.
Based on the novel combination of methods in this thesis, a generic model of karst landform evolution with focus on sinkhole and depression formation is developed. A deepening subrosion system related to preferential flow paths evolves and creates void spaces and subsurface conduits. This subsequently leads to hazardous subsidence, and the formation of sinkholes within large-scale depressions. Finally, a monitoring system for shallow natural hazard phenomena consisting of geodetic and geophysical observations is proposed for similarly affected areas.
Seit 2003 hat sich das politische Bild des Irak stark verändert. Dadurch begann der Prozess der Neugestaltung der irakischen Rechtsordnung. Die irakische Verfassung von 2005 legt erstmalig in der Geschichte des Irak den Islam und die Demokratie als zwei nebeneinander zu beachtende Grundprinzipien bei der Gesetzgebung fest. Trotz dieser signifikanten Veränderung im irakischen Rechtssystem und erheblicher Entwicklungen im internationalen Privat- und Zivilverfahrensrecht (IPR/IZVR) im internationalen Vergleich gilt die hauptsächlich im irakischen Zivilgesetzbuch (ZGB) von 1951 enthaltene gesetzliche Regelung des IPR/IZVR im Irak weiterhin. Deshalb entstand diese Arbeit für eine Reformierung des irakischen IPR/IZVR.
Die Arbeit gilt als erste umfassende wissenschaftliche Untersuchung, die sich mit dem jetzigen Inhalt und der zukünftigen Reformierung des irakischen internationalen Privatrecht- und Zivilverfahrensrechts (IPR/IZVR) beschäftigt.
Die Verfasserin vermittelt einen Gesamtüberblick über das jetzt geltende irakische internationale Privat- und Zivilverfahrensrecht mit gelegentlicher punktueller und stichwortartiger Heranziehung des deutschen, islamischen, türkischen und tunesischen Rechts, zeigt dessen Schwachstellen auf und unterbreitet entsprechende Reformvorschläge.
Wegen der besonderen Bedeutung des internationalen Vertragsrechts für die Wirtschaft im Irak und auch zum Teil für Deutschland gibt die Verfasserin einen genaueren Überblick über das irakische internationale Vertragsrecht und bekräftigt gleichzeitig dessen Reformbedürftigkeit.
Die Darstellung der wichtigen Entwicklungen im deutsch-europäischen, im traditionellen islamischen Recht und im türkischen und tunesischen internationalen Privat- und Zivilverfahrensrecht im zweiten Kapitel dienen als Grundlage, auf die bei der Reformierung des irakischen IPR/ IZVR zurück gegriffen werden kann. Da die Kenntnisse des islamischen Rechts nicht zwingend zum Rechtsstudium gehören, wird das islamische Recht dazu in Bezug auf seine Entstehung und die Rechtsquellen dargestellt.
Am Ende der Arbeit wird ein Entwurf eines föderalen Gesetzes zum internationalen Privatrecht im Irak katalogisiert, der sich im Rahmen der irakischen Verfassung gleichzeitig mit dem Islam und der Demokratie vereinbaren lässt.
Predators can have numerical and behavioral effects on prey animals. While numerical effects are well explored, the impact of behavioral effects is unclear. Furthermore, behavioral effects are generally either analyzed with a focus on single individuals or with a focus on consequences for other trophic levels. Thereby, the impact of fear on the level of prey communities is overlooked, despite potential consequences for conservation and nature management. In order to improve our understanding of predator-prey interactions, an assessment of the consequences of fear in shaping prey community structures is crucial.
In this thesis, I evaluated how fear alters prey space use, community structure and composition, focusing on terrestrial mammals. By integrating landscapes of fear in an existing individual-based and spatially-explicit model, I simulated community assembly of prey animals via individual home range formation. The model comprises multiple hierarchical levels from individual home range behavior to patterns of prey community structure and composition. The mechanistic approach of the model allowed for the identification of underlying mechanism driving prey community responses under fear.
My results show that fear modified prey space use and community patterns. Under fear, prey animals shifted their home ranges towards safer areas of the landscape. Furthermore, fear decreased the total biomass and the diversity of the prey community and reinforced shifts in community composition towards smaller animals. These effects could be mediated by an increasing availability of refuges in the landscape. Under landscape changes, such as habitat loss and fragmentation, fear intensified negative effects on prey communities. Prey communities in risky environments were subject to a non-proportional diversity loss of up to 30% if fear was taken into account. Regarding habitat properties, I found that well-connected, large safe patches can reduce the negative consequences of habitat loss and fragmentation on prey communities. Including variation in risk perception between prey animals had consequences on prey space use. Animals with a high risk perception predominantly used safe areas of the landscape, while animals with a low risk perception preferred areas with a high food availability. On the community level, prey diversity was higher in heterogeneous landscapes of fear if individuals varied in their risk perception compared to scenarios in which all individuals had the same risk perception.
Overall, my findings give a first, comprehensive assessment of the role of fear in shaping prey communities. The linkage between individual home range behavior and patterns at the community level allows for a mechanistic understanding of the underlying processes. My results underline the importance of the structure of the landscape of fear as a key driver of prey community responses, especially if the habitat is threatened by landscape changes. Furthermore, I show that individual landscapes of fear can improve our understanding of the consequences of trait variation on community structures. Regarding conservation and nature management, my results support calls for modern conservation approaches that go beyond single species and address the protection of biotic interactions.
A contemporary challenge in Ecology and Evolutionary Biology is to anticipate the fate of populations of organisms in the context of a changing world. Climate change and landscape changes due to anthropic activities have been of major concern in the contemporary history. Organisms facing these threats are expected to respond by local adaptation (i.e., genetic changes or phenotypic plasticity) or by shifting their distributional range (migration). However, there are limits to their responses. For example, isolated populations will have more difficulties in developing adaptive innovations by means of genetic changes than interconnected metapopulations. Similarly, the topography of the environment can limit dispersal opportunities for crawling organisms as compared to those that rely on wind. Thus, populations of species with different life history strategy may differ in their ability to cope with changing environmental conditions. However, depending on the taxon, empirical studies investigating organisms’ responses to environmental change may become too complex, long and expensive; plus, complications arising from dealing with endangered species. In consequence, eco-evolutionary modeling offers an opportunity to overcome these limitations and complement empirical studies, understand the action and limitations of underlying mechanisms, and project into possible future scenarios. In this work I take a modeling approach and investigate the effect and relative importance of evolutionary mechanisms (including phenotypic plasticity) on the ability for local adaptation of populations with different life strategy experiencing climate change scenarios. For this, I performed a review on the state of the art of eco-evolutionary Individual-Based Models (IBMs) and identify gaps for future research. Then, I used the results from the review to develop an eco-evolutionary individual-based modeling tool to study the role of genetic and plastic mechanisms in promoting local adaption of populations of organisms with different life strategies experiencing scenarios of climate change and environmental stochasticity. The environment was simulated through a climate variable (e.g., temperature) defining a phenotypic optimum moving at a given rate of change. The rate of change was changed to simulate different scenarios of climate change (no change, slow, medium, rapid climate change). Several scenarios of stochastic noise color resembling different climatic conditions were explored. Results show that populations of sexual species will rely mainly on standing genetic variation and phenotypic plasticity for local adaptation. Population of species with relatively slow growth rate (e.g., large mammals) – especially those of small size – are the most vulnerable, particularly if their plasticity is limited (i.e., specialist species). In addition, whenever organisms from these populations are capable of adaptive plasticity, they can buffer fitness losses in reddish climatic conditions. Likewise, whenever they can adjust their plastic response (e.g., bed-hedging strategy) they will cope with bluish environmental conditions as well. In contrast, life strategies of high fecundity can rely on non-adaptive plasticity for their local adaptation to novel environmental conditions, unless the rate of change is too rapid. A recommended management measure is to guarantee interconnection of isolated populations into metapopulations, such that the supply of useful genetic variation can be increased, and, at the same time, provide them with movement opportunities to follow their preferred niche, when local adaptation becomes problematic. This is particularly important for bluish and reddish climatic conditions, when the rate of change is slow, or for any climatic condition when the level of stress (rate of change) is relatively high.
Einleitung
Die Implantation einer Knie- oder Hüft-Totalendoprothese (TEP) ist eine der häufigsten operativen Eingriffe. Im Anschluss an die Operation und die postoperative Rehabilitation stellt die Bewegungstherapie einen wesentlichen Bestandteil der Behandlung zur Verbesserung der Gelenkfunktion und der Lebensqualität dar. In strukturschwachen Gebieten werden entsprechende Angebote nur in unzureichender Dichte vorgehalten. Zudem zeichnet sich ein flächendeckender Fachkräftemangel im Bereich der Physiotherapie ab. Die Tele-Nachsorge bietet daher einen innovativen Ansatz für die postrehabilitative Versorgung der Patienten. Das Ziel der vorliegenden Untersuchung war die Überprüfung der Wirksamkeit einer interaktiven Tele-Nachsorgeintervention für Patienten mit Knie- oder Hüft-TEP im Vergleich zur herkömmlichen Versorgung (usual care). Dazu wurden die Funktionalität und die berufliche Wiedereingliederung untersucht.
Methode
Zwischen August 2016 und August 2017 wurden 111 Patienten (54,9 ± 6,8 Jahre, 54,3 % weiblich) zu Beginn ihrer stationären Anschlussheilbehandlung nach Implantation einer Knie- oder Hüft-TEP in diese randomisiert, kontrolliert, multizentrische Studie eingeschlossen. Nach Entlassung aus der orthopädischen Anschlussrehabilitation (Baseline) führte die Interventionsgruppe (IG) ein dreimonatiges interaktives Training über ein Telerehabilitationssystem durch. Hierfür erstellte ein betreuender Physiotherapeut einen individuellen Trainingsplan aus 38 Übungen zur Verbesserung der Kraft sowie der posturalen Kontrolle. Zur Anpassung des Trainingsplans übermittelte das System dem Physiotherapeuten Daten zur Quantität sowie zur Qualität des Trainings. Die Kontrollgruppe (KG) konnte die herkömmlichen Versorgungsangebote nutzen. Zur Beurteilung der Wirksamkeit der Intervention wurde die Differenz der Verbesserung im 6MWT zwischen der IG und der KG nach drei Monaten als primärer Endpunkt definiert. Als sekundäre Endpunkte wurden die Return-to-Work-Rate sowie die funktionelle Mobilität mittels des Stair Ascend Tests, des Five-Times-Sit-to-Stand Test und des Timed Up and Go Tests untersucht. Weiterhin wurden die gesundheitsbezogene Lebensqualität mit dem Short-Form 36 (SF-36) und die gelenkbezogenen Einschränkungen mit dem Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) evaluiert. Der primäre und die sekundären Endpunkte wurden anhand von baseline-adjustierten Kovarianzanalysen im intention-to-treat-Ansatz ausgewertet. Zusätzlich wurde die Teilnahme an Nachsorgeangeboten und die Adhärenz der Interventionsgruppe an der Tele-Nachsorge erfasst und evaluiert.
Ergebnisse
Zum Ende der Intervention wiesen beide Gruppen einen statistisch signifikanten Anstieg ihrer 6MWT Strecke auf (p < 0,001). Zu diesem Zeitpunkt legten die Teilnehmer der IG im Mittel 530,8 ± 79,7 m, die der KG 514,2 ± 71,2 m zurück. Dabei betrug die Differenz der Verbesserung der Gehstrecke in der IG 88,3 ± 57,7 m und in der KG 79,6 ± 48,7 m. Damit zeigt der primäre Endpunkt keine signifikanten Gruppenunterschiede (p = 0,951). Bezüglich der beruflichen Wiedereingliederung konnte jedoch eine signifikant höhere Rate in der IG (64,6 % versus 46,2 %; p = 0,014) festgestellt werden. Für die sekundären Endpunkte der funktionellen Mobilität, der Lebensqualität und der gelenkbezogenen Beschwerden belegen die Ergebnisse eine Gleichwertigkeit beider Gruppen zum Ende der Intervention.
Schlussfolgerung
Die telemedizinisch assistierte Bewegungstherapie für Knie- oder Hüft-TEP Patienten ist der herkömmlichen Versorgung zur Nachsorge hinsichtlich der erzielten Verbesserungen der funktionellen Mobilität, der gesundheitsbezogenen Lebensqualität und der gelenkbezogenen Beschwerden gleichwertig. In dieser Patientenpopulation ließen sich klinisch relevante Verbesserungen unabhängig von der Form der Bewegungstherapie erzielen. Im Hinblick auf die berufliche Wiedereingliederung zeigte sich eine signifikant höhere Rate in der Interventionsgruppe. Die telemedizinisch assistierte Bewegungstherapie scheint eine geeignete Versorgungsform der Nachsorge zu sein, die orts- und zeitunabhängig durchgeführt werden kann und somit den Bedürfnissen berufstätiger Patienten entgegenkommt und in den Alltag der Patienten integriert werden kann. Die Tele-Nachsorge sollte daher als optionale und komplementäre Form der postrehabilitativen Nachsorge angeboten werden. Auch im Hinblick auf den zunehmenden Fachkräftemangel im Bereich der Physiotherapie und bestehende Versorgungslücken in strukturschwachen Gebieten kann der Einsatz der Tele-Nachsorge innovative und bedarfsgerechte Lösungsansätze bieten.
Supercapacitors are electrochemical energy storage devices with rapid charge/discharge rate and long cycle life. Their biggest challenge is the inferior energy density compared to other electrochemical energy storage devices such as batteries. Being the most widely spread type of supercapacitors, electrochemical double-layer capacitors (EDLCs) store energy by electrosorption of electrolyte ions on the surface of charged electrodes. As a more recent development, Na-ion capacitors (NICs) are expected to be a more promising tactic to tackle the inferior energy density due to their higher-capacity electrodes and larger operating voltage. The charges are simultaneously stored by ion adsorption on the capacitive-type cathode surface and via faradic process in the battery-type anode, respectively. Porous carbon electrodes are of great importance in these devices, but the paramount problems are the facile synthetic routes for high-performance carbons and the lack of fundamental understanding of the energy storage mechanisms. Therefore, the aim of the present dissertation is to develop novel synthetic methods for (nitrogen-doped) porous carbon materials with superior performance, and to reveal a deeper understanding energy storage mechanisms of EDLCs and NICs.
The first part introduces a novel synthetic method towards hierarchical ordered meso-microporous carbon electrode materials for EDLCs. The large amount of micropores and highly ordered mesopores endow abundant sites for charge storage and efficient electrolyte transport, respectively, giving rise to superior EDLC performance in different electrolytes. More importantly, the controversial energy storage mechanism of EDLCs employing ionic liquid (IL) electrolytes is investigated by employing a series of porous model carbons as electrodes. The results not only allow to conclude on the relations between the porosity and ion transport dynamics, but also deliver deeper insights into the energy storage mechanism of IL-based EDLCs which is different from the one usually dominating in solvent-based electrolytes leading to compression double-layers.
The other part focuses on anodes of NICs, where novel synthesis of nitrogen-rich porous carbon electrodes and their sodium storage mechanism are investigated. Free-standing fibrous nitrogen-doped carbon materials are synthesized by electrospinning using the nitrogen-rich monomer (hexaazatriphenylene-hexacarbonitrile, C18N12) as the precursor followed by condensation at high temperature. These fibers provide superior capacity and desirable charge/discharge rate for sodium storage. This work also allows insights into the sodium storage mechanism in nitrogen-doped carbons. Based on this mechanism, further optimization is done by designing a composite material composed of nitrogen-rich carbon nanoparticles embedded in conductive carbon matrix for a better charge/discharge rate. The energy density of the assembled NICs significantly prevails that of common EDLCs while maintaining the high power density and long cycle life.
Die vorliegende Dissertation zielt generell darauf ab, die Anwendung der dialektischen Methodologie auf den Bereich der Sprachphilosophie zu rechtfertigen und eine systematische Bearbeitung eines begrenzten Teils der Sprachphilosophie mithilfe der Dialektik durchzuführen. Um diese Herangehensweise, die in der Forschung kaum oder gar nicht vertreten ist, aufzuklären und festzustellen, werde ich zuerst auf die philosophischen Überlegungen von zwei Autoren zurückgreifen: Hegel und Wittgenstein.
Hegel und Wittgenstein sind, auf den ersten Blick, Autoren, die kaum Gemeinsamkeiten haben, außer dass sie sich beide mit der Philosophie als Fach beschäftigt und unvermeidlich ein gemeinschaftliches Thema, die Sprache, behandelt haben, wobei jedoch weder eine inhaltliche noch eine methodologische Verbindung hervorgehoben werden könnte. Die erste Voraussetzung dieser Dissertation, in Bezug auf die Geschichte der Idee, besteht darin, darauf hinzudeuten, dass der hegelsche Geistesbegriff und Wittgensteins Lebensform zwei Ansätze und Resultat einer philosophischen Bemühung sind, die gemeinsam die notwendige Auflösung bzw. Überwindung skeptischer Argumentation vornehmen. Tatsächlich hat Wittgenstein in seinen Philosophischen Untersuchungen eine Argumentation entwickelt, die als „Paradox des Regelfolgens“ bezeichnet und in der sekundären Literatur (hauptsächlich bei Kripke) als eine Art skeptische Argumentation betrachtet wurde. Demnach wird Wittgensteins Theorie der Sprache entweder als eine Auflösung dieses Skeptizismus oder einfach als ein skeptischer Text selbst ausgelegt (Brandom). Das erste Ziel meiner Dissertation besteht darin, zu zeigen, dass dieses Paradox als skeptische Argumentation allerdings unvollständig geblieben ist dass dieses Paradox als der erster entscheidender Moment zu der höchsten Form der skeptischen Herausforderung, der Antinomie, betrachtet werden kann. Eine vollständige skeptische Argumentation heißt, dass die alleinige Auflösung des Paradoxes, der Dispositionalismus und die Negation dieser Theorie, beide beweisbar sind. Ich werde also versuchen, aus der in den PU dargestellten Auflösung des Paradoxes des Regelfolgens die Vervollständigung einer Antinomie des Begriffes der Normativität in Bezug auf die Sprachregeln festzulegen, ähnlich der von Kant entwickelten kosmologischen Antinomie (Thesis cum Antithesis). Das zweite Ziel meiner Dissertation besteht folglich darin, zu zeigen, 1. dass die kantische Auflösung der Antinomie unwirksam bezüglich der Antinomie der Normativität ist, 2. dass diese Antinomie eine notwendige Auseinandersetzung mit einem radikalen Skeptizismus bedeutet und dass wir logisch gezwungen sind, nicht nur irgendeine Theorie der Sprachphilosophie neu zu bestimmen, sondern unsere Methodologie – das heißt die Anwendung der üblichen Normen der Rationalität – selbst grundsätzlich tiefer gehend in Frage zu stellen, und 3. dass die hegelsche Dialektik sich als die methodologische Auflösung einer solchen radikalen skeptischen Herausforderung bzw. als die Auflösung einer Antinomie überhaupt ergibt. Anlässlich dieser methodologischen Revidierung wird auf die hegelsche Dialektik zurückgegriffen.
Dennoch begrenzt sich der Zweck dieser Dissertation nicht darauf, eine Interpretation von Hegels Dialektik oder eine Überwindung von Wittgensteins Lebensform darzustellen, vielmehr geht es darum, auf die Problematik und die Grundsätze des Begriffs der Lebensform bzw. des theoretischen Geistes zurückzugreifen und kraft Hegels Dialektik darüber hinauszuführen, um den Platz und die Funktion der Sprache besser zu verstehen. Diese Arbeit erfolgt vielmehr im Rahmen eines wissenschaftlichen Projekts, oder anders gesagt, sie nutzt die methodologischen Resultate von zwei Autoren der Philosophie, um ein wissenschaftliches Programm vorzustellen. Der Anspruch dieser Arbeit ist dementsprechend, durch das Zurückgreifen auf Hegels Dialektik eine neue Erkenntnis über die Sprache zu gewinnen, wobei die beiden kontradiktorischen Momente der Kognition – die Normativität, die durch das Bewusstsein erfolgt und diejenige, die durch Dispositionen erfolgt –, konstruktiv verbinden sind. Der konkrete Gewinn dieser Methodologie ist es demnach, eine Sprachphilosophie überhaupt als System festlegen zu können, ein System, das es ermöglicht, sprachliche Phänomene in all ihren Aspekten in kohärenter Weise zu fassen. Inhaltlich betrachtet zielt dieses Programm darauf ab, die allgemeine Stufe des Begriffs der Sprache als Moment des Begriffs des Geistes dialektisch abzuleiten, d. h. den richtigen Sinn der Sprache festzulegen. Eine vollständige Bearbeitung der Sprachphilosophie mithilfe der Dialektik konnte ich allerdings nicht durchführen, und der Umfang der mithilfe der Dialektik hergeleiteten Sprachkategorien begrenzt sich auf die Lehre der Einbildungskraft, die die Lehre der allgemeinen Semiologie und der Grammatik einschließt.
The Central Andes host large reserves of base and precious metals. The region represented, in 2017, an important part of the worldwide mining activity. Three principal types of deposits have been identified and studied: 1) porphyry type deposits extending from central Chile and Argentina to Bolivia, and Northern Peru, 2) iron oxide-copper-gold (IOCG) deposits, extending from central Peru to central Chile, and 3) epithermal tin polymetallic deposits extending from Southern Peru to Northern Argentina, which compose a large part of the deposits of the Bolivian Tin Belt (BTB). Deposits in the BTB can be divided into two major types: (1) tin-tungsten-zinc pluton-related polymetallic deposits, and (2) tin-silver-lead-zinc epithermal polymetallic vein deposits.
Mina Pirquitas is a tin-silver-lead-zinc epithermal polymetallic vein deposit, located in north-west Argentina, that used to be one of the most important tin-silver producing mine of the country. It was interpreted to be part of the BTB and it shares similar mineral associations with southern pluton related BTB epithermal deposits. Two major mineralization events related to three pulses of magmatic fluids mixed with meteoric water have been identified. The first event can be divided in two stages: 1) stage I-1 with quartz, pyrite, and cassiterite precipitating from fluids between 233 and 370 °C and salinity between 0 and 7.5 wt%, corresponding to a first pulse of fluids, and 2) stage I-2 with sphalerite and tin-silver-lead-antimony sulfosalts precipitating from fluids between 213 and 274 °C with salinity up to 10.6 wt%, corresponding to a new pulse of magmatic fluids in the hydrothermal system. The mineralization event II deposited the richest silver ores at Pirquitas. Event II fluids temperatures and salinities range between 190 and 252 °C and between 0.9 and 4.3 wt% respectively. This corresponds to the waning supply of magmatic fluids. Noble gas isotopic compositions and concentrations in ore-hosted fluid inclusions demonstrate a significant contribution of magmatic fluids to the Pirquitas mineralization although no intrusive rocks are exposed in the mine area.
Lead and sulfur isotopic measurements on ore minerals show that Pirquitas shares a similar signature with southern pluton related polymetallic deposits in the BTB. Furthermore, the major part of the sulfur isotopic values of sulfide and sulfosalt minerals from Pirquitas ranges in the field for sulfur derived from igneous rocks. This suggests that the main contribution of sulfur to the hydrothermal system at Pirquitas is likely to be magma-derived. The precise age of the deposit is still unknown but the results of wolframite dating of 2.9 ± 9.1 Ma and local structural observations suggest that the late mineralization event is younger than 12 Ma.
Predation drives coexistence, evolution and population dynamics of species in food webs, and has strong impacts on related ecosystem functions (e.g. primary production). The effect of predation on these processes largely depends on the trade-offs between functional traits in the predator and prey community. Trade-offs between defence against predation and competitive ability, for example, allow for prey speciation and predator-mediated coexistence of prey species with different strategies (defended or competitive), which may stabilize the overall food web dynamics. While the importance of such trade-offs for coexistence is widely known, we lack an understanding and the empirical evidence of how the variety of differently shaped trade-offs at multiple trophic levels affect biodiversity, trait adaptation and biomass dynamics in food webs. Such mechanistic understanding is crucial for predictions and management decisions that aim to maintain biodiversity and the capability of communities to adapt to environmental change ensuring their persistence.
In this dissertation, after a general introduction to predator-prey interactions and tradeoffs, I first focus on trade-offs in the prey between qualitatively different types of defence (e.g. camouflage or escape behaviour) and their costs. I show that these different types lead to different patterns of predator-mediated coexistence and population dynamics, by using a simple predator-prey model. In a second step, I elaborate quantitative aspects of trade-offs and demonstrates that the shape of the trade-off curve in combination with trait-fitness relationships strongly affects competition among different prey types: Either specialized species with extreme trait combinations (undefended or completely defended) coexist, or a species with an intermediate defence level dominates. The developed theory on trade-off shapes and coexistence is kept general, allowing for applications apart from defence-competitiveness trade-offs. Thirdly, I tested the theory on trade-off shapes on a long-term field data set of phytoplankton from Lake Constance. The measured concave trade-off between defence and growth governs seasonal trait changes of phytoplankton in response to an altering grazing pressure by zooplankton, and affects the maintenance of trait variation in the community. In a fourth step, I analyse the interplay of different tradeoffs at multiple trophic levels with plankton data of Lake Constance and a corresponding tritrophic food web model. The results show that the trait and biomass dynamics of the different three trophic levels are interrelated in a trophic biomass-trait cascade, leading to unintuitive patterns of trait changes that are reversed in comparison to predictions from bitrophic systems. Finally, in the general discussion, I extract main ideas on trade-offs in multitrophic systems, develop a graphical theory on trade-off-based coexistence, discuss the interplay of intra- and interspecific trade-offs, and end with a management-oriented view on the results of the dissertation, describing how food webs may respond to future global changes, given their trade-offs.
Geomagnetic paleosecular variations (PSVs) are an expression of geodynamo processes inside the Earth’s liquid outer core. These paleomagnetic time series provide insights into the properties of the Earth’s magnetic field, from normal behavior with a dominating dipolar geometry, over field crises, such as pronounced intensity lows and geomagnetic excursions with a distorted field geometry, to the complete reversal of the dominating dipole contribution. Particularly, long-term high-resolution and high-quality PSV time series are needed for properly reconstructing the higher frequency components in the spectrum of geomagnetic field variations and for a better understanding of the effects of smoothing during the recording of such paleomagnetic records by sedimentary archives.
In this doctorate study, full vector paleomagnetic records were derived from 16 sediment cores recovered from the southeastern Black Sea. Age models are based on radiocarbon dating and correlations of warming/cooling cycles monitored by high-resolution X-ray fluorescence (XRF) elementary ratios as well as ice-rafted debris (IRD) in Black Sea sediments to the sequence of ‘Dansgaard-Oeschger’ (DO) events defined from Greenland ice core oxygen isotope stratigraphy.
In order to identify the carriers of magnetization in Black Sea sediments, core MSM33-55-1 recovered from the southeast Black Sea was subjected to detailed rock magnetic and electron microscopy investigations. The younger part of core MSM33-55-1 was continuously deposited since 41 ka. Before 17.5 ka, the magnetic minerals were dominated by a mixture of greigite (Fe3S4) and titanomagnetite (Fe3-xTixO4) in samples with SIRM/κLF >10 kAm-1, or exclusively by titanomagnetite in samples with SIRM/κLF ≤10 kAm-1. It was found that greigite is generally present as crustal aggregates in locally reducing micro-environments. From 17.5 ka to 8.3 ka, the dominant magnetic mineral in this transition phase was changing from greigite (17.5 – ~10.0 ka) to probably silicate-hosted titanomagnetite (~10.0 – 8.3 ka). After 8.3 ka, the anoxic Black Sea was a favorable environment for the formation of non-magnetic pyrite (FeS2) framboids.
Aiming to avoid compromising of paleomagnetic data by erroneous directions carried by greigite, paleomagnetic data from samples with SIRM/κLF >10 kAm-1, shown to contain greigite by various methods, were removed from obtained records. Consequently, full vector paleomagnetic records, comprising directional data and relative paleointensity (rPI), were derived only from samples with SIRM/κLF ≤10 kAm-1 from 16 Black Sea sediment cores. The obtained data sets were used to create a stack covering the time window between 68.9 and 14.5 ka with temporal resolution between 40 and 100 years, depending on sedimentation rates.
At 64.5 ka, according to obtained results from Black Sea sediments, the second deepest minimum in relative paleointensity during the past 69 ka occurred. The field minimum during MIS 4 is associated with large declination swings beginning about 3 ka before the minimum. While a swing to 50°E is associated with steep inclinations (50-60°) according to the coring site at 42°N, the subsequent declination swing to 30°W is associated with shallow inclinations of down to 40°. Nevertheless, these large deviations from the direction of a geocentric axial dipole field (I=61°, D=0°) still can not yet be termed as 'excursional', since latitudes of corresponding VGPs only reach down to 51.5°N (120°E) and 61.5°N (75°W), respectively. However, these VGP positions at opposite sides of the globe are linked with VGP drift rates of up to 0.2° per year in between. These extreme secular variations might be the mid-latitude expression of the Norwegian–Greenland Sea excursion found at several sites much further North in Arctic marine sediments between 69°N and 81°N.
At about 34.5 ka, the Mono Lake excursion is evidenced in the stacked Black Sea PSV record by both a rPI minimum and directional shifts. Associated VGPs from stacked Black Sea data migrated from Alaska, via central Asia and the Tibetan Plateau, to Greenland, performing a clockwise loop. This agrees with data recorded in the Wilson Creek Formation, USA., and Arctic sediment core PS2644-5 from the Iceland Sea, suggesting a dominant dipole field. On the other hand, the Auckland lava flows, New Zealand, the Summer Lake, USA., and Arctic sediment core from ODP Site-919 yield distinct VGPs located in the central Pacific Ocean due to a presumably non-dipole (multi-pole) field configuration.
A directional anomaly at 18.5 ka, associated with pronounced swings in inclination and declination, as well as a low in rPI, is probably contemporaneous with the Hilina Pali excursion, originally reported from Hawaiian lava flows. However, virtual geomagnetic poles (VGPs) calculated from Black Sea sediments are not located at latitudes lower than 60° N, which denotes normal, though pronounced secular variations. During the postulated Hilina Pali excursion, the VGPs calculated from Black Sea data migrated clockwise only along the coasts of the Arctic Ocean from NE Canada (20.0 ka), via Alaska (18.6 ka) and NE Siberia (18.0 ka) to Svalbard (17.0 ka), then looping clockwise through the Eastern Arctic Ocean.
In addition to the Mono Lake and the Norwegian–Greenland Sea excursions, the Laschamp excursion was evidenced in the Black Sea PSV record with the lowest paleointensities at about 41.6 ka and a short-term (~500 years) full reversal centered at 41 ka. These excursions are further evidenced by an abnormal PSV index, though only the Laschamp and the Mono Lake excursions exhibit excursional VGP positions. The stacked Black Sea paleomagnetic record was also converted into one component parallel to the direction expected from a geocentric axial dipole (GAD) and two components perpendicular to it, representing only non-GAD components of the geomagnetic field. The Laschamp and the Norwegian–Greenland Sea excursions are characterized by extremely low GAD components, while the Mono Lake excursion is marked by large non-GAD contributions. Notably, negative values of the GAD component, indicating a fully reversed geomagnetic field, are observed only during the Laschamp excursion.
In summary, this doctoral thesis reconstructed high-resolution and high-fidelity PSV records from SE Black Sea sediments. The obtained record comprises three geomagnetic excursions, the Norwegian–Greenland Sea excursion, the Laschamp excursion, and the Mono Lake excursion. They are characterized by abnormal secular variations of different amplitudes centered at about 64.5 ka, 41.0 ka and 34.5 ka, respectively. In addition, the obtained PSV record from the Black Sea do not provide evidence for the postulated 'Hilina Pali excursion' at about 18.5 ka. Anyway, the obtained Black Sea paleomagnetic record, covering field fluctuations from normal secular variations, over excursions, to a short but full reversal, points to a geomagnetic field characterized by a large dynamic range in intensity and a highly variable superposition of dipole and non-dipole contributions from the geodynamo during the past 68.9 to 14.5 ka.
The thesis comprises three experimental studies, which were carried out to unravel the short- as well as the long-term mechanical properties of shale rocks. Short-term mechanical properties such as compressive strength and Young’s modulus were taken from recorded stress-strain curves of constant strain rate tests. Long-term mechanical properties are represented by the time– dependent creep behavior of shales. This was obtained from constant stress experiments, where the test duration ranged from a couple minutes up to two weeks. A profound knowledge of the mechanical behavior of shales is crucial to reliably estimate the potential of a shale reservoir for an economical and sustainable extraction of hydrocarbons (HC). In addition, healing of clay-rich forming cap rocks involving creep and compaction is important for underground storage of carbon dioxide and nuclear waste.
Chapter 1 introduces general aspects of the research topic at hand and highlights the motivation for conducting this study. At present, a shift from energy recovered from conventional resources e.g., coal towards energy provided by renewable resources such as wind or water is a big challenge. Gas recovered from unconventional reservoirs (shale plays) is considered a potential bridge technology.
In Chapter 2, short-term mechanical properties of two European mature shale rocks are presented, which were determined from constant strain rate experiments performed at ambient and in situ deformation conditions (confining pressure, pc ≤ 100 MPa, temperature, T ≤ 125 °C, representing pc, T - conditions at < 4 km depth) using a Paterson– type gas deformation apparatus. The investigated shales were mainly from drill core material of Posidonia (Germany) shale and weathered material of Bowland (United Kingdom) shale. The results are compared with mechanical properties of North American shales. Triaxial compression tests performed perpendicular to bedding revealed semibrittle deformation behavior of Posidonia shale with pronounced inelastic deformation. This is in contrast to Bowland shale samples that deformed brittle and displayed predominantly elastic deformation. The static Young’s modulus, E, and triaxial compressive strength, σTCS, determined from recorded stress-strain curves strongly depended on the applied confining pressure and sample composition, whereas the influence of temperature and strain rate on E and σTCS was minor. Shales with larger amounts of weak minerals (clay, mica, total organic carbon) yielded decreasing E and σTCS. This may be related to a shift from deformation supported by a load-bearing framework of hard phases (e.g., quartz) towards deformation of interconnected weak minerals, particularly for higher fractions of about 25 – 30 vol% weak phases. Comparing mechanical properties determined at reservoir conditions with mechanical data applying effective medium theories revealed that E and σTCS of Posidonia and Bowland shale are close to the lower (Reuss) bound. Brittleness B is often quoted as a measure indicating the response of a shale formation to stimulation and economic production. The brittleness, B, of Posidonia and Bowland shale, estimated from E, is in good agreement with the experimental results. This correlation may be useful to predict B from sonic logs, from which the (dynamic) Young’s modulus can be retrieved.
Chapter 3 presents a study of the long-term creep properties of an immature Posidonia shale. Constant stress experiments (σ = const.) were performed at elevated confining pressures (pc = 50 – 200 MPa) and temperatures (T = 50 – 200 °C) to simulate reservoir pc, T - conditions. The Posidonia shale samples were acquired from a quarry in South Germany. At stresses below ≈ 84 % compressive strength of Posidonia shale, at high temperature and low confining pressure, samples showed pronounced transient (primary) creep with high deformation rates in the semibrittle regime. Sample deformation was mainly accommodated by creep of weak sample constituents and pore space reduction. An empirical power law relation between strain and time, which also accounts for the influence of pc, T and σ on creep strain was formulated to describe the primary creep phase. Extrapolation of the results to a creep period of several years, which is the typical time interval for a large production decline, suggest that fracture closure is unlikely at low stresses. At high stresses as expected for example at the contact between the fracture surfaces and proppants added during stimulation measures, subcritical crack growth may lead to secondary and tertiary creep. An empirical power law is suggested to describe secondary creep of shale rocks as a function of stress, pressure and temperature. The predicted closure rates agree with typical production decline curves recorded during the extraction of hydrocarbons. At the investigated conditions, the creep behavior of Posidonia shale was found to correlate with brittleness, calculated from sample composition.
In Chapter 4 the creep properties of mature Posidonia and Bowland shales are presented. The observed long-term creep behavior is compared to the short-term behavior determined in Chapter 2. Creep experiments were performed at simulated reservoir conditions of pc = 50 – 115 MPa and T = 75 – 150 °C. Similar to the mechanical response of immature Posidonia shale samples investigated in Chapter 3, creep strain rates of mature Bowland and Posidonia shales were enhanced with increasing stress and temperature and decreasing confining pressures. Depending on applied deformation conditions, samples displayed either only a primary (decelerating) or in addition also a secondary (quasi-steady state) and subsequently a tertiary (accelerating) creep phase before failure. At the same deformation conditions, creep strain of Posidonia shale, which is rich in weak constituents, is tremendously higher than of quartz-rich Bowland shale. Typically, primary creep strain is again mostly accommodated by deformation of weak minerals and local pore space reduction. At the onset of tertiary creep most of the deformation was accommodated by micro crack growth. A power law was used to characterize the primary creep phase of Posidonia and Bowland shale. Primary creep strain of shale rocks is inversely correlated to triaxial compressive strength and brittleness, as described in Chapter 2.
Chapter 5 provides a synthesis of the experimental findings and summarizes the major results of the studies presented in Chapters 2 – 4 and potential applications in the Exploration & Production industry.
Chapter 6 gives a brief outlook on potential future experimental research that would help to further improve our understanding of processes leading to fracture closure involving proppant embedment in unconventional shale gas reservoirs. Such insights may allow to improve stimulation techniques aimed at maintaining economical extraction of hydrocarbons over several years.
The advances in modern geodetic techniques such as the global navigation satellite system (GNSS) and synthetic aperture radar (SAR) provide surface deformation measurements with an unprecedented accuracy and temporal and spatial resolutions even at most remote volcanoes on Earth. Modelling of the high-quality geodetic data is crucial for understanding the underlying physics of volcano deformation processes. Among various approaches, mathematical models are the most effective for establishing a quantitative link between the surface displacements and the shape and strength of deformation sources. Advancing the geodetic data analyses and hence, the knowledge on the Earth’s interior processes, demands sophisticated and efficient deformation modelling approaches. Yet the majority of these models rely on simplistic assumptions for deformation source geometries and ignore complexities such as the Earth’s surface topography and interactions between multiple sources.
This thesis addresses this problem in the context of analytical and numerical volcano deformation modelling. In the first part, new analytical solutions for triangular dislocations (TDs) in uniform infinite and semi-infinite elastic media have been developed. Through a comprehensive investigation, the locations and causes of artefact singularities and numerical instabilities associated with TDs have been determined and these long-standing drawbacks have been addressed thoroughly. This approach has then been extended to rectangular dislocations (RDs) with full rotational degrees of freedom. Using this solution in a configuration of three orthogonal RDs a compound dislocation model (CDM) has been developed. The CDM can represent generalized volumetric and planar deformation sources efficiently. Thus, the CDM is relevant for rapid inversions in early warning systems and can also be used for detailed deformation analyses. In order to account for complex source geometries and realistic topography in the deformation models, in this thesis the boundary element method (BEM) has been applied to the new solutions for TDs. In this scheme, complex surfaces are simulated as a continuous mesh of TDs that may possess any displacement or stress boundary conditions in the BEM calculations. In the second part of this thesis, the developed modelling techniques have been applied to five different real-world deformation scenarios. As the first and second case studies the deformation sources associated with the 2015 Calbuco eruption and 2013–2016 Copahue inflation period have been constrained by using the CDM. The highly anisotropic source geometries in these two cases highlight the importance of using generalized deformation models such as the CDM, for geodetic data inversions. The other three case studies in this thesis involve high-resolution dislocation models and BEM calculations. As the third case, the 2013 pre-explosive inflation of Volcán de Colima has been simulated by using two ellipsoidal cavities, which locate zones of pressurization in the volcano’s lava dome. The fourth case study, which serves as an example for volcanotectonics interactions, the 3-D kinematics of an active ring-fault at Tendürek volcano has been investigated through modelling displacement time series over the 2003–2010 time period. As the fifth example, the deformation sources associated with North Korea’s underground nuclear test in September 2017 have been constrained. These examples demonstrate the advancement and increasing level of complexity and the general applicability of the developed dislocation modelling techniques.
This thesis establishes a unified framework for rapid and high-resolution dislocation modelling, which in addition to volcano deformations can also be applied to tectonic and humanmade deformations.
This dissertation combines field and geochemical observations and analyses with numerical modeling to understand the formation of vein-hosted Sn-W ore in the Panasqueira deposit of Portugal, which is among the ten largest worldwide. The deposit is located above a granite body that is altered by magmatic-hydrothermal fluids in its upper part (greisen). These fluids are thought to be the source of metals, but that was still under debate. The goal of this study is to determine the composition and temperature of hydrothermal fluids at Panasqueira, and with that information to construct a numerical model of the hydrothermal system. The focus is on analysis of the minerals tourmaline and white mica, which formed during mineralization and are widespread throughout the deposit. Tourmaline occurs mainly in alteration zones around mineralized veins and is less abundant in the vein margins. White mica is more widespread. It is abundant in vein margins as well as alteration zones, and also occurs in the granite greisen. The laboratory work involved in-situ microanalysis of major- and trace elements in tourmaline and white mica, and boron-isotope analysis in both minerals by secondary ion mass spectrometry (SIMS).
The boron-isotope composition of tourmaline and white mica suggests a magmatic source. Comparison of hydrothermally-altered and unaltered rocks from drill cores shows that the ore metals (W, Sn, Cu, and Zn) and As, F, Li, Rb, and Cs were introduced during the alteration. Most of these elements are also enriched in tourmaline and mica, which confirms their potential value as exploration guides to Sn-W ores elsewhere.
The thermal evolution of the hydrothermal system was estimated by B-isotope exchange thermometry and the Ti-in-quartz method. Both methods yielded similar temperatures for the early hydrothermal phase: 430° to 460°C for B-isotopes and 503° ± 24°C for Ti-in-quartz. Mineral pairs from a late fault zone yield significantly lower median temperatures of 250°C. The combined results of thermometry with variations in chemical and B-isotope composition of tourmaline and mica suggest that a similar magmatic-hydrothermal fluid was active at all stages of mineralization. Mineralization in the late stage shows the same B-isotope composition as in the main stage despite a ca. 250°C cooling, which supports a multiple injection model of magmatic-hydrothermal fluids.
Two-dimensional numerical simulations of convection in a multiphase NaCl hydrothermal system were conducted: (a) in order to test a new approach (lower dimensional elements) for flow through fractures and faults and (b) in order to identify conditions for horizontal fluid flow as observed in the flat-lying veins at Panasqueira. The results show that fluid flow over an intrusion (heat and fluid source) develops a horizontal component if there is sufficient fracture connectivity. Late, steep fault zones have been identified in the deposit area, which locally contain low-temperature Zn-Pb mineralization. The model results confirm that the presence of subvertical faults with enhanced permeability play a crucial role in the ascent of magmatic fluids to the surface and the recharge of meteoric waters. Finally, our model results suggest that recharge of meteoric fluids and mixing processes may be important at later stages, while flow of magmatic fluids dominate the early stages of the hydrothermal fluid circulation.
The natural abundance of Coiled Coil (CC) motifs in cytoskeleton and extracellular matrix proteins suggests that CCs play an important role as passive (structural) and active (regulatory) mechanical building blocks. CCs are self-assembled superhelical structures consisting of 2-7 α-helices. Self-assembly is driven by hydrophobic and ionic interactions, while the helix propensity of the individual helices contributes additional stability to the structure. As a direct result of this simple sequence-structure relationship, CCs serve as templates for protein design and sequences with a pre-defined thermodynamic stability have been synthesized de novo. Despite this quickly increasing knowledge and the vast number of possible CC applications, the mechanical function of CCs has been largely overlooked and little is known about how different CC design parameters determine the mechanical stability of CCs. Once available, this knowledge will open up new applications for CCs as nanomechanical building blocks, e.g. in biomaterials and nanobiotechnology.
With the goal of shedding light on the sequence-structure-mechanics relationship of CCs, a well-characterized heterodimeric CC was utilized as a model system. The sequence of this model system was systematically modified to investigate how different design parameters affect the CC response when the force is applied to opposing termini in a shear geometry or separated in a zipper-like fashion from the same termini (unzip geometry). The force was applied using an atomic force microscope set-up and dynamic single-molecule force spectroscopy was performed to determine the rupture forces and energy landscape properties of the CC heterodimers under study. Using force as a denaturant, CC chain separation is initiated by helix uncoiling from the force application points. In the shear geometry, this allows uncoiling-assisted sliding parallel to the force vector or dissociation perpendicular to the force vector. Both competing processes involve the opening of stabilizing hydrophobic (and ionic) interactions. Also in the unzip geometry, helix uncoiling precedes the rupture of hydrophobic contacts.
In a first series of experiments, the focus was placed on canonical modifications in the hydrophobic core and the helix propensity. Using the shear geometry, it was shown that both a reduced core packing and helix propensity lower the thermodynamic and mechanical stability of the CC; however, with different effects on the energy landscape of the system. A less tightly packed hydrophobic core increases the distance to the transition state, with only a small effect on the barrier height. This originates from a more dynamic and less tightly packed core, which provides more degrees of freedom to respond to the applied force in the direction of the force vector. In contrast, a reduced helix propensity decreases both the distance to the transition state and the barrier height. The helices are ‘easier’ to unfold and the remaining structure is less thermodynamically stable so that dissociation perpendicular to the force axis can occur at smaller deformations.
Having elucidated how canonical sequence modifications influence CC mechanics, the pulling geometry was investigated in the next step. Using one and the same sequence, the force application points were exchanged and two different shear and one unzipping geometry were compared. It was shown that the pulling geometry determines the mechanical stability of the CC. Different rupture forces were observed in the different shear as well as in the unzipping geometries, suggesting that chain separation follows different pathways on the energy landscape. Whereas the difference between CC shearing and unzipping was anticipated and has also been observed for other biological structures, the observed difference for the two shear geometries was less expected. It can be explained with the structural asymmetry of the CC heterodimer. It is proposed that the direction of the α-helices, the different local helix propensities and the position of a polar asparagine in the hydrophobic core are responsible for the observed difference in the chain separation pathways. In combination, these factors are considered to influence the interplay between processes parallel and perpendicular to the force axis.
To obtain more detailed insights into the role of helix stability, helical turns were reinforced locally using artificial constraints in the form of covalent and dynamic ‘staples’. A covalent staple bridges to adjacent helical turns, thus protecting them against uncoiling. The staple was inserted directly at the point of force application in one helix or in the same terminus of the other helix, which did not experience the force directly. It was shown that preventing helix uncoiling at the point of force application reduces the distance to the transition state while slightly increasing the barrier height. This confirms that helix uncoiling is critically important for CC chain separation. When inserted into the second helix, this stabilizing effect is transferred across the hydrophobic core and protects the force-loaded turns against uncoiling. If both helices were stapled, no additional increase in mechanical stability was observed. When replacing the covalent staple with a dynamic metal-coordination bond, a smaller decrease in the distance to the transition was observed, suggesting that the staple opens up while the CC is under load.
Using fluorinated amino acids as another type of non-natural modification, it was investigated how the enhanced hydrophobicity and the altered packing at the interface influences CC mechanics. The fluorinated amino acid was inserted into one central heptad of one or both α-helices. It was shown that this substitution destabilized the CC thermodynamically and mechanically. Specifically, the barrier height was decreased and the distance to the transition state increased. This suggests that a possible stabilizing effect of the increased hydrophobicity is overruled by a disturbed packing, which originates from a bad fit of the fluorinated amino acid into the local environment. This in turn increases the flexibility at the interface, as also observed for the hydrophobic core substitution described above. In combination, this confirms that the arrangement of the hydrophobic side chains is an additional crucial factor determining the mechanical stability of CCs.
In conclusion, this work shows that knowledge of the thermodynamic stability alone is not sufficient to predict the mechanical stability of CCs. It is the interplay between helix propensity and hydrophobic core packing that defines the sequence-structure-mechanics relationship. In combination, both parameters determine the relative contribution of processes parallel and perpendicular to the force axis, i.e. helix uncoiling and uncoiling-assisted sliding as well as dissociation. This new mechanistic knowledge provides insight into the mechanical function of CCs in tissues and opens up the road for designing CCs with pre-defined mechanical properties. The library of mechanically characterized CCs developed in this work is a powerful starting point for a wide spectrum of applications, ranging from molecular force sensors to mechanosensitive crosslinks in protein nanostructures and synthetic extracellular matrix mimics.
Synchronization – the adjustment of rhythms among coupled self-oscillatory systems – is a fascinating dynamical phenomenon found in many biological, social, and technical systems.
The present thesis deals with synchronization in finite ensembles of weakly coupled self-sustained oscillators with distributed frequencies.
The standard model for the description of this collective phenomenon is the Kuramoto model – partly due to its analytical tractability in the thermodynamic limit of infinitely many oscillators. Similar to a phase transition in the thermodynamic limit, an order parameter indicates the transition from incoherence to a partially synchronized state. In the latter, a part of the oscillators rotates at a common frequency. In the finite case, fluctuations occur, originating from the quenched noise of the finite natural frequency sample.
We study intermediate ensembles of a few hundred oscillators in which fluctuations are comparably strong but which also allow for a comparison to frequency distributions in the infinite limit.
First, we define an alternative order parameter for the indication of a collective mode in the finite case. Then we test the dependence of the degree of synchronization and the mean rotation frequency of the collective mode on different characteristics for different coupling strengths.
We find, first numerically, that the degree of synchronization depends strongly on the form (quantified by kurtosis) of the natural frequency sample and the rotation frequency of the collective mode depends on the asymmetry (quantified by skewness) of the sample. Both findings are verified in the infinite limit.
With these findings, we better understand and generalize observations of other authors. A bit aside of the general line of thoughts, we find an analytical expression for the volume contraction in phase space.
The second part of this thesis concentrates on an ordering effect of the finite-size fluctuations. In the infinite limit, the oscillators are separated into coherent and incoherent thus ordered and disordered oscillators. In finite ensembles, finite-size fluctuations can generate additional order among the asynchronous oscillators. The basic principle – noise-induced synchronization – is known from several recent papers. Among coupled oscillators, phases are pushed together by the order parameter fluctuations, as we on the one hand show directly and on the other hand quantify with a synchronization measure from directed statistics between pairs of passive oscillators.
We determine the dependence of this synchronization measure from the ratio of pairwise natural frequency difference and variance of the order parameter fluctuations. We find a good agreement with a simple analytical model, in which we replace the deterministic fluctuations of the order parameter by white noise.
Organic semiconductors are a promising class of materials. Their special properties are the particularly good absorption, low weight and easy processing into thin films. Therefore, intense research has been devoted to the realization of thin film organic solar cells (OPVs). Because of the low dielectric constant of organic semiconductors, primary excitations (excitons) are strongly bound and a type II heterojunction needs to be introduced to split these excitations into free charges. Therefore, most organic solar cells consist of at least an electron donor and electron acceptor material. For such donor acceptor systems mainly three states are relevant; the photoexcited exciton on the donor or acceptor material, the charge transfer state at the donor-acceptor interface and the charge separated state of a free electron and hole. The interplay between these states significantly determines the efficiency of organic solar cells. Due to the high absorption and the low charge carrier mobilities, the active layers are usually thin but also, exciton dissociation and free charge formation proceeds rapidely, which makes the study of carrier dynamics highly challenging.
Therefore, the focus of this work was first to install new experimental setups for the investigation of the charge carrier dynamics in complete devices with superior sensitivity and time resolution and, second, to apply these methods to prototypical photovoltaic materials to address specific questions in the field of organic and hybrid photovoltaics.
Regarding the first goal, a new setup combining transient absorption spectroscopy (TAS) and time delayed collection field (TDCF) was designed and installed in Potsdam. An important part of this work concerned the improvement of the electronic components with respect to time resolution and sensitivity. To this end, a highly sensitive amplifier for driving and detecting the device response in TDCF was developed. This system was then applied to selected organic and hybrid model systems with a particular focus on the understanding of the loss mechanisms that limit the fill factor and short circuit current of organic solar cells.
The first model system was a hybrid photovoltaic material comprising inorganic quantum dots decorated with organic ligands. Measurements with TDCF revealed fast free carrier recombination, in part assisted by traps, while bias-assisted charge extraction measurements showed high mobility. The measured parameters then served as input for a successful description of the device performance with an analytical model.
With a further improvement of the instrumentation, a second topic was the detailed analysis of non-geminate recombination in a disordered polymer:fullerene blend where an important question was the effect of disorder on the carrier dynamics. The measurements revealed that early time highly mobile charges undergo fast non-geminate recombination at the contacts, causing an apparent field dependence of free charge generation in TDCF experiments if not conducted properly. On the other hand, recombination the later time scale was determined by dispersive recombination in the bulk of the active layer, showing the characteristics of carrier dynamics in an exponential density of state distribution. Importantly, the comparison with steady state recombination data suggested a very weak impact of non-thermalized carriers on the recombination properties of the solar cells under application relevant illumination conditions.
Finally, temperature and field dependent studies of free charge generation were performed on three donor-acceptor combinations, with two donor polymers of the same material family blended with two different fullerene acceptor molecules. These particular material combinations were chosen to analyze the influence of the energetic and morphology of the blend on the efficiency of charge generation. To this end, activation energies for photocurrent generation were accurately determined for a wide range of excitation energies. The results prove that the formation of free charge is via thermalized charge transfer states and does not involve hot exciton splitting. Surprisingly, activation energies were of the order of thermal energy at room temperature. This led to the important conclusion that organic solar cells perform well not because of predominate high energy pathways but because the thermalized CT states are weakly bound. In addition, a model is introduced to interconnect the dissociation efficiency of the charge transfer state with its recombination observable with photoluminescence, which rules out a previously proposed two-pool model for free charge formation and recombination. Finally, based on the results, proposals for the further development of organic solar cells are formulated.
On a planetary scale human populations need to adapt to both socio-economic and environmental problems amidst rapid global change. This holds true for coupled human-environment (socio-ecological) systems in rural and urban settings alike. Two examples are drylands and urban coasts. Such socio-ecological systems have a global distribution. Therefore, advancing the knowledge base for identifying socio-ecological adaptation needs with local vulnerability assessments alone is infeasible: The systems cover vast areas, while funding, time, and human resources for local assessments are limited. They are lacking in low an middle-income countries (LICs and MICs) in particular.
But places in a specific socio-ecological system are not only unique and complex – they also exhibit similarities. A global patchwork of local rural drylands vulnerability assessments of human populations to socio-ecological and environmental problems has already been reduced to a limited number of problem structures, which typically cause vulnerability. However, the question arises whether this is also possible in urban socio-ecological systems. The question also arises whether these typologies provide added value in research beyond global change. Finally, the methodology employed for drylands needs refining and standardizing to increase its uptake in the scientific community. In this dissertation, I set out to fill these three gaps in research.
The geographical focus in my dissertation is on LICs and MICs, which generally have lower capacities to adapt, and greater adaptation needs, regarding rapid global change. Using a spatially explicit indicator-based methodology, I combine geospatial and clustering methods to identify typical configurations of key factors in case studies causing vulnerability to human populations in two specific socio-ecological systems. Then I use statistical and analytical methods to interpret and appraise both the typical configurations and the global typologies they constitute.
First, I improve the indicator-based methodology and then reanalyze typical global problem structures of socio-ecological drylands vulnerability with seven indicator datasets. The reanalysis confirms the key tenets and produces a more realistic and nuanced typology of eight spatially explicit problem structures, or vulnerability profiles: Two new profiles with typically high natural resource endowment emerge, in which overpopulation has led to medium or high soil erosion. Second, I determine whether the new drylands typology and its socio-ecological vulnerability concept advance a thematically linked scientific debate in human security studies: what drives violent conflict in drylands? The typology is a much better predictor for conflict distribution and incidence in drylands than regression models typically used in peace research. Third, I analyze global problem structures typically causing vulnerability in an urban socio-ecological system - the rapidly urbanizing coastal fringe (RUCF) – with eleven indicator datasets. The RUCF also shows a robust typology, and its seven profiles show huge asymmetries in vulnerability and adaptive capacity. The fastest population increase, lowest income, most ineffective governments, most prevalent poverty, and lowest adaptive capacity are all typically stacked in two profiles in LICs. This shows that beyond local case studies tropical cyclones and/or coastal flooding are neither stalling rapid population growth, nor urban expansion, in the RUCF. I propose entry points for scaling up successful vulnerability reduction strategies in coastal cities within the same vulnerability profile.
This dissertation shows that patchworks of local vulnerability assessments can be generalized to structure global socio-ecological vulnerabilities in both rural and urban socio-ecological systems according to typical problems. In terms of climate-related extreme events in the RUCF, conflicting problem structures and means to deal with them are threatening to widen the development gap between LICs and high-income countries unless successful vulnerability reduction measures are comprehensively scaled up. The explanatory power for human security in drylands warrants further applications of the methodology beyond global environmental change research in the future. Thus, analyzing spatially explicit global typologies of socio-ecological vulnerability is a useful complement to local assessments: The typologies provide entry points for where to consider which generic measures to reduce typical problem structures – including the countless places without local assessments. This can save limited time and financial resources for adaptation under rapid global change.
The unprecedented increase in atmospheric concentrations of carbon dioxide (CO2) and other greenhouse gases (GHG) by anthropogenic activities since the Industrial Revolution impacts on various earth system processes, commonly referred to as `climate change´ (CC). CC faces aquatic ecosystems with extreme abiotic perturbations that potentially alter the interrelations between functional autotrophic and heterotrophic plankton groups. These relations, however, modulate biogeochemical cycling and mediate the functioning of aquatic ecosystems as C sources or sinks to the atmosphere. The aim of this thesis was therefore to investigate how different aspects of CC influence community composition and functioning of pelagic heterotrophic bacteria. These organisms constitute a major component of biogeochemical cycling and largely determine the balance between autotrophic and heterotrophic processes.
Due to the vast amount of potential CC impacts, this thesis focuses on the following two aspects: (1) Increased exchange of CO2 across the atmosphere-water interface and reaction of CO2 with seawater leads to profound shifts in seawater carbonate chemistry, commonly termed as `ocean acidification´ (OA), with consequences for organism physiology and the availability of dissolved inorganic carbon (DIC) in seawater. (2) The increase in atmospheric GHG concentration impacts on the efficiency with which the Earth cools to space, affecting global surface temperature and climate. With ongoing CC, shifts in frequency and severity of episodic weather events, such as storms, are expected that in particular might affect lake ecosystems by disrupting thermal summer stratification. Both aspects of CC were studied at the ecosystem-level in large-volume mesocosm experiments by using the Kiel Off-shore Mesocosms for Future Ocean Simulations (KOSMOS) deployed at different coastal marine locations, and the LakeLab facility in Lake Stechlin.
We evaluated the impact of OA on heterotrophic bacterial metabolism in a brackish coastal ecosystem during low-nutrient summer months in the Baltic Sea. There are several in situ experiments that already assessed potential OA-induced changes in natural plankton communities at diverse spatial and seasonal conditions. However, most studies were performed at high phytoplankton biomass conditions, partly provoked by nutrient amendments. Our study highlights potential OA effects at low-nutrient conditions that are representative for most parts of the ocean and of particular interest in current OA research. The results suggest that during extended periods at low-nutrient concentrations, increasing pCO2 levels indirectly impact the growth balance of heterotrophic bacteria via trophic bacteria-phytoplankton interactions and shift the ecosystem to a more autotrophic system.
Further work investigated how OA affects heterotrophic bacterial dissolved organic matter (DOM) transformation in two mesocsom studies, performed at different nutrient conditions. We observed similar succession patterns for individual compound pools during a phytoplankton bloom and subsequent accumulation of these compounds irrespective of the pCO2 treatment. Our results indicate that OA-induced changes in the dynamics of bacterial DOM transformation and potential impacts on DOM quality are unlikely. In addition, there have been no indications that in dependence of nutrient conditions, different amounts of photosynthetic organic matter are channelled into the more recalcitrant DOM pool. This provides novel insights into the general dynamics of the marine DOM pool.
A fourth enclosure experiment in oligo-mesotrophic Lake Stechlin assessed the impact of a severe summer storm on lake bacterial communities during thermal stratification by artificially mixing. Mixing disrupted and lowered the thermocline, increasing the upper mixed layer and substantially changed water physical-chemical variables. Deep water entrainment and associated changes in water physical-chemical variables significantly affected relative bacterial abundances for about one week. Afterwards a pronounced cyanobacterial bloom developed in response to mixing which affected community assembly of heterotrophic bacteria. Colonization and mineralization of senescent phytoplankton cells by heterotrophic bacteria largely determined C-sequestration to the sediment. About six weeks after mixing, bacterial communities and measured activity parameters converged to control conditions. As such, summer storms have the potential to affect bacterial communities for a prolonged period during summer stratification. The results highlight effects on community assembly and heterotrophic bacterial metabolism that are associated to entrainment of deep water into the mixed water layer and assess consequences of an episodic disturbance event for the coupling between bacterial metabolism and autochthonous DOM production in large volume clear-water lakes.
Altogether, this doctoral thesis reveales substantial sensitivities of heterotrophic bacterial metabolism and community structure in response to OA and a simulated summer storm event, which should be considered when assessing the impact of climate change on marine and lake ecosystems.
Simulating the impact of herbicide drift exposure on non-target terrestrial plant communities
(2019)
In Europe, almost half of the terrestrial landscape is used for agriculture. Thus, semi-natural habitats such as field margins are substantial for maintaining diversity in intensively managed farmlands. However, plants located at field margins are threatened by agricultural practices such as the application of pesticides within the fields. Pesticides are chemicals developed to control for undesired species within agricultural fields to enhance yields. The use of pesticides implies, however, effects on non-target organisms within and outside of the agricultural fields. Non-target organisms are organisms not intended to be sprayed or controlled for. For example, plants occurring in field margins are not intended to be sprayed, however, can be impaired due to herbicide drift exposure. The authorization of plant protection products such as herbicides requires risk assessments to ensure that the application of the product has no unacceptable effects on the environment. For non-target terrestrial plants (NTTPs), the risk assessment is based on standardized greenhouse studies on plant individual level. To account for the protection of plant populations and communities under realistic field conditions, i.e. extrapolating from greenhouse studies to field conditions and from individual-level to community-level, assessment factors are applied. However, recent studies question the current risk assessment scheme to meet the specific protection goals for non-target terrestrial plants as suggested by the European Food Safety Authority (EFSA). There is a need to clarify the gaps of the current risk assessment and to include suitable higher tier options in the upcoming guidance document for non-target terrestrial plants.
In my thesis, I studied the impact of herbicide drift exposure on NTTP communities using a mechanistic modelling approach. I addressed main gaps and uncertainties of the current risk assessment and finally suggested this modelling approach as a novel higher tier option in future risk assessments. Specifically, I extended the plant community model IBC-grass (Individual-based community model for grasslands) to reflect herbicide impacts on plant individuals. In the first study, I compared model predictions of short-term herbicide impacts on artificial plant communities with empirical data. I demonstrated the capability of the model to realistically reflect herbicide impacts. In the second study, I addressed the research question whether or not reproductive endpoints need to be included in future risk assessments to protect plant populations and communities. I compared the consequences of theoretical herbicide impacts on different plant attributes for long-term plant population dynamics in the community context. I concluded that reproductive endpoints only need to be considered if the herbicide effect is assumed to be very high. The endpoints measured in the current vegetative vigour and seedling emergence studies had high impacts for the dynamic of plant populations and communities already at lower effect intensities. Finally, the third study analysed long-term impacts of herbicide application for three different plant communities. This study highlighted the suitability of the modelling approach to simulate different communities and thus detecting sensitive environmental conditions.
Overall, my thesis demonstrates the suitability of mechanistic modelling approaches to be used as higher tier options for risk assessments. Specifically, IBC-grass can incorporate available individual-level effect data of standardized greenhouse experiments to extrapolate to community-level under various environmental conditions. Thus, future risk assessments can be improved by detecting sensitive scenarios and including worst-case impacts on non-target plant communities.
Membrane adhesion is a fundamental biological process in which membranes are attached to neighboring membranes or surfaces. Membrane adhesion emerges from a complex interplay between the binding of membrane-anchored receptors/ligands and the membrane properties. In this work, we study membrane adhesion mediated by lipid-anchored saccharides using microsecond-long full-atomistic molecular dynamics simulations. Motivated by neutron scattering experiments on membrane adhesion via lipid-anchored saccharides, we investigate the role of LeX, Lac1, and Lac2 saccharides and membrane fluctuations in membrane adhesion.
We study the binding of saccharides in three different systems: for saccharides in water, for saccharides anchored to essentially planar membranes at fixed separations, and for saccharides anchored to apposing fluctuating membranes. Our simulations of two saccharides in water indicate that the saccharides engage in weak interactions to form dimers. We find that the binding occurs in a continuum of bound states instead of a certain number of well-defined bound structures, which we term as "diffuse binding".
The binding of saccharides anchored to essentially planar membranes strongly depends on separation of the membranes, which is fixed in our simulation system. We show that the binding constants for trans-interactions of two lipid-anchored saccharides monotonically decrease with increasing separation. Saccharides anchored to the same membrane leaflet engage in cis-interactions with binding constants comparable to the trans-binding constants at the smallest membrane separations. The interplay of cis- and trans-binding can be investigated in simulation systems with many lipid-anchored saccharides. For Lac2, our simulation results indicate a positive cooperativity of trans- and cis-binding. In this cooperative binding the trans-binding constant is enhanced by the cis-interactions. For LeX, in contrast, we observe no cooperativity between trans- and cis-binding. In addition, we determine the forces generated by trans-binding of lipid-anchored saccharides in planar membranes from the binding-induced deviations of the lipid-anchors. We find that the forces acting on trans-bound saccharides increase with increasing membrane separation to values of the order of 10 pN.
The binding of saccharides anchored to the fluctuating membranes results from an interplay between the binding properties of the lipid-anchored saccharides and membrane fluctuations. Our simulations, which have the same average separation of the membranes as obtained from the neutron scattering experiments, yield a binding constant larger than in planar membranes with the same separation. This result demonstrates that membrane fluctuations play an important role at average membrane separations which are seemingly too large for effective binding. We further show that the probability distribution of the local separation can be well approximated by a Gaussian distribution. We calculate the relative membrane roughness and show that our results are in good agreement with the roughness values reported from the neutron scattering experiments.
The present dissertation about teachers’ cultural diversity beliefs and culturally responsive practices includes a general introduction (Chapter 1), a systematic literature review (Chapter 2), three empirical studies (Chapter 3, 4, and 5) and it ends with a general discussion and conclusion (Chapter 6). The major focus of investigation laid in creating a deeper understanding of teachers’ beliefs about cultural diversity and how those beliefs are related to teaching practices, which could or could not be considered to be culturally responsive. In this dissertation, I relied on insights from theoretical perspectives that derived from the field of psychology such as social cognitive theory and intergroup ideologies, as well as from the field of multicultural education such as culturally responsive teaching.
In Chapter 1, I provide the background of this dissertation, with contextual information regarding the German educational system, the theoretical framework used and the main research objectives of each study.
In Chapter 2, I conducted a systematic review of the existing international studies on trainings addressing cultural diversity beliefs with pre-service teachers. More specifically, the aims of the systematic literature review were (1) to provide a description of main components and contextual characteristics of teacher trainings targeting cultural diversity beliefs, (2) report the training effects, and (3) detail the methodological strengths and weaknesses of these studies. By examining the main components and contextual characteristics of teacher trainings, the effects on beliefs about cultural diversity as well as the methodological strengths and weaknesses of these studies in a single review, I took an integrated approach to these three processes. To review the final pool of studies (N = 36) I used a descriptive and narrative approach, relying primarily on the use of words and text to summarise and explain findings of the synthesis.
The three empirical studies that follow, all highlight aspects of how far and how teacher beliefs about cultural diversity translate into real-world practices in schools. In Chapter 3, to expand the validity of culturally responsive teaching to the German context, I aimed at verifying the dimensional structure of German version of the Culturally Responsive Classroom Management Self-Efficacy Scale (CRCMSES; Siwatu, Putman, Starker-Glass, & Lewis, 2015). I conducted Exploratory and Confirmatory Factor Analysis, and run correlations between the subscales of the CRCMSES and a measure of cultural diversity- related stress. Data (n = 504) used for the first empirical study (Chapter 3) were collected in the InTePP-project (Inclusive Teaching Professionalization Panel) in which pre-service teachers’ competencies and beliefs were assessed longitudinally at two universities: the University of Potsdam and the University of Cologne.
In the second empirical study, which forms Chapter 4, the focus is on teachers’ practices resembling school approaches to cultural diversity. In this study, I investigated two research questions: (1a) What types of descriptive norms regarding cultural diversity are perceived by teachers and students with and without an immigrant background and (1b) what is their degree of congruence? Additionally, I was also interested in how are teachers’ and students’ perceptions of descriptive norms about cultural diversity related to practices and artefacts in the physical and virtual school environment? Data for the second empirical study (Chapter 4) were previously collected in a dissertation project of doctor Maja Schachner funded by the federal program “ProExzellenz” of the Free State of Thuringia. Adopting a mixed-methods research design I conducted a secondary analysis of data from teachers’ (n = 207) and students’ (n = 1,644) gathered in 22 secondary schools in south-west Germany. Additional sources of data in this study were based on pictures of school interiors (hall and corridors) and sixth-grade classrooms’ walls (n = 2,995), and screenshots from each school website (n = 6,499).
Chapter 5 addresses the question of how culturally responsive teaching, teacher cultural diversity beliefs, and self-reflection on own teaching are related. More specifically, in this study I addressed two research questions: (1) How does CRT relate to teachers’ beliefs about incorporating cultural diversity content into daily teaching and learning activities? And (2) how does the level of teachers’ self-reflection on their own teaching relate to CRT?
For this last empirical chapter, I conducted a multiple case study with four ethnic German teachers who work in one culturally and ethnically diverse high school in Berlin, using classroom video observations and post-observation interviews.
In the final chapter (Chapter 6), I summarised the main findings of the systematic literature review and three empirical studies, and discuss their scientific and practical implications.
This dissertation makes a significant contribution to the field of educational science to understanding culturally responsive teaching in terms of its measurement, focus on both beliefs and practices and the link between the two, and theoretical, practical, and future study implications.
In this work we investigated ultrafast demagnetization in a Heusler-alloy. This material belongs to the halfmetal and exists in a ferromagnetic phase. A special feature of investigated alloy is a structure of electronic bands. The last leads to the specific density of the states. Majority electrons form a metallic like structure while minority electrons form a gap near the Fermi-level, like in semiconductor. This particularity offers a good possibility to use this material as model-like structure and to make some proof of principles concerning demagnetization. Using pump-probe experiments we carried out time-resolved measurements to figure out the times of demagnetization. For the pumping we used ultrashort laser pulses with duration around 100 fs. Simultaneously we used two excitation regimes with two different wavelengths namely 400 nm and 1240 nm. Decreasing the energy of photons to the gap size of the minority electrons we explored the effect of the gap on the demagnetization dynamics. During this work we used for the first time OPA (Optical Parametrical Amplifier) for the generation of the laser irradiation in a long-wave regime. We tested it on the FETOSPEX-beamline in BASSYII electron storage ring. With this new technique we measured wavelength dependent demagnetization dynamics. We estimated that the demagnetization time is in a correlation with photon energy of the excitation pulse. Higher photon energy leads to the faster demagnetization in our material. We associate this result with the existence of the energy-gap for minority electrons and explained it with Elliot-Yaffet-scattering events. Additionally we applied new probe-method for magnetization state in this work and verified their effectivity. It is about the well-known XMCD (X-ray magnetic circular dichroism) which we adopted for the measurements in reflection geometry. Static experiments confirmed that the pure electronic dynamics can be separated from the magnetic one. We used photon energy fixed on the L3 of the corresponding elements with circular polarization. Appropriate incidence angel was estimated from static measurements. Using this probe method in dynamic measurements we explored electronic and magnetic dynamics in this alloy.
Skarn deposits are found on every continents and were formed at different times from Precambrian to Tertiary. Typically, the formation of a skarn is induced by a granitic intrusion in carbonates-rich sedimentary rocks. During contact metamorphism, fluids derived from the granite interact with the sedimentary host rocks, which results in the formation of calc-silicate minerals at the expense of carbonates. Those newly formed minerals generally develop in a metamorphic zoned aureole with garnet in the proximal and pyroxene in the distal zone. Ore elements contained in magmatic fluids are precipitated due to the change in fluid composition. The temperature decrease of the entire system, due to the cooling of magmatic fluids and the entering of meteoric water, allows retrogression of some prograde minerals.
The Hämmerlein skarn deposit has a multi-stage history with a skarn formation during regional metamorphism and a retrogression of primary skarn minerals during the granitic intrusion. Tin was mobilized during both events. The 340 Ma old tin-bearing skarn minerals show that tin was present in sediments before the granite intrusion, and that the first Sn enrichment occurred during the skarn formation by regional metamorphism fluids. In a second step at ca. 320 Ma, tin-bearing fluids were produced with the intrusion of the Eibenstock granite. Tin, which has been added by the granite and remobilized from skarn calc-silicates, precipitated as cassiterite.
Compared to clay or marl, the skarn is enriched in Sn, W, In, Zn, and Cu. These metals have been supplied during both regional metamorphism and granite emplacement. In addition, the several isotopic and chemical data of skarn samples show that the granite selectively added elements such as Sn, and that there was no visible granitic contribution to the sedimentary signature of the skarn
The example of Hämmerlein shows that it is possible to form a tin-rich skarn without associated granite when tin has already been transported from tin-bearing sediments during regional metamorphism by aqueous metamorphic fluids. These skarns are economically not interesting if tin is only contained in the skarn minerals. Later alteration of the skarn (the heat and fluid source is not necessarily a granite), however, can lead to the formation of secondary cassiterite (SnO2), with which the skarn can become economically highly interesting.
Force plays a fundamental role in the regulation of biological processes. Cells can sense the mechanical properties of the extracellular matrix (ECM) by applying forces and transmitting mechanical signals. They further use mechanical information for regulating a wide range of cellular functions, including adhesion, migration, proliferation, as well as differentiation and apoptosis. Even though it is well understood that mechanical signals play a crucial role in directing cell fate, surprisingly little is known about the range of forces that define cell-ECM interactions at the molecular level.
Recently, synthetic molecular force sensor (MFS) designs have been established for measuring the molecular forces acting at the cell-ECM interface. MFSs detect the traction forces generated by cells and convert this mechanical input into an optical readout. They are composed of calibrated mechanoresponsive building blocks and are usually equipped with a fluorescence reporter system. Up to date, many different MFS designs have been introduced and successfully used for measuring forces involved in the adhesion of mammalian cells. These MFSs utilize different molecular building blocks, such as double-stranded deoxyribonucleic acid (dsDNA) molecules, DNA hairpins and synthetic polymers like polyethylene glycol (PEG). These currently available MFS designs lack ECM mimicking properties.
In this work, I introduce a new MFS building block for cell biology applications, derived from the natural ECM. It combines mechanical tunability with the ability to mimic the native cellular microenvironment. Inspired by structural ECM proteins with load bearing function, this new MFS design utilizes coiled coil (CC)-forming peptides. CCs are involved in structural and mechanical tasks in the cellular microenvironment and many of the key protein components of the cytoskeleton and the ECM contain CC structures. The well-known folding motif of CC structures, an easy synthesis via solid phase methods and the many roles CCs play in biological processes have inspired studies to use CCs as tunable model systems for protein design and assembly. All these properties make CCs ideal candidates as building blocks for MFSs. In this work, a series of heterodimeric CCs were designed, characterized and further used as molecular building blocks for establishing a novel, next-generation MFS prototype.
A mechanistic molecular understanding of their structural response to mechanical load is essential for revealing the sequence-structure-mechanics relationships of CCs. Here, synthetic heterodimeric CCs of different length were loaded in shear geometry and their mechanical response was investigated using a combination of atomic force microscope (AFM)-based single-molecule force spectroscopy (SMFS) and steered molecular dynamics (SMD) simulations. SMFS showed that the rupture forces of short heterodimeric CCs (3-5 heptads) lie in the range of 20-50 pN, depending on CC length, pulling geometry and the applied loading rate (dF/dt). Upon shearing, an initial rise in the force, followed by a force plateau and ultimately strand separation was observed in SMD simulations. A detailed structural analysis revealed that CC response to shear load depends on the loading rate and involves helix uncoiling, uncoiling-assisted sliding in the direction of the applied force and uncoiling-assisted dissociation perpendicular to the force axis.
The application potential of these mechanically characterized CCs as building blocks for MFSs has been tested in 2D cell culture applications with the goal of determining the threshold force for cell adhesion. Fully calibrated, 4- to 5-heptad long, CC motifs (CC-A4B4 and CC-A5B5) were used for functionalizing glass surfaces with MFSs. 3T3 fibroblasts and endothelial cells carrying mutations in a signaling pathway linked to cell adhesion and mechanotransduction processes were used as model systems for time-dependent adhesion experiments. A5B5-MFS efficiently supported cell attachment to the functionalized surfaces for both cell types, while A4B4-MFS failed to maintain attachment of 3T3 fibroblasts after the first 2 hours of initial cell adhesion. This difference in cell adhesion behavior demonstrates that the magnitude of cell-ECM forces varies depending on the cell type and further supports the application potential of CCs as mechanoresponsive and tunable molecular building blocks for the development of next-generation protein-based MFSs.This novel CC-based MFS design is expected to provide a powerful new tool for observing cellular mechanosensing processes at the molecular level and to deliver new insights into the mechanisms and forces involved. This MFS design, utilizing mechanically tunable CC building blocks, will not only allow for measuring the molecular forces acting at the cell-ECM interface, but also yield a new platform for the development of mechanically controlled materials for a large number of biological and medical applications.
Im Rahmen dieser Arbeit wird anhand von neuartigen Materialien das Potential der Europium-Lumineszenz für die strukturelle Analyse dargestellt. Bei diesen Materialien handelt es sich zum einen um Nanopartikel mit Matrizes aus mehreren Metall-Mischoxiden und Dotierungen durch die Sonde Europium und zum anderen um Metallorganische Netzwerke (MOFs), die mit Neodym , Samarium- und Europium-Ionen beladen sind.
Die Synthese der aus der Kombination von Metalloxiden enthaltenen Nanopartikel ist unter milden Bedingungen mithilfe von speziell dafür hergestellten Reagenzien erfolgt und hat zu sehr kleinen, amorphen Nanopartikeln geführt. Durch eine nachfolgende Temperaturbehandlung hat sich die Kristallinität erhöht. Damit verbunden haben sich auch die Kristallstruktur sowie die Position des Dotanden Europium verändert.
Während die etablierte Methode der Röntgendiffraktometrie einen Blick auf das Kristallgitter als Gesamtes ermöglicht, so trifft die Lumineszenz des Europiums durch die Sichtbarkeit einzelner Stark-Aufspaltungen Aussagen über dessen lokale Symmetrien. Die Symmetrie wird durch Sauerstofffehlstellen verändert, welche die Sauerstoffleitfähigkeit der Nanopartikel beeinflussen. Diese ist für die Anwendung als Katalysatoren in industriellen Prozessen und ebenso als Sensoren und Therapeutika in biologischen Systemen von Bedeutung.
Zur ersten katalytischen Charakterisierung werden die Proben mittels Temperatur-programmierter Reduktion untersucht. Des Weiteren werden die Mischoxid-Nanopartikel auch hinsichtlich ihrer Verwendbarkeit als Matrix in Aufkonversionsprozessen untersucht.
Die Metallorganischen Netzwerke eignen sich aufgrund ihrer mikroporösen Struktur für Anwendungen in der Speicherung gleichermaßen von Nutzgasen wie auch von Schadstoffen. Ebenfalls ist eine biologische Anwendung denkbar, die insbesondere den Bereich der drug delivery-Reagenzien betrifft.
Erfolgt in die mikroporösen Strukturen der Metallorganischen Netzwerke die Einlagerung von Lanthanoid-Ionen, so können diese bei der entsprechenden Kombination als Weißlicht-Emittierer fungieren. Dabei ist neben den Verhältnissen zwischen den Lanthanoid-Ionen auch die genaue Position innerhalb des Netzwerks sowie die Distanz zu anderen Ionen von Interesse. Zur Untersuchung dieser Fragestellungen wird die Umgebungssensitivität der Europium-Lumineszenz ausgenutzt. Die auf diese Weise festgestellte Formiat-Bildung hängt von zahlreichen Parametern ab.
Insgesamt stellt sich die im Rahmen dieser Arbeit verwendete Methodik des Einsatzes von Europium als strukturelle Sonde in höchstem Maße vielseitig dar und zeigt seine größte Stärke in der Kombination mit weiteren Methoden der Strukturanalytik. Die auf diese Weise genauestens charakterisierten neuartigen Materialien können nun gezielt und anwendungsfokussiert weiterentwickelt werden.
Predator-prey interactions provide central links in food webs. These interaction are directly or indirectly impacted by a number of factors. These factors range from physiological characteristics of individual organisms, over specifics of their interaction to impacts of the environment. They may generate the potential for the application of different strategies by predators and prey. Within this thesis, I modelled predator-prey interactions and investigated a broad range of different factors driving the application of certain strategies, that affect the individuals or their populations. In doing so, I focused on phytoplankton-zooplankton systems as established model systems of predator-prey interactions.
At the level of predator physiology I proposed, and partly confirmed, adaptations to fluctuating availability of co-limiting nutrients as beneficial strategies. These may allow to store ingested nutrients or to regulate the effort put into nutrient assimilation. We found that these two strategies are beneficial at different fluctuation frequencies of the nutrients, but may positively interact at intermediate frequencies. The corresponding experiments supported our model results. We found that the temporal structure of nutrient fluctuations indeed has strong effects on the juvenile somatic growth rate of {\itshape Daphnia}.
Predator colimitation by energy and essential biochemical nutrients gave rise to another physiological strategy. High-quality prey species may render themselves indispensable in a scenario of predator-mediated coexistence by being the only source of essential biochemical nutrients, such as cholesterol. Thereby, the high-quality prey may even compensate for a lacking defense and ensure its persistence in competition with other more defended prey species.
We found a similar effect in a model where algae and bacteria compete for nutrients. Now, being the only source of a compound that is required by the competitor (bacteria) prevented the competitive exclusion of the algae. In this case, the essential compounds were the organic carbon provided by the algae. Here again, being indispensable served as a prey strategy that ensured its coexistence.
The latter scenario also gave rise to the application of the two metabolic strategies of autotrophy and heterotrophy by algae and bacteria, respectively. We found that their coexistence allowed the recycling of resources in a microbial loop that would otherwise be lost. Instead, these resources were made available to higher trophic levels, increasing the trophic transfer efficiency in food webs.
The predation process comprises the next higher level of factors shaping the predator-prey interaction, besides these factors that originated from the functioning or composition of individuals. Here, I focused on defensive mechanisms and investigated multiple scenarios of static or adaptive combinations of prey defense and predator offense. I confirmed and extended earlier reports on the coexistence-promoting effects of partially lower palatability of the prey community. When bacteria and algae are coexisting, a higher palatability of bacteria may increase the average predator biomass, with the side effect of making the population dynamics more regular. This may facilitate experimental investigations and interpretations. If defense and offense are adaptive, this allows organisms to maximize their growth rate. Besides this fitness-enhancing effect, I found that co-adaptation may provide the predator-prey system with the flexibility to buffer external perturbations.
On top of these rather internal factors, environmental drivers also affect predator-prey interactions. I showed that environmental nutrient fluctuations may create a spatio-temporal resource heterogeneity that selects for different predator strategies. I hypothesized that this might favour either storage or acclimation specialists, depending on the frequency of the environmental fluctuations.
We found that many of these factors promote the coexistence of different strategies and may therefore support and sustain biodiversity. Thus, they might be relevant for the maintenance of crucial ecosystem functions that also affect us humans. Besides this, the richness of factors that impact predator-prey interactions might explain why so many species, especially in the planktonic regime, are able to coexist.
A reliable inference of networks from data is of key interest in many scientific fields. Several methods have been suggested in the literature to reliably determine links in a network. These techniques rely on statistical methods, typically controlling the number of false positive links, but not considering false negative links. In this thesis new methodologies to improve network inference are suggested. Initial analyses demonstrate the impact of falsepositive and false negative conclusions about the presence or absence of links on the resulting inferred network. Consequently, revealing the importance of making well-considered choices leads to suggest new approaches to enhance existing network reconstruction methods.
A simulation study, presented in Chapter 3, shows that different values to balance false positive and false negative conclusions about links should be used in order to reliably estimate network characteristics. The existence of type I and type II errors in the reconstructed network, also called biased network, is accepted. Consequently, an analytic method that describes the influence of these two errors on the network structure is explored. As a result of this analysis, an analytic formula of the density of the biased vertex degree distribution is found (Chapter 4).
In the inverse problem, the vertex degree distribution of the true underlying network is analytically reconstructed, assuming the probabilities of type I and type II errors. Chapters 4-5 show that the method is robust to incorrect estimates of α and β within reasonable limits. In Chapter 6, an iterative procedure to enhance this method is presented in the case of large errors on the estimates of α and β.
The investigations presented so far focus on the influence of false positive and false negative links on the network characteristics. In Chapter 7, the analysis is reversed - the study focuses on the influence of network characteristics on the probability of type I and type II errors, in the case of networks of coupled oscillators. The probabilities of α and β are influenced by the shortest path length and the detour degree, respectively. These results have been used to improve the network reconstruction, when the true underlying network is not known a priori, introducing a novel and advanced concept of threshold.
The identification of vulnerabilities in IT infrastructures is a crucial problem in enhancing the security, because many incidents resulted from already known vulnerabilities, which could have been resolved. Thus, the initial identification of vulnerabilities has to be used to directly resolve the related weaknesses and mitigate attack possibilities. The nature of vulnerability information requires a collection and normalization of the information prior to any utilization, because the information is widely distributed in different sources with their unique formats. Therefore, the comprehensive vulnerability model was defined and different sources have been integrated into one database. Furthermore, different analytic approaches have been designed and implemented into the HPI-VDB, which directly benefit from the comprehensive vulnerability model and especially from the logical preconditions and postconditions.
Firstly, different approaches to detect vulnerabilities in both IT systems of average users and corporate networks of large companies are presented. Therefore, the approaches mainly focus on the identification of all installed applications, since it is a fundamental step in the detection. This detection is realized differently depending on the target use-case. Thus, the experience of the user, as well as the layout and possibilities of the target infrastructure are considered. Furthermore, a passive lightweight detection approach was invented that utilizes existing information on corporate networks to identify applications.
In addition, two different approaches to represent the results using attack graphs are illustrated in the comparison between traditional attack graphs and a simplistic graph version, which was integrated into the database as well. The implementation of those use-cases for vulnerability information especially considers the usability. Beside the analytic approaches, the high data quality of the vulnerability information had to be achieved and guaranteed. The different problems of receiving incomplete or unreliable information for the vulnerabilities are addressed with different correction mechanisms. The corrections can be carried out with correlation or lookup mechanisms in reliable sources or identifier dictionaries. Furthermore, a machine learning based verification procedure was presented that allows an automatic derivation of important characteristics from the textual description of the vulnerabilities.
Advancing charge selective contacts for efficient monolithic perovskite-silicon tandem solar cells
(2019)
Hybrid organic-inorganic perovskites are one of the most promising material classes for photovoltaic energy conversion. In solar cells, the perovskite absorber is sandwiched between n- and p-type contact layers which selectively transport electrons and holes to the cell’s cathode and anode, respectively. This thesis aims to advance contact layers in perovskite solar cells and unravel the impact of interface and contact properties on the device performance. Further, the contact materials are applied in monolithic perovskite-silicon heterojunction (SHJ) tandem solar cells, which can overcome the single junction efficiency limits and attract increasing attention. Therefore, all contact layers must be highly transparent to foster light harvesting in the tandem solar cell design. Besides, the SHJ device restricts processing temperatures for the selective contacts to below 200°C.
A comparative study of various electron selective contact materials, all processed below 180°C, in n-i-p type perovskite solar cells highlights that selective contacts and their interfaces to the absorber govern the overall device performance. Combining fullerenes and metal-oxides in a TiO2/PC60BM (phenyl-C60-butyric acid methyl ester) double-layer contact allows to merge good charge extraction with minimized interface recombination. The layer sequence thereby achieved high stabilized solar cell performances up to 18.0% and negligible current-voltage hysteresis, an otherwise pronounced phenomenon in this device design. Double-layer structures are therefore emphasized as a general concept to establish efficient and highly selective contacts.
Based on this success, the concept to combine desired properties of different materials is transferred to the p-type contact. Here, a mixture of the small molecule Spiro-OMeTAD [2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluoren] and the doped polymer PEDOT [poly(3,4-ethylenedioxythiophene)] is presented as a novel hole selective contact. PEDOT thereby remarkably suppresses charge recombination at the perovskite surface, allowing an increase of quasi-Fermi level splitting in the absorber. Further, the addition of Spiro-OMeTAD into the PEDOT layer is shown to enhance charge extraction at the interface and allow high efficiencies up to 16.8%.
Finally, the knowledge on contact properties is applied to monolithic perovskite-SHJ tandem solar cells. The main goal is to optimize the top contact stack of doped Spiro-OMeTAD/molybdenum oxide(MoOx)/ITO towards higher transparency by two different routes. First, fine-tuning of the ITO deposition to mitigate chemical reduction of MoOx and increase the transmittance of MoOx/ITO stacks by 25%. Second, replacing Spiro-OMeTAD with the alternative hole transport materials PEDOT/Spiro-OMeTAD mixtures, CuSCN or PTAA [poly(triaryl amine)]. Experimental results determine layer thickness constrains and validate optical simulations, which subsequently allow to realistically estimate the respective tandem device performances. As a result, PTAA represents the most promising replacement for Spiro-OMeTAD, with a projected increase of the optimum tandem device efficiency for the herein used architecture by 2.9% relative to 26.5% absolute. The results also reveal general guidelines for further performance gains of the technology.
Kosmologie beschreibt die Entwicklung des Universums als Ganzes. Kosmologische Entdeckungen in Theorie und Praxis haben daher unser modernes wissenschaftliches Weltbild entscheidend geprägt. Die Vermittlung eines modernen Weltbildes durch Unterricht ist ein häufiger Wunsch in der naturwissenschaftlichen Bildungsdiskussion. Dennoch existieren weiterhin Forschungs- und Entwicklungsbedarfe. Kosmologische Themen finden sich häufig in den Medien und sind gleichzeitig weiter vom Alltag entfernt, so dass sich hier besonders leicht wissenschaftlich inkorrekte Vorstellungen entwickeln können, die zu Problemen im Unterricht führen können.
Das Ziel dieser wissenschaftlichen Arbeit ist es, zu diesem Forschungsgebiet beizutragen und die Voraussetzungen hinsichtlich vorhandener Vorkenntnisse und Präkonzepte in Kosmologie, mit denen Schülerinnen und Schüler in den Unterricht kommen, zu untersuchen und anschließend mit denen anderer Länder zu vergleichen. Dies erfolgt anhand einer qualitativen Inhaltsanalyse eines offenen Fragebogens. Auf dieser Grundlage wird schließlich ein Multiple-Choice Fragebogen entwickelt, angewendet und evaluiert.
Die Ergebnisse zeigen große Wissenslücken im Bereich der Kosmologie auf und geben erste Hinweise auf vorhandene Unterschiede zwischen den Ländern. Es existieren ebenfalls einige teils weit verbreitete wissenschaftlich inkorrekte Vorstellungen wie beispielsweise die Assoziation des Urknalls mit einer Explosion, der Urknall verursacht durch eine Kollision von Teilchen oder größeren Objekten, oder die Vorstellung der Ausdehnung des Universums als neue Entdeckungen und/oder Wissen. Des Weiteren gab nur etwa jeder Fünfte das korrekte Alter des Universums oder die Ausdehnung des Universums als einen der drei Belege der Urknalltheorie an, während fast 40% keinen einzigen Beleg nennen konnten. Für den geschlossenen Fragebogen konnten gute Hinweise für verschiedene Validitätsaspekte herausgearbeitet werden und es existieren erste Hinweise darauf, dass der Fragebogen Wissenszuwachs messen kann und damit wahrscheinlich zur Untersuchung der Wirksamkeit von Lerneinheiten eingesetzt werden kann. Auch ein entsprechendes Modell zur Verständnisentwicklung der Ausdehnung des Universums zeigte sich vielversprechend.
Diese Arbeit liefert insgesamt einen Forschungsbeitrag zum Schülervorwissen und Vorstellungen in der Kosmologie und deren Large Scale Assessment. Dies eröffnet die Möglichkeit zukünftiger Forschungen im Bereich von Gruppenvergleichen insbesondere hinsichtlich objektiver Ländervergleiche sowie der Untersuchungen der Wirksamkeit von einzelnen Lerneinheiten als auch Vergleiche verschiedener Lerneinheiten untereinander.
Hyperspectral remote sensing of the spatial and temporal heterogeneity of low Arctic vegetation
(2019)
Arctic tundra ecosystems are experiencing warming twice the global average and Arctic vegetation is responding in complex and heterogeneous ways. Shifting productivity, growth, species composition, and phenology at local and regional scales have implications for ecosystem functioning as well as the global carbon and energy balance. Optical remote sensing is an effective tool for monitoring ecosystem functioning in this remote biome. However, limited field-based spectral characterization of the spatial and temporal heterogeneity limits the accuracy of quantitative optical remote sensing at landscape scales. To address this research gap and support current and future satellite missions, three central research questions were posed:
• Does canopy-level spectral variability differ between dominant low Arctic vegetation communities and does this variability change between major phenological phases?
• How does canopy-level vegetation colour images recorded with high and low spectral resolution devices relate to phenological changes in leaf-level photosynthetic pigment concentrations?
• How does spatial aggregation of high spectral resolution data from the ground to satellite scale influence low Arctic tundra vegetation signatures and thereby what is the potential of upcoming hyperspectral spaceborne systems for low Arctic vegetation characterization?
To answer these questions a unique and detailed database was assembled. Field-based canopy-level spectral reflectance measurements, nadir digital photographs, and photosynthetic pigment concentrations of dominant low Arctic vegetation communities were acquired at three major phenological phases representing early, peak and late season. Data were collected in 2015 and 2016 in the Toolik Lake Research Natural Area located in north central Alaska on the North Slope of the Brooks Range. In addition to field data an aerial AISA hyperspectral image was acquired in the late season of 2016. Simulations of broadband Sentinel-2 and hyperspectral Environmental and Mapping Analysis Program (EnMAP) satellite reflectance spectra from ground-based reflectance spectra as well as simulations of EnMAP imagery from aerial hyperspectral imagery were also obtained.
Results showed that canopy-level spectral variability within and between vegetation communities differed by phenological phase. The late season was identified as the most discriminative for identifying many dominant vegetation communities using both ground-based and simulated hyperspectral reflectance spectra. This was due to an overall reduction in spectral variability and comparable or greater differences in spectral reflectance between vegetation communities in the visible near infrared spectrum.
Red, green, and blue (RGB) indices extracted from nadir digital photographs and pigment-driven vegetation indices extracted from ground-based spectral measurements showed strong significant relationships. RGB indices also showed moderate relationships with chlorophyll and carotenoid pigment concentrations. The observed relationships with the broadband RGB channels of the digital camera indicate that vegetation colour strongly influences the response of pigment-driven spectral indices and digital cameras can track the seasonal development and degradation of photosynthetic pigments.
Spatial aggregation of hyperspectral data from the ground to airborne, to simulated satel-lite scale was influenced by non-photosynthetic components as demonstrated by the distinct shift of the red edge to shorter wavelengths. Correspondence between spectral reflectance at the three scales was highest in the red spectrum and lowest in the near infra-red. By artificially mixing litter spectra at different proportions to ground-based spectra, correspondence with aerial and satellite spectra increased. Greater proportions of litter were required to achieve correspondence at the satellite scale.
Overall this thesis found that integrating multiple temporal, spectral, and spatial data is necessary to monitor the complexity and heterogeneity of Arctic tundra ecosystems. The identification of spectrally similar vegetation communities can be optimized using non-peak season hyperspectral data leading to more detailed identification of vegetation communities. The results also highlight the power of vegetation colour to link ground-based and satellite data. Finally, a detailed characterization non-photosynthetic ecosystem components is crucial for accurate interpretation of vegetation signals at landscape scales.
Carbonate-rich silicate and carbonate melts play a crucial role in deep Earth magmatic processes and their melt structure is a key parameter, as it controls physical and chemical properties. Carbonate-rich melts can be strongly enriched in geochemically important trace elements. The structural incorporation mechanisms of these elements are difficult to study because such melts generally cannot be quenched to glasses, which are usually employed for structural investigations. This thesis investigates the influence of CO2 on the local environments of trace elements contained in silicate glasses with variable CO2 concentrations as well as in silicate and carbonate melts. The compositions studied include sodium-rich peralkaline silicate melts and glasses and carbonate melts similar to those occurring naturally at Oldoinyo Lengai volcano, Tanzania.
The local environments of the three elements yttrium (Y), lanthanum (La) and strontium (Sr) were investigated in synthesized glasses and melts using X-ray absorption fine structure (XAFS) spectroscopy. Especially extended X-ray absorption fine structure spectroscopy (EXAFS) provides element specific information on local structure, such as bond lengths, coordination numbers and the degree of disorder. To cope with the enhanced structural disorder present in glasses and melts, EXAFS analysis was based on fitting approaches using an asymmetric distribution function as well as a correlation model according to bond valence theory. Firstly, silicate glasses quenched from high pressure/temperature melts with up to 7.6 wt % CO2 were investigated. In strongly and extremely peralkaline glasses the local structure of Y is unaffected by the CO2 content (with oxygen bond lengths of ~ 2.29 Å). Contrary, the bond lengths for Sr-O and La-O increase with increasing CO2 content in the strongly peralkaline glasses from ~ 2.53 to ~ 2.57 Å and from ~ 2.52 to ~ 2.54 Å, respectively, while they remain constant in extremely peralkaline glasses (at ~ 2.55 Å and 2.54 Å, respectively). Furthermore, silicate and unquenchable carbonate melts were investigated in-situ at high pressure/temperature conditions (2.2 to 2.6 GPa, 1200 to 1500 °C) using a Paris-Edinburgh press. A novel design of the pressure medium assembly for this press was developed, which features increased mechanical stability as well as enhanced transmittance at relevant energies to allow for low content element EXAFS in transmission. Compared to glasses the bond lengths of Y-O, La-O and Sr-O are elongated by up to + 3 % in the melt and exhibit higher asymmetric pair distributions. For all investigated silicate melt compositions Y-O bond lengths were found constant at ~ 2.37 Å, while in the carbonate melt the Y-O length increases slightly to 2.41 Å. The La-O bond lengths in turn, increase systematically over the whole silicate – carbonate melt joint from 2.55 to 2.60 Å. Sr-O bond lengths in melts increase from ~ 2.60 to 2.64 Å from pure silicate to silicate-bearing carbonate composition with constant elevated bond length within the carbonate region.
For comparison and deeper insight, glass and melt structures of Y and Sr bearing sodium-rich silicate to carbonate compositions were simulated in an explorative ab initio molecular dynamics (MD) study. The simulations confirm observed patterns of CO2-dependent local changes around Y and Sr and additionally provide further insights into detailed incorporation mechanisms of the trace elements and CO2. Principle findings include that in sodium-rich silicate compositions carbon either is mainly incorporated as a free carbonate-group or shares one oxygen with a network former (Si or [4]Al) to form a non-bridging carbonate. Of minor importance are bridging carbonates between two network formers. Here, a clear preference for two [4]Al as adjacent network formers occurs, compared to what a statistical distribution would suggest. In C-bearing silicate melts minor amounts of molecular CO2 are present, which is almost totally dissolved as carbonate in the quenched glasses.
The combination of experiment and simulation provides extraordinary insights into glass and melt structures. The new data is interpreted on the basis of bond valence theory and is used to deduce potential mechanisms for structural incorporation of investigated elements, which allow for prediction on their partitioning behavior in natural melts. Furthermore, it provides unique insights into the dissolution mechanisms of CO2 in silicate melts and into the carbonate melt structure. For the latter, a structural model is suggested, which is based on planar CO3-groups linking 7- to 9-fold cation polyhedra, in accordance to structural units as found in the Na-Ca carbonate nyerereite. Ultimately, the outcome of this study contributes to rationalize the unique physical properties and geological phenomena related to carbonated silicate-carbonate melts.
Untersuchungen an neuartigen sauerstoffsubstituierten Donoren und Akzeptoren für Singulettsauerstoff
(2019)
Im Verlauf dieser Arbeit wurden Aromaten wie Naphthaline und Anthracene mit Singulettsauerstoff, einer reaktiven Form des gewöhnlichen Sauerstoffs, zu sogenannten Endoperoxiden umgesetzt. Die hier eingesetzten Systeme wurden mit funktionellen Gruppen modifiziert, die über eine Sauerstoffbrücke mit dem Aromaten verknüpft sind. Die daraus entstandenen Endoperoxide sind meist besonders labil und konnten in dieser Arbeit isoliert und umfassend untersucht werden.
Hierbei wurde zum einen das Reaktionsverhalten untersucht. Es konnte gezeigt werden, dass die Aromaten in Abhängigkeit ihrer funktionellen Gruppen unterschiedlich schnell mit Singulettsauerstoff reagieren. Die so ermittelten Reaktivitäten wurden zusätzlich durch theoretische Berechnungen gestützt.
Die resultierenden Endoperoxide wurden unter verschiedenen Bedingungen wie erhöhter Temperatur oder einem sauren bzw. basischen Milieu auf ihre Stabilität hin untersucht. Dabei konnte gezeigt werden, dass die auf Naphthalinen basierenden Endoperoxiden den gebundenen Singulettsauerstoff in guten Ausbeuten oft schon bei sehr niedrigen Temperaturen (−40 bis 0 °C) freisetzen. Diese Verbindungen können daher als milde Quellen dieser reaktiven Sauerstoffspezies eingesetzt werden. Weiterhin konnten bei den Anthracenendoperoxiden Zerfallsmechanismen aufgeklärt und andere reaktive Sauerstoffspezies wie Wasserstoffperoxid oder Persäuren nachgewiesen werden.
Zu den Modifikationen der Aromaten gehören auch Glucosereste. Dadurch könnten sich die hier hergestellten Endoperoxide als vielversprechende Verbindungen in der Krebstherapie herausstellen, da Krebszellen deutlich stärker als gesunde Zellen kohlenhydratreiche Verbindungen für ihren Stoffwechsel benötigen. Bei der Spaltung von Endoperoxiden mit Glucosesubstituenten werden ebenfalls reaktive Sauerstoffspezies frei, die so zum Zelltod führen könnten.
The main goal of this thesis is to explore the feasibility of using cross-lingual annotation projection as a method of alleviating the task of manual coreference annotation.
To reach our goal, we build a first trilingual parallel coreference corpus that encompasses multiple genres. For the annotation of the corpus, we develop common coreference annotation guidelines that are applicable to three languages (English, German, Russian) and include a novel domain-independent typology of bridging relations as well as state-of-the-art near-identity categories.
Thereafter, we design and perform several annotation projection experiments. In the first experiment, we implement a direct projection method with only one source language. Our results indicate that, already in a knowledge-lean scenario, our projection approach is superior to the most closely related work of Postolache et al. (2006). Since the quality of the resulting annotations is to a high degree dependent on the word alignment, we demonstrate how using limited syntactic information helps to further improve mention extraction on the target side. As a next step, in our second experiment, we show how exploiting two source languages helps to improve the quality of target annotations for both language pairs by concatenating annotations projected from two source languages. Finally, we assess the projection quality in a fully automatic scenario (using automatically produced source annotations), and propose a pilot experiment on manual projection of bridging pairs.
For each of the experiments, we carry out an in-depth error analysis, and we conclude that noisy word alignments, translation divergences and morphological and syntactic differences between languages are responsible for projection errors. We systematically compare and evaluate our projection methods, and we investigate the errors both qualitatively and quantitatively in order to identify problematic cases. Finally, we discuss the applicability of our method to coreference annotations and propose several avenues of future research.
Die Anfechtbarkeit und die Feststellbarkeit der Mutterschaft de lege lata und de lege ferenda
(2019)
Der althergebrachte Grundsatz, wonach das Kind von der Frau abstammt, welche es geboren hat, ist durch die moderne Fortpflanzungsmedizin ins Wanken geraten. Dennoch ordnet § 1591 BGB das Kind unanfechtbar der Geburtsmutter zu. Rechtliche und genetische Mutterschaft fallen deshalb dauerhaft auseinander, wenn das Kind im Wege der Leihmutterschaft oder nach einer Eizell- bzw. Embryospende zur Welt kommt. Die auf diese Methoden der artifiziellen Reproduktion bezogenen, im Inland bestehenden Verbote halten Paare mit Kinderwunsch nicht davon ab, auf entsprechende Angebote im Ausland zurückzugreifen. Daraus resultierende kollisions- und verfassungsrechtliche Probleme sind Gegenstand der vorliegenden Arbeit.
Für den Bereich der Leihmutterschaft wird der Frage nachgegangen, ob die mit dem Anfechtungsausschluss verfolgten Ziele des Gesetzgebers die damit einhergehenden Beeinträchtigungen grundrechtlich geschützter Rechtspositionen von genetischer Mutter und Kind rechtfertigen können. Besonderes Augenmerk liegt auf dem von Art. 6 Abs. 2 S. 1 GG geschützten Interesse von leiblichen Eltern und Kindern, die verfahrensrechtliche Möglichkeit zu erhalten, rechtlich einander zugeordnet zu werden. Dieses Interesse wird den Zielen des Gesetzgebers, der mit dem Anfechtungsausschluss die Rechte von Leihmüttern und Kindern zu schützen beabsichtigt, im Rahmen einer umfassenden Verhältnismäßigkeitsprüfung gegenübergestellt.
In den Konstellationen der Eizell- und Embryospende tritt schwerpunktmäßig das Recht des Kindes auf Kenntnis der eigenen Abstammung in den Vordergrund und mit ihm die Frage, ob sich daraus eine Verpflichtung des Gesetzgebers ableiten lässt, den Tatbestand von § 1598a BGB so zu erweitern, dass die vermuteten genetischen Eltern für den Bereich der artifiziellen Reproduktion in den Kreis der Klärungsverpflichteten aufgenommen werden.
Neben diesen Schwerpunkten werden viele weitere Probleme angesprochen. Im Ergebnis mündet die Arbeit in einen Vorschlag für die Legislative.
In this thesis we introduce the concept of the degree of formality. It is directed against a dualistic point of view, which only distinguishes between formal and informal proofs. This dualistic attitude does not respect the differences between the argumentations classified as informal and it is unproductive because the individual potential of the respective argumentation styles cannot be appreciated and remains untapped.
This thesis has two parts. In the first of them we analyse the concept of the degree of formality (including a discussion about the respective benefits for each degree) while in the second we demonstrate its usefulness in three case studies. In the first case study we will repair Haskell B. Curry's view of mathematics, which incidentally is of great importance in the first part of this thesis, in light of the different degrees of formality. In the second case study we delineate how awareness of the different degrees of formality can be used to help students to learn how to prove. Third, we will show how the advantages of proofs of different degrees of formality can be combined by the development of so called tactics having a medium degree of formality. Together the three case studies show that the degrees of formality provide a convincing solution to the problem of untapped potential.
Domestication syndrome has resulted in the large loss of genetic variation of crop plants. Because of such genetic loss, productivity of various beneficial secondary (specialized) metabolites that protect against abiotic/biotic stresses, has been narrowed in many domesticated crops. Many key regulators or structural genes of secondary metabolic pathways in the domesticated as well as wild tomatoes are still largely unknown. In recent studies, metabolic quantitative trait loci (mQTL) analysis using the population of introgression lines (ILs), each containing a single introgression from Solanum pennellii (wild tomato) in the genetic background of domesticated tomato (M82, Solanum lycopersicum), has been used for investigation of metabolic regulation and key genes involved in both primary and secondary metabolism. In this thesis, three research projects, i) understanding of metabolic linkage between branched chain amino acids (BCAAs) and secondary metabolism using antisense lines of BCAAs metabolic genes, ii) investigation of novel key genes involved in tomato secondary metabolism and fruit ripening, iii) mapping of drought stress responsive mQTLs in tomato, are presented and discussed. In the first part, metabolic linkage between leucine and secondary metabolism is investigated by analyzing antisense lines of four key genes (ketol-acid reductoisomerase, KARI; dihydroxy-acid dehydratase, DHAD; isopropylmalate dehydratase, IPMD and branched chain aminotransferases1, BCAT1) found previously in mQTL of leucine contents. Obtained results indicate that KARI might be a rate limiting enzyme for iC5 acyl-sucrose synthesis in young leaf but not in red ripe fruits. By integrating obtained results with previous reports, inductive metabolic linkage between BCAAs and other secondary metabolic pathways at DHAD transcriptional levels in fruit is proposed. In the second part, candidate genes that are involved in secondary metabolism and fruit ripening in tomato were found by the approach of expression quantitative trait loci (eQTL) analysis. To predict functions of those candidate genes, functional validation by virus induced gene silencing and transient overexpression were performed. Results obtained by analyzing T0 overexpression and artificial miRNA lines for some of those candidates confirm their predicted functions, for example involved in fruit ripening (WD40, Solyc04g005020) and iC5 acyl-sucrose synthesis (P450, Solyc03g111940). In the third part, mapping of drought stress responsive mQTLs was performed using 57 S. pennellii ILs population. Evaluation of genetic architecture of mQTL analysis resulted in identifying drought responsive ILs (11-2, 8-3-1, 10-1-1 and 3-1). Location of well characterized regulators in these ILs helped to filter potential new key genes involved in drought stress tolerance. Obtained results suggests us our approaches could be viable for narrowing down potential candidates involved in creating interspecific variation in secondary metabolite content and at the level of fruit ripening.
Der historische Spielfilm zählt zu den populärsten Formen geschichtskultureller Artikulation. Als solche ist er Gegenstand kontroverser Diskussionen über einen angemessenen didaktischen Umgang. Vor diesem Hintergrund ist es das Ziel der vorliegenden Arbeit, ein integratives, theoretisch und empirisch abgesichertes Analysemodell zu entwickeln, das nach den Tiefenstrukturen historischen Erzählens im Medium des Spielfilms fragt und dabei unterschiedliche Erscheinungsformen historischer Spielfilme berücksichtigt. Die Überlegungen bewegen sich deshalb in einem interdisziplinären Spannungsfeld von Theorien zum historischen Erzählen und Konzepten der Literatur- und Filmwissenschaft. Die Diskussion und Synthese dieser unterschiedlichen Konzepte geht dabei – auf der Grundlage einer großen Materialbasis – vom Gegenstand aus und ist induktiv angelegt. Als Orientierung für die praktische Arbeit werden am Ende der einzelnen Kapitel Toolkits entwickelt, die zu einer vertieften Auseinandersetzung mit historischen Spielfilmen anregen sollen.
Partial melting is a first order process for the chemical differentiation of the crust (Vielzeuf et al., 1990). Redistribution of chemical elements during melt generation crucially influences the composition of the lower and upper crust and provides a mechanism to concentrate and transport chemical elements that may also be of economic interest. Understanding of the diverse processes and their controlling factors is therefore not only of scientific interest but also of high economic importance to cover the demand for rare metals.
The redistribution of major and trace elements during partial melting represents a central step for the understanding how granite-bound mineralization develops (Hedenquist and Lowenstern, 1994). The partial melt generation and mobilization of ore elements (e.g. Sn, W, Nb, Ta) into the melt depends on the composition of the sedimentary source and melting conditions. Distinct source rocks have different compositions reflecting their deposition and alteration histories. This specific chemical “memory” results in different mineral assemblages and melting reactions for different protolith compositions during prograde metamorphism (Brown and Fyfe, 1970; Thompson, 1982; Vielzeuf and Holloway, 1988). These factors do not only exert an important influence on the distribution of chemical elements during melt generation, they also influence the volume of melt that is produced, extraction of the melt from its source, and its ascent through the crust (Le Breton and Thompson, 1988). On a larger scale, protolith distribution and chemical alteration (weathering), prograde metamorphism with partial melting, melt extraction, and granite emplacement are ultimately depending on a (plate-)tectonic control (Romer and Kroner, 2016). Comprehension of the individual stages and their interaction is crucial in understanding how granite-related mineralization forms, thereby allowing estimation of the mineralization potential of certain areas. Partial melting also influences the isotope systematics of melt and restite. Radiogenic and stable isotopes of magmatic rocks are commonly used to trace back the source of intrusions or to quantify mixing of magmas from different sources with distinct isotopic signatures (DePaolo and Wasserburg, 1979; Lesher, 1990; Chappell, 1996). These applications are based on the fundamental requirement that the isotopic signature in the melt reflects that of the bulk source from which it is derived. Different minerals in a protolith may have isotopic compositions of radiogenic isotopes that deviate from their whole rock signature (Ayres and Harris, 1997; Knesel and Davidson, 2002). In particular, old minerals with a distinct parent-to-daughter (P/D) ratio are expected to have a specific radiogenic isotope signature. As the partial melting reaction only involves selective phases in a protolith, the isotopic signature of the melt reflects that of the minerals involved in the melting reaction and, therefore, should be different from the bulk source signature. Similar considerations hold true for stable isotopes.
The trace gases CO2 and CH4 pertain to the most relevant greenhouse gases and are important exchange fluxes of the global carbon (C) cycle. Their atmospheric quantity increased significantly as a result of the intensification of anthropogenic activities, such as especially land-use and land-use change, since the mid of the 18th century. To mitigate global climate change and ensure food security, land-use systems need to be developed, which favor reduced trace gas emissions and a sustainable soil carbon management. This requires the accurate and precise quantification of the influence of land-use and land-use change on CO2 and CH4 emissions. A common method to determine the trace gas dynamics and C sink or source function of a particular ecosystem is the closed chamber method. This method is often used assuming that accuracy and precision are high enough to determine differences in C gas emissions for e.g., treatment comparisons or different ecosystem components.
However, the broad range of different chamber designs, related operational procedures and data-processing strategies which are described in the scientific literature contribute to the overall uncertainty of closed chamber-based emission estimates. Hence, the outcomes of meta-analyses are limited, since these methodical differences hamper the comparability between studies. Thus, a standardization of closed chamber data acquisition and processing is much-needed.
Within this thesis, a set of case studies were performed to: (I) develop standardized routines for an unbiased data acquisition and processing, with the aim of providing traceable, reproducible and comparable closed chamber based C emission estimates; (II) validate those routines by comparing C emissions derived using closed chambers with independent C emission estimates; and (III) reveal processes driving the spatio-temporal dynamics of C emissions by developing (data processing based) flux separation approaches.
The case studies showed: (I) the importance to test chamber designs under field conditions for an appropriate sealing integrity and to ensure an unbiased flux measurement. Compared to the sealing integrity, the use of a pressure vent and fan was of minor importance, affecting mainly measurement precision; (II) that the developed standardized data processing routines proved to be a powerful and flexible tool to estimate C gas emissions and that this tool can be successfully applied on a broad range of flux data sets from very different ecosystem; (III) that automatic chamber measurements display temporal dynamics of CO2 and CH4 fluxes very well and most importantly, that they accurately detect small-scale spatial differences in the development of soil C when validated against repeated soil inventories; and (IV) that a simple algorithm to separate CH4 fluxes into ebullition and diffusion improves the identification of environmental drivers, which allows for an accurate gap-filling of measured CH4 fluxes.
Overall, the proposed standardized data acquisition and processing routines strongly improved the detection accuracy and precision of source/sink patterns of gaseous C emissions. Hence, future studies, which consider the recommended improvements, will deliver valuable new data and insights to broaden our understanding of spatio-temporal C gas dynamics, their particular environmental drivers and underlying processes.