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The main objective of this dissertation is to analyse prerequisites, expectations, apprehensions, and attitudes of students studying computer science, who are willing to gain a bachelor degree. The research will also investigate in the students’ learning style according to the Felder-Silverman model. These investigations fall in the attempt to make an impact on reducing the “dropout”/shrinkage rate among students, and to suggest a better learning environment.
The first investigation starts with a survey that has been made at the computer science department at the University of Baghdad to investigate the attitudes of computer science students in an environment dominated by women, showing the differences in attitudes between male and female students in different study years. Students are accepted to university studies via a centrally controlled admission procedure depending mainly on their final score at school. This leads to a high percentage of students studying subjects they do not want. Our analysis shows that 75% of the female students do not regret studying computer science although it was not their first choice. And according to statistics over previous years, women manage to succeed in their study and often graduate on top of their class. We finish with a comparison of attitudes between the freshman students of two different cultures and two different university enrolment procedures (University of Baghdad, in Iraq, and the University of Potsdam, in Germany) both with opposite gender majority.
The second step of investigation took place at the department of computer science at the University of Potsdam in Germany and analyzes the learning styles of students studying the three major fields of study offered by the department (computer science, business informatics, and computer science teaching). Investigating the differences in learning styles between the students of those study fields who usually take some joint courses is important to be aware of which changes are necessary to be adopted in the teaching methods to address those different students. It was a two stage study using two questionnaires; the main one is based on the Index of Learning Styles Questionnaire of B. A. Solomon and R. M. Felder, and the second questionnaire was an investigation on the students’ attitudes towards the findings of their personal first questionnaire. Our analysis shows differences in the preferences of learning style between male and female students of the different study fields, as well as differences between students with the different specialties (computer science, business informatics, and computer science teaching).
The third investigation looks closely into the difficulties, issues, apprehensions and expectations of freshman students studying computer science. The study took place at the computer science department at the University of Potsdam with a volunteer sample of students. The goal is to determine and discuss the difficulties and issues that they are facing in their study that may lead them to think in dropping-out, changing the study field, or changing the university. The research continued with the same sample of students (with business informatics students being the majority) through more than three semesters. Difficulties and issues during the study were documented, as well as students’ attitudes, apprehensions, and expectations. Some of the professors and lecturers opinions and solutions to some students’ problems were also documented. Many participants had apprehensions and difficulties, especially towards informatics subjects. Some business informatics participants began to think of changing the university, in particular when they reached their third semester, others thought about changing their field of study. Till the end of this research, most of the participants continued in their studies (the study they have started with or the new study they have changed to) without leaving the higher education system.
Changing the perspective sometimes offers completely new insights to an already well-known phenomenon. Exercising behavior, defined as planned, structured and repeated bodily movements with the intention to maintain or increase the physical fitness (Caspersen, Powell, & Christenson, 1985), can be thought of as such a well-known phenomenon that has been in the scientific focus for many decades (Dishman & O’Connor, 2005). Within these decades a perspective that assumes rational and controlled evaluations as the basis for decision making, was predominantly used to understand why some people engage in physical activity and others do not (Ekkekakis & Zenko, 2015).
Dual-process theories (Ekkekakis & Zenko, 2015; Payne & Gawronski, 2010) provide another perspective, that is not exclusively influenced by rational reasoning. These theories differentiate two different processes that guide behavior “depending on whether they operate automatically or in a controlled fashion“ (Gawronski & Creighton, 2012, p. 282). Following this line of thought, exercise behavior is not solely influenced by thoughtful deliberations (e.g. concluding that exercising is healthy) but also by spontaneous affective reactions (e.g. disliking being sweaty while exercising). The theoretical frameworks of dual-process models are not new in psychology (Chaiken & Trope, 1999) and have already been used for the explanation of numerous behaviors (e.g. Hofmann, Friese, & Wiers, 2008; Huijding, de Jong, Wiers, & Verkooijen, 2005). However, they have only rarely been used for the explanation of exercise behavior (e.g. Bluemke, Brand, Schweizer, & Kahlert, 2010; Conroy, Hyde, Doerksen, & Ribeiro, 2010; Hyde, Doerksen, Ribeiro, & Conroy, 2010). The assumption of two dissimilar behavior influencing processes, differs fundamentally from previous theories and thus from the research that has been conducted in the last decades in exercise psychology. Research mainly concentrated on predictors of the controlled processes and addressed the identified predictors in exercise interventions (Ekkekakis & Zenko, 2015; Hagger, Chatzisarantis, & Biddle, 2002).
Predictors arising from the described automatic processes, for example automatic evaluations for exercising (AEE), have been neglected in exercise psychology for many years. Until now, only a few researchers investigated the influence of these AEE for exercising behavior (Bluemke et al., 2010; Brand & Schweizer, 2015; Markland, Hall, Duncan, & Simatovic, 2015). Marginally more researchers focused on the impact of AEE for physical activity behavior (Calitri, Lowe, Eves, & Bennett, 2009; Conroy et al., 2010; Hyde et al., 2010; Hyde, Elavsky, Doerksen, & Conroy, 2012). The extant studies mainly focused on the quality of AEE and the associated quantity of exercise (exercise much or little; Bluemke et al., 2010; Calitri et al., 2009; Conroy et al., 2010; Hyde et al., 2012). In sum, there is still a dramatic lack of empirical knowledge, when applying dual-process theories to exercising behavior, even though these theories have proven to be successful in explaining behavior in many other health-relevant domains like eating, drinking or smoking behavior (e.g. Hofmann et al., 2008).
The main goal of the present dissertation was to collect empirical evidence for the influence of AEE on exercise behavior and to expand the so far exclusively correlational studies by experimentally controlled studies. By doing so, the ongoing debate on a paradigm shift from controlled and deliberative influences of exercise behavior towards approaches that consider automatic and affective influences (Ekkekakis & Zenko, 2015) should be encouraged. All three conducted publications are embedded in dual-process theorizing (Gawronski & Bodenhausen, 2006, 2014; Strack & Deutsch, 2004). These theories offer a theoretical framework that could integrate the established controlled variables of exercise behavior explanation and additionally consider automatic factors for exercise behavior like AEE.
Taken together, the empirical findings collected suggest that AEE play an important and diverse role for exercise behavior. They represent exercise setting preferences, are a cause for short-term exercise decisions and are decisive for long-term exercise adherence. Adding to the few already present studies in this field, the influence of (positive) AEE for exercise behavior was confirmed in all three presented publications. Even though the available set of studies needs to be extended in prospectively studies, first steps towards a more complete picture have been taken. Closing with the beginning of the synopsis: I think that time is right for a change of perspectives! This means a careful extension of the present theories with controlled evaluations explaining exercise behavior. Dual-process theories including controlled and automatic evaluations could provide such a basis for future research endeavors in exercise psychology.
In der modernen Kampfführung ist ein steigender Trend zu unbemannten und autonomen Systemen zu beobachten. Doch inwieweit gelingt es dem Recht, mit den technischen Entwicklungen Schritt zu halten? Ist der Einsatz vollautonomer Systeme noch mit dem geltenden Völkerrecht vereinbar? Die Autorin untersucht zunächst die rechtlichen Rahmenbedingungen einer Programmierung von vollautonomen Systemen und geht, sofern möglich, hierbei bereits auf technische Umsetzungsmöglichkeiten ein. Zugleich werden Grenzen der autonomen Entscheidungsfindung, wie z. B. bei der Bestimmung der Verhältnismäßigkeit eines Angriffs, aufgezeigt. In einem zweiten Teil untersucht die Autorin die Problematik der Entscheidungs- und Legitimitätskette bei Einsätzen autonomer Systeme. Waren bisher stets einzelne Soldaten bzw. ihre Befehlshaber für Kriegsverbrechen verantwortlich, so stellt sich bei vollautonomen Systemen die Frage der Verantwortlichkeit im Falle eines rechtswidrigen Einsatzes. Inwieweit kann ein technischer Defekt oder die Fehlprogrammierung eines Systems noch zu einer strafrechtlichen Verantwortlichkeit von Befehlshabern und militärischem Personal führen? Hierbei werden die Lücken des geltenden Völkerstrafrechts deutlich, welches bisher nur begrenzt eine Strafbarkeit für Fahrlässigkeit und Unterlassen vorsieht.
From dark to light
(2016)
In the current paradigm of cosmology, the formation of large-scale structures is mainly driven by non-radiating dark matter, making up the dominant part of the matter budget of the Universe. Cosmological observations however, rely on the detection of luminous galaxies, which are biased tracers of the underlying dark matter. In this thesis I present cosmological reconstructions of both, the dark matter density field that forms the cosmic web, and cosmic velocities, for which both aspects of my work are delved into, the theoretical formalism and the results of its applications to cosmological simulations and also to a galaxy redshift survey.The foundation of our method is relying on a statistical approach, in which a given galaxy catalogue is interpreted as a biased realization of the underlying dark matter density field. The inference is computationally performed on a mesh grid by sampling from a probability density function, which describes the joint posterior distribution of matter density and the three dimensional velocity field. The statistical background of our method is described in Chapter ”Implementation of argo”, where the introduction in sampling methods is given, paying special attention to Markov Chain Monte-Carlo techniques. In Chapter ”Phase-Space Reconstructions with N-body Simulations”, I introduce and implement a novel biasing scheme to relate the galaxy number density to the underlying dark matter, which I decompose into a deterministic part, described by a non-linear and scale-dependent analytic expression, and a stochastic part, by presenting a negative binomial (NB) likelihood function that models deviations from Poissonity. Both bias components had already been studied theoretically, but were so far never tested in a reconstruction algorithm. I test these new contributions againstN-body simulations to quantify improvements and show that, compared to state-of-the-art methods, the stochastic bias is inevitable at wave numbers of k≥0.15h Mpc^−1 in the power spectrum in order to obtain unbiased results from the reconstructions. In the second part of Chapter ”Phase-Space Reconstructions with N-body Simulations” I describe and validate our approach to infer the three dimensional cosmic velocity field jointly with the dark matter density. I use linear perturbation theory for the large-scale bulk flows and a dispersion term to model virialized galaxy motions, showing that our method is accurately recovering the real-space positions of the redshift-space distorted galaxies. I analyze the results with the isotropic and also the two-dimensional power spectrum.Finally, in Chapter ”Phase-space Reconstructions with Galaxy Redshift Surveys”, I show how I combine all findings and results and apply the method to the CMASS (for Constant (stellar) Mass) galaxy catalogue of the Baryon Oscillation Spectroscopic Survey (BOSS). I describe how our method is accounting for the observational selection effects inside our reconstruction algorithm. Also, I demonstrate that the renormalization of the prior distribution function is mandatory to account for higher order contributions in the structure formation model, and finally a redshift-dependent bias factor is theoretically motivated and implemented into our method. The various refinements yield unbiased results of the dark matter until scales of k≤0.2 h Mpc^−1in the power spectrum and isotropize the galaxy catalogue down to distances of r∼20h^−1 Mpc in the correlation function. We further test the results of our cosmic velocity field reconstruction by comparing them to a synthetic mock galaxy catalogue, finding a strong correlation between the mock and the reconstructed velocities. The applications of both, the density field without redshift-space distortions, and the velocity reconstructions, are very broad and can be used for improved analyses of the baryonic acoustic oscillations, environmental studies of the cosmic web, the kinematic Sunyaev-Zel’dovic or integrated Sachs-Wolfe effect.
Z,E-Diene sind ein häufig auftretendes Strukturmerkmal in Naturstoffen. Aus diesem Grund ist die einfache Darstellung dieser Struktureinheit von großen Interesse in der organischen Chemie.
Das erste Ziel der vorliegenden Arbeit war daher die Weiterentwicklung der Ringschlussmetathese-/ baseninduzierten Ringöffnungs-/ Veresterungssequenz (RBRV-Sequenz) zur Synthese von (2Z,4E)-Diencarbonsäureethylestern ausgehend von Butenoaten. Dazu wurde zunächst die RBRV-Sequenz optimiert. Diese aus drei Schritten bestehende Sequenz konnte in einem Eintopf-Verfahren angewendet werden. Die Ringschlussmetathese gelang mit einer Katalysatorbeladung von 1 mol% des GRUBBS-Katalysators der zweiten Generation in Dichlormethan. Für die baseninduzierte Ringöffnung des β,γ-ungesättigten δ Valerolactons wurde NaHMDS verwendet. Die Alkylierung der Carboxylatspezies gelang mit dem MEERWEIN-Reagenz. Die Anwendbarkeit der Sequenz wurde für verschiedene Substrate demonstriert.
Die Erweiterung der Methode auf α-substituierte Butenoate unterlag starken Einschränkungen. So konnte der Zugang für α Hydroxyderivate realisiert werden. Bei der Anwendung der RBRV-Sequenz auf die α-substituierten Butenoate wurde festgestellt, dass diese sich nur in moderaten Ausbeuten umsetzen ließen und zudem nicht selektiv zu den (2E,4E)-konfigurierten α-substituierten-Dienestern reagierten.
Der Einsatz von Eninen unter den Standardbedingungen der RBRV-Sequenz gelang nicht. Erst nach Modifizierung der Sequenz (höhere Katalysatorbeladung, Wechsel des Lösungsmittels) konnten die [3]Dendralen-Produkte in geringen Ausbeuten erhalten werden.
Im zweiten Teil der Arbeit wurde der Einsatz von (2Z,4E)-Diencarbonsäureethylestern in der Totalsynthese von Naturstoffen untersucht. Dazu wurden zunächst die Transformationsmöglichkeiten der Ester geprüft. Es konnte gezeigt werden, dass sich (2Z,4E)-Diencarbonsäureethylester insbesondere zur Synthese von (2Z,4E)-Aldehyden sowie zum Aufbau der (3Z,5E)-Dien-1-in-Struktur eignen.
Anhand dieser Ergebnisse wurde im Anschluss die RBRV-Sequenz in der Totalsynthese eingesetzt. Dazu wurde zunächst der (2Z,4E)-Dienester Microsphaerodiolin in seiner ersten Totalsynthese auf drei verschiedene Routen hergestellt. Im Anschluss wurden sechs verschiedene Polyacetylene mit einer (3Z,5E)-Dien-1-in-Einheit hergestellt. Schlüsselschritte in ihrer Synthese waren immer die RBRV-Sequenz zum Aufbau der Z,E-Dien-Einheit, die Transformation des Esters in ein terminales Alkin sowie die CADIOT-CHODKIEWICZ-Kupplung zum Aufbau unsymmetrischer Polyine. Alle sechs Polyacetylene wurden zum ersten Mal in einer Totalsynthese synthetisiert. Drei Polyacetylene wurden ausgehend von (S)-Butantriol enantiomerenrein dargestellt. Anhand ihrer Drehwerte konnte eine Revision der von YAO und Mitarbeitern vorgenommen Zuordnung der Absolutkonfiguration der Naturstoffe vorgenommen werden.
Europa im Rathaus
(2016)
Seit den 90er Jahren gehen von der europäischen Integration zunehmend Rückwirkungen auf die subnationalen Ebenen aus. In der Folge kann eine Vervielfachung der kommunalen EU-bezogenen Tätigkeiten sowie die Einrichtung spezieller Koordinierungsstellen beobachtet werden. Aufbauend auf einer Befragung unter allen deutschen Großstädten und anhand von Experteninterviews in Bremerhaven, Dresden und Bochum widmet sich dieses Buch der Ausgestaltung der kommunalen EU-Arbeit in der Praxis. Im Mittelpunkt der Untersuchung steht die Frage nach dem Mehrwert einer zentralen EU-Stelle in der Stadtverwaltung.
Intracontinental deformation usually is a result of tectonic forces associated with distant plate collisions. In general, the evolution of mountain ranges and basins in this environment is strongly controlled by the distribution and geometries of preexisting structures. Thus, predictive models usually fail in forecasting the deformation evolution in these kinds of settings. Detailed information on each range and basin-fill is vital to comprehend the evolution of intracontinental mountain belts and basins. In this dissertation, I have investigated the complex Cenozoic tectonic evolution of the western Tien Shan in Central Asia, which is one of the most active intracontinental ranges in the world. The work presented here combines a broad array of datasets, including thermo- and geochronology, paleoenvironmental interpretations, sediment provenance and subsurface interpretations in order to track changes in tectonic deformation. Most of the identified changes are connected and can be related to regional-scale processes that governed the evolution of the western Tien Shan.
The NW-SE trending Talas-Fergana fault (TFF) separates the western from the central Tien Shan and constitutes a world-class example of the influence of preexisting anisotropies on the subsequent structural development of a contractile orogen. While to the east most of ranges and basins have a sub-parallel E-W trend, the triangular-shaped Fergana basin forms a substantial feature in the western Tien Shan morphology with ranges on all three sides. In this thesis, I present 55 new thermochronologic ages (apatite fission track and zircon (U-Th)/He)) used to constrain exhumation histories of several mountain ranges in the western Tien Shan. At the same time, I analyzed the Fergana basin-fill looking for progressive changes in sedimentary paleoenvironments, source areas and stratal geometrical configurations in the subsurface and outcrops.
The data presented in this thesis suggests that low cooling rates (<1°C Myr-1), calm depositional environments, and low depositional rates (<10 m Myr-1) were widely distributed across the western Tien Shan, describing a quiescent tectonic period throughout the Paleogene. Increased cooling rates in the late Cenozoic occurred diachronously and with variable magnitudes in different ranges. This rapid cooling stage is interpreted to represent increased erosion caused by active deformation and constrains the onset of Cenozoic deformation in the western Tien Shan. Time-temperature histories derived from the northwestern Tien Shan samples show an increase in cooling rates by ~25 Ma. This event is correlated with a synchronous pulse
iv
in the South Tien Shan. I suggest that strike-slip motion along the TFF commenced at the Oligo-Miocene boundary, facilitating CCW rotation of the Fergana basin and enabling exhumation of the linked horsetail splays. Higher depositional rates (~150 m Myr-1) in the Oligo-Miocene section (Massaget Fm.) of the Fergana basin suggest synchronous deformation in the surrounding ranges. The central Alai Range also experienced rapid cooling around this time, suggesting that the onset of intramontane basin fragmentation and isolation is coeval. These results point to deformation starting simultaneously in the late Oligocene – early Miocene in geographically distant mountain ranges. I suggest that these early uplifts are controlled by reactivated structures (like the TFF), which are probably the frictionally weakest and most-suitably oriented for accommodating and transferring N-S horizontal shortening along the western Tien Shan.
Afterwards, in the late Miocene (~10 Ma), a period of renewed rapid cooling affected the Tien Shan and most mountain ranges and inherited structures started to actively deform. This episode is widely distributed and an increase in exhumation is interpreted in most of the sampled ranges. Moreover, the Pliocene section in the basin subsurface shows the higher depositional rates (>180 m Myr-1) and higher energy facies. The deformation and exhumation increase further contributed to intramontane basin partitioning. Overall, the interpretation is that the Tien Shan and much of Central Asia suffered a global increase in the rate of horizontal crustal shortening. Previously, stress transfer along the rigid Tarim block or Pamir indentation has been proposed to account for Himalayan hinterland deformation. However, the extent of the episode requires a different and broader geodynamic driver.
In Gelehrte – Republik – Gelehrtenrepublik untersucht Marc Banditt die Eigenheiten aufklärerischer Tendenzen der Stadt Danzig. Deren Nukleus bildete die zur Jahreswende 1742/43 gegründete Naturforschende Gesellschaft, einer der am längsten existierenden privaten Zusammenschlüsse auf diesem Gebiet. Der strukturelle Wandel dieser Sozietät in den ersten knapp 80 Jahren ihres Bestehens wird dabei als die Summe einer Vielzahl von ineinandergreifenden Entwicklungssträngen verstanden, die die voranschreitende gesellschaftliche Durchdringung der Aufklärungsideen und -inhalte im Laufe des 18. Jahrhunderts kennzeichneten. Trotz der Kräfteverschiebungen in Nordosteuropa, die in Gestalt der Teilungen Polen-Litauens der autonomen Stellung der Hansestadt im Jahr 1793 ein Ende bereiteten, offenbart sich, dass die Geschichte des Danziger Naturforscherzirkels mehr Kontinuitäten als Brüche aufweist. Sowohl auf lokaler als auch auf transregionaler Ebene generierte sich die Vereinigung als eine elementare Schnittstelle zwischenmenschlicher Beziehungen, die von familiären Verflechtungen, weitreichenden Gelehrtennetzwerken und patronalen Abhängigkeitsverhältnissen geprägt waren. Auf diese Weise verkörperte die Naturforschende Gesellschaft zum einen den Aufklärungsprozess innerhalb der Stadt Danzig und zum anderen deren Stellenwert als ein wissenschaftlicher Standort im damaligen Europa.
Characterization of the Clp protease complex and identification of putative substrates in N. tabacum
(2016)
We do magnetohydrodynamic (MHD) simulations of local box models of turbulent Interstellar Medium (ISM) and analyse the process of amplification and saturation of mean magnetic fields with methods of mean field dynamo theory. It is shown that the process of saturation of mean fields can be partially described by the prolonged diffusion time scales in presence of the dynamically significant magnetic fields. However, the outward wind also plays an essential role in the saturation in higher SN rate case. Algebraic expressions for the back reaction of the magnetic field onto the turbulent transport coefficients are derived, which allow a complete description of the nonlinear dynamo. We also present the effects of dynamically significant mean fields on the ISM configuration and pressure distribution. We further add the cosmic ray component in the simulations and investigate the kinematic growth of mean fields with a dynamo perspective.
Change points in time series are perceived as heterogeneities in the statistical or dynamical characteristics of the observations. Unraveling such transitions yields essential information for the understanding of the observed system’s intrinsic evolution and potential external influences. A precise detection of multiple changes is therefore of great importance for various research disciplines, such as environmental sciences, bioinformatics and economics. The primary purpose of the detection approach introduced in this thesis is the investigation of transitions underlying direct or indirect climate observations. In order to develop a diagnostic approach capable to capture such a variety of natural processes, the generic statistical features in terms of central tendency and dispersion are employed in the light of Bayesian inversion. In contrast to established Bayesian approaches to multiple changes, the generic approach proposed in this thesis is not formulated in the framework of specialized partition models of high dimensionality requiring prior specification, but as a robust kernel-based approach of low dimensionality employing least informative prior distributions.
First of all, a local Bayesian inversion approach is developed to robustly infer on the location and the generic patterns of a single transition. The analysis of synthetic time series comprising changes of different observational evidence, data loss and outliers validates the performance, consistency and sensitivity of the inference algorithm. To systematically investigate time series for multiple changes, the Bayesian inversion is extended to a kernel-based inference approach. By introducing basic kernel measures, the weighted kernel inference results are composed into a proxy probability to a posterior distribution of multiple transitions. The detection approach is applied to environmental time series from the Nile river in Aswan and the weather station Tuscaloosa, Alabama comprising documented changes. The method’s performance confirms the approach as a powerful diagnostic tool to decipher multiple changes underlying direct climate observations.
Finally, the kernel-based Bayesian inference approach is used to investigate a set of complex terrigenous dust records interpreted as climate indicators of the African region of the Plio-Pleistocene period. A detailed inference unravels multiple transitions underlying the indirect climate observations, that are interpreted as conjoint changes. The identified conjoint changes coincide with established global climate events. In particular, the two-step transition associated to the establishment of the modern Walker-Circulation contributes to the current discussion about the influence of paleoclimate changes on the environmental conditions in tropical and subtropical Africa at around two million years ago.
Die Geschichte der Landtage in der SBZ und in der frühen DDR ist weithin in Vergessenheit geraten. Obwohl die allgemeine Forschungsmeinung ihnen bislang nur die Rolle einer Fußnote der Landesgeschichte beigemessen hat, besaßen die Parlamente in Wirklichkeit für die Nachkriegszeit eine nicht zu unterschätzende Bedeutung.
Die vorliegende Studie untersucht am Beispiel der Landtage von Brandenburg und Thüringen den Wandel der Volksvertretungen von ihren Anfängen 1946 bis zur Auflösung 1952. Im Sinne einer vergleichenden Landesgeschichte werden die Parlamente nicht nur in den von der Besatzungsmacht vorgegebenen politischen und administrativen Rahmen eingeordnet, sondern es wird auch nach ihren strukturellen Gemeinsamkeiten und Besonderheiten gefragt. Das Augenmerk richtet sich zudem auf die Wandlung der Landtagsfraktionen von CDU und LDP: Pochten diese anfangs auf Eigenständigkeit und Gleichberechtigung, wurden sie rasch einem Prozess der politischen Anpassung und schließlich der Ausschaltung unterworfen. An dessen Ende stand die vollständige Unterordnung unter den Willen der Einheitspartei. Die Publikation versteht sich somit als ein Beitrag zum besseren Verständnis der Diktaturdurchsetzung in der SBZ/DDR auf Landesebene.
This publications-based thesis summarizes my contribution to the scientific field of ultrafast structural dynamics. It consists of 16 publications, about the generation, detection and coupling of coherent gigahertz longitudinal acoustic phonons, also called hypersonic waves. To generate such high frequency phonons, femtosecond near infrared laser pulses were used to heat nanostructures composed of perovskite oxides on an ultrashort timescale. As a consequence the heated regions of such a nanostructure expand and a high frequency acoustic phonon pulse is generated. To detect such coherent acoustic sound pulses I use ultrafast variants of optical Brillouin and x-ray scattering. Here an incident optical or x-ray photon is scattered by the excited sound wave in the sample. The scattered light intensity measures the occupation of the phonon modes.
The central part of this work is the investigation of coherent high amplitude phonon wave packets which can behave nonlinearly, quite similar to shallow water waves which show a steepening of wave fronts or solitons well known as tsunamis. Due to the high amplitude of the acoustic wave packets in the solid, the acoustic properties can change significantly in the vicinity of the sound pulse. This may lead to a shape change of the pulse. I have observed by time-resolved Brillouin scattering, that a single cycle hypersound pulse shows a wavefront steepening. I excited hypersound pulses with strain amplitudes until 1% which I have calibrated by ultrafast x-ray diffraction (UXRD).
On the basis of this first experiment we developed the idea of the nonlinear mixing of narrowband phonon wave packets which we call "nonlinear phononics" in analogy with the nonlinear optics, which summarizes a kaleidoscope of surprising optical phenomena showing up at very high electric fields. Such phenomena are for instance Second Harmonic Generation, four-wave-mixing or solitons. But in case of excited coherent phonons the wave packets have usually very broad spectra which make it nearly impossible to look at elementary scattering processes between phonons with certain momentum and energy.
For that purpose I tested different techniques to excite narrowband phonon wave packets which mainly consist of phonons with a certain momentum and frequency. To this end epitaxially grown metal films on a dielectric substrate were excited with a train of laser pulses. These excitation pulses drive the metal film to oscillate with the frequency given by their inverse temporal displacement and send a hypersonic wave of this frequency into the substrate. The monochromaticity of these wave packets was proven by ultrafast optical Brillouin and x-ray scattering.
Using the excitation of such narrowband phonon wave packets I was able to observe the Second Harmonic Generation (SHG) of coherent phonons as a first example of nonlinear wave mixing of nanometric phonon wave packets.
Datenbankbasierte epidemiologische Untersuchung über die Versorgung demenzerkrankter Patienten
(2016)
Hintergrund:
Demenz wird von der Weltgesundheitsorganisation als ein in der Regel chronisch oder progressiv verlaufendes Syndrom definiert, das von einer Vielzahl von Hirnerkrankungen verursacht wird, welche das Gedächtnis, das Denkvermögen, das Verhalten und die Fähigkeit, alltägliche Tätigkeiten auszuführen, beeinflussen. Weltweit leiden 47,5 Millionen Menschen unter Demenz und diese Zahl wird sich voraussichtlich bis zum Jahr 2050 verdreifachen.
In den vorliegenden Studien wurden zum Einem die Faktoren, welche mit dem Risiko einhergehen eine Demenz zu entwickeln, analysiert. Zum Anderen wurde die Persistenz der medikamentösen Behandlung von depressiven Zuständen mit Antidepressiva sowie die Persistenz der medikamentösen Behandlung von Verhaltensstörungen, therapiert mit Antipsychotika, bei Demenzpatienten untersucht.
Durchführung:
Alle drei Studien basieren auf den Daten der IMS Disease Analyzer-Datenbank.
Die Daten der Disease Analyzer-Datenbank werden über standardisierte Schnittstellen direkt monatlich aus dem Praxiscomputer generiert. Die Daten werden vor der Übertragung verschlüsselt und entsprechen in Umfang und Detaillierungsgrad der Patientenakte.
Risikofaktoren für eine Demenzdiagnose
Methode:
Insgesamt wurden in die Studie 11.956 Patienten mit einer Erstdiagnose (Indexdatum) einer Demenz (ICD 10: F01, F03, G30) zwischen Januar 2010 und Dezember 2014 eingeschlossen. 11.956 Kontrollpatienten (ohne Demenz) wurden den Patienten nach Alter, Geschlecht, Art der Krankenversicherung und Arzt zugeordnet. In beiden Fällen wurden die Praxisaufzeichnungen dazu verwendet, sicherzustellen, dass die Patienten vor dem Indexdatum jeweils 10 Jahre kontinuierlich beobachtet worden waren. Insgesamt wurden 23.912 Personen betrachtet.
Mehrere Erkrankungen, die möglicherweise mit Demenz assoziiert sind, wurden anhand von allgemeinärztlichen Diagnosen bestimmt (ICD-10-Codes): Diabetes (E10-E14), Hypertonie (I10), Adipositas (E66), Hyperlipidämie (E78), Schlaganfall (einschließlich transitorische ischämische Attacke, TIA) (I63, I64, G45), Parkinson-Krankheit (G20, G21), intrakranielle Verletzung (S06), koronare Herzkrankheit (I20-I25), leichte kognitive Beeinträchtigung (F06) und psychische und Verhaltensstörungen durch Alkohol (F10). Das Vorhandensein mehrerer Medikamente, wie z. B. Statine, Protonenpumpenhemmer und Antihypertensiva (einschließlich Diuretika, Beta-Blocker, Calciumkanalblocker, ACE-Hemmer und Angiotensin-II), wurde ebenfalls bemessen.
Ergebnisse:
Das Durchschnittsalter für die 11.956 Demenzpatienten und die 11.956 der Kontrollkohorte war 80,4 (SD 5,3) Jahre. 39,0% der waren männlich. In dem multivariaten Regressionsmodell, wurden folgende Variablen mit einem erhöhten Risiko von Demenz in einem signifikanten Einfluß assoziiert: milde kognitive Beeinträchtigung (MCI) (OR: 2,12), psychische und Verhaltensstörungen durch Alkohol (1,96), Parkinson-Krankheit (PD) (1,89), Schlaganfall (1,68), intrakranielle Verletzung (1,30), Diabetes (1,17), Fettstoffwechselstörung (1,07), koronare Herzkrankheit (1,06). Der Einsatz von Antihypertensiva (0,96), Statinen (OR: 0,94) und Protonen-Pumpen-Inhibitoren (PPI) (0,93) wurden mit einem verringerten Risiko der Entwicklung von Demenz.
Schlussfolgerung:
Die gefundenen Risikofaktoren für Demenz stehen in Einklang mit der Literatur. Nichtsdestotrotz bedürfen die Zusammenhänge zwischen der Verwendung von Statinen, PPI und Antihypertensiva und einem verringerten Demenzrisiko weiterer Untersuchungen.
Persistenz der Behandlung mit Antidepressiva bei Patienten mit Demenz
Methode:
Patienten wurden ausgewählt, wenn bei ihnen im Zeitraum zwischen Januar 2004 und Dezember 2013 eine Demenzdiagnose (ICD 10: F01, F03, G30) und eine erste Verordnung eines trizyklischen Antidepressivums oder selektiven Serotonin-
Wiederaufnahmehemmers (SSRI) oder Serotonin-Noradrenalin-Wiederaufnahmehemmers (SSNRI) vorlagen. Ausgewählte Patienten wurden über einen Zeitraum von bis zu zwei Jahre nach dem Indexdatum beobachtet. Das letzte Nachbeobachtungsdatum eines Patienten war der 31. Dezember 2014. Insgesamt standen 12.281 Patienten für die Persistenzanalyse zur Verfügung. Der Hauptzielparameter war die Abbruchrate der Antidepressivabehandlung innerhalb von sechs Monaten nach dem Indexdatum. Behandlungsabbruch wurde definiert als ein Zeitraum von 90 Tagen ohne diese Therapie.
Als demographische Daten wurden Alter, Art der Krankenversicherung (privat oder gesetzlich), Art der Praxis (Neurologe oder Allgemeinmediziner) und Praxisregion (Ost- oder Westdeutschland) erhoben. Die folgenden Demenzdiagnosen wurden berücksichtigt: Alzheimer-Krankheit (G30), vaskuläre Demenz (F01) und nicht näher bezeichnete Demenz (F03). Darüber hinaus wurde der Charlson-Komorbiditäts-Index als allgemeiner Marker für Komorbidität verwendet. Darüber hinaus wurden die folgenden Diagnosen als Komorbiditäten in die Studie aufgenommen: Depression (ICD 10: F32-33), Delir (F05), Typ-2-Diabetes mellitus (E11, E14), Hypertonie (I10), koronare Herzkrankheit (I24, I25), Schlaganfall (I63, I64), Myokardinfarkt (I21-23) und Herzinsuffizienz (I50).
Ergebnisse:
Nach sechs Monaten Nachbeobachtung hatten 52,7 % (von 12,281 Demenzpatienten) der mit Antidepressiva behandelten Demenzpatienten die Medikamenteneinnahme abgebrochen. Die multivariaten Regressionsanalysen zeigten ein signifikant geringeres Risiko für einen Behandlungsabbruch bei mit SSRRI oder SSNRI behandelten Patienten verglichen mit Patienten, die trizyklische Antidepressiva einnahmen. Es zeigte sich ein signifikant geringeres Risiko eines Behandlungsabbruchs bei jüngeren Patienten.
Schlussfolgerung:
Die Ergebnisse zeigen eine unzureichende Persistenz mit Antipsychotika bei Demenzpatienten unter Alltagsbedingungen. Es muss eine Verbesserung erreicht werden, um die in den Richtlinien empfohlene Behandlung sicherzustellen.
Persistenz der Behandlung mit Antipsychotika bei Patienten mit Demenz
Methode:
Diese Studie umfasste Patienten im Alter ab 60 Jahren mit Demenz beliebigen Ursprungs, die zwischen Januar 2009 und Dezember 2013 (Indexdatum) zum ersten Mal Antipsychotikaverordnungen (ATC: N05A) von deutschen Psychiatern erhielten. Der Nachbeobachtungszeitraum endete im Oktober 2015. Die Demenz wurde auf Grundlage der ICD-10-Codes für vaskuläre Demenz (F01), nicht näher bezeichnete Demenz (F03) und Alzheimer-Krankheit (G30) bewertet.
Der Hauptzielparameter war die Behandlungspersistenzrate über einen Zeitraum von mehr als 6 Monaten nach dem Indexdatum. Die Persistenz wurde als Therapiezeit ohne Absetzen der Behandlung, definiert als mindestens 180 Tage ohne Antipsychotikatherapie, geschätzt. Alle Patienten wurden für eine Dauer von bis zu zwei Jahren ab ihrem Indexdatum beobachtet.
Gleichzeitig auftretende Erkrankungen wurden anhand von Diagnosen (ICD-10-Codes) von Depression (F32, F33), Parkinson-Krankheit (G20), psychischer Störungen aufgrund bekannter physiologischer Erkrankungen (F06) und Persönlichkeits- und Verhaltensstörungen aufgrund physiologischer Erkrankungen (F07) bestimmt. Als demographische Daten wurden Alter, Geschlecht und Art der Krankenversicherung (privat/gesetzlich) erhoben.
Ergebnisse:
12,979 Demenzpatienten mit einem Durchschnittsalter von 82 Jahre (52.1% leben in Pflegeheimen) wurden in diese Studie analysiert. Nach zwei Jahren Nachbeobachtung hatten 54,8 %, 57,2 %, 61,1 % bzw. 65,4 % der Patienten zwischen 60-69, 70-79, 80-89 bzw. 90-99 Jahren Antipsychotikaverordnungen erhalten (p<0,001). 82,6 % der in Pflegeheimen lebenden Patienten und 76,2 % der Patienten in häuslicher Pflege setzten ihre Behandlung ebenfalls länger als 6 Monate fort; nach zwei Jahren lag der Anteil bei 63,9 % (in Pflegeheimen) bzw. 55,0 % (in häuslicher Pflege) (p<0,001).
Schlussfolgerung:
Die Studie zeigt, dass der Anteil der mit Antipsychotika behandelten Demenzpatienten sehr hoch ist. Weitere Studien, einschließlich qualitativer Untersuchungen, sind nötig, um die Gründe für dieses Verschreibungsverhalten zu verstehen und zu erklären.
In the debate on how to govern sustainable development, a central question concerns the interaction between knowledge about sustainability and policy developments. The discourse on what constitutes sustainable development conflict on some of the most basic issues, including the proper definitions, instruments and indicators of what should be ‘developed’ or ‘sustained’. Whereas earlier research on the role of (scientific) knowledge in policy adopted a rationalist-positivist view of knowledge as the basis for ‘evidence-based policy making’, recent literature on knowledge creation and transfer processes has instead pointed towards aspects of knowledge-policy ‘co-production’ (Jasanoff 2004). It is highlighted that knowledge utilisation is not just a matter of the quality of the knowledge as such, but a question of which knowledge fits with the institutional context and dominant power structures. Just as knowledge supports and justifies certain policy, policy can produce and stabilise certain knowledge. Moreover, rather than viewing knowledge-policy interaction as a linear and uni-directional model, this conceptualization is based on an assumption of the policy process as being more anarchic and unpredictable, something Cohen, March and Olsen (1972) has famously termed the ‘garbage-can model’.
The present dissertation focuses on the interplay between knowledge and policy in sustainability governance. It takes stock with the practice of ‘Management by Objectives and Results’ (MBOR: Lundqvist 2004) whereby policy actors define sustainable development goals (based on certain knowledge) and are expected to let these definitions guide policy developments as well as evaluate whether sustainability improves or not. As such a knowledge-policy instrument, Sustainability Indicators (SI:s) help both (subjectively) construct ‘social meaning’ about sustainability and (objectively) influence policy and measure its success. The different articles in this cumulative dissertation analyse the development, implementation and policy support (personal and institutional) of Sustainability Indicators as an instrument for MBOR in a variety of settings. More specifically, the articles centre on the question of how sustainability definitions and measurement tools on the one hand (knowledge) and policy instruments and political power structures on the other, are co-produced.
A first article examines the normative foundations of popular international SI:s and country rankings. Combining theoretical (constructivist) analysis with factor analysis, it analyses how the input variable structure of SI:s are related to different sustainability paradigms, producing a different output in terms of which countries (developed versus developing) are most highly ranked. Such a theoretical input-output analysis points towards a potential problem of SI:s becoming a sort of ‘circular argumentation constructs’. The article thus, highlights on a quantitative basis what others have noted qualitatively – that different definitions and interpretations of sustainability influence indicator output to the point of contradiction. The normative aspects of SI:s does thereby not merely concern the question of which indicators to use for what purposes, but also the more fundamental question of how normative and political bias are intrinsically a part of the measurement instrument as such. The study argues that, although no indicator can be expected to tell the sustainability ‘truth-out-there’, a theoretical localization of indicators – and of the input variable structure – may help facilitate interpretation of SI output and the choice of which indicators to use for what (policy or academic) purpose.
A second article examines the co-production of knowledge and policy in German sustainability governance. It focuses on the German sustainability strategy ‘Perspektiven für Deutschland’ (2002), a strategy that stands out both in an international comparison of national sustainability strategies as well as among German government policy strategies because of its relative stability over five consecutive government constellations, its rather high status and increasingly coercive nature. The study analyses what impact the sustainability strategy has had on the policy process between 2002 and 2015, in terms of defining problems and shaping policy processes. Contrasting rationalist and constructivist perspectives on the role of knowledge in policy, two factors, namely the level of (scientific and political) consensus about policy goals and the ‘contextual fit’ of problem definitions, are found to be main factors explaining how different aspects of the strategy is used. Moreover, the study argues that SI:s are part of a continuous process of ‘structuring’ in which indicator, user and context factors together help structure the sustainability challenge in such a way that it becomes more manageable for government policy.
A third article examines how 31 European countries have built supportive institutions of MBOR between 1992 and 2012. In particular during the 1990s and early 2000s much hope was put into the institutionalisation of Environmental Policy Integration (EPI) as a way to overcome sectoral thinking in sustainability policy making and integrate issues of environmental sustainability into all government policy. However, despite high political backing (FN, EU, OECD), implementation of EPI seems to differ widely among countries. The study is a quantitative longitudinal cross-country comparison of how countries’ ‘EPI architectures’ have developed over time. Moreover, it asks which ‘EPI architectures’ seem to be more effective in producing more ‘stringent’ sustainability policy.
Begriffe wie „Türken“, „Menschen mit türkischem Migrationshintergrund“, etc., die in vielen Bereichen des Lebens verwendet werden, sind Ausdruck der vorliegenden Differenzordnungen und Machtstrukturen und können diskriminierend wirken. Das ist z.B. dann der Fall, wenn bestimmte Begriffe verwendet werden, obwohl eine Kontextrelevanz nicht unbedingt vorliegt. Einige ethnische Bezeichnungen werden dabei häufiger verwendet als andere, trotz vergleichbarer Kontextrelevanz: „türkische/arabische Kinder“ aber nicht „englische/spanische Kinder“ (Wiese 2012), „Deutsch-Türke“ Mesut Özil aber nicht „Deutsch-Tunesier“ Sami Khedira. Erst die Bezeichnungen schaffen hier die Subjekte. Die besondere Auszeichnung macht es in der Folge möglich, dass ihnen Eigenschaften zugeschrieben werden (do Mar Castro Varela/Dhawan 2004). Aus Studien geht hervor, dass Ethnisierung mit Unterschichtung (Hormel 2007) in Verbindung gebracht wird und Begriffe wie „Migrant“ mit negativen Eigenschaften (Scarvagliere/Zech 2013). Durch die Auszeichnung von Abweichungen von dem von der Mehrheit definierten unmarkierten Normalfall wird eine Differenzordnung (Mecheril/Melter 2012) hergestellt, die das vermeintliche Anders-Sein ins Zentrum der Aufmerksamkeit rückt. Folgen sind Abwertung bestimmter (Erst-)Sprachen, Unterwerfung durch Beschreibungspraxen und Restriktionen auf dem Feld der Repräsentation (Broden/Mecheril 2007).
Ausgehend von diesen Überlegungen wird in der Arbeit „Ethnizität“ diskutiert, worauf viele dieser Bezeichnungen rekurrieren. Barth (1969, 1994) stellt fest, dass Ethnizität der Abgrenzung dient und Zugehörigkeit zu ethnische Gruppen durch kategoriale Selbst- und Fremdzuschreibungen bestimmt wird. Brubaker (2004) folgert daher, dass „Gruppen“ nur in Form von Vorstellungen existieren, die Individuen davon haben und diese Subjektivität zu unterschiedlichen Konstruktionen ethnischer Identität führt. Dementsprechend können auch „multiple ethnische Identitäten“ (Keupp 2002) und „Hybriditäten“ (Foroutan 2013) das Ergebnis der individuellen Konstruktion sein, ohne dass diese Formen gemeinhin akzeptierte Bezeichnungen darstellen.
Um die individuelle Entstehung ethnischer Identität nachvollziehen zu können, werden in der Arbeit Spracherwerbsgeschichten analysiert, da verschiedene Studien nahelegen, dass das Sprechen einer Sprache in engem Zusammenhang zur Ethnizität steht. Ohm (2008) zeigt, dass Zweitsprachenerwerb mit Identitätsprozessen in einem wechselseitigen Bedingungsverhältnis steht. Giles/Bourhis/Taylor (1977: 326) zeigen anhand von Untersuchungen in mehrsprachigen Gebieten wie Quebec und Wales, dass Sprache enger mit ethnischer Identität verbunden ist als Nationalität oder „Kultur“. Rosenberg (2015) führt am Beispiel der ehemaligen UdSSR auf, dass das Sprechen einer Sprache gleichbedeutend mit dem Zugehörigkeit zu einer ethnischen „Gruppe“ war. Sprache greift auch als Ausschlusskriterium: Nur wer eine Sprache gut spricht, darf die damit verbundene Identität in Anspruch nehmen (Schroeder/Dollnick, 2013: 104).
Mithilfe der Methode des narrativen Interviews können Spracherwerbsgeschichten produziert, und individuelle kognitive Perspektiven und gesellschaftliche Prozesse aufgedeckt werden. In der Analyse können vier Wege der Entstehung ethnischer Identität unterschieden werden: I. Ethnizität als primäre und dauerhafte Dimension, II. Multiple ethnische Identität, III. Unmarkierte ethnische Identität, IV. Selbstbestimmtheit. So kommt die Untersuchung zu dem Schluss, dass Ethnische Identität bei „Menschen mit türkischem Migrationshintergrund“ durch individuelle Erfahrungen entsteht, sich verändern und Mehrfachzugehörigkeiten oder Hybriditäten zulassen kann. Dieses Ergebnis widerspricht dem alltäglichen Gebrauch bestimmter Begriffe und stellt damit gängige Bezeichnungsweisen und Differenzordnungen in Frage.
The Milky Way is only one out of billions of galaxies in the universe. However, it is a special galaxy because it allows to explore the main mechanisms involved in its evolution and formation history by unpicking the system star-by-star. Especially, the chemical fingerprints of its stars provide clues and evidence of past events in the Galaxy’s lifetime. These information help not only to decipher the current structure and building blocks of the Milky Way, but to learn more about the general formation process of galaxies.
In the past decade a multitude of stellar spectroscopic Galactic surveys have scanned millions of stars far beyond the rim of the solar neighbourhood. The obtained spectroscopic information provide unprecedented insights to the chemo-dynamics of the Milky Way. In addition analytic models and numerical simulations of the Milky Way provide necessary descriptions and predictions suited for comparison with observations in order to decode the physical properties that underlie the complex system of the Galaxy.
In the thesis various approaches are taken to connect modern theoretical modelling of galaxy formation and evolution with observations from Galactic stellar surveys. With its focus on the chemo-kinematics of the Galactic disk this work aims to determine new observational constraints on the formation of the Milky Way providing also proper comparisons with two different models. These are the population synthesis model TRILEGAL based on analytical distribution functions, which aims to simulate the number and distribution of stars in the Milky Way and its different components, and a hybrid model (MCM) that combines an N-body simulation of a Milky Way like galaxy in the cosmological framework with a semi-analytic chemical evolution model for the Milky Way. The major observational data sets in use come from two surveys, namely the “Radial Velocity Experiment” (RAVE) and the “Sloan Extension for Galactic Understanding and Exploration” (SEGUE).
In the first approach the chemo-kinematic properties of the thin and thick disk of the Galaxy as traced by a selection of about 20000 SEGUE G-dwarf stars are directly compared to the predictions by the MCM model. As a necessary condition for this, SEGUE's selection function and its survey volume are evaluated in detail to correct the spectroscopic observations for their survey specific selection biases. Also, based on a Bayesian method spectro-photometric distances with uncertainties below 15% are computed for the selection of SEGUE G-dwarfs that are studied up to a distance of 3 kpc from the Sun.
For the second approach two synthetic versions of the SEGUE survey are generated based on the above models. The obtained synthetic stellar catalogues are then used to create mock samples best resembling the compiled sample of observed SEGUE G-dwarfs. Generally, mock samples are not only ideal to compare predictions from various models. They also allow validation of the models' quality and improvement as with this work could be especially achieved for TRILEGAL. While TRILEGAL reproduces the statistical properties of the thin and thick disk as seen in the observations, the MCM model has shown to be more suitable in reproducing many chemo-kinematic correlations as revealed by the SEGUE stars. However, evidence has been found that the MCM model may be missing a stellar component with the properties of the thick disk that the observations clearly show. While the SEGUE stars do indicate a thin-thick dichotomy of the stellar Galactic disk in agreement with other spectroscopic stellar studies, no sign for a distinct metal-poor disk is seen in the MCM model.
Usually stellar spectroscopic surveys are limited to a certain volume around the Sun covering different regions of the Galaxy’s disk. This often prevents to obtain a global view on the chemo-dynamics of the Galactic disk. Hence, a suitable combination of stellar samples from independent surveys is not only useful for the verification of results but it also helps to complete the picture of the Milky Way. Therefore, the thesis closes with a comparison of the SEGUE G-dwarfs and a sample of RAVE giants. The comparison reveals that the chemo-kinematic relations agree in disk regions where the samples of both surveys show a similar number of stars. For those parts of the survey volumes where one of the surveys lacks statistics they beautifully complement each other. This demonstrates that the comparison of theoretical models on the one side, and the combined observational data gathered by multiple surveys on the other side, are key ingredients to understand and disentangle the structure and formation history of the Milky Way.
In this thesis sentence processing was investigated using a psychophysiological measure known as pupillometry as well as Event-Related Potentials (ERP). The scope of the the- sis was broad, investigating the processing of several different movement constructions with native speakers of English and second language learners of English, as well as word order and case marking in German speaking adults and children. Pupillometry and ERP allowed us to test competing linguistic theories and use novel methodologies to investigate the processing of word order. In doing so we also aimed to establish pupillometry as an effective way to investigate the processing of word order thus broadening the methodological spectrum.
This work reports about new high-resolution imaging and spectroscopic observations of solar type III radio bursts at low radio frequencies in the range from 30 to 80 MHz. Solar type III radio bursts are understood as result of the beam-plasma interaction of electron beams in the corona. The Sun provides a unique opportunity to study these plasma processes of an active star. Its activity appears in eruptive events like flares, coronal mass ejections and radio bursts which are all accompanied by enhanced radio emission. Therefore solar radio emission carries important information about plasma processes associated with the Sun’s activity. Moreover, the Sun’s atmosphere is a unique plasma laboratory with plasma processes under conditions not found in terrestrial laboratories. Because of the Sun’s proximity to Earth, it can be studied in greater detail than any other star but new knowledge about the Sun can be transfer to them. This “solar stellar connection” is important for the understanding of processes on other stars.
The novel radio interferometer LOFAR provides imaging and spectroscopic capabilities to study these processes at low frequencies. Here it was used for solar observations.
LOFAR, the characteristics of its solar data and the processing and analysis of the latter with the Solar Imaging Pipeline and Solar Data Center are described. The Solar Imaging Pipeline is the central software that allows using LOFAR for solar observations. So its development was necessary for the analysis of solar LOFAR data and realized here. Moreover a new density model with heat conduction and Alfvén waves was developed that provides the distance of radio bursts to the Sun from dynamic radio spectra.
Its application to the dynamic spectrum of a type III burst observed on March 16, 2016 by LOFAR shows a nonuniform radial propagation velocity of the radio emission. The analysis of an imaging observation of type III bursts on June 23, 2012 resolves a burst as bright, compact region localized in the corona propagating in radial direction along magnetic field lines with an average velocity of 0.23c. A nonuniform propagation velocity is revealed. A new beam model is presented that explains the nonuniform motion of the radio source as a propagation effect of an electron ensemble with a spread velocity distribution and rules out a monoenergetic electron distribution. The coronal electron number density is derived in the region from 1.5 to 2.5 R☉ and fitted with the newly developed density model. It determines the plasma density for the interplanetary space between Sun and Earth. The values correspond to a 1.25- and 5-fold Newkirk model for harmonic and fundamental emission, respectively. In comparison to data from other radio instruments the LOFAR data shows a high sensitivity and resolution in space, time and frequency.
The new results from LOFAR’s high resolution imaging spectroscopy are consistent with current theories of solar type III radio bursts and demonstrate its capability to track fast moving radio sources in the corona. LOFAR solar data is found to be a valuable source for solar radio physics and opens a new window for studying plasma processes associated with highly energetic electrons in the solar corona.
Bedeutung der abhängigen Streuung für die optischen Eigenschaften hochkonzentrierter Dispersionen
(2016)
The cytoskeleton is an essential component of living cells. It is composed of different types of protein filaments that form complex, dynamically rearranging, and interconnected networks. The cytoskeleton serves a multitude of cellular functions which further depend on the cell context. In animal cells, the cytoskeleton prominently shapes the cell's mechanical properties and movement. In plant cells, in contrast, the presence of a rigid cell wall as well as their larger sizes highlight the role of the cytoskeleton in long-distance intracellular transport. As it provides the basis for cell growth and biomass production, cytoskeletal transport in plant cells is of direct environmental and economical relevance. However, while knowledge about the molecular details of the cytoskeletal transport is growing rapidly, the organizational principles that shape these processes on a whole-cell level remain elusive.
This thesis is devoted to the following question: How does the complex architecture of the plant cytoskeleton relate to its transport functionality? The answer requires a systems level perspective of plant cytoskeletal structure and transport. To this end, I combined state-of-the-art confocal microscopy, quantitative digital image analysis, and mathematically powerful, intuitively accessible graph-theoretical approaches.
This thesis summarizes five of my publications that shed light on the plant cytoskeleton as a transportation network: (1) I developed network-based frameworks for accurate, automated quantification of cytoskeletal structures, applicable in, e.g., genetic or chemical screens; (2) I showed that the actin cytoskeleton displays properties of efficient transport networks, hinting at its biological design principles; (3) Using multi-objective optimization, I demonstrated that different plant cell types sustain cytoskeletal networks with cell-type specific and near-optimal organization; (4) By investigating actual transport of organelles through the cell, I showed that properties of the actin cytoskeleton are predictive of organelle flow and provided quantitative evidence for a coordination of transport at a cellular level; (5) I devised a robust, optimization-based method to identify individual cytoskeletal filaments from a given network representation, allowing the investigation of single filament properties in the network context. The developed methods were made publicly available as open-source software tools.
Altogether, my findings and proposed frameworks provide quantitative, system-level insights into intracellular transport in living cells. Despite my focus on the plant cytoskeleton, the established combination of experimental and theoretical approaches is readily applicable to different organisms. Despite the necessity of detailed molecular studies, only a complementary, systemic perspective, as presented here, enables both understanding of cytoskeletal function in its evolutionary context as well as its future technological control and utilization.
Selbstverständnis und Image der Unternehmensberatung, das Bewerbern, Mitarbeitern und Kunden gleichermaßen Wissensvorsprung durch Ballung der besten Köpfe verspricht, scheinen sowohl für den Berater als auch den Kunden einen Erfolgsfaktor einzunehmen. Die Karriere des Unternehmensberaters wird im Vergleich zu anderen Branchen durch eine starke Formalisierung anhand von Kompetenzen und Entwicklungspfaden begleitet. Talentgewinnung und -entwicklung sind dabei Kernaufgaben des Personalmanagements, das gerade aufgrund seiner kompetenzbasierten Instrumente und formalistischen Strukturen als Erfolgsfaktor gilt. Die Analyse der Autorin setzt beim Personalmanagement der Unternehmensberatung an. Auffällig erscheinen dabei zunächst ähnliche Strukturen und Instrumente zur Talentidentifikation und -entwicklung, die für eine gesamte Branche charakteristisch sind. Speziell für Professional Service Firms ist der Mitarbeiter die entscheidende ökonomische Größe in der Leistungserbringung. Der Kunde beurteilt die Unternehmensleistung im Zusammenspiel mit seinem Kontakt zum Mitarbeiter, der maßgeblich für die Leistungserbringung und Qualitätssicherung verantwortlich ist. Der Analysefokus liegt deshalb im Personalmanagement von Unternehmensberatungen als Teil der Professional Service Firms und wird vor dem Hintergrund systemtheoretischer Überlegungen beleuchtet. Eckpfeiler des Systems zeigen sich insbesondere in Form von branchenüblichen Rekrutierungsstrategien, der formalistischen Leistungsbeurteilung, dem vergleichsweise steilen Karriereverlauf sowie anhand überdurchschnittlicher Gehälter. Hat die Unternehmensberatung die Qualifizierung und Entwicklung ihrer Mitarbeiter zum Erfolgsfaktor gemacht? Die Autorin analysiert, ob das Personalmanagement und seine Verfahren berechtigterweise als Erfolgsfaktor einer Branche gelten, welche Faktoren den wirtschaftlichen Erfolg der Branche beeinflussen und welche Grenzen die Nutzenanalyse in Bezug auf die Beratungsleistung erfährt. ?
Investigation of novel proteins and polysaccharides associated with coccoliths of Emiliania huxleyi
(2016)
The humid tropics are the region with the highest rate of land-cover change worldwide. Especially prevalent is the deforestation of old-growth tropical forests to create space for cattle pastures and soybean fields.
The regional water cycle is influenced by vegetation cover in various ways. Especially evapotranspiration considerably contributes to water vapor content in the lower atmosphere. Besides active transpiration by plants, evaporation from wetted plant surfaces further known as interception loss is an important supply of water vapor. Changes in interception loss due to change in land cover and the related consequences on the regional water cycle in the humid tropics of Latin America are the research focus of my thesis. (1) In an experimental setup I assess differences in interception loss between an old-growth tropical forest and a soybean plantation. (2) In a modeling study, I examine interception losses of these two vegetation types compared to a younger secondary forest with the use of the Gash interception model, including an uncertainty analysis for the estimation of the necessary model parameters. (3) Studying the water balance of a 192-km² catchment I disentangle the influences of changes in land cover and climatic factors on interception loss.
The three different research sites in my thesis represent a currently typical spectrum for land-cover changes in Latin America. In the first example I study the consequences of deforestation of transitional forest, which forms the transition from the Brazilian tree savanna (cerrado) to tropical rain forest, for the establishment of soybean fields in the southern Amazon basin. The second study site is a young secondary forest within the “Agua Salud” project area in Panama as an example of reforestation of former pastures. The third study site is the Cirí Grande river catchment which comprises a mixture of young and old forests as well as pastures, which is typical for the southern sub-catchments of the Panama Canal.
The experimental approach consists of the indirect estimation of interception loss by measuring throughfall and stem flow. For the first experimental study I measured throughfall as well as stem flow manually. Measurements of the leaf area index of the two land covers do not show distinct differences; hence it could not serve as an explanation for the differences in the measured interception loss. The considerably higher interception loss at the soybean field is attributed to a possible underestimation of stemflow but also to the stronger ventilation within the well-structured plant rows causing higher evaporation rates. This situation is valid only for two months of the rainy season, when soybean plants are fully developed. In the annual balance evapotranspiration at the soybean site is clearly less than at the forest site, accelerating the development of fast runoff components and consequently discharge. In the medium term, a reduction of water availability in the study area can be expected.
For the modeling study, throughfall in a young secondary forest is sampled automatically. The resulting temporally high-resolution dataset allows the distinction between different precipitation and interception events. The core of this study is the sensitivity and uncertainty analysis of the Gash interception model parameters and the consequences for its results. Canopy storage capacity plays a key role for the model and parameter uncertainty. With increasing storage capacity uncertainty in parameter delineation also increases. Evaporation rate as the driving component of the interception process incorporates in this context the largest parameter uncertainty. Depending on the selected method for parameter estimation, parameter values may vary tremendously.
In the third study, I analyze the influence of interception loss on the water balance of the Cirí Grande catchment, incorporating the interlinked effects of temperature, precipitation and changes of the land use mosaic using the SWAT (soil water assessment tool) model. Constructing several land-cover scenarios I assess their influence on the catchment’s discharge. The results show that land-cover change exerts only a small influence on annual discharge in the Cirí Grande catchment whereas an increase in temperature markedly influences evapotranspiration. The temperature-induced larger transpiration and interception loss balances the simultaneous increase in annual precipitation, such that the resulting changes in annual discharge are negligible.
The results of the three studies show the considerable effect of land cover on interception. However, the magnitude of this effect can be masked by changes in local conditions, especially by an increase in temperature. Hence, the results cannot be transferred easily between the different study sites. For modeling purposes, this means that measurements of vegetation characteristics as well as interception loss at the respective sites are indispensable.
Este libro adopta un enfoque semántico-funcional en el estudio de la imperfectividad en el español. La imperfectividad, como categoría semántico-funcional, encuentra afinidades con otras funciones semánticas, donde el valor de verdad de una situación se presenta como indeterminado o impreciso como, por ejemplo, en la reproducción de citas y distanciamiento del hablante frente a lo dicho; de manera que la imperfectividad se solapa con la modalidad y evidencialidad. Asimismo, se analizan las funciones secundarias de la imperfectividad relacionadas con la modalidad epistémica y evidencialidad indirecta en la prensa española. En todos los casos, los textos analizados proceden de corpus reales del español (CREA, Corpus del Español y GlossaNet).
Das Ziel der Doktorarbeit war die Entwicklung und Evaluation eines skillsbasierten primären Präventionsprogramms (Mainzer Schultraining zur Essstörungsprävention (MaiStep)) für partielle und manifeste Essstörungen. Dabei wurde die Wirksamkeit durch einen primären (Reduktion vorhandener Essstörungssymptome) und sekundären (assoziierte Psychopathologie) Zielparameter 3 und 12 Monate nach Durchführung des Trainings überprüft. Innerhalb der randomisiert kontrollierten Studie gab es zwei Interventionsgruppe und eine aktive Kontrollgruppe. 1.654 Jugendliche (weiblich/männlich: 781/873; mittleres Alter: 13.1±0.7; BMI: 20.0±3.5) konnten für die Studie, an zufällig ausgewählten Schulen in Rheinland-Pfalz, rekrutiert werden. Die Entwicklung des Präventionsprogramms basiert auf einem systematischen Literaturreview von 63 wissenschaftlichen Studien über die Prävention von Essstörungen im Kindes- und Jugendalter. Eine Interventionsgruppe wurde durch Psychologinnen/Psychologen und eine zweite durch Lehrkräfte angeleitet. Das in der aktiven Kontrollgruppe durchgeführte Sucht- bzw. Stresspräventionsprogramm wurde durch Lehrkräfte geleitet. MaiStep zeigte zur 3-Monatskatamnese keine signifikanten Effekte im Vergleich zur aktiven Kontrollgruppe. Allerdings zeigten sich nach 12 Monaten multiple signifikante Effekte zwischen den Interventions- und der aktiven Kontrollgruppe. Im Rahmen der Analyse des primären Parameters wurden in den Interventionsgruppen signifikant weniger Jugendliche mit einer partiellen Anorexia nervosa (CHI²(2) = 8.74, p = .01**) und/oder partiellen Bulimia nervosa (CHI²(2) = 7.25, p = .02*) gefunden. Im Rahmen der sekundären Zielparameter zeigten sich signifikante Veränderungen in Subskalen des Eating Disorder Inventory (EDI-2) Schlankheitsstreben (F (2, 355) = 3.94, p = .02*) und Perfektionismus (F (2, 355) = 4.19, p = .01**) sowie dem Body Image Avoidance Questionnaire (BIAQ) (F (2, 525) = 18.79, p = .01**) zwischen den Interventions- und der aktiven Kontrollgruppe. MaiStep kann somit als erfolgreiches Programm zur Reduktion von partiellen Essstörungen für die Altersgruppe der 13- 15-jährigen bezeichnet werden. Trotz unterschiedlicher Wirkmechanismen zeigten sich die Lehrkräfte im Vergleich zu den Psychologinnen/Psychologen ebenso erfolgreich in der Durchführung.
Trial registration MaiStep is registered at the German Clinical Trials Register (DRKS00005050).
Eye movements serve as a window into ongoing visual-cognitive processes and can thus be used to investigate how people perceive real-world scenes. A key issue for understanding eye-movement control during scene viewing is the roles of central and peripheral vision, which process information differently and are therefore specialized for different tasks (object identification and peripheral target selection respectively). Yet, rather little is known about the contributions of central and peripheral processing to gaze control and how they are coordinated within a fixation during scene viewing. Additionally, the factors determining fixation durations have long been neglected, as scene perception research has mainly been focused on the factors determining fixation locations. The present thesis aimed at increasing the knowledge on how central and peripheral vision contribute to spatial and, in particular, to temporal aspects of eye-movement control during scene viewing. In a series of five experiments, we varied processing difficulty in the central or the peripheral visual field by attenuating selective parts of the spatial-frequency spectrum within these regions. Furthermore, we developed a computational model on how foveal and peripheral processing might be coordinated for the control of fixation duration. The thesis provides three main findings. First, the experiments indicate that increasing processing demands in central or peripheral vision do not necessarily prolong fixation durations; instead, stimulus-independent timing is adapted when processing becomes too difficult. Second, peripheral vision seems to play a prominent role in the control of fixation durations, a notion also implemented in the computational model. The model assumes that foveal and peripheral processing proceed largely in parallel and independently during fixation, but can interact to modulate fixation duration. Thus, we propose that the variation in fixation durations can in part be accounted for by the interaction between central and peripheral processing. Third, the experiments indicate that saccadic behavior largely adapts to processing demands, with a bias of avoiding spatial-frequency filtered scene regions as saccade targets. We demonstrate that the observed saccade amplitude patterns reflect corresponding modulations of visual attention. The present work highlights the individual contributions and the interplay of central and peripheral vision for gaze control during scene viewing, particularly for the control of fixation duration. Our results entail new implications for computational models and for experimental research on scene perception.
Extreme hydro-meteorological events, such as severe droughts or heavy rainstorms, constitute primary manifestations of climate variability and exert a critical impact on the natural environment and human society. This is particularly true for high-mountain areas, such as the eastern flank of the southern Central Andes of NW Argentina, a region impacted by deep convection processes that form the basis of extreme events, often resulting in floods, a variety of mass movements, and hillslope processes. This region is characterized by pronounced E-W gradients in topography, precipitation, and vegetation cover, spanning low to medium-elevation, humid and densely vegetated areas to high-elevation, arid and sparsely vegetated environments. This strong E-W gradient is mirrored by differences in the efficiency of surface processes, which mobilize and transport large amounts of sediment through the fluvial system, from the steep hillslopes to the intermontane basins and further to the foreland. In a highly sensitive high-mountain environment like this, even small changes in the spatiotemporal distribution, magnitude and rates of extreme events may strongly impact environmental conditions, anthropogenic activity, and the well-being of mountain communities and beyond. However, although the NW Argentine Andes comprise the catchments for the La Plata river that traverses one of the most populated and economically relevant areas of South America, there are only few detailed investigations of climate variability and extreme hydro-meteorological events.
In this thesis, I focus on deciphering the spatiotemporal variability of rainfall and river discharge, with particular emphasis on extreme hydro-meteorological events in the subtropical southern Central Andes of NW Argentina during the past seven decades. I employ various methods to assess and quantify statistically significant trend patterns of rainfall and river discharge, integrating high-quality daily time series from gauging stations (40 rainfall and 8 river discharge stations) with gridded datasets (CPC-uni and TRMM 3B42 V7), for the period between 1940 and 2015. Evidence for a general intensification of the hydrological cycle at intermediate elevations (~ 0.5 – 3 km asl) at the eastern flank of the southern Central Andes is found both from rainfall and river-discharge time-series analysis during the period from 1940 to 2015. This intensification is associated with the increase of the annual total amount of rainfall and the mean annual discharge. However, most pronounced trends are found at high percentiles, i.e. extreme hydro-meteorological events, particularly during the wet season from December to February.An important outcome of my studies is the recognition of a rapid increase in the amount of river discharge during the period between 1971 and 1977, most likely linked to the 1976-77 global climate shift, which is associated with the North Pacific Ocean sea surface temperature variability. Interestingly, after this rapid increase, both rainfall and river discharge decreased at low and intermediate elevations along the eastern flank of the Andes. In contrast, during the same time interval, at high elevations, extensive areas on the arid Puna de Atacama plateau have recorded increasing annual rainfall totals. This has been associated with more intense extreme hydro-meteorological events from 1979 to 2014. This part of the study reveals that low-, intermediate, and high-elevation sectors in the Andes of NW Argentina respond differently to changing climate conditions.
Possible forcing mechanisms of the pronounced hydro-meteorological variability observed in the study area are also investigated. For the period between 1940 and 2015, I analyzed modes of oscillation of river discharge from small to medium drainage basins (102 to 104 km2), located on the eastern flank of the orogen. First, I decomposed the relevant monthly time series using the Hilbert-Huang Transform, which is particularly appropriate for non-stationary time series that result from non-linear natural processes. I observed that in the study region discharge variability can be described by five quasi-periodic oscillatory modes on timescales varying from 1 to ~20 years. Secondly, I tested the link between river-discharge variations and large-scale climate modes of variability, using different climate indices, such as the BEST ENSO (Bivariate El Niño-Southern Oscillation Time-series) index. This analysis reveals that, although most of the variance on the annual timescale is associated with the South American Monsoon System, a relatively large part of river-discharge variability is linked to Pacific Ocean variability (PDO phases) at multi-decadal timescales (~20 years). To a lesser degree, river discharge variability is also linked to the Tropical South Atlantic (TSA) sea surface temperature anomaly at multi-annual timescales (~2-5 years).
Taken together, these findings exemplify the high degree of sensitivity of high-mountain environments with respect to climatic variability and change. This is particularly true for the topographic transitions between the humid, low-moderate elevations and the semi-arid to arid highlands of the southern Central Andes. Even subtle changes in the hydro-meteorological regime of these areas of the mountain belt react with major impacts on erosional hillslope processes and generate mass movements that fundamentally impact the transport capacity of mountain streams. Despite more severe storms in these areas, the fluvial system is characterized by pronounced variability of the stream power on different timescales, leading to cycles of sediment aggradation, the loss of agriculturally used land and severe impacts on infrastructure.
Over the past decades, rapid and constant advances have motivated GNSS technology to approach the ability to monitor transient ground motions with mm to cm accuracy in real-time. As a result, the potential of using real-time GNSS for natural hazards prediction and early warning has been exploited intensively in recent years, e.g., landslides and volcanic eruptions monitoring. Of particular note, compared with traditional seismic instruments, GNSS does not saturate or tilt in terms of co-seismic displacement retrieving, which makes it especially valuable for earthquake and earthquake induced tsunami early warning. In this thesis, we focus on the application of real-time GNSS to fast seismic source inversion and tsunami early warning.
Firstly, we present a new approach to get precise co-seismic displacements using cost effective single-frequency receivers. As is well known, with regard to high precision positioning, the main obstacle for single-frequency GPS receiver is ionospheric delay. Considering that over a few minutes, the change of ionospheric delay is almost linear, we constructed a linear model for each satellite to predict ionospheric delay. The effectiveness of this method has been validated by an out-door experiment and 2011 Tohoku event, which confirms feasibility of using dense GPS networks for geo-hazard early warning at an affordable cost.
Secondly, we extended temporal point positioning from GPS-only to GPS/GLONASS and assessed the potential benefits of multi-GNSS for co-seismic displacement determination. Out-door experiments reveal that when observations are conducted in an adversary environment, adding a couple of GLONASS satellites could provide more reliable results. The case study of 2015 Illapel Mw 8.3 earthquake shows that the biases between co-seismic displacements derived from GPS-only and GPS/GLONASS vary from station to station, and could be up to 2 cm in horizontal direction and almost 3 cm in vertical direction. Furthermore, slips inverted from GPS/GLONASS co-seismic displacements using a layered crust structure on a curved plane are shallower and larger for the Illapel event.
Thirdly, we tested different inversion tools and discussed the uncertainties of using real-time GNSS for tsunami early warning. To be exact, centroid moment tensor inversion, uniform slip inversion using a single Okada fault and distributed slip inversion in layered crust on a curved plane were conducted using co-seismic displacements recorded during 2014 Pisagua earthquake. While the inversion results give similar magnitude and the rupture center, there are significant differences in depth, strike, dip and rake angles, which lead to different tsunami propagation scenarios. Even though, resulting tsunami forecasting along the Chilean coast is close to each other for all three models.
Finally, based on the fact that the positioning performance of BDS is now equivalent to GPS in Asia-Pacific area and Manila subduction zone has been identified as a zone of potential tsunami hazard, we suggested a conceptual BDS/GPS network for tsunami early warning in South China Sea. Numerical simulations with two earthquakes (Mw 8.0 and Mw 7.5) and induced tsunamis demonstrate the viability of this network. In addition, the advantage of BDS/GPS over a single GNSS system by source inversion grows with decreasing earthquake magnitudes.
Seit der Einführung von Antibiotika in die medizinische Behandlung von bakteriellen Infektionskrankheiten existiert ein Wettlauf zwischen der Evolution von Bakterienresistenzen und der Entwicklung wirksamer Antibiotika. Während bis in die 80er Jahre verstärkt an neuen Antibiotika geforscht wurde, gewinnen multiresistente Keime heute zunehmend die Oberhand. Um einzelne Pathogene erfolgreich nachzuweisen und zu bekämpfen, ist ein grundlegendes Wissen über den Erreger unumgänglich. Bakterielle Proteine, die bei einer Infektion vorrangig vom Immunsystem prozessiert und präsentiert werden, könnten für die Entwicklung von Impfstoffen oder gezielten Therapeutika nützlich sein. Auch für die Diagnostik wären diese immundominanten Proteine interessant. Allerdings herrscht ein Mangel an Wissen über spezifische Antigene vieler pathogener Bakterien, die eine eindeutige Diagnostik eines einzelnen Erregers erlauben würden.
Daher wurden in dieser Arbeit vier verschiedene Humanpathogene mittels Phage Display untersucht: Neisseria gonorrhoeae, Neisseria meningitidis, Borrelia burgdorferi und Clostridium difficile. Hierfür wurden aus der genomischen DNA der vier Erreger Bibliotheken konstruiert und durch wiederholte Selektion und Amplifikation, dem sogenannten Panning, immunogene Proteine isoliert. Für alle Erreger bis auf C. difficile wurden immunogene Proteine aus den jeweiligen Bibliotheken isoliert. Die identifizierten Proteine von N. meningitidis und B. burgdorferi waren größtenteils bekannt, konnten aber in dieser Arbeit durch Phage Display verifiziert werden. Für N. gonorrhoeae wurden 21 potentiell immunogene Oligopeptide isoliert, von denen sechs Proteine als neue zuvor unbeschriebene Proteine mit immunogenem Charakter identifiziert wurden. Von den Phagen-präsentierten Oligopeptide der 21 immunogenen Proteine wurden Epitopmappings mit verschiedenen polyklonalen Antikörpern durchgeführt, um immunogene Bereiche näher zu identifizieren und zu charakterisieren. Bei zehn Proteinen wurden lineare Epitope eindeutig mit drei polyklonalen Antikörpern identifiziert, von fünf weiteren Proteinen waren Epitope mit mindestens einem Antikörper detektierbar. Für eine weitere Charakterisierung der ermittelten Epitope wurden Alaninscans durchgeführt, die eine detaillierte Auskunft über kritische Aminosäuren für die Bindung des Antikörpers an das Epitop geben.
Ausgehend von dem neu identifizierten Protein mit immunogenem Charakter NGO1634 wurden 26 weitere Proteine aufgrund ihrer funktionellen Ähnlichkeit ausgewählt und mithilfe bioinformatischer Analysen auf ihre Eignung zur Entwicklung einer diagnostischen Anwendung analysiert. Durch Ausschluss der meisten Proteine aufgrund ihrer Lokalisation, Membrantopologie oder unspezifischen Proteinsequenz wurden scFv-Antikörper gegen acht Proteine mittels Phage Display generiert und anschließend als scFv-Fc-Fusionsantikörper produziert und charakterisiert.
Die hier identifizierten Proteine und linearen Epitope könnten einen Ansatzpunkt für die Entwicklung einer diagnostischen oder therapeutischen Anwendung bieten. Lineare Epitopsequenzen werden häufig für die Impfstoffentwicklung eingesetzt, sodass vor allem die in dieser Arbeit bestimmten Epitope von Membranproteinen interessante Kandidaten für weitere Untersuchungen in diese Richtung sind. Durch weitere Untersuchungen könnten möglicherweise unbekannte Virulenzfaktoren entdeckt werden, deren Inhibierung einen entscheidenden Einfluss auf Infektionen haben könnten.
In this thesis, a route to temperature-, pH-, solvent-, 1,2-diol-, and protein-responsive sensors made of biocompatible and low-fouling materials is established. These sensor devices are based on the sensitivemodulation of the visual band gap of a photonic crystal (PhC), which is induced by the selective binding of analytes, triggering a volume phase transition.
The PhCs introduced by this work show a high sensitivity not only for small biomolecules, but also for large analytes, such as glycopolymers or proteins. This enables the PhC to act as a sensor that detects analytes without the need of complex equipment.
Due to their periodical dielectric structure, PhCs prevent the propagation of specific wavelengths. A change of the periodicity parameters is thus indicated by a change in the reflected wavelengths. In the case explored, the PhC sensors are implemented as periodically structured responsive hydrogels in formof an inverse opal.
The stimuli-sensitive inverse opal hydrogels (IOHs) were prepared using a sacrificial opal template of monodispersed silica particles. First, monodisperse silica particles were assembled with a hexagonally packed structure via vertical deposition onto glass slides. The obtained silica crystals, also named colloidal crystals (CCs), exhibit structural color. Subsequently, the CCs templates were embedded in polymer matrix with low-fouling properties. The polymer matrices were composed of oligo(ethylene glycol) methacrylate derivatives (OEGMAs) that render the hydrogels thermoresponsive. Finally, the silica particles were etched, to produce highly porous hydrogel replicas of the CC. Importantly, the inner structure and thus the ability for light diffraction of the IOHs formed was maintained.
The IOH membrane was shown to have interconnected pores with a diameter as well as interconnections between the pores of several hundred nanometers. This enables not only the detection of small analytes, but also, the detection of even large analytes that can diffuse into the nanostructured IOH membrane. Various recognition unit – analyte model systems, such as benzoboroxole – 1,2-diols, biotin – avidin and mannose – concanavalin A, were studied by incorporating functional
comonomers of benzoboroxole, biotin and mannose into the copolymers. The incorporated recognition units specifically bind to certain low and highmolar mass biomolecules, namely to certain saccharides, catechols, glycopolymers or proteins.
Their specific binding strongly changes the overall hydrophilicity, thus modulating the swelling of the IOH matrices, and in consequence, drastically changes their internal periodicity. This swelling is amplified by the thermoresponsive properties of the polymer matrix. The shift of the interference band gap due to the specific molecular recognition is easily visible by the naked eye (up to 150 nm shifts). Moreover, preliminary trial were attempted to detect even larger entities. Therefore anti-bodies were immobilized on hydrogel platforms via polymer-analogous esterification. These platforms incorporate comonomers made of tri(ethylene glycol) methacrylate end-functionalized with a carboxylic acid. In these model systems, the bacteria analytes are too big to penetrate into the IOH membranes, but can only interact with their surfaces. The selected model bacteria, as Escherichia coli, show a specific affinity to anti-body-functionalized hydrogels. Surprisingly in the case functionalized IOHs, this study produced weak color shifts, possibly opening a path to detect directly living organism, which will need further investigations.
Dynamics of mantle plumes
(2016)
Mantle plumes are a link between different scales in the Earth’s mantle: They are an important part of large-scale mantle convection, transporting material and heat from the core-mantle boundary to the surface, but also affect processes on a smaller scale, such as melt generation and transport and surface magmatism. When they reach the base of the lithosphere, they cause massive magmatism associated with the generation of large igneous provinces, and they can be related to mass extinction events (Wignall, 2001) and continental breakup (White and McKenzie, 1989).
Thus, mantle plumes have been the subject of many previous numerical modelling studies (e.g. Farnetani and Richards, 1995; d’Acremont et al., 2003; Lin and van Keken, 2005; Sobolev et al., 2011; Ballmer et al., 2013). However, complex mechanisms, such as the development and implications of chemical heterogeneities in plumes, their interaction with mid-ocean ridges and global mantle flow, and melt ascent from the source region to the surface are still not very well understood; and disagreements between observations and the predictions of classical plume models have led to a challenge of the plume concept in general (Czamanske et al., 1998; Anderson, 2000; Foulger, 2011). Hence, there is a need for more sophisticated models that can explain the underlying physics, assess which properties and processes are important, explain how they cause the observations visible at the Earth’s surface and provide a link between the different scales.
In this work, integrated plume models are developed that investigate the effect of dense recycled oceanic crust on the development of mantle plumes, plume–ridge interaction under the influence of global mantle flow and melting and melt migration in form of two-phase flow.
The presented analysis of these models leads to a new, updated picture of mantle plumes: Models considering a realistic depth-dependent density of recycled oceanic crust and peridotitic mantle material show that plumes with excess temperatures of up to 300 K can transport up to 15% of recycled oceanic crust through the whole mantle. However, due to the high density of recycled crust, plumes can only advance to the base of the lithosphere directly if they have high excess temperatures, high plume volumes and the lowermost mantle is subadiabatic, or plumes rise from the top or edges of thermo-chemical piles. They might only cause minor surface uplift, and instead of the classical head–tail structure, these low-buoyancy plumes are predicted to be broad features in the lower mantle with much less pronounced plume heads. They can form a variety of shapes and regimes, including primary plumes directly advancing to the base of the lithosphere, stagnating plumes, secondary plumes rising from the core–mantle boundary or a pool of eclogitic material in the upper mantle and failing plumes. In the upper mantle, plumes are tilted and deflected by global mantle flow, and the shape, size and stability of the melting region is influenced by the distance from nearby plate boundaries, the speed of the overlying plate and the movement of the plume tail arriving from the lower mantle. Furthermore, the structure of the lithosphere controls where hot material is accumulated and melt is generated. In addition to melting in the plume tail at the plume arrival position, hot plume material flows upwards towards opening rifts, towards mid-ocean ridges and towards other regions of thinner lithosphere, where it produces additional melt due to decompression. This leads to the generation of either broad ridges of thickened magmatic crust or the separation into multiple thinner lines of sea mount chains at the surface. Once melt is generated within the plume, it influences its dynamics, lowering the viscosity and density, and while it rises the melt volume is increased up to 20% due to decompression. Melt has the tendency to accumulate at the top of the plume head, forming diapirs and initiating small-scale convection when the plume reaches the base of the lithosphere. Together with the introduced unstable, high-density material produced by freezing of melt, this provides an efficient mechanism to thin the lithosphere above plume heads.
In summary, this thesis shows that mantle plumes are more complex than previously considered, and linking the scales and coupling the physics of different processes occurring in mantle plumes can provide insights into how mantle plumes are influenced by chemical heterogeneities, interact with the lithosphere and global mantle flow, and are affected by melting and melt migration. Including these complexities in geodynamic models shows that plumes can also have broad plume tails, might produce only negligible surface uplift, can generate one or several volcanic island chains in interaction with a mid–ocean ridge, and can magmatically thin the lithosphere.
Thermophony in real gases
(2016)
A thermophone is an electrical device for sound generation. The advantages of thermophones over conventional sound transducers such as electromagnetic, electrostatic or piezoelectric transducers are their operational principle which does not require any moving parts, their resonance-free behavior, their simple construction and their low production costs.
In this PhD thesis, a novel theoretical model of thermophonic sound generation in real gases has been developed. The model is experimentally validated in a frequency range from 2 kHz to 1 MHz by testing more then fifty thermophones of different materials, including Carbon nano-wires, Titanium, Indium-Tin-Oxide, different sizes and shapes for sound generation in gases such as air, argon, helium, oxygen, nitrogen and sulfur hexafluoride.
Unlike previous approaches, the presented model can be applied to different kinds of thermophones and various gases, taking into account the thermodynamic properties of thermophone materials and of adjacent gases, degrees of freedom and the volume occupied by the gas atoms and molecules, as well as sound attenuation effects, the shape and size of the thermophone surface and the reduction of the generated acoustic power due to photonic emission. As a result, the model features better prediction accuracy than the existing models by a factor up to 100. Moreover, the new model explains previous experimental findings on thermophones which can not be explained with the existing models.
The acoustic properties of the thermophones have been tested in several gases using unique, highly precise experimental setups comprising a Laser-Doppler-Vibrometer combined with a thin polyethylene film which acts as a broadband and resonance-free sound-pressure detector. Several outstanding properties of the thermophones have been demonstrated for the first time, including the ability to generate arbitrarily shaped acoustic signals, a greater acoustic efficiency compared to conventional piezoelectric and electrostatic airborne ultrasound transducers, and applicability as powerful and tunable sound sources with a bandwidth up to the megahertz range and beyond.
Additionally, new applications of thermophones such as the study of physical properties of gases, the thermo-acoustic gas spectroscopy, broad-band characterization of transfer functions of sound and ultrasound detection systems, and applications in non-destructive materials testing are discussed and experimentally demonstrated.