School of Economics, Diss.--Helsinki, 2004. / Zsfassung in finn. Sprache.

Zugl.: Gießen, Univ., Habil.-Schr., 2003.

Hohenheim, Univ., Diss., 2005.

Habilitationsschrift--Heidelberg, 1965. / Includes indexes. Bibliography: p. 703-725.

The formal definition of network coding by Ahlswede et al. in 2000 has led to several breakthroughs in information theory, for example solving the bottleneck problem in butterfly networks and breaking the min-cut max-flow theorem for multicast communication. Especially promising is the usage of network coding as a packet-level Forward Error Correction (FEC) scheme to increase the robustness of a data stream against packet loss, also known as intra-session coding. Yet, despite these benefits, network coding-based FEC is still rarely deployed in real-world networks. To bridge this gap between information theory and real-world usage, this cumulative thesis will present our contributions to the integration, evaluation, and optimization of network coding-based FEC. The first set of contributions introduces and evaluates efficient ways to integrate coding into UDP-based IoT protocols to speed up bulk data transfers in lossy scenarios. This includes a packet-level FEC extension for the Constrained Application Protocol (CoAP) [P1] and one for MQTT for Sensor Networks (MQTT-SN), which levels the underlying publish-subscribe architecture [P2]. The second set of contributions addresses the development of novel evaluation tools and methods to better quantify possible coding gains. This includes link ’em, our award-winning link emulation bridge for reproducible networking research [P3], and also SPQER, a word recognition-based metric to evaluate the impact of packet loss on the Quality of Experience of Voice over IP applications [P5]. Finally, we highlight the impact of padding overhead for applications with heterogeneous packet lengths [P6] and introduce a novel packet-preserving coding scheme to significantly reduce this problem [P4]. Because many of the shown contributions can be applied to other areas of network coding research as well, this thesis does not only make meaningful contributions to specific network coding challenges, but also paves the way for future work to further close the gap between information theory and real-world usage.

Die vorliegende kumulative Dissertation untersucht Konflikte um Abschiebungen. Hierfür entwickle ich die Forschungsperspektive einer materialistischen Grenzregimeanalyse weiter, indem ich den in dieser Perspektive verwendeten Regimebegriff um hegemonietheoretische Überlegungen ergänze. Aus diesem Blickwinkel diskutiere ich zum einen, inwiefern Ausei-nandersetzungen durch hegemoniale Migrationspolitiken, Grenzziehungen und die tief veran-kerte Hegemonie der Grenze geprägt sind. Zum anderen nehme ich in den Blick, inwiefern es Akteur:innen gelingt, Verschiebungen im hegemonialen Gefüge zu erzeugen. Hierdurch lässt sich die Gleichzeitigkeit von Stabilität und Instabilität im Migrations- und Grenzregime analy-tisch fassen. Die Arbeit basiert auf vier qualitativen Fallstudien sowie einer quantitativen me-dienbasierten Protestereignisanalyse. Während die ersten drei Fallstudien lokale Auseinander-setzungen um Abschiebungen auf dem zivilgesellschaftlichen Terrain untersuchen, fokussiert die vierte Fallstudie juridische Auseinandersetzungen um subjektive Rechte nach der Dublin-Verordnung. Die Dissertation besteht aus insgesamt sechs publizierten beziehungsweise zur Publikation angenommenen Artikeln und Sammelbandbeiträgen sowie einem Rahmenpapier, in welchem ich die Beiträge zusammenhängend diskutiere. Sie erweitert bestehende For-schungen zur Umstrittenheit von Abschiebungen und zu Auseinandersetzungen im und um das Migrations- und Grenzregime, indem sie sowohl Momente der Transformation als auch der Reproduktion im hegemonialen Gefüge greifbar macht. Die Untersuchung zeigt, dass die Auseinandersetzungen um Abschiebungen im Sinne strategischer Selektivität durch das Mig-rations- und Grenzregime beeinflusst werden. Zugleich können Akteur:innen strategisch auf diese Strukturen reagieren und so Veränderungen herbeiführen.

This dissertation presents three studies that examined the effects of diverse cultural backgrounds on maternal socialization strategies and how these were related to the development of their pre-school aged children. Specifically, the investigations focused on mother-child discourses about past events when children were three and four years of age. The present work systematically applied the ecocultural approach by investigating relatively homogenous samples, which were selected based on population parameters and sociodemographic characteristics. These sociocultural contexts represented three different cultural models: (1) the model of psychological autonomy (urban middle-class families from Western societies), (2) the model of relational adaptation (rural farming families from no-Western societies), and (3) the model of autonomy-relatedness (urban middle-class families from non-Western societies). We could demonstrate that the three cultural models manifest in mother-child reminiscing: both, how mothers and children reminisced -the structure- and what they talked about -the content. Mothers of the psychological autonomous contexts structured conversations with many elaborations and evaluations in order to actively involve the child to participate. On the content level, conversations were child-centered, with many child references and talk about personal judgments and opinions. Consequently, children were more expressive and self-centered in these contexts. Thus, conversations mirror the socialization strategy and social roles associated with the cultural model of psychological autonomy: The mother treats the child as a quasi-equal interlocutor and reinforces the child to express her- or himself. Mothers of relational adapted contexts structured conversations rather rigidly by using many repetitions, and few elaborations and evaluations. On the content level, they focused more on social contexts than on the child compared to the autonomous contexts. Accordingly, children contributed less information to conversations and showed a greater focus on social contexts. Thus, conversations mirror the socialization strategy and social roles associated with the cultural model of relational adaptation: The mother is the expert and the child the adaptive apprentice. There was greater heterogeneity for conversational structure and content of mothers and children from autonomous-related contexts. However, overall they mirrored the hybrid orientation in their cultural emphases. The different reminiscing styles and thematic foci were thus meaningful within the different sociocultural environments and fostered children’s cultural development of becoming a competent societal member. Furthermore, we could also demonstrate variations within the elaborative style of mothers all valuing autonomy. Thus, when looking at more specific categories, differences also existed among cultural contexts with the same cultural model. Children’s internalization of the respective cultural orientation was also mirrored in another, adult independent task we conducted: children’s self-drawings. Children of autonomous contexts drew themselves bigger -pronounced and space-demanding- whereas children of the relational contexts drew themselves smaller -mirroring greater self-effacement. Drawings of children from the autonomous-related contexts were intermediate in size. Correlation patterns among maternal and child variables varied across the different cultural contexts. Thus, the studies support the notion that psychological processes have to be considered and interpreted in relation to the sociocultural context in which they unfold. This refers to level-oriented (mean differences) as well as functional (correlation based) analyses: Becoming a competent member of a specific cultural context requires very different skills within universal domains, such as mother-child discourse. Additionally, in this process the effect of socialization strategies on the adults’ part may vary across different sociocultural contexts. Results are also discussed in light of practical implications for culture sensitive intervention programs.

Die Dissertation hat die wissenschaftliche Zielsetzung, zu einer möglichst fundierten Aussage darüber zu gelangen, ob und inwieweit dem Hochschulsport die Befähigung zugesprochen werden kann, in seinen Tätigkeitsbereichen berufsqualifizierende Bildungsprozesse für engagierte Studierende zu generieren, welche sich mit den veränderten Anforderungen an den universitären Kompetenzerwerb decken. Der Lösungsansatz, der dabei hinterfragt werden soll, steht im Zusammenhang mit einem veränderten Bildungsbegriff bzw. -bewusstsein und den damit verbundenen Chancen des Systems Hochschulsport, sich durch eine fundierte Analyse der eigenen Ressourcen über seine Rolle als sportbezogener Dienstleister hinweg auch als bildende Instanz neu im Hochschulbereich zu positionieren. Die methodische Vorgehensweise dieser Arbeit orientiert sich grundsätzlich an den gängigen wissenschaftlichen Standards zur Untersuchung eines Forschungsanliegens im sozialwissenschaftlichen Kontext. Die beiden großen inhaltlichen Blöcke, die den Aufbau dieser Arbeit charakterisieren, sind eine hermeneutische Einbettung und Reflexion des Themas in Form einer ausdifferenzierten Literaturanalyse, sowie ein empirischer Teil, in dem eine eigenständige Datenerhebung und -auswertung am betroffenen Personenkreis stattfindet. In einem abschließen Fazit werden die aus dieser Arbeit hervorgegangenen Daten, Ideen und Handlungsansätze im übergreifenden Gesamtkontext bewertet und in ihrer Signifikanz für weitere zukünftige Entwicklungen reflektiert. Dabei wird auch auf die Einschränkungen dieser Studie und den weiteren Forschungsbedarf eingegangen.

During the past decade, lanthanide doped alkali metal rare earth fluorides have been intensively studied due to their unique properties. Also, nanoparticles of these materials have gained much importance because NaYF4, NaGdF4, NaLuF4 and LiYF4 nanocrystals doped with Yb/Er or Yb/Tm display efficient upconversion emission. The synthesis of NaREF4 nanocrystals (RE = rare earths) has therefore attracted many researchers worldwide. While a large number of procedures is already available for the synthesis of NaREF4 particles of the heavier rare earth ions and for NaYF4, only a very limited number of methods exists for nanocrystals of the lighter rare earth ions, RE = La, Ce, Pr and Nd. In this work, a synthesis method was therefore developed to produce monodisperse sub-10 nm sodium rare earth fluoride nanocrystals of the lighter rare earths, NaREF4 (RE = La, Ce, Pr and Nd) from single-source precursors. Based on this method, the Ostwald ripening, the size focusing and the stability of these nanocrystals were studied; also, the versatility of the method was demonstrated by developing doped nanocrystals of these particles. The procedures developed in this thesis not only allow to prepare the hexagonal β-phase of these materials but also the meta-stable cubic α-phase. The latter is found to be very sensitive to decomposition. This decomposition affects also the synthesis of NaREF4 particles of the hexagonal β-phase where particles of the cubic α-phase form an intermediate product. This thesis also shows that highly sodium deficient α-NaYF4 nanocrystals with a size of less than 10 nm can be prepared which contain much less sodium than the bulk material. These nanocrystals were used as precursor to produce monodisperse sub-10 nm lithium rare earth fluoride (LiREF4, RE = Y, Gd, Lu) nanocrystals. Using this new approach also LiYF4:Yb,Er/LiYF4 core/shell upconversion nanocrystals were prepared, displaying a 35 times enhancement in luminescence intensity compared to the corresponding core particles. Further, this approach provided new insights on intermediate phases formed during the synthesis. Our studies confirmed, for instance, that LiREF4 nanocrystals were formed through an ‘available intermediate phase’, that is, a phase having a composition which is determined by the available cations in the reaction mixture.

This thesis focuses on the surface patterning by using nanoporous block copolymer (BCP) stamps. Polystyrene‐block‐poly(2‐vinylpyridine) (PS‐b‐P2VP) was used as model BCP. Nanoporous BCP stamps were fabricated by replication of lithographically patterned silicon molds. Nanopores inside of BCP stamps were generated by swelling‐induced pore formation. A method for scanner-based capillary stamping (SCS) with spongy nanoporous BCP stamps was developed. First, in the course of stamps design using replication molding of PS-b-P2VP against surface-modified macroporous silicon molds, PS-b-P2VP fiber rings remaining on the macroporous silicon molds were obtained that allow immobilization of water drops on the hydrophobically modified surfaces of the macroporous silicon molds. Water drops immobilized by these rings can be prevented from dewetting within the PS‐b‐P2VP fiber rings. Second, after spongy nanoporous PS-b-P2VP stamps had been obtained, preliminary experiments with non-inked PS-b-P2VP stamps revealed that parts of the stamps’ contact elements can be lithographically transferred onto counterpart surfaces. As a result, arrays of nanostructured submicron PS‐b‐P2VP dots with heights of ∼100 nm onto silicon wafers and glass slides were produced. Lastly, the SCS technique was developed, which overcomes the limitation of time-consuming re-inking procedures associated with classical soft lithography including microcontact printing (µCP) and polymer pen lithography (PPL) with solid stamps, as well as the limitations regarding throughput of scanning probe‐based serial writing approaches such as nanoscale dispensing (NADIS) and other micropipetting techniques. In addition, sizes of stamped droplets can be controlled by adjusting surface wettability and dwell time.