Filtern
Erscheinungsjahr
- 2024 (93) (entfernen)
Dokumenttyp
- Dissertation (57)
- Wissenschaftlicher Artikel (15)
- Arbeitspapier (6)
- Teil eines Buches (Kapitel) (4)
- Konferenzveröffentlichung (3)
- Monographie/Sammelband (2)
- Sonstiges (2)
- Ausgabe (Heft) zu einer Zeitschrift (2)
- Postprint (1)
- Preprint (1)
Sprache
- Englisch (93) (entfernen)
Schlagworte
- Arctic (3)
- Arktis (3)
- Satzverarbeitung (3)
- experiment (3)
- sentence processing (3)
- Atmosphäre (2)
- Carotinoide (2)
- Deep Learning (2)
- Jüdische Studien (2)
- Klimawandel (2)
- Kohlenstoff (2)
- atmosphere (2)
- carbon (2)
- carotenoids (2)
- climate change (2)
- communication (2)
- deep learning (2)
- enterprise systems (2)
- entrepreneurship (2)
- machine learning (2)
- modular production (2)
- production control (2)
- uncertainty (2)
- voting (2)
- (latente) Mehrebenen-(Kovariaten-)Modelle (1)
- 3D-Einbettung (1)
- 3D-embedding (1)
- Acetobacteraceae (1)
- Achtsamkeit (1)
- Aktin (1)
- Amblystegiaceae (1)
- Ancient Rome (1)
- Anfänge der systematischen lateinische Epigraphik (1)
- Anode (1)
- Antibeschlag-Additive (1)
- Antifouling (1)
- Aphasie (1)
- Archiv (1)
- Atmosphärenforschung (1)
- Ausbreitung der kosmischen Strahlung (1)
- Austausch zwischen zwei Spezies (1)
- Bachdenitrifikation (1)
- Beschriftung (1)
- Beweidung (1)
- Bias in Science (1)
- Biklausalität (1)
- Bilingualismus (1)
- Biotechnologie (1)
- Blazar (1)
- Blickbewegungen (1)
- Bodenbewegungsmodellierung (1)
- Bodenfeuchtigkeit (1)
- Bodenhydrologie (1)
- Braunmoose (1)
- Bryophyten (1)
- CN (1)
- Central Andes (1)
- Central Europe (1)
- Chronosequenzstudie (1)
- Cicero (1)
- Copolymere (1)
- Corpus Inscriptionum Latinarum (1)
- Counseling (1)
- Dateistruktur (1)
- Datenaufbereitung (1)
- Datenbank (1)
- Datenbanksysteme (1)
- Datenmonetarisierung (1)
- Datenschutz (1)
- Datenschutz-Grundverordnung (DSGVO) (1)
- Datenschutzmanagement (1)
- Datenverwaltung (1)
- Decarbonisation (1)
- Dekarbonisierung (1)
- Designparameter (1)
- Diamantstempelzelle (1)
- Dichte (1)
- Diffraktion (1)
- Digitale Bildung (1)
- Drohnen-Fernerkundung (1)
- Dynamische kognitive Modellierung (1)
- Dürre (1)
- ENTH domain proteins (1)
- ENTH-Domänen Proteine (1)
- ERP (1)
- Eigenspannung (1)
- Einzugsgebietshydrologie Wasserqualitätsmodell (1)
- Elektronenrückstreubeugung (1)
- Endophyten (1)
- Energie (1)
- Epigenetik (1)
- Epiphyten (1)
- Erdmantel (1)
- Erneuerbare Energie (1)
- Essigsäurebakterien (1)
- Essverhalten (1)
- Exhaustivität (1)
- Exoplaneten (1)
- Exoplanetenatmosphären (1)
- Experience Sampling Method (ESM) (1)
- Exziton-Dissoziation (1)
- Eye-Tracking-Verfahren (1)
- Eye-tracking (1)
- Familiarität (1)
- Faulkner studies (1)
- Faulknerforschung (1)
- Fernerkundung (1)
- Fernerkundung an Vulkanen (1)
- Ferroperiklas (1)
- Flavonoide (1)
- Fokus (1)
- Folientunnel (1)
- Frauen (1)
- Freud-Forschung (1)
- Freud-research (1)
- Frieden (1)
- GNSS (1)
- GPS (1)
- Gammastrahlen: allgemein (1)
- Gender (1)
- General Data Protection Regulation (GDPR) (1)
- Genomik (1)
- Geomorphologie (1)
- Geophysik (1)
- Geschlecht (1)
- Gletscherschmelze (1)
- Greek mythology (1)
- Grenzschicht (1)
- Habsburg Empire (1)
- Habsburg Studies (1)
- Habsburgisches Reich (1)
- Habsburgstudien (1)
- Halophyten (1)
- Hitzestress (1)
- Hochdruck (1)
- Hohlraumeffekte (1)
- Hydrogele (1)
- Hydrologie (1)
- In-situ Experimente (1)
- Inconel 718 (1)
- Indexauswahl (1)
- Individual Participant Data Metaanalyse (1)
- Indoor farming (1)
- Informationsstruktur (1)
- Instabilitäten (1)
- Interessengrad-Techniken (1)
- Intersections (1)
- Intraklassenkorrelation (1)
- Investitionsverhalten (1)
- Investment Behavior (1)
- Jewish Law (1)
- Jewish Studies (1)
- Jewish studies (1)
- Jonathan Muroya (1)
- Jüdische Sprachen (1)
- Kalibrierung an mehreren Standorten (1)
- Kasus (1)
- Koartikulation (1)
- Kognitionspsychologie (1)
- Kohlenstoffnitrid (CN) (1)
- Kopfsalat (1)
- Kovariatenwahl (1)
- Kunststoff-Additive (1)
- Kursdesign (1)
- Ladungsgenerierung (1)
- Landschaftsentwicklung (1)
- Large-Scale Assessment (1)
- Laserstrahlschmelzen (1)
- Lastverteilung (1)
- Lesen (1)
- Lösungsmittel (1)
- MOOC (1)
- Market Dynamics (1)
- Marktdynamik (1)
- Marriage Preparations (1)
- Massenspektrometrie (1)
- Meereis (1)
- Mehrsprachigkeit (1)
- Meta-Selbstanpassung (1)
- Meteorologie (1)
- Micro Degree (1)
- Mikroalgen (1)
- Molekularbiologie (1)
- Moorsukzession (1)
- Moos-Mikroben-Interaktion (1)
- Moos-assoziierte Methanoxidation (1)
- Moos-assoziierte Methanproduktion (1)
- Morphologie (1)
- Nahrung der Zukunft (1)
- Nationale Aktionspläne (1)
- Natrium-Ionen-Batterie (1)
- Naturgefahren (1)
- Negotiation Performance (1)
- Nicht-Fulleren-Akzeptoren (1)
- Numerus (1)
- Nutzer-Engagement (1)
- Online-Lehre (1)
- Onlinekurs (1)
- Onlinekurs-Produktion (1)
- Permafrost (1)
- Perowskit-Solarzellen (1)
- Pflanzenwachstum (1)
- Phonetik (1)
- Phonologie (1)
- Physik (1)
- Policy Changes (1)
- Politikänderungen (1)
- Poweranalyse (1)
- Produktionssteuerung (1)
- Psychoanalyse (1)
- Psycholinguistik (1)
- Reinforcement Learning (1)
- Relativized Minimality (1)
- Relativsätze (1)
- Renewable Energy (1)
- Reproduktion von Inschriften (1)
- Restaurierung von Flüssen (1)
- Russian (1)
- Russisch (1)
- Saline Landwirtschaft (1)
- Schuld (1)
- Schulleistung (1)
- Schwefel (1)
- Scientific Narratives (1)
- Sebastian Kurz (1)
- Seismologie (1)
- Selection-Linked Integration (1)
- Sequenzielle Likelihood (1)
- Shidduchin (1)
- Simulation (1)
- Simulation, Größe (1)
- Social Bots erkennen (1)
- Softwareanalytik (1)
- Softwarevisualisierung (1)
- Solarzellen (1)
- Spaltsätze (1)
- Spartacus (1)
- Spektroskopie (1)
- Sphagnum (1)
- Spracherwerb (1)
- Sprachideologie (1)
- Sprachverständnis (1)
- Stern-Planeten-Wechselwirkung (1)
- Sternphysik (1)
- Strömungsneigung (1)
- Synchrotronstrahlung (1)
- Synthese (1)
- Talmudic Judaism (1)
- Talmudisches Judentum (1)
- Textur (1)
- Theorie (1)
- Theory (1)
- Thermoelektrizität (1)
- Torfmoose (1)
- Transkriptomik (1)
- Translanguaging (1)
- Treemaps (1)
- Ultraschall (1)
- Ungewissheit (1)
- Untereinheitenimpfstoff (1)
- Utility-Funktionen (1)
- Verhandlungsleistung (1)
- Voreingenommenheit in der Wissenschaft (1)
- Vorhersagemodelle (1)
- Vulkanüberwachung (1)
- WPS Agenda (1)
- WPS agenda (1)
- Wahrnehmungsdialektologie (1)
- Wasserdampf (1)
- Web-basiertes Rendering (1)
- Wellen (1)
- William Faulkner (1)
- Wirtsspezifität (1)
- Wurzelhaarbildung (1)
- Wärmefluss (1)
- Wärmekapazität (1)
- Zellmotilität (1)
- Zentraleuropa (1)
- Zoom (1)
- Zustandsverwaltung (1)
- Zuweisung thematischer Rollen (1)
- Zwitterionen (1)
- Zyklone (1)
- achtsames Essen (1)
- actin (1)
- additive Fertigung (1)
- additive manufacturing (1)
- agents (1)
- anode (1)
- anthropocene (1)
- antifogging additives (1)
- antifouling (1)
- aphasia (1)
- architecture-based software adaptation (1)
- architekturbasierte Softwareanpassung (1)
- assimilatorische Aufnahme (1)
- assimilatory uptake (1)
- atmospheric science (1)
- beliefs (1)
- biclausality (1)
- bilingualism (1)
- biotechnology (1)
- blazar (1)
- bleifreie Perowskit-Solarzellen (1)
- boundary layer (1)
- bribery (1)
- brown mosses (1)
- bryophytes (1)
- business models (1)
- cartoons (1)
- case (1)
- catchment hydrology Water quality model (1)
- cavity effects (1)
- cell motility (1)
- charge generation (1)
- chemically induced dislocation (1)
- chemisch-induzierte Dislokation (1)
- chronosequence study (1)
- classical reception (1)
- clefts (1)
- coarticulation (1)
- code of conduct (1)
- cognitive psychology (1)
- continuation thesis (1)
- cooperation (1)
- coordination (1)
- copolymers (1)
- corruption (1)
- cosmic ray propagation (1)
- covariate selection (1)
- curriculum design (1)
- curriculum development (1)
- curtailment thesis (1)
- cyclones (1)
- data and methods (1)
- data management (1)
- data monetization (1)
- data preparation (1)
- data privacy (1)
- data-driven artifacts (1)
- database (1)
- database systems (1)
- dating (1)
- deep reinforcement learning (1)
- degree-of-interest techniques (1)
- density (1)
- design parameters (1)
- design-science research (1)
- diamond anvil cell (1)
- diffraction (1)
- diffraction elastic constants (1)
- diffraktionselastische Konstanten (1)
- digital education (1)
- digital platform openness (1)
- digital product development (1)
- digitale Produktentwicklung (1)
- discrete event simulation (1)
- discretion (1)
- discrimination (1)
- drought (1)
- dynamical cognitive modeling (1)
- e-learning (1)
- earth mantle (1)
- earth system governance (1)
- eating behavior (1)
- elections (1)
- electron backscatter diffraction (1)
- embezzlement (1)
- emotions (1)
- enablement thesis (1)
- endophytes (1)
- energy (1)
- enteprise-level (1)
- enterprise architecture (1)
- enterprise ecosystems: the integrated enterprise (1)
- entrepreneurship education (1)
- epigenetics (1)
- epiphytes (1)
- equity crowdfunding (1)
- erklärte Varianz (1)
- evaluation (1)
- exciton dissociation (1)
- executive functions (1)
- exekutive Funktionen (1)
- exhaustivity (1)
- exoplanet atmospheres (1)
- exoplanets (1)
- experimental studies (1)
- experimentelle Studien (1)
- explained variance (1)
- eye movements (1)
- eye tracking (1)
- eye-tracking (1)
- familiarity (1)
- federated industrial platform ecosystems (1)
- feminist foreign policy (1)
- feministische Außenpolitik (1)
- ferropericlase (1)
- file structure (1)
- finance (1)
- financial access and inclusion (1)
- flavonoids (1)
- focus (1)
- follower turnover intentions (1)
- future food (1)
- galactic magnetic fields (1)
- galaktische Magnetfelder (1)
- gamma rays: general (1)
- ganzzahlige lineare Optimierung (1)
- gender (1)
- gender pay gap (1)
- genetic screen (1)
- genetischer Screen (1)
- genomics (1)
- geographische Großstudie (1)
- geomorphology (1)
- geophysics (1)
- geschützter Anbau (1)
- gift-giving (1)
- glacier melt (1)
- global commons (1)
- globales Navigationssatellitensystem (1)
- globales Positionsbestimmungssystem (1)
- graph neural networks (1)
- graphische neuronale Netze (1)
- grazing (1)
- ground motion modeling (1)
- guilt (1)
- halophytes (1)
- heat capacity (1)
- heat flux (1)
- heat stress (1)
- hierarchical data (1)
- hierarchische Daten (1)
- hierarchy (1)
- high pressure (1)
- high resolution (1)
- historical consciousness (1)
- historiography (1)
- history (1)
- history teaching (1)
- history textbooks (1)
- hohe Auflösung (1)
- homeostasis (1)
- host-specificity (1)
- human diet (1)
- hybrid Bayesian-classical precision simulations (1)
- hybride Bayesianisch-klassische Simulationen der Schätzgenauigkeit (1)
- hydrogels (1)
- hydrology (1)
- hydrothermale Alteration (1)
- in-operando SAXS (1)
- in-situ testing (1)
- index selection (1)
- individual participant data meta-analysis (1)
- individually, multisite, and cluster randomized trials (1)
- individuell-, block- und cluster-randomisierte Studien (1)
- indoor farming (1)
- infinitely repeated game (1)
- informal organization (1)
- information structure (1)
- information systems research (1)
- instabilities (1)
- integer linear programming (1)
- interactive visualization (1)
- interaktive Visualisierung (1)
- international law (1)
- interspecies interchange (1)
- intraclass correlation (1)
- is governance (1)
- it/business alignment (1)
- knowledge sharing (1)
- labeling (1)
- landscape evolution (1)
- language acquisition (1)
- large-scale assessment (1)
- large-scale study (1)
- laser powder bed fusion (1)
- lead-free perovskites (1)
- leadership (1)
- learning environment (1)
- lettuce (1)
- levels of information systems research (process, enterprise-, ecosystem- & industry-level) (1)
- linked employer-employee data (1)
- load balancing (1)
- mHM-Nitrat-Modell (1)
- mHM-Nitrate model (1)
- margins of error (1)
- marriage (1)
- maschinelles Lernen (1)
- mass spectrometry (1)
- mating (1)
- mechanical behavior (1)
- mechanisches Verhalten (1)
- menschliche Ernährung (1)
- meta self-adaptation (1)
- meteorology (1)
- methanogenic archaea (1)
- methanotrophic bacteria (1)
- methanoxidierende Bakterien (1)
- methanproduzierende Archaeen (1)
- miRNA Regulation (1)
- miRNA regulation (1)
- micro degree (1)
- micro-credential (1)
- microalgae (1)
- mikrobielle Moor-Kerngemeinschaft (1)
- mindful eating (1)
- mindfulness (1)
- model-driven engineering (1)
- modellgesteuerte Entwicklung (1)
- modulare Produktion (1)
- molecular biology (1)
- morpho-syntactic features (1)
- morpho-syntaktische Merkmale (1)
- morphological analysis (1)
- morphology (1)
- moss-associated archaea (1)
- moss-associated bacteria (1)
- moss-associated methanogenesis (1)
- moss-associated methanotrophy (1)
- moss-microbe-interactions (1)
- motivation (1)
- multi-agent system (1)
- multi-party systems (1)
- multi-site calibration (1)
- multilevel (latent covariate) models (1)
- multiplexity (1)
- national action plans (1)
- natural hazards (1)
- nicht-thermische Strahlung (1)
- non-fullerene acceptors (1)
- non-thermal radiation (1)
- northern peatlands (1)
- number (1)
- nördliche Moore (1)
- observational data (1)
- occupational gender segregation (1)
- online course creation (1)
- online course design (1)
- online teaching (1)
- opinion polls (1)
- optical properties (1)
- optische Eigenschaften (1)
- organic solar cell (1)
- organic-inorganic hybrids (1)
- organisch-anorganische Hybride (1)
- organische Solarzelle (1)
- organizational level (1)
- parameter transferability (1)
- partial replication (1)
- partielle Replikation (1)
- partnership (1)
- party competition (1)
- peace (1)
- peatland core microbiome (1)
- peatland development (1)
- perceived meaningfulness (1)
- permafrost (1)
- perovskite (1)
- perovskite solar cells (1)
- persistent memory (1)
- persistenter Speicher (1)
- pflanzliche Sekundär Metabolite (1)
- phonetics (1)
- phonology (1)
- photovoltaische Materialien (1)
- physics (1)
- physiological needs (1)
- planetary boundaries (1)
- plant growth (1)
- plant secondary metabolites (1)
- plastic additives (1)
- pmem (1)
- politics and the media (1)
- polling (1)
- polytunnel (1)
- power analysis (1)
- prediction models (1)
- prisoner’s dilemma (1)
- privacy management (1)
- progressive rendering (1)
- progressives Rendering (1)
- promises (1)
- protected cultivation (1)
- psychoanalysis (1)
- psycholinguistics (1)
- public good (1)
- rapid earthquake impact assessment (1)
- reading (1)
- reinforcement learning (1)
- relative clauses (1)
- relativierte Minimalitätstheorie (1)
- relativistic processes (1)
- relativistische Prozesse (1)
- remote sensing (1)
- residual stress (1)
- river restoration (1)
- root hair formation (1)
- räumlich-zeitliche Validierung (1)
- saline agriculture (1)
- scalable (1)
- schnelle Einschätzung von Erdbebenauswirkungen (1)
- schwach elektrischer Fisch (1)
- sea ice (1)
- secondary plant metabolites (1)
- seismic hazard (1)
- seismische Gefährdung (1)
- seismology (1)
- sekundäre Pflanzenstoffe (1)
- selbstanpassende Systeme (1)
- selbstheilende Systeme (1)
- selection-linked integration (1)
- self-adaptive systems (1)
- self-awarenesssender-receiver framework zoom (1)
- self-healing (1)
- self-view,virtual meetings (1)
- sender-receiver framework (1)
- sequential likelihood (1)
- simulation (1)
- simulation, size (1)
- skalierbar (1)
- slavery (1)
- social bot detection (1)
- social network (1)
- sodium-ion battery (1)
- soft information (1)
- software analytics (1)
- software visualization (1)
- soil hydrology (1)
- soil moisture (1)
- solar cells (1)
- spatiotemporal validation (1)
- spectroscopy (1)
- spoken sentence comprehension (1)
- stabile Schichtung (1)
- stable stratification (1)
- star-planet interaction (1)
- state management (1)
- stellar physics (1)
- stereotypes (1)
- strategic uncertainty (1)
- stream denitrification (1)
- stream sinuosity (1)
- street-level bureaucracy (1)
- student achievement (1)
- städtisch (1)
- städtischer Wärmeinseleffekt (1)
- subunit vaccine (1)
- sulfur (1)
- suspended sediment (1)
- suspendiertes Sediment (1)
- synchrotron radiation (1)
- synthesis (1)
- tabellarische Dateien (1)
- tabular data (1)
- technologies (1)
- textbook research (1)
- texture (1)
- thematic-role assignment (1)
- thermoelectricity (1)
- tin perovskites (1)
- transcriptomics (1)
- transfers (1)
- treemaps (1)
- tropical freshwater fish (1)
- tropische Süßwasserfische (1)
- ultra-high energy cosmic rays (1)
- ultrahochenergetische kosmische Strahlung (1)
- ultrasound tongue imaging (1)
- urban heat island (1)
- user engagement (1)
- utility functions (1)
- video games (1)
- visionary leadership (1)
- visuell-linguistische Integration (1)
- visuo-linguistic integration (1)
- volcanic hydrothermal systems (1)
- volcano remote sensing (1)
- vote switching (1)
- voters (1)
- vulkanische Entgasungs-und Hydrothermalsysteme (1)
- vulkanische Entgasungssysteme (1)
- water vapour (1)
- waves (1)
- weakly electric fish (1)
- web-based rendering (1)
- wissenschaftliche Narrative (1)
- women (1)
- zentrale Anden (1)
- zwitterions (1)
- ÖVP (1)
- Überschneidungen (1)
- Übertragbarkeit der Parameter (1)
Institut
- Extern (12)
- Fachgruppe Betriebswirtschaftslehre (10)
- Institut für Physik und Astronomie (10)
- Institut für Biochemie und Biologie (9)
- Fachgruppe Politik- & Verwaltungswissenschaft (7)
- Hasso-Plattner-Institut für Digital Engineering GmbH (7)
- Fachgruppe Volkswirtschaftslehre (6)
- Center for Economic Policy Analysis (CEPA) (5)
- Historisches Institut (5)
- Institut für Geowissenschaften (5)
Actin is one of the most highly conserved proteins in eukaryotes and distinct actin-related proteins with filament-forming properties are even found in prokaryotes. Due to these commonalities, actin-modulating proteins of many species share similar structural properties and proposed functions. The polymerization and depolymerization of actin are critical processes for a cell as they can contribute to shape changes to adapt to its environment and to move and distribute nutrients and cellular components within the cell. However, to what extent functions of actin-binding proteins are conserved between distantly related species, has only been addressed in a few cases. In this work, functions of Coronin-A (CorA) and Actin-interacting protein 1 (Aip1), two proteins involved in actin dynamics, were characterized. In addition, the interchangeability and function of Aip1 were investigated in two phylogenetically distant model organisms. The flowering plant Arabidopsis thaliana (encoding two homologs, AIP1-1 and AIP1-2) and in the amoeba Dictyostelium discoideum (encoding one homolog, DdAip1) were chosen because the functions of their actin cytoskeletons may differ in many aspects. Functional analyses between species were conducted for AIP1 homologs as flowering plants do not harbor a CorA gene.
In the first part of the study, the effect of four different mutation methods on the function of Coronin-A protein and the resulting phenotype in D. discoideum was revealed in two genetic knockouts, one RNAi knockdown and a sudden loss-of-function mutant created by chemical-induced dislocation (CID). The advantages and disadvantages of the different mutation methods on the motility, appearance and development of the amoebae were investigated, and the results showed that not all observed properties were affected with the same intensity. Remarkably, a new combination of Selection-Linked Integration and CID could be established.
In the second and third parts of the thesis, the exchange of Aip1 between plant and amoeba was carried out. For A. thaliana, the two homologs (AIP1-1 and AIP1-2) were analyzed for functionality as well as in D. discoideum. In the Aip1-deficient amoeba, rescue with AIP1-1 was more effective than with AIP1-2. The main results in the plant showed that in the aip1-2 mutant background, reintroduced AIP1-2 displayed the most efficient rescue and A. thaliana AIP1-1 rescued better than DdAip1. The choice of the tagging site was important for the function of Aip1 as steric hindrance is a problem. The DdAip1 was less effective when tagged at the C-terminus, while the plant AIP1s showed mixed results depending on the tag position. In conclusion, the foreign proteins partially rescued phenotypes of mutant plants and mutant amoebae, despite the organisms only being very distantly related in evolutionary terms.
Access to digital finance
(2024)
Financing entrepreneurship spurs innovation and economic growth. Digital financial platforms that crowdfund equity for entrepreneurs have emerged globally, yet they remain poorly understood. We model equity crowdfunding in terms of the relationship between the number of investors and the amount of money raised per pitch. We examine heterogeneity in the average amount raised per pitch that is associated with differences across three countries and seven platforms. Using a novel dataset of successful fundraising on the most prominent platforms in the UK, Germany, and the USA, we find the underlying relationship between the number of investors and the amount of money raised for entrepreneurs is loglinear, with a coefficient less than one and concave to the origin. We identify significant variation in the average amount invested in each pitch across countries and platforms. Our findings have implications for market actors as well as regulators who set competitive frameworks.
Climate change fundamentally transforms glaciated high-alpine regions, with well-known cryospheric and hydrological implications, such as accelerating glacier retreat, transiently increased runoff, longer snow-free periods and more frequent and intense summer rainstorms. These changes affect the availability and transport of sediments in high alpine areas by altering the interaction and intensity of different erosion processes and catchment properties.
Gaining insight into the future alterations in suspended sediment transport by high alpine streams is crucial, given its wide-ranging implications, e.g. for flood damage potential, flood hazard in downstream river reaches, hydropower production, riverine ecology and water quality. However, the current understanding of how climate change will impact suspended sediment dynamics in these high alpine regions is limited. For one, this is due to the scarcity of measurement time series that are long enough to e.g. infer trends. On the other hand, it is difficult – if not impossible – to develop process-based models, due to the complexity and multitude of processes involved in high alpine sediment dynamics. Therefore, knowledge has so far been confined to conceptual models (which do not facilitate deriving concrete timings or magnitudes for individual catchments) or qualitative estimates (‘higher export in warmer years’) that may not be able to capture decreases in sediment export. Recently, machine-learning approaches have gained in popularity for modeling sediment dynamics, since their black box nature tailors them to the problem at hand, i.e. relatively well-understood input and output data, linked by very complex processes.
Therefore, the overarching aim of this thesis is to estimate sediment export from the high alpine Ötztal valley in Tyrol, Austria, over decadal timescales in the past and future – i.e. timescales relevant to anthropogenic climate change. This is achieved by informing, extending, evaluating and applying a quantile regression forest (QRF) approach, i.e. a nonparametric, multivariate machine-learning technique based on random forest.
The first study included in this thesis aimed to understand present sediment dynamics, i.e. in the period with available measurements (up to 15 years). To inform the modeling setup for the two subsequent studies, this study identified the most important predictors, areas within the catchments and time periods. To that end, water and sediment yields from three nested gauges in the upper Ötztal, Vent, Sölden and Tumpen (98 to almost 800 km² catchment area, 930 to 3772 m a.s.l.) were analyzed for their distribution in space, their seasonality and spatial differences therein, and the relative importance of short-term events. The findings suggest that the areas situated above 2500 m a.s.l., containing glacier tongues and recently deglaciated areas, play a pivotal role in sediment generation across all sub-catchments. In contrast, precipitation events were relatively unimportant (on average, 21 % of annual sediment yield was associated to precipitation events). Thus, the second and third study focused on the Vent catchment and its sub-catchment above gauge Vernagt (11.4 and 98 km², 1891 to 3772 m a.s.l.), due to their higher share of areas above 2500 m. Additionally, they included discharge, precipitation and air temperature (as well as their antecedent conditions) as predictors.
The second study aimed to estimate sediment export since the 1960s/70s at gauges Vent and Vernagt. This was facilitated by the availability of long records of the predictors, discharge, precipitation and air temperature, and shorter records (four and 15 years) of turbidity-derived sediment concentrations at the two gauges. The third study aimed to estimate future sediment export until 2100, by applying the QRF models developed in the second study to pre-existing precipitation and temperature projections (EURO-CORDEX) and discharge projections (physically-based hydroclimatological and snow model AMUNDSEN) for the three representative concentration pathways RCP2.6, RCP4.5 and RCP8.5.
The combined results of the second and third study show overall increasing sediment export in the past and decreasing export in the future. This suggests that peak sediment is underway or has already passed – unless precipitation changes unfold differently than represented in the projections or changes in the catchment erodibility prevail and override these trends. Despite the overall future decrease, very high sediment export is possible in response to precipitation events. This two-fold development has important implications for managing sediment, flood hazard and riverine ecology.
This thesis shows that QRF can be a very useful tool to model sediment export in high-alpine areas. Several validations in the second study showed good performance of QRF and its superiority to traditional sediment rating curves – especially in periods that contained high sediment export events, which points to its ability to deal with threshold effects. A technical limitation of QRF is the inability to extrapolate beyond the range of values represented in the training data. We assessed the number and severity of such out-of-observation-range (OOOR) days in both studies, which showed that there were few OOOR days in the second study and that uncertainties associated with OOOR days were small before 2070 in the third study. As the pre-processed data and model code have been made publically available, future studies can easily test further approaches or apply QRF to further catchments.
Advancing digitalization is changing society and has far-reaching effects on people and companies. Fundamental to these changes are the new technological possibilities for processing data on an ever-increasing scale and for various purposes. The availability of large and high-quality data sets, especially those based on personal data, is crucial. They are used either to improve the productivity, quality, and individuality of products and services or to develop new types of services. Today, user behavior is tracked more actively and comprehensively than ever despite increasing legal requirements for protecting personal data worldwide. That increasingly raises ethical, moral, and social questions, which have moved to the forefront of the political debate, not least due to popular cases of data misuse. Given this discourse and the legal requirements, today's data management must fulfill three conditions: Legality or legal conformity of use and ethical legitimacy. Thirdly, the use of data should add value from a business perspective. Within the framework of these conditions, this cumulative dissertation pursues four research objectives with a focus on gaining a better understanding of
(1) the challenges of implementing privacy laws,
(2) the factors that influence customers' willingness to share personal data,
(3) the role of data protection for digital entrepreneurship, and
(4) the interdisciplinary scientific significance, its development, and its interrelationships.
Classification, prediction and evaluation of graph neural networks on online social media platforms
(2024)
The vast amount of data generated on social media platforms have made them a valuable source of information for businesses, governments and researchers. Social media data can provide insights into user behavior, preferences, and opinions. In this work, we address two important challenges in social media analytics. Predicting user engagement with online content has become a critical task for content creators to increase user engagement and reach larger audiences. Traditional user engagement prediction approaches rely solely on features derived from the user and content. However, a new class of deep learning methods based on graphs captures not only the content features but also the graph structure of social media networks.
This thesis proposes a novel Graph Neural Network (GNN) approach to predict user interaction with tweets. The proposed approach combines the features of users, tweets and their engagement graphs. The tweet text features are extracted using pre-trained embeddings from language models, and a GNN layer is used to embed the user in a vector space. The GNN model then combines the features and graph structure to predict user engagement. The proposed approach achieves an accuracy value of 94.22% in classifying user interactions, including likes, retweets, replies, and quotes.
Another major challenge in social media analysis is detecting and classifying social bot accounts. Social bots are automated accounts used to manipulate public opinion by spreading misinformation or generating fake interactions. Detecting social bots is critical to prevent their negative impact on public opinion and trust in social media. In this thesis, we classify social bots on Twitter by applying Graph Neural Networks. The proposed approach uses a combination of both the features of a node and an aggregation of the features of a node’s neighborhood to classify social bot accounts. Our final results indicate a 6% improvement in the area under the curve score in the final predictions through the utilization of GNN.
Overall, our work highlights the importance of social media data and the potential of new methods such as GNNs to predict user engagement and detect social bots. These methods have important implications for improving the quality and reliability of information on social media platforms and mitigating the negative impact of social bots on public opinion and discourse.
The present dissertation investigates changes in lingual coarticulation across childhood in German-speaking children from three to nine years of age and adults. Coarticulation refers to the mismatch between the abstract phonological units and their seemingly commingled realization in continuous speech. Being a process at the intersection of phonology and phonetics, addressing its changes across childhood allows for insights in speech motor as well as phonological developments. Because specific predictions for changes in coarticulation across childhood can be derived from existing speech production models, investigating children’s coarticulatory patterns can help us model human speech production.
While coarticulatory changes may shed light on some of the central questions of speech production development, previous studies on the topic were sparse and presented a puzzling picture of conflicting findings. One of the reasons for this lack is the difficulty in articulatory data acquisition in a young population. Within the research program this dissertation is embedded in, we accepted this challenge and successfully set up the hitherto largest corpus of articulatory data from children using ultrasound tongue imaging. In contrast to earlier studies, a high number of participants in tight age cohorts across a wide age range and a thoroughly controlled set of pseudowords allowed for statistically powerful investigations of a process known as variable and complicated to track.
The specific focus of my studies is on lingual vocalic coarticulation as measured in the horizontal position of the highest point of the tongue dorsum. Based on three studies on a) anticipatory coarticulation towards the left, b) carryover coarticulation towards the right side of the utterance, and c) anticipatory coarticulatory extent in repeated versus read aloud speech, I deduct the following main theses:
1. Maturing speech motor control is responsible for some developmental changes in coarticulation.
2. Coarticulation can be modeled as the coproduction of articulatory gestures.
3. The developmental change in coarticulation results from a decrease of vocalic activation width.
Comparative vote switching
(2024)
Large literatures focus on voter reactions to parties’ policy strategies, agency, or legislative performance. While many inquiries make explicit assumptions about the direction and magnitude of voter flows between parties, comparative empirical analyses of vote switching remain rare. In this article, we overcome three challenges that have previously impeded the comparative study of dynamic party competition based on voter flows: we present a novel conceptual framework for studying voter retention, defection, and attraction in multiparty systems, showcase a newly compiled data infrastructure that marries comparative vote switching data with information on party behavior and party systems in over 250 electoral contexts, and introduce a statistical model that renders our conceptual framework operable. These innovations enable first-time inquiries into the polyadic vote switching patterns underlying multiparty competition and unlock major research potentials on party competition and party system change.
Concepts and techniques for 3D-embedded treemaps and their application to software visualization
(2024)
This thesis addresses concepts and techniques for interactive visualization of hierarchical data using treemaps. It explores (1) how treemaps can be embedded in 3D space to improve their information content and expressiveness, (2) how the readability of treemaps can be improved using level-of-detail and degree-of-interest techniques, and (3) how to design and implement a software framework for the real-time web-based rendering of treemaps embedded in 3D. With a particular emphasis on their application, use cases from software analytics are taken to test and evaluate the presented concepts and techniques.
Concerning the first challenge, this thesis shows that a 3D attribute space offers enhanced possibilities for the visual mapping of data compared to classical 2D treemaps. In particular, embedding in 3D allows for improved implementation of visual variables (e.g., by sketchiness and color weaving), provision of new visual variables (e.g., by physically based materials and in situ templates), and integration of visual metaphors (e.g., by reference surfaces and renderings of natural phenomena) into the three-dimensional representation of treemaps.
For the second challenge—the readability of an information visualization—the work shows that the generally higher visual clutter and increased cognitive load typically associated with three-dimensional information representations can be kept low in treemap-based representations of both small and large hierarchical datasets. By introducing an adaptive level-of-detail technique, we cannot only declutter the visualization results, thereby reducing cognitive load and mitigating occlusion problems, but also summarize and highlight relevant data. Furthermore, this approach facilitates automatic labeling, supports the emphasis on data outliers, and allows visual variables to be adjusted via degree-of-interest measures.
The third challenge is addressed by developing a real-time rendering framework with WebGL and accumulative multi-frame rendering. The framework removes hardware constraints and graphics API requirements, reduces interaction response times, and simplifies high-quality rendering. At the same time, the implementation effort for a web-based deployment of treemaps is kept reasonable.
The presented visualization concepts and techniques are applied and evaluated for use cases in software analysis. In this domain, data about software systems, especially about the state and evolution of the source code, does not have a descriptive appearance or natural geometric mapping, making information visualization a key technology here. In particular, software source code can be visualized with treemap-based approaches because of its inherently hierarchical structure. With treemaps embedded in 3D, we can create interactive software maps that visually map, software metrics, software developer activities, or information about the evolution of software systems alongside their hierarchical module structure.
Discussions on remaining challenges and opportunities for future research for 3D-embedded treemaps and their applications conclude the thesis.