Refine
Has Fulltext
- yes (89) (remove)
Year of publication
- 2013 (89) (remove)
Document Type
- Doctoral Thesis (89) (remove)
Language
- English (89) (remove)
Keywords
- remote sensing (3)
- Arctic (2)
- Fernerkundung (2)
- HCI (2)
- Hochwasser (2)
- Kontext (2)
- Morphologie (2)
- Populationsdynamik (2)
- Proteom (2)
- Vorhersage (2)
- arbuscular mycorrhizal symbiosis (2)
- carbon (2)
- climate change (2)
- eye movements (2)
- floods (2)
- microbial communities (2)
- population dynamics (2)
- probiotics (2)
- prosody (2)
- sensor (2)
- 3-D Modellierung (1)
- 3-D outcrop modeling (1)
- 3D Computer Grafik (1)
- 3D Computer Graphics (1)
- AGN (1)
- Abbildende Spektroskopie (1)
- Affiliationsnetzwerke (1)
- African states (1)
- Afrikanische Staaten (1)
- Akan (1)
- Aktiven Galaxienkerne (1)
- Aktuatoren (1)
- Alaunschiefer (1)
- Altersunterschiede (1)
- Alum shale (1)
- Ambiguität (1)
- Anaphora (1)
- Anisotroper Kuwahara Filter (1)
- Anomalien (1)
- Anoxie (1)
- Anpassung (1)
- Antarctica (1)
- Antarktis (1)
- Antibiotika-Toleranz (1)
- Antibiotikaresistenz (1)
- Antimikrobielle Peptide (1)
- Arabian Plate (1)
- Arabische Platte (1)
- Arbeitsgedächtniskapazität (1)
- Arctic tundra (1)
- Arktis (1)
- Aspect-Oriented Programming (1)
- Aspektorientierte Programmierung (1)
- Astroteilchenphysik (1)
- Aufmerksamkeitskontrolle (1)
- Aufschluss-Modellierung (1)
- Augenbewegungen (1)
- Ausbreitung (1)
- Ausführungsgeschichte (1)
- Ausschüsse (1)
- BMI (1)
- BRDF (1)
- Bayes'sche Netze (1)
- Bayesian networks (1)
- Berührungseingaben (1)
- Binding Theory (1)
- Blickbewegungen (1)
- Boden (1)
- Bodenfeuchte (1)
- Bodenhydrologie (1)
- Bodenparameter (1)
- Bohrlochmessungen (1)
- Brazil (1)
- Breast cancer (1)
- Brownification (1)
- Brustkrebs (1)
- CRS (1)
- CSCW (1)
- Cambodia (1)
- Carbide (1)
- Carbides (1)
- Carbon Cycling (1)
- Carbon cycling (1)
- Carbonate (1)
- Cell proliferation (1)
- Cellulose (1)
- Centering Theory (1)
- Chile (1)
- Chlorogensäure (1)
- Cloud Computing (1)
- Cloud computing (1)
- Clusteranalyse (1)
- Cobalt (1)
- Composites (1)
- Corruption (1)
- Cue-Gewichtung (1)
- Darmbakterien (1)
- Darmlänge (1)
- Data Privacy (1)
- Databases (1)
- Datenabhängigkeiten-Entdeckung (1)
- Datenanalyse (1)
- Datenbanken (1)
- Datenintegration (1)
- Datenschutz (1)
- Dekomposition (1)
- Design Thinking (1)
- Deutschland (1)
- Dezentralisierung (1)
- Differenz von Gauss Filtern (1)
- Digitale Whiteboards (1)
- Disambiguierung (1)
- Diskursgegebenheit (1)
- Diversität (1)
- Downstep (1)
- Durchmusterung (1)
- E. coli (1)
- ETAS (1)
- Ecology (1)
- Ecotoxicology (1)
- Eingabegenauigkeit (1)
- Einstein manifolds (1)
- Einstein-Hilbert action (1)
- Einstein-Hilbert-Wirkung (1)
- Einstein-Mannigfaltigkeiten (1)
- Einzugsgebietsklassifizierung (1)
- Elementarteilchen (1)
- EnMAP (1)
- Enterolignanen (1)
- Enterolignans (1)
- Entwicklungsökonomik (1)
- Erdbeben (1)
- Erdrutsch (1)
- Ereignisdokumentation (1)
- Ernährungsfaktoren (1)
- Erosion (1)
- Escherichia coli (1)
- European Union (1)
- Europäische Union (1)
- Evolution (1)
- Extension (1)
- Fehlerbeseitigung (1)
- Fehlerquellen der Modellierung (1)
- Feld (1)
- Flagellenbewegung (1)
- Fluktuations-Dissipations-Theorem (1)
- Fluoreszenz (1)
- Fluoreszenzbildgebung (1)
- Flussgesteuerter Bilateraler Filter (1)
- Focus+Context Visualization (1)
- Fokus-&-Kontext Visualisierung (1)
- Forstwirtschaft (1)
- Fragmentierung (1)
- Galaxienhaufen (1)
- Galaxy Struktur (1)
- Gas Sorption (1)
- Gefahrenanalyse (1)
- Georgia (1)
- Georgien (1)
- German (1)
- German past participles (1)
- Germany (1)
- Gitterdynamik (1)
- Gletschervorfeld (1)
- Glycopeptoid (1)
- Glykogen (1)
- Grauliteratur (1)
- Hemmung (1)
- Hochenergiephysik (1)
- Hydrogenase (1)
- Hydrologie (1)
- Hyperschnellläufersterne (1)
- IBD (1)
- Imaging spectroscopy (1)
- Impakt (1)
- InSAR (1)
- InSAR Datenanalyse (1)
- Index (1)
- Index Structures (1)
- Indexstrukturen (1)
- Informationsflüsse (1)
- Inklusionsabhängigkeit (1)
- Integralfeld-Spektroskopie (1)
- Interactive Rendering (1)
- Interaktives Rendering (1)
- Internet applications (1)
- Internetanwendungen (1)
- Ionic Liquid (1)
- Ivy (1)
- Java Security Framework (1)
- Kaffeeproteine (1)
- Kambodscha (1)
- Karbonat (1)
- Klassifikator (1)
- Klimawandel (1)
- Kohlenstoff (1)
- Komposite (1)
- Konjugierten polyelektrolyt (1)
- Koreferenz (1)
- Korrektursakkaden (1)
- Korruption (1)
- Kugelsternhaufen (1)
- Kultivierung (1)
- Kurzkettige Fettsäuren (1)
- Körperbautyp (1)
- Körperfett (1)
- Lafora disease (1)
- Landepositionsfehler (1)
- Landnutzungswandel (1)
- Landschaftseffekte (1)
- Landslide (1)
- Leistungsfähigkeit (1)
- Lesen (1)
- Lexikon (1)
- Lignan-converting bacteria (1)
- Lignan-umwandelnde Bakterien (1)
- Link-Entdeckung (1)
- Lipide (1)
- Lithosphäre (1)
- Medicago truncatula (1)
- Metal-organic framework (1)
- Methan (1)
- Mikrobiologie (1)
- Mikrobiota (1)
- Mikrosakkaden (1)
- Milchstrassenmasse (1)
- Minderheiten (1)
- Mischmodelle (1)
- Mobilgeräte (1)
- Modell (1)
- Modellierung (1)
- Molkenproteine (1)
- Monoschichten (1)
- Motilität (1)
- Multivariate Analyse (1)
- Multivariate statistic (1)
- Musikrhythmus (1)
- Muttergalaxien (1)
- NCA (1)
- NMR (1)
- NW Himalaja (1)
- NW Himalaya (1)
- Nachbeben (1)
- Nanoparticles (1)
- Nanopartikel (1)
- Nanostruktur (1)
- Naturgefahren (1)
- Neotektonik (1)
- Netzwerkanalyse (1)
- Nicht-photorealistisches Rendering (1)
- Niedrigwasser (1)
- Nordostdeutsches Becken (1)
- Northeast German Basin (1)
- OT-Modellierung (1)
- Oberflächenwärmefluß (1)
- Optical sensor (1)
- Optische Sensoren (1)
- Owner-Retained Access Control (ORAC) (1)
- OxyR (1)
- PRM/Alf Maus (1)
- PRM/Alf mouse (1)
- PSF Analyse (1)
- PSF fitting (1)
- Paläo-Strain-Berechnung (1)
- Peptid-Membran-Wechselwirkung (1)
- Performance (1)
- Permafrost (1)
- Perowskit (1)
- Pflanzengemeinschaften (1)
- Pflanzliches Lignan (1)
- Phonetik (1)
- Phosphorylierung (1)
- Photonischer Kristall (1)
- Physik schwarzer Löcher (1)
- Phänotypische Heterogenität (1)
- Plant lignan (1)
- Policy Languages (1)
- Policy Sprachen (1)
- Polyamine (1)
- Polyglycin (1)
- Polythiophen (1)
- Primärproduktion (1)
- Probenahmestrategie (1)
- Probiotika (1)
- Pronomen (1)
- Pronouns (1)
- Prosodie (1)
- Protein-Wechselwirkungen (1)
- Proteinmodifizierung (1)
- Prozessmodellsuche (1)
- Präsentation (1)
- Pseudobeobachtungen (1)
- Pseudomonas putida (1)
- Psycholinguistik (1)
- Qualitätsbewertung (1)
- Quantenfeldtheorie (1)
- Quantitative Daten (1)
- Query (1)
- RAVE (1)
- Random-Walk-Theorie (1)
- Raumzeitgeometrie (1)
- Reaktionszeitmethoden (1)
- Regressionsanalyse (1)
- Resonanzfluoreszenz (1)
- Responsive Polymere (1)
- Rhizophagus irregularis (1)
- Rhizosphere (1)
- Ricci flow (1)
- Ricci-Fluss (1)
- Rotationskurven (1)
- Röntgenastronomie (1)
- Sauerstoff (1)
- Scalability (1)
- Schema-Entdeckung (1)
- Schwimmende Mikroorganismen (1)
- Search Algorithms (1)
- Seismische Geschwindigkeiten (1)
- Seismische Interferometrie (1)
- Seismische Tomographie (1)
- Sekundärsakkaden (1)
- Semantik (1)
- Semantische Analyse (1)
- Sensor (1)
- Service-orientierte Systeme (1)
- Similarity Measures (1)
- Similarity Search (1)
- Skala (1)
- Skalierbarkeit (1)
- Skeletal robustness (1)
- Skelettrobustizität (1)
- Softwaretest (1)
- Soil hydrology (1)
- Sorption (1)
- Sprachrhythmus (1)
- Sterndynamik (1)
- Stochastischer Algorithmus (1)
- Strahlung Mechanismen (1)
- Stärke (1)
- Subsurface Biosphere (1)
- Suchverfahren (1)
- Suigetsu (1)
- Systems of Systems (1)
- Temperaturfeld (1)
- Test-getriebene Fehlernavigation (1)
- Thermal-conductivity (1)
- Tien Shan (1)
- Tonsprache (1)
- Transitionmetals (1)
- Transkriptionsfaktoren (1)
- Transkriptom Sequenzierung (1)
- Transkriptomanalyse (1)
- Tritium Assay (1)
- Tritium Versuchsanordnung (1)
- Tropen (1)
- Unruh effect (1)
- Unruh-Effekt (1)
- Unsicherheiten (1)
- Untergrunduntersuchung der Biosphäre (1)
- Variationsstabilität (1)
- Verifikation (1)
- Verteiltes Arbeiten (1)
- Videoanalyse (1)
- Videometadaten (1)
- Vietnamese (1)
- Vietnamesen (1)
- Vulnerabilität (1)
- Waldbewirtschaftung (1)
- Web of Data (1)
- Well-log analysis (1)
- Wärmeleitfähigkeit (1)
- X-ray astronomy (1)
- Zellmembranen (1)
- Zellproliferation (1)
- Zelltyp-spezifisch (1)
- Zellulose (1)
- Zellulärmaterialien (1)
- Zinc (1)
- Zuckertransporter (1)
- actuating materials (1)
- adaptation (1)
- affiliation networks (1)
- aftershock (1)
- age differences (1)
- anaphora (1)
- anisotropic Kuwahara filter (1)
- anomalies (1)
- anoxia (1)
- antibiotic resistance (1)
- antimicrobial peptides (1)
- apoptosis (1)
- arbuskuläre Mykorrhiza-Symbiose (1)
- arbuskuläre Mykorrhizasymbiose (1)
- architectured materials (1)
- arktische Tundra (1)
- astroparticle physics (1)
- attentional control (1)
- automated planning (1)
- back-in-time (1)
- behavioral specification (1)
- biomaterials (1)
- biopolymers (1)
- biorelevant (1)
- black hole physics (1)
- brownification (1)
- carbon flow (1)
- case ambiguity (1)
- catchment classification (1)
- cell tracking (1)
- cell type-specific (1)
- cellular materials (1)
- child language (1)
- childhood abuse (1)
- chlorogenic acid (1)
- chronic and acute inflammation (1)
- chronisch-entzündliche Darmerkrankungen (1)
- classifier (1)
- climate (1)
- clustering (1)
- clusters of galaxies (1)
- cobalt (1)
- coffee proteins (1)
- coherence-enhancing filtering (1)
- commensal (1)
- committee governance (1)
- conjugated polyelectrolyte (1)
- context (1)
- context awareness (1)
- coreference (1)
- corrective saccades (1)
- cosmic-ray (1)
- cscw (1)
- cultivation (1)
- cytokines (1)
- dark matter (1)
- data analysis (1)
- data integration (1)
- debugging (1)
- decentralization (1)
- decomposition (1)
- dependency discovery (1)
- design thinking (1)
- deutsche Partizipien (1)
- development economics (1)
- dietary factors (1)
- difference of Gaussians (1)
- digital whiteboard (1)
- discourse-givenness (1)
- dispersal (1)
- displacement (1)
- diversity (1)
- downstep (1)
- drug tolerance (1)
- dunkle Materie (1)
- earthquake (1)
- eco-hydrological modelling (1)
- ecological modelling (1)
- effective discourse (1)
- elementary particles (1)
- energy density (1)
- entity alignment (1)
- erosion (1)
- event documentation (1)
- evolution (1)
- extension (1)
- flagellar filaments (1)
- flood events (1)
- flow-based bilateral filter (1)
- fluctuation dissipation theorem (1)
- fluorescence (1)
- fluorescence imaging (1)
- forecast (1)
- forest management (1)
- forestry (1)
- formal cognitive models (1)
- formale kognitive Modelle (1)
- fragmentation (1)
- galactic structure (1)
- galaxy structure (1)
- gas sorption (1)
- gesture (1)
- glacier forefield (1)
- globular clusters (1)
- glycogen (1)
- glycopeptoid (1)
- goblet cells (1)
- good governance (1)
- graph clustering (1)
- grey literature (1)
- gut length (1)
- gut microbiota (1)
- hazard assessments (1)
- heteroatom (1)
- high energy astrophysics (1)
- high energy physics (1)
- hochenergetische Astrophysik (1)
- host galaxies (1)
- human-computer interaction (1)
- hydrogel (1)
- hydrogels (1)
- hydrological flow paths (1)
- hydrologische Fließpfade (1)
- hydrology (1)
- hypervelocity stars (1)
- immune response (1)
- impact (1)
- inclusion dependency (1)
- index (1)
- indigene Völker (1)
- indigenous peoples (1)
- infection (1)
- inflammatory bowel disease (1)
- information flow (1)
- inhibition (1)
- input accuracy (1)
- integral field spectroscopy (1)
- interaction (1)
- interactive simulation (1)
- interface (1)
- ionic liquid (1)
- kindliche Sprachverarbeitung (1)
- kosmische Neutronenstrahlung (1)
- körperliche Bewegung (1)
- land-use change (1)
- landscape effects (1)
- landscape hydrology (1)
- lattice dynamics (1)
- lexicon (1)
- lineare spektrale Entmischung (1)
- link discovery (1)
- lipid biomarkers (1)
- lipids (1)
- lithosphere (1)
- low flow (1)
- machine learning (1)
- map/reduce (1)
- maschinelles Lernen (1)
- membranes (1)
- metabolism (1)
- metal-organic framework (1)
- methane (1)
- microbiology (1)
- microbiota (1)
- microsaccades (1)
- mikrobielle Gemeinschaften (1)
- minorities (1)
- mixture models (1)
- mobile (1)
- mobile devices (1)
- model (1)
- model-based prototyping (1)
- modelling (1)
- modelling error sources (1)
- molecular doping (1)
- molekulares Dotieren (1)
- monitoring (1)
- monolayer (1)
- morphological processing (1)
- morphology (1)
- motility (1)
- mucus (1)
- multivariate Statistik (1)
- multivariate statistics (1)
- musical rhythm (1)
- nanostructure (1)
- natural hazards (1)
- natural language generation (1)
- neotectonics (1)
- network analysis (1)
- neutron field (1)
- nicht-Markovsche Dynamik (1)
- non-Markovian dynamics (1)
- non-photorealistic rendering (1)
- offenes Quantensystem (1)
- opal (1)
- open quantum system (1)
- optische Anregung (1)
- organic electronics (1)
- organic semiconductor (1)
- organische Elektronik (1)
- organischer Halbleiter (1)
- organischer Kohlenstoff (1)
- orogenic evolution (1)
- oxygen (1)
- pH (1)
- paleo-strain calculation (1)
- parafoveal processing (1)
- parafoveale Verarbeitung (1)
- pathogen (1)
- peptide-membrane-interaction (1)
- percentage of body fat (1)
- perovskite (1)
- phenotypic heterogeneity (1)
- phonetics (1)
- phosphorylation (1)
- photoexcitation (1)
- photonic crystal (1)
- physical activity (1)
- plant communities (1)
- political economics (1)
- politische Ökonomik (1)
- polyamines (1)
- polyglycine (1)
- polythiohene (1)
- pornography (1)
- prediction (1)
- presentation (1)
- primary production (1)
- process model search (1)
- prosodisch (1)
- protein (1)
- protein interactions (1)
- protein modification (1)
- proteome (1)
- proteomics (1)
- pseudomonas putida (1)
- psycholinguistics (1)
- qualitative pathway interpretation (1)
- quality assessment framework (1)
- quantitative data (1)
- quantum field theory (1)
- querying (1)
- radiation mechanisms (1)
- radiocarbon (1)
- random walk (1)
- rapid prototyping (1)
- reaction time methods (1)
- reading (1)
- reconfigurable matter (1)
- regionale Hydrologie (1)
- regression analysis (1)
- remote collaboration (1)
- requirements engineering (1)
- resonance fluorescence (1)
- responsive (1)
- responsive polymer (1)
- rhizosphere (1)
- rotation curves (1)
- räumliche Kalibrierung (1)
- saccadic error (1)
- scale (1)
- schema discovery (1)
- secondary saccades (1)
- seismic interferometry (1)
- seismic tomography (1)
- seismic velocities (1)
- semantic analysis (1)
- semantics (1)
- service-oriented systems (1)
- sexual aggression (1)
- sexual scripts (1)
- short chain fatty acids (1)
- similarity (1)
- situated context (1)
- soil (1)
- soil constituents mapping (1)
- soil moisture (1)
- soil organic carbon (1)
- sol-gel (1)
- somatotype (1)
- spacetime geometry (1)
- spatial calibration (1)
- spectral unmixing (1)
- spectro-directional (1)
- speech rhythm (1)
- spektro-direktional (1)
- stable isotope tracing (1)
- starch (1)
- stellar dynamics (1)
- stochastic algorithms (1)
- sucrose (1)
- sugar transporter (1)
- supercapacitor (1)
- surface heat flow (1)
- survey (1)
- swelling (1)
- syntactic processing (1)
- syntaktische Ambiguität (1)
- systems of systems (1)
- tectonics (1)
- temperature field analysis (1)
- test-driven fault navigation (1)
- testing (1)
- tf-idf (1)
- thermal model (1)
- thermisches Modell (1)
- thermochronology (1)
- thermoresponsiv (1)
- thermoresponsive (1)
- thermosensitive (1)
- tone language (1)
- topics (1)
- touch input (1)
- transcription factors (1)
- transcriptome analysis (1)
- transcriptome sequencing (1)
- tropics (1)
- ultrafast X-ray diffraction (1)
- ultraschnelle Röntgendiffraktion (1)
- uncertainties (1)
- variational stability (1)
- verification (1)
- video analysis (1)
- video metadata (1)
- vulnerability (1)
- whey proteins (1)
- word sense disambiguation (1)
- working memory capacity (1)
- zinc (1)
- Ähnlichkeit (1)
- Ähnlichkeitsmaße (1)
- Ähnlichkeitssuche (1)
- Ökologie (1)
- Ökotoxikologie (1)
- Übergangsmetalle (1)
- ökohydrologische Modellierung (1)
- ökologische Modellierung (1)
Institute
- Institut für Geowissenschaften (22)
- Hasso-Plattner-Institut für Digital Engineering gGmbH (14)
- Institut für Physik und Astronomie (14)
- Institut für Biochemie und Biologie (9)
- Institut für Informatik und Computational Science (7)
- Department Linguistik (6)
- Institut für Chemie (6)
- Institut für Ernährungswissenschaft (6)
- Department Psychologie (5)
- Extern (4)
Multi-messenger constraints and pressure from dark matter annihilation into electron-positron pairs
(2013)
Despite striking evidence for the existence of dark matter from astrophysical observations, dark matter has still escaped any direct or indirect detection until today. Therefore a proof for its existence and the revelation of its nature belongs to one of the most intriguing challenges of nowadays cosmology and particle physics. The present work tries to investigate the nature of dark matter through indirect signatures from dark matter annihilation into electron-positron pairs in two different ways, pressure from dark matter annihilation and multi-messenger constraints on the dark matter annihilation cross-section. We focus on dark matter annihilation into electron-positron pairs and adopt a model-independent approach, where all the electrons and positrons are injected with the same initial energy E_0 ~ m_dm*c^2. The propagation of these particles is determined by solving the diffusion-loss equation, considering inverse Compton scattering, synchrotron radiation, Coulomb collisions, bremsstrahlung, and ionization. The first part of this work, focusing on pressure from dark matter annihilation, demonstrates that dark matter annihilation into electron-positron pairs may affect the observed rotation curve by a significant amount. The injection rate of this calculation is constrained by INTEGRAL, Fermi, and H.E.S.S. data. The pressure of the relativistic electron-positron gas is computed from the energy spectrum predicted by the diffusion-loss equation. For values of the gas density and magnetic field that are representative of the Milky Way, it is estimated that the pressure gradients are strong enough to balance gravity in the central parts if E_0 < 1 GeV. The exact value depends somewhat on the astrophysical parameters, and it changes dramatically with the slope of the dark matter density profile. For very steep slopes, as those expected from adiabatic contraction, the rotation curves of spiral galaxies would be affected on kiloparsec scales for most values of E_0. By comparing the predicted rotation curves with observations of dwarf and low surface brightness galaxies, we show that the pressure from dark matter annihilation may improve the agreement between theory and observations in some cases, but it also imposes severe constraints on the model parameters (most notably, the inner slope of the halo density profile, as well as the mass and the annihilation cross-section of dark matter particles into electron-positron pairs). In the second part, upper limits on the dark matter annihilation cross-section into electron-positron pairs are obtained by combining observed data at different wavelengths (from Haslam, WMAP, and Fermi all-sky intensity maps) with recent measurements of the electron and positron spectra in the solar neighbourhood by PAMELA, Fermi, and H.E.S.S.. We consider synchrotron emission in the radio and microwave bands, as well as inverse Compton scattering and final-state radiation at gamma-ray energies. For most values of the model parameters, the tightest constraints are imposed by the local positron spectrum and synchrotron emission from the central regions of the Galaxy. According to our results, the annihilation cross-section should not be higher than the canonical value for a thermal relic if the mass of the dark matter candidate is smaller than a few GeV. In addition, we also derive a stringent upper limit on the inner logarithmic slope α of the density profile of the Milky Way dark matter halo (α < 1 if m_dm < 5 GeV, α < 1.3 if m_dm < 100 GeV and α < 1.5 if m_dm < 2 TeV) assuming a dark matter annihilation cross-section into electron-positron pairs (σv) = 3*10^−26 cm^3 s^−1, as predicted for thermal relics from the big bang.
Even though quite different in occurrence and consequences, from a modeling perspective many natural hazards share similar properties and challenges. Their complex nature as well as lacking knowledge about their driving forces and potential effects make their analysis demanding: uncertainty about the modeling framework, inaccurate or incomplete event observations and the intrinsic randomness of the natural phenomenon add up to different interacting layers of uncertainty, which require a careful handling. Nevertheless deterministic approaches are still widely used in natural hazard assessments, holding the risk of underestimating the hazard with disastrous effects. The all-round probabilistic framework of Bayesian networks constitutes an attractive alternative. In contrast to deterministic proceedings, it treats response variables as well as explanatory variables as random variables making no difference between input and output variables. Using a graphical representation Bayesian networks encode the dependency relations between the variables in a directed acyclic graph: variables are represented as nodes and (in-)dependencies between variables as (missing) edges between the nodes. The joint distribution of all variables can thus be described by decomposing it, according to the depicted independences, into a product of local conditional probability distributions, which are defined by the parameters of the Bayesian network. In the framework of this thesis the Bayesian network approach is applied to different natural hazard domains (i.e. seismic hazard, flood damage and landslide assessments). Learning the network structure and parameters from data, Bayesian networks reveal relevant dependency relations between the included variables and help to gain knowledge about the underlying processes. The problem of Bayesian network learning is cast in a Bayesian framework, considering the network structure and parameters as random variables itself and searching for the most likely combination of both, which corresponds to the maximum a posteriori (MAP score) of their joint distribution given the observed data. Although well studied in theory the learning of Bayesian networks based on real-world data is usually not straight forward and requires an adoption of existing algorithms. Typically arising problems are the handling of continuous variables, incomplete observations and the interaction of both. Working with continuous distributions requires assumptions about the allowed families of distributions. To "let the data speak" and avoid wrong assumptions, continuous variables are instead discretized here, thus allowing for a completely data-driven and distribution-free learning. An extension of the MAP score, considering the discretization as random variable as well, is developed for an automatic multivariate discretization, that takes interactions between the variables into account. The discretization process is nested into the network learning and requires several iterations. Having to face incomplete observations on top, this may pose a computational burden. Iterative proceedings for missing value estimation become quickly infeasible. A more efficient albeit approximate method is used instead, estimating the missing values based only on the observations of variables directly interacting with the missing variable. Moreover natural hazard assessments often have a primary interest in a certain target variable. The discretization learned for this variable does not always have the required resolution for a good prediction performance. Finer resolutions for (conditional) continuous distributions are achieved with continuous approximations subsequent to the Bayesian network learning, using kernel density estimations or mixtures of truncated exponential functions. All our proceedings are completely data-driven. We thus avoid assumptions that require expert knowledge and instead provide domain independent solutions, that are applicable not only in other natural hazard assessments, but in a variety of domains struggling with uncertainties.
Large Central European flood events of the past have demonstrated that flooding can affect several river basins at the same time leading to catastrophic economic and humanitarian losses that can stretch emergency resources beyond planned levels of service. For Germany, the spatial coherence of flooding, the contributing processes and the role of trans-basin floods for a national risk assessment is largely unknown and analysis is limited by a lack of systematic data, information and knowledge on past events. This study investigates the frequency and intensity of trans-basin flood events in Germany. It evaluates the data and information basis on which knowledge about trans-basin floods can be generated in order to improve any future flood risk assessment. In particu-lar, the study assesses whether flood documentations and related reports can provide a valuable data source for understanding trans-basin floods. An adaptive algorithm was developed that systematically captures trans-basin floods using series of mean daily discharge at a large number of sites of even time series length (1952-2002). It identifies the simultaneous occurrence of flood peaks based on the exceedance of an initial threshold of a 10 year flood at one location and consecutively pools all causally related, spatially and temporally lagged peak recordings at the other locations. A weighted cumulative index was developed that accounts for the spatial extent and the individual flood magnitudes within an event and allows quantifying the overall event severity. The parameters of the method were tested in a sensitivity analysis. An intensive study on sources and ways of information dissemination of flood-relevant publications in Germany was conducted. Based on the method of systematic reviews a strategic search approach was developed to identify relevant documentations for each of the 40 strongest trans-basin flood events. A novel framework for assessing the quality of event specific flood reports from a user’s perspective was developed and validated by independent peers. The framework was designed to be generally applicable for any natural hazard type and assesses the quality of a document addressing accessibility as well as representational, contextual, and intrinsic dimensions of quality. The analysis of time-series of mean daily discharge resulted in the identification of 80 trans-basin flood events within the period 1952-2002 in Germany. The set is dominated by events that were recorded in the hydrological winter (64%); 36% occurred during the summer months. The occurrence of floods is characterised by a distinct clustering in time. Dividing the study period into two sub-periods, we find an increase in the percentage of winter events from 58% in the first to 70.5% in the second sub-period. Accordingly, we find a significant increase in the number of extreme trans-basin floods in the second sub-period. A large body of 186 flood relevant documentations was identified. For 87.5% of the 40 strongest trans-basin floods in Germany at least one report has been found and for the most severe floods a substantial amount of documentation could be obtained. 80% of the material can be considered grey literature (i.e. literature not controlled by commercial publishers). The results of the quality assessment show that the majority of flood event specific reports are of a good quality, i.e. they are well enough drafted, largely accurate and objective, and contain a substantial amount of information on the sources, pathways and receptors/consequences of the floods. The inclusion of this information in the process of knowledge building for flood risk assessment is recommended. Both the results as well as the data produced in this study are openly accessible and can be used for further research. The results of this study contribute to an improved spatial risk assessment in Germany. The identified set of trans-basin floods provides the basis for an assessment of the chance that flooding occurs simultaneously at a number of sites. The information obtained from flood event documentation can usefully supplement the analysis of the processes that govern flood risk.
Interactive rendering techniques for focus+context visualization of 3D geovirtual environments
(2013)
This thesis introduces a collection of new real-time rendering techniques and applications for focus+context visualization of interactive 3D geovirtual environments such as virtual 3D city and landscape models. These environments are generally characterized by a large number of objects and are of high complexity with respect to geometry and textures. For these reasons, their interactive 3D rendering represents a major challenge. Their 3D depiction implies a number of weaknesses such as occlusions, cluttered image contents, and partial screen-space usage. To overcome these limitations and, thus, to facilitate the effective communication of geo-information, principles of focus+context visualization can be used for the design of real-time 3D rendering techniques for 3D geovirtual environments (see Figure). In general, detailed views of a 3D geovirtual environment are combined seamlessly with abstracted views of the context within a single image. To perform the real-time image synthesis required for interactive visualization, dedicated parallel processors (GPUs) for rasterization of computer graphics primitives are used. For this purpose, the design and implementation of appropriate data structures and rendering pipelines are necessary. The contribution of this work comprises the following five real-time rendering methods: • The rendering technique for 3D generalization lenses enables the combination of different 3D city geometries (e.g., generalized versions of a 3D city model) in a single image in real time. The method is based on a generalized and fragment-precise clipping approach, which uses a compressible, raster-based data structure. It enables the combination of detailed views in the focus area with the representation of abstracted variants in the context area. • The rendering technique for the interactive visualization of dynamic raster data in 3D geovirtual environments facilitates the rendering of 2D surface lenses. It enables a flexible combination of different raster layers (e.g., aerial images or videos) using projective texturing for decoupling image and geometry data. Thus, various overlapping and nested 2D surface lenses of different contents can be visualized interactively. • The interactive rendering technique for image-based deformation of 3D geovirtual environments enables the real-time image synthesis of non-planar projections, such as cylindrical and spherical projections, as well as multi-focal 3D fisheye-lenses and the combination of planar and non-planar projections. • The rendering technique for view-dependent multi-perspective views of 3D geovirtual environments, based on the application of global deformations to the 3D scene geometry, can be used for synthesizing interactive panorama maps to combine detailed views close to the camera (focus) with abstract views in the background (context). This approach reduces occlusions, increases the usage the available screen space, and reduces the overload of image contents. • The object-based and image-based rendering techniques for highlighting objects and focus areas inside and outside the view frustum facilitate preattentive perception. The concepts and implementations of interactive image synthesis for focus+context visualization and their selected applications enable a more effective communication of spatial information, and provide building blocks for design and development of new applications and systems in the field of 3D geovirtual environments.
Water management and environmental protection is vulnerable to extreme low flows during streamflow droughts. During the last decades, in most rivers of Central Europe summer runoff and low flows have decreased. Discharge projections agree that future decrease in runoff is likely for catchments in Brandenburg, Germany. Depending on the first-order controls on low flows, different adaption measures are expected to be appropriate. Small catchments were analyzed because they are expected to be more vulnerable to a changing climate than larger rivers. They are mainly headwater catchments with smaller ground water storage. Local characteristics are more important at this scale and can increase vulnerability. This thesis mutually evaluates potential adaption measures to sustain minimum runoff in small catchments of Brandenburg, Germany, and similarities of these catchments regarding low flows. The following guiding questions are addressed: (i) Which first-order controls on low flows and related time scales exist? (ii) Which are the differences between small catchments regarding low flow vulnerability? (iii) Which adaption measures to sustain minimum runoff in small catchments of Brandenburg are appropriate considering regional low flow patterns? Potential adaption measures to sustain minimum runoff during periods of low flows can be classified into three categories: (i) increase of groundwater recharge and subsequent baseflow by land use change, land management and artificial ground water recharge, (ii) increase of water storage with regulated outflow by reservoirs, lakes and wetland water management and (iii) regional low flow patterns have to be considered during planning of measures with multiple purposes (urban water management, waste water recycling and inter-basin water transfer). The question remained whether water management of areas with shallow groundwater tables can efficiently sustain minimum runoff. Exemplary, water management scenarios of a ditch irrigated area were evaluated using the model Hydrus-2D. Increasing antecedent water levels and stopping ditch irrigation during periods of low flows increased fluxes from the pasture to the stream, but storage was depleted faster during the summer months due to higher evapotranspiration. Fluxes from this approx. 1 km long pasture with an area of approx. 13 ha ranged from 0.3 to 0.7 l\s depending on scenario. This demonstrates that numerous of such small decentralized measures are necessary to sustain minimum runoff in meso-scale catchments. Differences in the low flow risk of catchments and meteorological low flow predictors were analyzed. A principal component analysis was applied on daily discharge of 37 catchments between 1991 and 2006. Flows decreased more in Southeast Brandenburg according to meteorological forcing. Low flow risk was highest in a region east of Berlin because of intersection of a more continental climate and the specific geohydrology. In these catchments, flows decreased faster during summer and the low flow period was prolonged. A non-linear support vector machine regression was applied to iteratively select meteorological predictors for annual 30-day minimum runoff in 16 catchments between 1965 and 2006. The potential evapotranspiration sum of the previous 48 months was the most important predictor (r²=0.28). The potential evapotranspiration of the previous 3 months and the precipitation of the previous 3 months and last year increased model performance (r²=0.49, including all four predictors). Model performance was higher for catchments with low yield and more damped runoff. In catchments with high low flow risk, explanatory power of long term potential evapotranspiration was high. Catchments with a high low flow risk as well as catchments with a considerable decrease in flows in southeast Brandenburg have the highest demand for adaption. Measures increasing groundwater recharge are to be preferred. Catchments with high low flow risk showed relatively deep and decreasing groundwater heads allowing increased groundwater recharge at recharge areas with higher altitude away from the streams. Low flows are expected to stay low or decrease even further because long term potential evapotranspiration was the most important low flow predictor and is projected to increase during climate change. Differences in low flow risk and runoff dynamics between catchments have to be considered for management and planning of measures which do not only have the task to sustain minimum runoff.
In the presence of a solid-liquid or liquid-air interface, bacteria can choose between a planktonic and a sessile lifestyle. Depending on environmental conditions, cells swimming in close proximity to the interface can irreversibly attach to the surface and grow into three-dimensional aggregates where the majority of cells is sessile and embedded in an extracellular polymer matrix (biofilm). We used microfluidic tools and time lapse microscopy to perform experiments with the polarly flagellated soil bacterium Pseudomonas putida (P. putida), a bacterial species that is able to form biofilms. We analyzed individual trajectories of swimming cells, both in the bulk fluid and in close proximity to a glass-liquid interface. Additionally, surface related growth during the early phase of biofilm formation was investigated. In the bulk fluid, P.putida shows a typical bacterial swimming pattern of alternating periods of persistent displacement along a line (runs) and fast reorientation events (turns) and cells swim with an average speed around 24 micrometer per second. We found that the distribution of turning angles is bimodal with a dominating peak around 180 degrees. In approximately six out of ten turning events, the cell reverses its swimming direction. In addition, our analysis revealed that upon a reversal, the cell systematically changes its swimming speed by a factor of two on average. Based on the experimentally observed values of mean runtime and rotational diffusion, we presented a model to describe the spreading of a population of cells by a run-reverse random walker with alternating speeds. We successfully recover the mean square displacement and, by an extended version of the model, also the negative dip in the directional autocorrelation function as observed in the experiments. The analytical solution of the model demonstrates that alternating speeds enhance a cells ability to explore its environment as compared to a bacterium moving at a constant intermediate speed. As compared to the bulk fluid, for cells swimming near a solid boundary we observed an increase in swimming speed at distances below d= 5 micrometer and an increase in average angular velocity at distances below d= 4 micrometer. While the average speed was maximal with an increase around 15% at a distance of d= 3 micrometer, the angular velocity was highest in closest proximity to the boundary at d=1 micrometer with an increase around 90% as compared to the bulk fluid. To investigate the swimming behavior in a confinement between two solid boundaries, we developed an experimental setup to acquire three-dimensional trajectories using a piezo driven objective mount coupled to a high speed camera. Results on speed and angular velocity were consistent with motility statistics in the presence of a single boundary. Additionally, an analysis of the probability density revealed that a majority of cells accumulated near the upper and lower boundaries of the microchannel. The increase in angular velocity is consistent with previous studies, where bacteria near a solid boundary were shown to swim on circular trajectories, an effect which can be attributed to a wall induced torque. The increase in speed at a distance of several times the size of the cell body, however, cannot be explained by existing theories which either consider the drag increase on cell body and flagellum near a boundary (resistive force theory) or model the swimming microorganism by a multipole expansion to account for the flow field interaction between cell and boundary. An accumulation of swimming bacteria near solid boundaries has been observed in similar experiments. Our results confirm that collisions with the surface play an important role and hydrodynamic interactions alone cannot explain the steady-state accumulation of cells near the channel walls. Furthermore, we monitored the number growth of cells in the microchannel under medium rich conditions. We observed that, after a lag time, initially isolated cells at the surface started to grow by division into colonies of increasing size, while coexisting with a comparable smaller number of swimming cells. After 5:50 hours, we observed a sudden jump in the number of swimming cells, which was accompanied by a breakup of bigger clusters on the surface. After approximately 30 minutes where planktonic cells dominated in the microchannel, individual swimming cells reattached to the surface. We interpret this process as an emigration and recolonization event. A number of complementary experiments were performed to investigate the influence of collective effects or a depletion of the growth medium on the transition. Similar to earlier observations on another bacterium from the same family we found that the release of cells to the swimming phase is most likely the result of an individual adaption process, where syntheses of proteins for flagellar motility are upregulated after a number of division cycles at the surface.
Galaxy clusters are the largest known gravitationally bound objects, their study is important for both an intrinsic understanding of their systems and an investigation of the large scale structure of the universe. The multi- component nature of galaxy clusters offers multiple observable signals across the electromagnetic spectrum. At X-ray wavelengths, galaxy clusters are simply identified as X-ray luminous, spatially extended, and extragalactic sources. X-ray observations offer the most powerful technique for constructing cluster catalogues. The main advantages of the X-ray cluster surveys are their excellent purity and completeness and the X-ray observables are tightly correlated with mass, which is indeed the most fundamental parameter of clusters. In my thesis I have conducted the 2XMMi/SDSS galaxy cluster survey, which is a serendipitous search for galaxy clusters based on the X-ray extended sources in the XMM-Newton Serendipitous Source Catalogue (2XMMi-DR3). The main aims of the survey are to identify new X-ray galaxy clusters, investigate their X-ray scaling relations, identify distant cluster candidates, and study the correlation of the X-ray and optical properties. The survey is constrained to those extended sources that are in the footprint of the Sloan Digital Sky Survey (SDSS) in order to be able to identify the optical counterparts as well as to measure their redshifts that are mandatory to measure their physical properties. The overlap area be- tween the XMM-Newton fields and the SDSS-DR7 imaging, the latest SDSS data release at the starting of the survey, is 210 deg^2. The survey comprises 1180 X-ray cluster candidates with at least 80 background-subtracted photon counts, which passed the quality control process. To measure the optical redshifts of the X-ray cluster candidates, I used three procedures; (i) cross-matching these candidates with the recent and largest optically selected cluster catalogues in the literature, which yielded the photometric redshifts of about a quarter of the X-ray cluster candidates. (ii) I developed a finding algorithm to search for overdensities of galaxies at the positions of the X-ray cluster candidates in the photometric redshift space and to measure their redshifts from the SDSS-DR8 data, which provided the photometric redshifts of 530 groups/clusters. (iii) I developed an algorithm to identify the cluster candidates associated with spectroscopically targeted Luminous Red Galaxies (LRGs) in the SDSS-DR9 and to measure the cluster spectroscopic redshift, which provided 324 groups and clusters with spectroscopic confirmation based on spectroscopic redshift of at least one LRG. In total, the optically confirmed cluster sample comprises 574 groups and clusters with redshifts (0.03 ≤ z ≤ 0.77), which is the largest X-ray selected cluster catalogue to date based on observations from the current X-ray observatories (XMM-Newton, Chandra, Suzaku, and Swift/XRT). Among the cluster sample, about 75 percent are newly X-ray discovered groups/clusters and 40 percent are new systems to the literature. To determine the X-ray properties of the optically confirmed cluster sample, I reduced and analysed their X-ray data in an automated way following the standard pipelines of processing the XMM-Newton data. In this analysis, I extracted the cluster spectra from EPIC(PN, MOS1, MOS2) images within an optimal aperture chosen to maximise the signal-to-noise ratio. The spectral fitting procedure provided the X-ray temperatures kT (0.5 - 7.5 keV) for 345 systems that have good quality X-ray data. For all the optically confirmed cluster sample, I measured the physical properties L500 (0.5 x 10^42 – 1.2 x 10^45 erg s-1 ) and M500 (1.1 x 10^13 – 4.9 x 10^14 M⊙) from an iterative procedure using published scaling relations. The present X-ray detected groups and clusters are in the low and intermediate luminosity regimes apart from few luminous systems, thanks to the XMM-Newton sensitivity and the available XMM-Newton deep fields The optically confirmed cluster sample with measurements of redshift and X-ray properties can be used for various astrophysical applications. As a first application, I investigated the LX - T relation for the first time based on a large cluster sample of 345 systems with X-ray spectroscopic parameters drawn from a single survey. The current sample includes groups and clusters with wide ranges of redshifts, temperatures, and luminosities. The slope of the relation is consistent with the published ones of nearby clusters with higher temperatures and luminosities. The derived relation is still much steeper than that predicted by self-similar evolution. I also investigated the evolution of the slope and the scatter of the LX - T relation with the cluster redshift. After excluding the low luminosity groups, I found no significant changes of the slope and the intrinsic scatter of the relation with redshift when dividing the sample into three redshift bins. When including the low luminosity groups in the low redshift subsample, I found its LX - T relation becomes after than the relation of the intermediate and high redshift subsamples. As a second application of the optically confirmed cluster sample from our ongoing survey, I investigated the correlation between the cluster X-ray and the optical parameters that have been determined in a homogenous way. Firstly, I investigated the correlations between the BCG properties (absolute magnitude and optical luminosity) and the cluster global proper- ties (redshift and mass). Secondly, I computed the richness and the optical luminosity within R500 of a nearby subsample (z ≤ 0.42, with a complete membership detection from the SDSS data) with measured X-ray temperatures from our survey. The relation between the estimated optical luminosity and richness is also presented. Finally, the correlation between the cluster optical properties (richness and luminosity) and the cluster global properties (X-ray luminosity, temperature, mass) are investigated.
In this work, the development of temperature- and protein-responsive sensor materials based on biocompatible, inverse hydrogel opals (IHOs) is presented. With these materials, large biomolecules can be specifically recognised and the binding event visualised. The preparation of the IHOs was performed with a template process, for which monodisperse silica particles were vertically deposited onto glass slides as the first step. The obtained colloidal crystals with a thickness of 5 μm displayed opalescent reflections because of the uniform alignment of the colloids. As a second step, the template was embedded in a matrix consisting of biocompatible, thermoresponsive hydrogels. The comonomers were selected from the family of oligo(ethylene glycol)methacrylates. The monomer solution was injected into a polymerisation mould, which contained the colloidal crystals as a template. The space in-between the template particles was filled with the monomer solution and the hydrogel was cured via UV-polymerisation. The particles were chemically etched, which resulted in a porous inner structure. The uniform alignment of the pores and therefore the opalescent reflection were maintained, so these system were denoted as inverse hydrogel opals. A pore diameter of several hundred nanometres as well as interconnections between the pores should facilitate a diffusion of bigger (bio)molecules, which was always a challenge in the presented systems until now. The copolymer composition was chosen to result in a hydrogel collapse over 35 °C. All hydrogels showed pronounced swelling in water below the critical temperature. The incorporation of a reactive monomer with hydroxyl groups ensured a potential coupling group for the introduction of recognition units for analytes, e.g. proteins. As a test system, biotin as a recognition unit for avidin was coupled to the IHO via polymer-analogous Steglich esterification. The amount of accessible biotin was quantified with a colorimetric binding assay. When avidin was added to the biotinylated IHO, the wavelength of the opalescent reflection was significantly shifted and therefore the binding event was visualised. This effect is based on the change in swelling behaviour of the hydrogel after binding of the hydrophilic avidin, which is amplified by the thermoresponsive nature of the hydrogel. A swelling or shrinking of the pores induces a change in distance of the crystal planes, which are responsible for the colour of the reflection. With these findings, the possibility of creating sensor materials or additional biomolecules in the size range of avidin is given.
The Semantic Web provides information contained in the World Wide Web as machine-readable facts. In comparison to a keyword-based inquiry, semantic search enables a more sophisticated exploration of web documents. By clarifying the meaning behind entities, search results are more precise and the semantics simultaneously enable an exploration of semantic relationships. However, unlike keyword searches, a semantic entity-focused search requires that web documents are annotated with semantic representations of common words and named entities. Manual semantic annotation of (web) documents is time-consuming; in response, automatic annotation services have emerged in recent years. These annotation services take continuous text as input, detect important key terms and named entities and annotate them with semantic entities contained in widely used semantic knowledge bases, such as Freebase or DBpedia. Metadata of video documents require special attention. Semantic analysis approaches for continuous text cannot be applied, because information of a context in video documents originates from multiple sources possessing different reliabilities and characteristics. This thesis presents a semantic analysis approach consisting of a context model and a disambiguation algorithm for video metadata. The context model takes into account the characteristics of video metadata and derives a confidence value for each metadata item. The confidence value represents the level of correctness and ambiguity of the textual information of the metadata item. The lower the ambiguity and the higher the prospective correctness, the higher the confidence value. The metadata items derived from the video metadata are analyzed in a specific order from high to low confidence level. Previously analyzed metadata are used as reference points in the context for subsequent disambiguation. The contextually most relevant entity is identified by means of descriptive texts and semantic relationships to the context. The context is created dynamically for each metadata item, taking into account the confidence value and other characteristics. The proposed semantic analysis follows two hypotheses: metadata items of a context should be processed in descendent order of their confidence value, and the metadata that pertains to a context should be limited by content-based segmentation boundaries. The evaluation results support the proposed hypotheses and show increased recall and precision for annotated entities, especially for metadata that originates from sources with low reliability. The algorithms have been evaluated against several state-of-the-art annotation approaches. The presented semantic analysis process is integrated into a video analysis framework and has been successfully applied in several projects for the purpose of semantic video exploration of videos.
Introduction: Intestinal bacteria influence gut morphology by affecting epithelial cell proliferation, development of the lamina propria, villus length and crypt depth [1]. Gut microbiota-derived factors have been proposed to also play a role in the development of a 30 % longer intestine, that is characteristic of PRM/Alf mice compared to other mouse strains [2, 3]. Polyamines and SCFAs produced by gut bacteria are important growth factors, which possibly influence mucosal morphology, in particular villus length and crypt depth and play a role in gut lengthening in the PRM/Alf mouse. However, experimental evidence is lacking. Aim: The objective of this work was to clarify the role of bacterially-produced polyamines on crypt depth, mucosa thickness and epithelial cell proliferation. For this purpose, C3H mice associated with a simplified human microbiota (SIHUMI) were compared with mice colonized with SIHUMI complemented by the polyamine-producing Fusobacterium varium (SIHUMI + Fv). In addition, the microbial impact on gut lengthening in PRM/Alf mice was characterized and the contribution of SCFAs and polyamines to this phenotype was examined. Results: SIHUMI + Fv mice exhibited an up to 1.7 fold higher intestinal polyamine concentration compared to SIHUMI mice, which was mainly due to increased putrescine concentrations. However, no differences were observed in crypt depth, mucosa thickness and epithelial proliferation. In PRM/Alf mice, the intestine of conventional mice was 8.5 % longer compared to germfree mice. In contrast, intestinal lengths of C3H mice were similar, independent of the colonization status. The comparison of PRM/Alf and C3H mice, both associated with SIHUMI + Fv, demonstrated that PRM/Alf mice had a 35.9 % longer intestine than C3H mice. However, intestinal SCFA and polyamine concentrations of PRM/Alf mice were similar or even lower, except N acetylcadaverine, which was 3.1-fold higher in PRM/Alf mice. When germfree PRM/Alf mice were associated with a complex PRM/Alf microbiota, the intestine was one quarter longer compared to PRM/Alf mice colonized with a C3H microbiota. This gut elongation correlated with levels of the polyamine N acetylspermine. Conclusion: The intestinal microbiota is able to influence intestinal length dependent on microbial composition and on the mouse genotype. Although SCFAs do not contribute to gut elongation, an influence of the polyamines N acetylcadaverine and N acetylspermine is conceivable. In addition, the study clearly demonstrated that bacterial putrescine does not influence gut morphology in C3H mice.