Refine
Year of publication
- 2019 (312) (remove)
Document Type
- Article (256)
- Doctoral Thesis (21)
- Other (19)
- Postprint (12)
- Review (3)
- Monograph/Edited Volume (1)
Is part of the Bibliography
- yes (312)
Keywords
- diffusion (9)
- stars: evolution (7)
- stars: winds, outflows (7)
- methods: numerical (6)
- quasars: absorption lines (6)
- stars: massive (6)
- anomalous diffusion (5)
- intergalactic medium (5)
- stars: mass-loss (5)
- subdwarfs (5)
- ISM: supernova remnants (4)
- acceleration of particles (4)
- binaries: close (4)
- galaxies: evolution (4)
- galaxies: formation (4)
- gamma rays: general (4)
- perovskite solar cells (4)
- radiative transfer (4)
- stars: Wolf-Rayet (4)
- stars: abundances (4)
- stars: atmospheres (4)
- stars: early-type (4)
- techniques: imaging spectroscopy (4)
- Langevin equation (3)
- X-rays: binaries (3)
- catalogs (3)
- cosmic rays (3)
- first-hitting time (3)
- first-passage time (3)
- galaxies: active (3)
- galaxies: haloes (3)
- galaxies: high-redshift (3)
- hydrodynamics (3)
- instabilities (3)
- interface engineering (3)
- planets and satellites: rings (3)
- quasi-Fermi level splitting (3)
- radiation mechanisms: non-thermal (3)
- recombination (3)
- roughness (3)
- stars: black holes (3)
- stars: neutron (3)
- techniques: spectroscopic (3)
- 4 (2)
- Brownian yet non-Gaussian diffusion (2)
- Equilibrium-line altitudes (2)
- Galaxy: halo (2)
- Holocene (2)
- Hong-Ou-Mandel effect (2)
- Irradiation (2)
- Levy flights (2)
- Lévy flights (2)
- Lévy walks (2)
- Magellanic Clouds (2)
- Magnetisierungsdynamik (2)
- NAP-XPS (2)
- Perovskite solar cell (2)
- Radiation belts (2)
- Shockley-Queisser model (2)
- Spektroskopie (2)
- Statistical and Nonlinear Physics (2)
- Sternentwicklung (2)
- Synchronisation (2)
- XPS (2)
- acceleration (2)
- additive manufacturing (2)
- autoregressive models (2)
- azobenzene elastomers (2)
- bacteria (2)
- bandgap (2)
- binaries: general (2)
- binaries: spectroscopic (2)
- birefringence (2)
- charge-transfer (2)
- chemotaxis (2)
- chorus waves (2)
- codifference (2)
- comets: general (2)
- comets: individual: 67P/Churyumov-Gerasimenko (2)
- complementarity (2)
- confinement (2)
- convection (2)
- dark ages, reionization, first stars (2)
- dark matter (2)
- diffuse radiation (2)
- diffusing diffusivity (2)
- entanglement (2)
- erasure (2)
- fill factor losses (2)
- first-passage time distribution (2)
- flexible (2)
- fractional Brownian motion (2)
- galaxies: ISM (2)
- galaxies: dwarf (2)
- gamma rays: galaxies (2)
- gravitational lensing: strong (2)
- induced deformation (2)
- magnetic fields (2)
- mass-transport (2)
- mean versus most probable reaction times (2)
- methods: data analysis (2)
- methods: observational (2)
- mixed boundary conditions (2)
- narrow escape problem (2)
- network (2)
- non-radiative recombination (2)
- nonradiative voltage losses (2)
- oscillations (2)
- photochemistry (2)
- photovoltaics (2)
- plasmas (2)
- power spectral analysis (2)
- pulsars: general (2)
- quasars: general (2)
- radiation belts (2)
- radiative limit (2)
- random walk (2)
- rectification (2)
- reflecting boundary conditions (2)
- reionization (2)
- relativistic processes (2)
- residual stress (2)
- scattering (2)
- shock waves (2)
- single trajectory analysis (2)
- solar wind (2)
- spectroscopy (2)
- spontaneous parametric down-conversion (2)
- stars (2)
- stars: distances (2)
- stars: emission-line, Be (2)
- stars: fundamental parameters (2)
- stars: rotation (2)
- supernovae: general (2)
- superstatistics (2)
- surface-relief gratings (2)
- surveys (2)
- thin-films (2)
- time series analysis (2)
- turbulence (2)
- vacuum fields (2)
- white dwarfs (2)
- 15 (1)
- 16 (1)
- 2D perovskites (1)
- 3D tomography (1)
- 4-nitrobenzenethiol (1)
- AI (1)
- ARTOF (1)
- AU (1)
- Accelerator mass spectrometry (1)
- Acoustic probing of electric-field profiles (1)
- Active galactic nuclei (1)
- Anomalous transport (1)
- Astronomie (1)
- Astroparticle physics (1)
- Atmospheric entry (1)
- Auger decay (1)
- BL Lacertae objects: individual (Mrk 501) (1)
- Beam-plasma instability (1)
- Bio-Hybrid (1)
- Biological Physics (1)
- Brownian motion (1)
- Brownian motors (1)
- Bryophyte (1)
- CMAS (1)
- Capella (1)
- Carbonfaser Herstellung (1)
- Carrier dynamics (1)
- Catalysis (1)
- Central asia (1)
- Charge stability (1)
- Charge storage and transport (1)
- Charge transport (1)
- Charging or poling (1)
- Chemotaxsis (1)
- Chorus waves (1)
- Chromosphere, quiet (1)
- Circumplanetary dust (1)
- Collision cross-section (1)
- Comets (1)
- Complex Network (1)
- Composition (1)
- Computertomographie (1)
- Convolutional neural networks (1)
- Cosmogenic isotopes (1)
- Cosmogenic nuclides (1)
- Cosmology (1)
- Datenanalyse (1)
- Deutschland (1)
- Dictyostelium discoideum (1)
- Dicytostelium (1)
- Dielectric materials (1)
- Diffuse radiation (1)
- Diffusion coefficients (1)
- Doped semiconductors (1)
- Dust dynamics (1)
- Dust sources and sinks (1)
- Dynamical invariants (1)
- Dynamik in rumpfangeregten Zuständen (1)
- EMIC (1)
- Eigenspannung (1)
- Electrets (1)
- Electric polarization (1)
- Electrical insulation (1)
- Electro-active and electro-passive dielectrics (1)
- Electron populations (1)
- Electronics, photonics and device physics (1)
- Electrospray ionization (1)
- Embedding (1)
- Emissionslinienklassifikation (1)
- Erhebungsinstrument (1)
- Extragalactic astronomy (1)
- Extreme precipitation (1)
- Extremotolerant (1)
- Fachdidaktik (1)
- Fachwissen (1)
- Fe2TiO5 (1)
- Ferroelektrete (1)
- Ferroelektrizität (1)
- Fiber-reinforced concrete (1)
- Field-emission-based quasi continuous-wave electron beam (1)
- Flashing ratchets (1)
- Fusion crust (1)
- GEANT4 modeling (1)
- Galaxiendynamik (1)
- Galaxienentwicklung (1)
- Galaxy: evolution (1)
- Galaxy: kinematics and dynamics (1)
- Galaxy: stellar content (1)
- Galaxy: structure (1)
- Gaussian processes (1)
- Generalized Langevin equation (1)
- Glaciation (1)
- Glaciation Central Asia (1)
- Gold (1)
- Gold@polydopamine (1)
- Grimmia sp (1)
- Hertzsprung-Russell and C-M diagrams (1)
- Heusler-Legierung (1)
- Heusler-alloy (1)
- Hexagonal grid (1)
- Hilbert Scales (1)
- Hilbert transform (1)
- Hydrodynamics (1)
- Hydrolyse (1)
- Hysterese (1)
- IMPTAM (1)
- ISM: general (1)
- ISM: kinematics and dynamics (1)
- ISM: magnetic fields (1)
- ISM: molecules (1)
- Ices (1)
- Impurity segregation (1)
- In-situ (1)
- In-situ Experimente (1)
- India (1)
- Inner magnetosphere (1)
- Instrumentation and data management (1)
- Instrumentierung (1)
- Integralfieldspektroskopie (1)
- Interdisciplinary Physics (1)
- Interface-Engineering (1)
- Interfaces (1)
- Interpretation (1)
- Interstellar medium (1)
- Ion mobility spectrometry (1)
- K-Kanten Weichröntgenspektroskopie (1)
- K-edge soft X-ray spectroscopy (1)
- Kapella (1)
- Kelvin probe (1)
- Kohlenstoff-Isotopen-Verhältnis (1)
- Kompetenzerwerb (1)
- Komplexes Netzwerk (1)
- Kontaktschichten (1)
- Konzeption (1)
- Kosmologie (1)
- Kp index (1)
- Kuramoto Oscillators (1)
- Kuramoto model (1)
- Kuramoto-Modell (1)
- Kuramoto-Oszillatore (1)
- Kurzzeitspektroskopie mit optischer Anregung und Röntgendetektion (1)
- LAEs (1)
- LDPE nanocomposites (1)
- Laboratory astrophysics (1)
- Lasers (1)
- Laserstrahlschmelzen (1)
- Lehramtsstudent (1)
- Lehrer (1)
- Levy walk (1)
- Levy walks (1)
- Lipidmembran (1)
- Local Group (1)
- Longitudinal Analysis (1)
- Lyman Kontinuum (1)
- Lyman alpha (1)
- Lyman continuum (1)
- Längsschnittuntersuchung (1)
- MATROSHKA-R (1)
- Magnesiumoxid (1)
- Magnetic field amplification (1)
- Magneto-Optik (1)
- Melting experiments (1)
- Membran-Adhäsionskräfte (1)
- Membranadhäsion (1)
- Memory effects (1)
- Messung (1)
- Meteorites (1)
- MgO nanoparticles (1)
- Minerals (1)
- Minimax convergence rates (1)
- Molar water content (1)
- Molecular dynamics (1)
- Molekulardynamik (1)
- Multi-dimensional Markovian embedding of non-Markovian dynamics (1)
- NMR (1)
- Nano-dielectrics (1)
- Nanoreactor (1)
- Netzwerk Inferenz (1)
- Netzwerk Rekonstruktion (1)
- Netzwerke (1)
- Neutronendiffraktion (1)
- Nichtlineare Dynamik (1)
- Nonlinear Dynamics (1)
- Optoelectronic devices and components (1)
- Optoelectronics (1)
- Organic LEDs (1)
- Organic electronics (1)
- Organic matter (1)
- Organic semiconductors (1)
- Ott - Antonsen reduction (1)
- Ott–Antonsen equation (1)
- P(VDF-TrFE-CFE) terpolymer (1)
- PAN (1)
- PBLG (1)
- PEDOT (1)
- Paleoclimate modeling (1)
- Partial wavelet coherence (1)
- Peptides (1)
- Performance Assessment (1)
- Perowskit (1)
- Phase modulation (1)
- Phasenübergang (1)
- Photon density wave spectroscopy (1)
- Photonic devices (1)
- Photothermal conversion (1)
- Physics (1)
- Physikunterricht (1)
- Piezoelectrically generated Pressure Steps (PPSs) (1)
- Piezoelektrizität (1)
- Planetary rings and tori (1)
- Plant performance (1)
- Poly(vinylidenfluorid) (1)
- Polyethylen-Nanokomposite (1)
- Polymerelektrete (1)
- Polypropylen (1)
- Precursor (1)
- Process analytical technology (1)
- Professional Knowledge (1)
- Prominences, magnetic field (1)
- Prominences, quiescent (1)
- Protonendynamik molekularer Systeme (1)
- Protonentransfer in angeregten Zuständen (1)
- Präkonzepte (1)
- Prästabilisierung (1)
- Pulverpartikelanalyse (1)
- PyTorch (1)
- QtClassify (1)
- Quartz (1)
- Radiation dose calculation (1)
- Radiation on the ISS (1)
- Radiation protection (1)
- Radio-frequency electron gun (1)
- Raman spectroscopy (1)
- Rauheit (1)
- Recurrence plots (1)
- Recurrence quantification analysis (1)
- Redox (1)
- Reflexion (Phil) (1)
- Reionisierung (1)
- Remagnetisierung (1)
- Reproducing kernel Hilbert space (1)
- Residue (1)
- Scanning transmission electron microscopy (1)
- Schulpraktikum (1)
- Schülervorstellungen (1)
- Shannon entropy (1)
- Shocks (1)
- Silica source (1)
- Silicon (1)
- Silizium (1)
- Solar Cycle, observations (1)
- Solar energy and photovoltaic technology (1)
- Space charge (1)
- Space plasmas (1)
- Space radiation (1)
- Statistical Physics (1)
- Statistical inverse problem (1)
- Stellar evolution (1)
- Stellar physics (1)
- Stellarphysik (1)
- Stern-Gerlach effect (1)
- Sternentstehung (1)
- Sternfeedback (1)
- Subdiffusion (1)
- Sun: Chromosphere (1)
- Sun: activity (1)
- Sun: chromosphere (1)
- Sun: filaments, prominences (1)
- Sun: heliosphere (1)
- Supernova remnants (1)
- Synchronization (1)
- TIC 278659026 (1)
- Tandem-Solarzelle (1)
- Teacher Education (1)
- Teleconnection patterns (1)
- Terrestrial cosmogenic nuclide (1)
- Test (1)
- Testauswertung (1)
- Testentwicklung (1)
- Thermal conductivity (1)
- Thermoclectrics (1)
- Thermodynamic efficiency (1)
- Ti-6Al-4V (1)
- Tikhonov regularization (1)
- US east coast river geomorphology (1)
- UV irradiation (1)
- Unterrichtsgestaltung (1)
- Unterrichtsplanung (1)
- V-OC loss (1)
- VERB (1)
- VERB code (1)
- VLT/MUSE (1)
- Validität (1)
- Van Allen Probes (1)
- Verständnisentwicklungsmodell (1)
- Viscoelasticity (1)
- Water Vapor (1)
- Wavelets (1)
- X-ray absorption (1)
- X-ray absorption spectroscopy (1)
- X-ray computed tomography (CT) (1)
- X-ray refraction (1)
- X-ray spectroscopy (1)
- X-rays (1)
- X-rays: ISM (1)
- X-rays: individual: SXP 1323 (1)
- X-rays: stars (1)
- XMCD (1)
- Zeolite synthesis (1)
- accretion, accretion disks (1)
- actin (1)
- activity (1)
- addenda (1)
- additive Fertigung (1)
- aminothiophenol (1)
- analytical model (1)
- anisotropic fiber orientation (1)
- asteroseismology (1)
- astronomy (1)
- astroparticle physics (1)
- astrophysical plasmas (1)
- azobenzene containing surfactants (1)
- beam splitter (1)
- binaries: eclipsing (1)
- bio-hybrid (1)
- biohybrid microsystems (1)
- biological physics (1)
- biological transport (1)
- block copolymer films (1)
- blue stragglers (1)
- brown dwarfs (1)
- carbon fiber manufacture (1)
- carbon-isotope-ratio (1)
- cataclysmic variables (1)
- catalogues (1)
- catalysis (1)
- celestial mechanics (1)
- characterization (1)
- charge generation (1)
- charge transfers (1)
- charge transport (1)
- chemotaxsis (1)
- chimera states (1)
- code (1)
- collective motion (1)
- computed tomography (1)
- condensed matter (1)
- conductivity (1)
- construct map (1)
- contact layers (1)
- continuation (1)
- continuous distribution model (1)
- contraction (1)
- core-excited state dynamics (1)
- cosmological parameters (1)
- cosmology (1)
- cosmology: observations (1)
- cosmology: theory (1)
- coupling (1)
- coupling function (1)
- dark ages (1)
- delay differential equation (1)
- density (1)
- density functional calculations (1)
- development of test instrument (1)
- diamagnetic currents (1)
- dicytostelium (1)
- dielectric relaxation spectroscopy (1)
- diffusion coefficients (1)
- doping (1)
- dynamical systems (1)
- dynamische Systeme (1)
- electrical insulation (1)
- electrical polarization hysteresis (1)
- electro-acoustic electric-charge and polarization profiling (1)
- electro-fused zirconia (1)
- electro-optical materials (1)
- electromagnetic ion cyclotron waves (1)
- electron spectroscopy (1)
- elektrische Isolierung (1)
- elektrische Raumladung (1)
- elektroakustische Abtastung elektrischer Ladungen und Dipolpolarisationen (1)
- ellipsometry (1)
- emic waves (1)
- emission line classification (1)
- empirical prediction (1)
- endliche Ensembles (1)
- energetic particle (1)
- enhanced raman-scattering (1)
- equatorial plasma depletions (1)
- errata (1)
- excited state proton transfer (1)
- excited-state proton-transfer (1)
- exclusion process (1)
- exclusion processes (1)
- femtosecond laser spectroscopy (1)
- ferroelectrets (1)
- ferroelectricity (1)
- finite size (1)
- first star (1)
- first-passage (1)
- flow network (1)
- forced symmetry breaking (1)
- forecast (1)
- fractional diffusion (1)
- galaxies: elliptical and lenticular, cD (1)
- galaxies: general (1)
- galaxies: individual (B2 1215+30) (1)
- galaxies: individual: ESO 338-4 (1)
- galaxies: jets (1)
- galaxies: kinematics and dynamics (1)
- galaxies: star formation (1)
- galaxies:distances and redshifts (1)
- galaxy dynamics (1)
- galaxy evolution (1)
- galaxy: kinematics and dynamics (1)
- gamma rays: ISM (1)
- gamma rays: diffuse background (1)
- gamma rays: stars (1)
- gamma-ray burst: general (1)
- gamma-rays: galaxies (1)
- geomagnetic activity (1)
- glacial-isostatic adjustment (1)
- global jets (1)
- globular clusters: general (1)
- globular clusters: individual: NGC 2808 (1)
- globular clusters: individual: NGC 3201 (1)
- globular clusters: individual: NGC 6656 (1)
- gravitational waves (1)
- guided self assembly (1)
- helical magnetic fields (1)
- heterogeneous ensemble of Brownian particles (1)
- high impact polystyrene (1)
- high latitude (1)
- hole extraction (1)
- hole selective materials (1)
- horizontal-branch (1)
- hydrolysis (1)
- hysteresis (1)
- in-situ testing (1)
- individual (1)
- infrared: ISM (1)
- infrared: planetary systems (1)
- instrumentation (1)
- integral field spectroscopy (1)
- interface recombination (1)
- interiors (1)
- intersystem crossing (1)
- inverse analysis (1)
- ion optics (1)
- iron (1)
- kinetic of cis-trans isomerization (1)
- kink-like instability (1)
- kondensierte Materie (1)
- laser powder bed fusion (1)
- lattice gas (1)
- lead halide perovskite films (1)
- lipid membranes (1)
- lipid-anchored saccharide (1)
- lipid-verankerte Saccharide (1)
- loss (1)
- magnesium oxide (1)
- magnetic microstructures (1)
- magnetic pressure (1)
- magnetization dynamics (1)
- magnetizationdynamic (1)
- magneto-optics (1)
- massive Sterne (1)
- massive stars (1)
- maximum entropy analysis (1)
- mean-field model (1)
- mechanisms (1)
- membrane adhesion (1)
- membrane adhesion forces (1)
- metal (1)
- methods: Data analysis (1)
- methods: Observational (1)
- methods: analytical (1)
- microcracking (1)
- microtransport and -assembly (1)
- modeling (1)
- molecular dynamics (1)
- molecular proton dynamics (1)
- mushroom instability (1)
- myosin II (1)
- nanoparticles (1)
- near-ambient pressure X-ray photoelectron spectroscopy (1)
- near-ambient pressure x-ray photoelectron spectroscopy (1)
- network inference (1)
- network reconstruction (1)
- networks (1)
- neutrinos (1)
- neutron diffraction (1)
- nitrogen (1)
- non-Langevin recombination (1)
- nonequilibrium physics (1)
- nonlocal coupling (1)
- nonlocally coupled phase oscillators (1)
- novae (1)
- novae, cataclysmic variables (1)
- nucleobase (1)
- optical pump - X-ray probe spectroscopy (1)
- organic solar cells (1)
- outflows (1)
- particle-in-cell simulations (1)
- passivation (1)
- perovskite (1)
- perovskite solar cell (1)
- persistence (1)
- phase approximation (1)
- phase oscillators (1)
- phase response curve (1)
- phase transition (1)
- photocatalysis (1)
- photoluminescence (1)
- photonic crystal fibers (1)
- photovoltaic devices (1)
- piezoelectricity (1)
- pitch angle scattering (1)
- planet-star interactions (1)
- planetary nebulae: individual: NGC40 (1)
- planets and satellites: detection (1)
- planets and satellites: dynamical evolution and stability (1)
- planets and satellites: gaseous planets (1)
- planets and satellites: general (1)
- planets and satellites: individual (Saturn) (1)
- plasma instabilities (1)
- plasma pressure (1)
- plasmaspheric hiss (1)
- plasmaspheric plume (1)
- poly(gamma-benzyl L-glutamate) (1)
- poly(vinylidene fluoride) (1)
- polyethylene nanocomposites (1)
- polymer (1)
- polymer electrets (1)
- polypropylene (1)
- powder particle analysis (1)
- preconceptions (1)
- precursor (1)
- prestabilization (1)
- probabilistic inference (1)
- pulsars: individual: PSR B0833-45 (1)
- pulse compression (1)
- pump-probe (1)
- quasars: individual: 3C 279 (1)
- radiation belt electrons (1)
- reanalysis (1)
- recollimation shocks (1)
- relativistic electron precipitation (1)
- relativistic jets (1)
- relaxor-ferroelectric polymers (1)
- remagnetization (1)
- ring current electrons (1)
- river dynamics on glacial timescales (1)
- search dynamics (1)
- selective contact (1)
- silicon (1)
- solvent vapor annealing (1)
- space charge (1)
- space-charge effects (1)
- spin-dependent forces (1)
- spin-related factors (1)
- spiro-OMeTAD (1)
- spread F (1)
- stability (1)
- stability analysis (1)
- star formation (1)
- stars: AGB and post-AGB (1)
- stars: activity (1)
- stars: binaries: spectroscopic (1)
- stars: carbon (1)
- stars: circumstellar matter (1)
- stars: horizontal-branch (1)
- stars: individual (PHL 457, EQ Psc) (1)
- stars: individual: Feige 46 (1)
- stars: individual: HD 137366 (1)
- stars: individual: K2-133 (1)
- stars: individual: LP 358-499 (1)
- stars: individual: LP 40-365 (1)
- stars: individual: PG 1610+062 (1)
- stars: individual: WD1751+106 (1)
- stars: individual: WD2134+125 (1)
- stars: individual: [MA93] 1393 (1)
- stars: kinematics and dynamics (1)
- stars: low-mass (1)
- stars: oscillations (including pulsations) (1)
- stars: solar-type (1)
- stars: subdwarfs (1)
- stars: winds (1)
- statistical methods (1)
- statistical physics (1)
- statistische Methoden (1)
- stellar evolution (1)
- stellar feedback (1)
- stellar kinematics (1)
- stellare Kinematik (1)
- stochastic processes (1)
- structure of water (1)
- students' conceptions (1)
- sulfur (1)
- supergiants (1)
- supermassereiche Schwarze Löcher (1)
- supermassive black holes (1)
- surface band bending (1)
- surface photovoltage (1)
- surface states (1)
- synchronization (1)
- synchrotron X-ray diffraction (1)
- synchrotron X-ray refraction radiography (1)
- synchrotron x-ray refraction radiography (SXRR) (1)
- tandem solar cell (1)
- techniques: Image processing (1)
- techniques: image processing (1)
- techniques: photometric (1)
- techniques: radial velocities (1)
- the Weibel instability (1)
- thermal barrier coatings (1)
- thermal expansion (1)
- thermally stimulated depolarization current (1)
- thermoactivational spectroscopy (1)
- thin films (1)
- time resolved pump probe spectroscopy (1)
- time-resolved X-ray probing (1)
- titanium dioxide (1)
- transition metals (1)
- transport layers (1)
- travelling waves (1)
- triple-cation perovskite (1)
- twisted state (1)
- ultrafast dynamics (1)
- ultrafast optics (1)
- ultrarelativistic electrons (1)
- ultraschnelle Dynamik (1)
- ultraviolet photoelectron spectroscopy (1)
- ultraviolet: ISM (1)
- ultraviolet: galaxies (1)
- ultraviolet: stars (1)
- upconversion nanoparticles (1)
- wave particle interaction (1)
- wave-particle interactions (1)
- wavelength (1)
- waves (1)
- weather (1)
- x-ray photoemission (1)
- Übergangsmetalle (1)
Institute
- Institut für Physik und Astronomie (312) (remove)
The goal of this thesis is to broaden the empirical basis for a better, comprehensive understanding
of massive star evolution, star formation and feedback at low metallicity. Low metallicity massive stars are a key to understand the early universe. Quantitative information on metal-poor massive stars was sparse before. The quantitative spectroscopic studies of massive star populations associated with large-scale ISM structures were not performed at low metallicity before, but are important to investigate star-formation histories and feedback in detail. Much of this work relies on spectroscopic observations with VLT-FLAMES of ~500 OB stars in the Magellanic Clouds. When available, the optical spectroscopy was complemented by UV spectra from the HST, IUE, and FUSE archives. The two representative young stellar populations that have been studied are associated with the superbubble N 206 in the Large Magellanic Cloud (LMC) and with the supergiant shell SMC-SGS 1 in the Wing of the Small Magellanic Cloud (SMC), respectively. We performed spectroscopic analyses of the massive stars using the nonLTE Potsdam Wolf-Rayet (PoWR) model atmosphere code. We estimated the stellar, wind, and feedback parameters of the individual massive stars and established their statistical distributions.
The mass-loss rates of N206 OB stars are consistent with theoretical expectations for LMC metallicity. The most massive and youngest stars show nitrogen enrichment at their surface and are found to be slower rotators than the rest of the sample. The N 206 complex has undergone star formation episodes since more than 30 Myr, with a current star formation rate higher than average in the LMC. The spatial age distribution of stars across the complex possibly indicates triggered star formation due to the expansion of the superbubble. Three very massive, young Of stars in the region dominate the ionizing and mechanical feedback among hundreds of other OB stars in the sample. The current stellar wind feedback rate from the two WR stars in the complex is comparable to that released by the whole OB sample. We see only a minor fraction of this stellar wind feedback converted into X-ray emission. In this LMC complex, stellar winds and supernovae equally contribute to the total energy feedback, which eventually powered the central superbubble. However, the total energy input accumulated over the time scale of the superbubble significantly exceeds the observed energy content of the complex. The lack of energy along with the morphology of the complex suggests a leakage of hot gas from the superbubble.
With a detailed spectroscopic study of massive stars in SMC-SGS 1, we provide the stellar and wind parameters of a large sample of OB stars at low metallicity, including those in the lower mass-range. The stellar rotation velocities show a broad, tentatively bimodal distribution, with Be stars being among the fastest. A few very luminous O stars are found close to the main sequence, while all other, slightly evolved stars obey a strict luminosity limit. Considering additional massive stars in evolved stages, with published parameters and located all over the SMC, essentially confirms this picture. The comparison with single-star evolutionary tracks suggests a dichotomy in the fate of massive stars in the SMC. Only stars with an initial mass below 30 solar masses seem to evolve from the main sequence to the cool side of the HRD to become a red supergiant and to explode as type II-P supernova. In contrast, more massive stars appear to stay always hot and might evolve quasi chemically homogeneously, finally collapsing to relatively massive black holes. However, we find no indication that chemical mixing is correlated with rapid rotation. We measured the key parameters of stellar feedback and established the links between the rates of star formation and supernovae. Our study demonstrates that in metal-poor environments stellar feedback is dominated by core-collapse supernovae in combination with winds and ionizing radiation supplied by a few of the most massive stars. We found indications of the stochastic mode of star formation, where the resulting stellar population is fully capable of producing large-scale structures such as the supergiant shell SMC-SGS 1 in the Wing. The low level of feedback in metal-poor stellar populations allows star formation episodes to persist over long timescales.
Our study showcases the importance of quantitative spectroscopy of massive stars with adequate stellar-atmosphere models in order to understand star-formation, evolution, and feedback. The stellar population analyses in the LMC and SMC make us understand that massive stars and their impact can be very different depending on their environment. Obviously, due to their different metallicity, the massive stars in the LMC and the SMC follow different evolutionary paths. Their winds differ significantly, and the key feedback agents are different. As a consequence, the star formation can proceed in different modes.
Binaries play an important role in observational and theoretical astrophysics. Since the mass and the chemical composition are key ingredients for stellar evolution, high-resolution spectroscopy is an important and necessary tool to derive those parameters to high confidence in binaries. This involves carefully measured orbital motion by the determination of radial velocity (RV) shifts and sophisticated techniques to derive the abundances of elements within the stellar atmosphere.
A technique superior to conventional cross-correlation methods to determine RV shifts in known as spectral disentangling. Hence, a major task of this thesis was the design of a sophisticated software package for this approach. In order to investigate secondary effects, such as flux and line-profile variations, imprinting changes on the spectrum the behavior of spectral disentangling on such variability is a key to understand the derived values, to improve them, and to get information about the variability itself. Therefore, the spectral disentangling code presented in this thesis and available to the community combines multiple advantages: separation of the spectra for detailed chemical analysis, derivation of orbital elements, derivation of individual RVs in order to investigate distorted systems (either by third body interaction or relativistic effects), the suppression of telluric contaminations, the derivation of variability, and the possibility to apply the technique to eclipsing binaries (important for orbital inclination) or in general to systems that undergo flux-variations.
This code in combination with the spectral synthesis codes MOOG and SME was used in order to derive the carbon 12C/13C isotope ratio (CIR) of the benchmark binary Capella. The observational result will be set into context with theoretical evolution by the use of MESA models and resolves the discrepancy of theory and observations existing since the first measurement of Capella's CIR in 1976.
The spectral disentangling code has been made available to the community and its applicability to completely different behaving systems, Wolf-Rayet stars, have also been investigated and resulted in a published article.
Additionally, since this technique relies strongly on data quality, continues development of scientific instruments to achieve best observational data is of great importance in observational astrophysics. That is the reason why there has also been effort in astronomical instrumentation during the work on this thesis.
Synchronization – the adjustment of rhythms among coupled self-oscillatory systems – is a fascinating dynamical phenomenon found in many biological, social, and technical systems.
The present thesis deals with synchronization in finite ensembles of weakly coupled self-sustained oscillators with distributed frequencies.
The standard model for the description of this collective phenomenon is the Kuramoto model – partly due to its analytical tractability in the thermodynamic limit of infinitely many oscillators. Similar to a phase transition in the thermodynamic limit, an order parameter indicates the transition from incoherence to a partially synchronized state. In the latter, a part of the oscillators rotates at a common frequency. In the finite case, fluctuations occur, originating from the quenched noise of the finite natural frequency sample.
We study intermediate ensembles of a few hundred oscillators in which fluctuations are comparably strong but which also allow for a comparison to frequency distributions in the infinite limit.
First, we define an alternative order parameter for the indication of a collective mode in the finite case. Then we test the dependence of the degree of synchronization and the mean rotation frequency of the collective mode on different characteristics for different coupling strengths.
We find, first numerically, that the degree of synchronization depends strongly on the form (quantified by kurtosis) of the natural frequency sample and the rotation frequency of the collective mode depends on the asymmetry (quantified by skewness) of the sample. Both findings are verified in the infinite limit.
With these findings, we better understand and generalize observations of other authors. A bit aside of the general line of thoughts, we find an analytical expression for the volume contraction in phase space.
The second part of this thesis concentrates on an ordering effect of the finite-size fluctuations. In the infinite limit, the oscillators are separated into coherent and incoherent thus ordered and disordered oscillators. In finite ensembles, finite-size fluctuations can generate additional order among the asynchronous oscillators. The basic principle – noise-induced synchronization – is known from several recent papers. Among coupled oscillators, phases are pushed together by the order parameter fluctuations, as we on the one hand show directly and on the other hand quantify with a synchronization measure from directed statistics between pairs of passive oscillators.
We determine the dependence of this synchronization measure from the ratio of pairwise natural frequency difference and variance of the order parameter fluctuations. We find a good agreement with a simple analytical model, in which we replace the deterministic fluctuations of the order parameter by white noise.
Organic semiconductors are a promising class of materials. Their special properties are the particularly good absorption, low weight and easy processing into thin films. Therefore, intense research has been devoted to the realization of thin film organic solar cells (OPVs). Because of the low dielectric constant of organic semiconductors, primary excitations (excitons) are strongly bound and a type II heterojunction needs to be introduced to split these excitations into free charges. Therefore, most organic solar cells consist of at least an electron donor and electron acceptor material. For such donor acceptor systems mainly three states are relevant; the photoexcited exciton on the donor or acceptor material, the charge transfer state at the donor-acceptor interface and the charge separated state of a free electron and hole. The interplay between these states significantly determines the efficiency of organic solar cells. Due to the high absorption and the low charge carrier mobilities, the active layers are usually thin but also, exciton dissociation and free charge formation proceeds rapidely, which makes the study of carrier dynamics highly challenging.
Therefore, the focus of this work was first to install new experimental setups for the investigation of the charge carrier dynamics in complete devices with superior sensitivity and time resolution and, second, to apply these methods to prototypical photovoltaic materials to address specific questions in the field of organic and hybrid photovoltaics.
Regarding the first goal, a new setup combining transient absorption spectroscopy (TAS) and time delayed collection field (TDCF) was designed and installed in Potsdam. An important part of this work concerned the improvement of the electronic components with respect to time resolution and sensitivity. To this end, a highly sensitive amplifier for driving and detecting the device response in TDCF was developed. This system was then applied to selected organic and hybrid model systems with a particular focus on the understanding of the loss mechanisms that limit the fill factor and short circuit current of organic solar cells.
The first model system was a hybrid photovoltaic material comprising inorganic quantum dots decorated with organic ligands. Measurements with TDCF revealed fast free carrier recombination, in part assisted by traps, while bias-assisted charge extraction measurements showed high mobility. The measured parameters then served as input for a successful description of the device performance with an analytical model.
With a further improvement of the instrumentation, a second topic was the detailed analysis of non-geminate recombination in a disordered polymer:fullerene blend where an important question was the effect of disorder on the carrier dynamics. The measurements revealed that early time highly mobile charges undergo fast non-geminate recombination at the contacts, causing an apparent field dependence of free charge generation in TDCF experiments if not conducted properly. On the other hand, recombination the later time scale was determined by dispersive recombination in the bulk of the active layer, showing the characteristics of carrier dynamics in an exponential density of state distribution. Importantly, the comparison with steady state recombination data suggested a very weak impact of non-thermalized carriers on the recombination properties of the solar cells under application relevant illumination conditions.
Finally, temperature and field dependent studies of free charge generation were performed on three donor-acceptor combinations, with two donor polymers of the same material family blended with two different fullerene acceptor molecules. These particular material combinations were chosen to analyze the influence of the energetic and morphology of the blend on the efficiency of charge generation. To this end, activation energies for photocurrent generation were accurately determined for a wide range of excitation energies. The results prove that the formation of free charge is via thermalized charge transfer states and does not involve hot exciton splitting. Surprisingly, activation energies were of the order of thermal energy at room temperature. This led to the important conclusion that organic solar cells perform well not because of predominate high energy pathways but because the thermalized CT states are weakly bound. In addition, a model is introduced to interconnect the dissociation efficiency of the charge transfer state with its recombination observable with photoluminescence, which rules out a previously proposed two-pool model for free charge formation and recombination. Finally, based on the results, proposals for the further development of organic solar cells are formulated.
Membrane adhesion is a fundamental biological process in which membranes are attached to neighboring membranes or surfaces. Membrane adhesion emerges from a complex interplay between the binding of membrane-anchored receptors/ligands and the membrane properties. In this work, we study membrane adhesion mediated by lipid-anchored saccharides using microsecond-long full-atomistic molecular dynamics simulations. Motivated by neutron scattering experiments on membrane adhesion via lipid-anchored saccharides, we investigate the role of LeX, Lac1, and Lac2 saccharides and membrane fluctuations in membrane adhesion.
We study the binding of saccharides in three different systems: for saccharides in water, for saccharides anchored to essentially planar membranes at fixed separations, and for saccharides anchored to apposing fluctuating membranes. Our simulations of two saccharides in water indicate that the saccharides engage in weak interactions to form dimers. We find that the binding occurs in a continuum of bound states instead of a certain number of well-defined bound structures, which we term as "diffuse binding".
The binding of saccharides anchored to essentially planar membranes strongly depends on separation of the membranes, which is fixed in our simulation system. We show that the binding constants for trans-interactions of two lipid-anchored saccharides monotonically decrease with increasing separation. Saccharides anchored to the same membrane leaflet engage in cis-interactions with binding constants comparable to the trans-binding constants at the smallest membrane separations. The interplay of cis- and trans-binding can be investigated in simulation systems with many lipid-anchored saccharides. For Lac2, our simulation results indicate a positive cooperativity of trans- and cis-binding. In this cooperative binding the trans-binding constant is enhanced by the cis-interactions. For LeX, in contrast, we observe no cooperativity between trans- and cis-binding. In addition, we determine the forces generated by trans-binding of lipid-anchored saccharides in planar membranes from the binding-induced deviations of the lipid-anchors. We find that the forces acting on trans-bound saccharides increase with increasing membrane separation to values of the order of 10 pN.
The binding of saccharides anchored to the fluctuating membranes results from an interplay between the binding properties of the lipid-anchored saccharides and membrane fluctuations. Our simulations, which have the same average separation of the membranes as obtained from the neutron scattering experiments, yield a binding constant larger than in planar membranes with the same separation. This result demonstrates that membrane fluctuations play an important role at average membrane separations which are seemingly too large for effective binding. We further show that the probability distribution of the local separation can be well approximated by a Gaussian distribution. We calculate the relative membrane roughness and show that our results are in good agreement with the roughness values reported from the neutron scattering experiments.
In this work we investigated ultrafast demagnetization in a Heusler-alloy. This material belongs to the halfmetal and exists in a ferromagnetic phase. A special feature of investigated alloy is a structure of electronic bands. The last leads to the specific density of the states. Majority electrons form a metallic like structure while minority electrons form a gap near the Fermi-level, like in semiconductor. This particularity offers a good possibility to use this material as model-like structure and to make some proof of principles concerning demagnetization. Using pump-probe experiments we carried out time-resolved measurements to figure out the times of demagnetization. For the pumping we used ultrashort laser pulses with duration around 100 fs. Simultaneously we used two excitation regimes with two different wavelengths namely 400 nm and 1240 nm. Decreasing the energy of photons to the gap size of the minority electrons we explored the effect of the gap on the demagnetization dynamics. During this work we used for the first time OPA (Optical Parametrical Amplifier) for the generation of the laser irradiation in a long-wave regime. We tested it on the FETOSPEX-beamline in BASSYII electron storage ring. With this new technique we measured wavelength dependent demagnetization dynamics. We estimated that the demagnetization time is in a correlation with photon energy of the excitation pulse. Higher photon energy leads to the faster demagnetization in our material. We associate this result with the existence of the energy-gap for minority electrons and explained it with Elliot-Yaffet-scattering events. Additionally we applied new probe-method for magnetization state in this work and verified their effectivity. It is about the well-known XMCD (X-ray magnetic circular dichroism) which we adopted for the measurements in reflection geometry. Static experiments confirmed that the pure electronic dynamics can be separated from the magnetic one. We used photon energy fixed on the L3 of the corresponding elements with circular polarization. Appropriate incidence angel was estimated from static measurements. Using this probe method in dynamic measurements we explored electronic and magnetic dynamics in this alloy.
The importance of plasmonic heating for the plasmondriven photodimerization of 4-nitrothiophenol
(2019)
Metal nanoparticles form potent nanoreactors, driven by the optical generation of energetic electrons and nanoscale heat. The relative influence of these two factors on nanoscale chemistry is strongly debated. This article discusses the temperature dependence of the dimerization of 4-nitrothiophenol (4-NTP) into 4,4′-dimercaptoazobenzene (DMAB) adsorbed on gold nanoflowers by Surface-Enhanced Raman Scattering (SERS). Raman thermometry shows a significant optical heating of the particles. The ratio of the Stokes and the anti-Stokes Raman signal moreover demonstrates that the molecular temperature during the reaction rises beyond the average crystal lattice temperature of the plasmonic particles. The product bands have an even higher temperature than reactant bands, which suggests that the reaction proceeds preferentially at thermal hot spots. In addition, kinetic measurements of the reaction during external heating of the reaction environment yield a considerable rise of the reaction rate with temperature. Despite this significant heating effects, a comparison of SERS spectra recorded after heating the sample by an external heater to spectra recorded after prolonged illumination shows that the reaction is strictly photo-driven. While in both cases the temperature increase is comparable, the dimerization occurs only in the presence of light. Intensity dependent measurements at fixed temperatures confirm this finding.
A reliable inference of networks from data is of key interest in many scientific fields. Several methods have been suggested in the literature to reliably determine links in a network. These techniques rely on statistical methods, typically controlling the number of false positive links, but not considering false negative links. In this thesis new methodologies to improve network inference are suggested. Initial analyses demonstrate the impact of falsepositive and false negative conclusions about the presence or absence of links on the resulting inferred network. Consequently, revealing the importance of making well-considered choices leads to suggest new approaches to enhance existing network reconstruction methods.
A simulation study, presented in Chapter 3, shows that different values to balance false positive and false negative conclusions about links should be used in order to reliably estimate network characteristics. The existence of type I and type II errors in the reconstructed network, also called biased network, is accepted. Consequently, an analytic method that describes the influence of these two errors on the network structure is explored. As a result of this analysis, an analytic formula of the density of the biased vertex degree distribution is found (Chapter 4).
In the inverse problem, the vertex degree distribution of the true underlying network is analytically reconstructed, assuming the probabilities of type I and type II errors. Chapters 4-5 show that the method is robust to incorrect estimates of α and β within reasonable limits. In Chapter 6, an iterative procedure to enhance this method is presented in the case of large errors on the estimates of α and β.
The investigations presented so far focus on the influence of false positive and false negative links on the network characteristics. In Chapter 7, the analysis is reversed - the study focuses on the influence of network characteristics on the probability of type I and type II errors, in the case of networks of coupled oscillators. The probabilities of α and β are influenced by the shortest path length and the detour degree, respectively. These results have been used to improve the network reconstruction, when the true underlying network is not known a priori, introducing a novel and advanced concept of threshold.
Advancing charge selective contacts for efficient monolithic perovskite-silicon tandem solar cells
(2019)
Hybrid organic-inorganic perovskites are one of the most promising material classes for photovoltaic energy conversion. In solar cells, the perovskite absorber is sandwiched between n- and p-type contact layers which selectively transport electrons and holes to the cell’s cathode and anode, respectively. This thesis aims to advance contact layers in perovskite solar cells and unravel the impact of interface and contact properties on the device performance. Further, the contact materials are applied in monolithic perovskite-silicon heterojunction (SHJ) tandem solar cells, which can overcome the single junction efficiency limits and attract increasing attention. Therefore, all contact layers must be highly transparent to foster light harvesting in the tandem solar cell design. Besides, the SHJ device restricts processing temperatures for the selective contacts to below 200°C.
A comparative study of various electron selective contact materials, all processed below 180°C, in n-i-p type perovskite solar cells highlights that selective contacts and their interfaces to the absorber govern the overall device performance. Combining fullerenes and metal-oxides in a TiO2/PC60BM (phenyl-C60-butyric acid methyl ester) double-layer contact allows to merge good charge extraction with minimized interface recombination. The layer sequence thereby achieved high stabilized solar cell performances up to 18.0% and negligible current-voltage hysteresis, an otherwise pronounced phenomenon in this device design. Double-layer structures are therefore emphasized as a general concept to establish efficient and highly selective contacts.
Based on this success, the concept to combine desired properties of different materials is transferred to the p-type contact. Here, a mixture of the small molecule Spiro-OMeTAD [2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluoren] and the doped polymer PEDOT [poly(3,4-ethylenedioxythiophene)] is presented as a novel hole selective contact. PEDOT thereby remarkably suppresses charge recombination at the perovskite surface, allowing an increase of quasi-Fermi level splitting in the absorber. Further, the addition of Spiro-OMeTAD into the PEDOT layer is shown to enhance charge extraction at the interface and allow high efficiencies up to 16.8%.
Finally, the knowledge on contact properties is applied to monolithic perovskite-SHJ tandem solar cells. The main goal is to optimize the top contact stack of doped Spiro-OMeTAD/molybdenum oxide(MoOx)/ITO towards higher transparency by two different routes. First, fine-tuning of the ITO deposition to mitigate chemical reduction of MoOx and increase the transmittance of MoOx/ITO stacks by 25%. Second, replacing Spiro-OMeTAD with the alternative hole transport materials PEDOT/Spiro-OMeTAD mixtures, CuSCN or PTAA [poly(triaryl amine)]. Experimental results determine layer thickness constrains and validate optical simulations, which subsequently allow to realistically estimate the respective tandem device performances. As a result, PTAA represents the most promising replacement for Spiro-OMeTAD, with a projected increase of the optimum tandem device efficiency for the herein used architecture by 2.9% relative to 26.5% absolute. The results also reveal general guidelines for further performance gains of the technology.