530 Physik
Refine
Year of publication
- 2020 (183) (remove)
Document Type
- Article (137)
- Postprint (27)
- Doctoral Thesis (17)
- Other (1)
- Review (1)
Is part of the Bibliography
- yes (183)
Keywords
- diffusion (16)
- anomalous diffusion (6)
- random diffusivity (5)
- dynamics (4)
- impact (4)
- model (4)
- perovskite solar cells (4)
- climate (3)
- coupled rotators (3)
- first-passage (3)
- fractional Brownian motion (3)
- hysteresis (3)
- noisy systems (3)
- non-fullerene acceptors (3)
- organic solar cells (3)
- physics education (3)
- synchronization transition (3)
- 2D perovskites (2)
- AG (2)
- Aluminum alloys (2)
- Amazon rainforest (2)
- Atlantic meridional overturning circulation (2)
- BL Lacertae objects: individual (2)
- Brownian motion (2)
- Diffusion (2)
- Donor-Acceptor (DA) interface (2)
- Greenland (2)
- ISOS-L-1I protocol (2)
- Kuramoto (2)
- Kuramoto model (2)
- Ornstein–Uhlenbeck process (2)
- Rashba effect (2)
- Rashba-Effekt (2)
- Resolved and unresolved sources as a function of wavelength (2)
- X-ray emission (2)
- X-ray photoelectron spectroscopy (2)
- atomic force microscopy (AFM) (2)
- cesium lead halides (2)
- chains (2)
- channel (2)
- complex networks (2)
- consequences (2)
- continuous time random walk (2)
- costs (2)
- crystal orientation (2)
- diselenide (2)
- donor (2)
- droughts (2)
- efficiency (2)
- electron-transfer (2)
- energy (2)
- ensemble and time averaged mean squared displacement (2)
- entropy production (2)
- excitonic materials (2)
- expanding medium (2)
- exploit (2)
- extremal values (2)
- fastest first-passage time of N walkers (2)
- flagellum (2)
- fluorinated organic spacer (2)
- galaxies: high-redshift (2)
- gamma rays: general (2)
- gamma-rays: general (2)
- global surface warming (2)
- grafted polymers (2)
- heterojunction silicon solar cells (2)
- inorganic perovskites (2)
- instability (2)
- interfaces (2)
- maximum and range (2)
- metal halide perovskites (2)
- methods: numerical (2)
- molecular bottle brushes (2)
- nanoparticles (2)
- non-Gaussianity (2)
- nonfullerene acceptors (2)
- numerical simulations (2)
- ocean heat uptake (2)
- organic photovoltaics (2)
- organic solar cell (2)
- origins (2)
- phase purity (2)
- phase transition (2)
- photocurrent generation (2)
- photoluminescence (2)
- photon recycling (2)
- photostability (2)
- photovoltaics (2)
- power spectrum (2)
- pre-service teachers (2)
- prediction (2)
- projections (2)
- quantum mechanics (2)
- quasi-Fermi level (2)
- quasi-steady-state photoinduced absorptions (2)
- radiation belts (2)
- recombinations (2)
- repertory grid (2)
- seperation (2)
- sequence-controlled polymers (2)
- single chain folding (2)
- single trajectories (2)
- soft X-ray beamline (2)
- soft X-ray spectroscopy (2)
- solar coronal mass ejections (2)
- solar storm (2)
- space-dependent diffusivity (2)
- splitting (2)
- stars: atmospheres (2)
- stars: low-mass (2)
- stationary stochastic process (2)
- statistics (2)
- stellar coronal mass ejections (2)
- subdiffusion (2)
- subdwarfs (2)
- surface (2)
- tandem solar cells (2)
- temperature dependence (2)
- thermodynamics (2)
- thin films (2)
- time (2)
- transfer dynamics (2)
- voltage losses (2)
- 3D field calculations (1)
- 3D printing (1)
- 3D-Feldsimulationen (1)
- APCI (1)
- ARPES (1)
- Anisotropy (1)
- Answer Set Programming (1)
- Arctic-midlatitude linkages (1)
- Arktis (1)
- Astronomical instrumentation (1)
- Astrophysics (1)
- Atmosphäre (1)
- BESSY II (1)
- BESSY II. (1)
- Bending energy (1)
- Bessel functions (1)
- Biegeenergie (1)
- Black– Scholes model (1)
- Bloch-Torrey equation (1)
- Boundary value problem (1)
- Brownian diffusion (1)
- Cattaneo equation (1)
- Ce/Zr (1)
- Conic compartments (1)
- Creep (1)
- CuI (1)
- Datenassimilation (1)
- Dielektrophorese (1)
- Diffusion NMR (1)
- Dislocation motion (1)
- Dispersion force (1)
- Dynamical systems (1)
- Einzel-Objekt-Nachweis (1)
- Einzelmolekül-Biosensor (1)
- El Niño-Southern Oscillation (ENSO) (1)
- El Niño-Südliche Oszillation (1)
- Elektret (1)
- Experimente (1)
- Explainable AI (1)
- FELS (1)
- Fibre-fed spectroscopy (1)
- Flims (1)
- Flow (1)
- Fluoreszenz-Mikroskopie (1)
- Fokker– Planck equation (1)
- Formgleichungen von Vesikeln (1)
- Forschend Entdeckendes Lernen (1)
- Fox H-function (1)
- Fox H-functions (1)
- Fractal (1)
- Fractals (1)
- Fraktale (1)
- Gammastrahlung (1)
- Genetic programming (1)
- Graphen (1)
- Green function (1)
- Green's function (1)
- Grenzflächenrekombination (1)
- Hermite polynomial expansion (1)
- Heterogenität (1)
- Hydrogen activation (1)
- ICON (1)
- ISM (1)
- ISM: clouds (1)
- ISM: supernova remnants (1)
- Jahreszeitenvorhersage (1)
- Kegelförmige Geometrien (1)
- Klima (1)
- Klimatologie (1)
- L-edge spectroscopy (1)
- Ladungsspeicherung und -transport (1)
- Lernumgebung (1)
- Levy walk (1)
- Localization regime (1)
- MHD (1)
- Machine learning control (1)
- Magellanic Cloud (1)
- Meteorologie (1)
- Min-Proteine (1)
- Min-proteins (1)
- Modal expansion method (1)
- Molecular motors (1)
- Molekulare Motoren (1)
- Motivation (1)
- Multi-object spectroscopy (1)
- Multimode fibres (1)
- Nano-Elektroden (1)
- Non-perturbative analysis (1)
- Ornstein-Uhlenbeck Process (1)
- Ornstein-Uhlenbeck Prozess (1)
- PEDOT:PSS (1)
- Percolation (1)
- Perkolation (1)
- Perovskite solar cells (1)
- Perowskit Solarzellen (1)
- Physikdidaktik (1)
- Plasma Physics (1)
- Polypropylen (1)
- Polystyrol Nano-Sphären (1)
- R-PE (1)
- REM (1)
- Random Environments (1)
- Random Walk (1)
- Reactive adsorption (1)
- Ringstromelektronen (1)
- SEM (1)
- Schottky junction (1)
- Schrödinger equation (1)
- Seasonal prediction (1)
- Shape equations of vesicles (1)
- Shockley-Read-Hall (1)
- Small (1)
- Smartphone (1)
- Spin Textur (1)
- Spin-echo (1)
- Strahlungsgürtel (1)
- Stratosphere-troposphere coupling (1)
- Stratospheric polar vortex (1)
- Stratosphären-Troposphären-Kopplung (1)
- Stratosphärischer Polarwirbel (1)
- Streuresonanzen (1)
- Supernovaüberrest (1)
- Surface properties (1)
- Svalbard (1)
- Synchronization control (1)
- Teilchenbeschleunigung (1)
- Ti-6Al-4V (1)
- Topological Crystalline Insulator (1)
- Topological Insulator (1)
- Topologischer Isolator (1)
- Topologischer kristalliner Isolator (1)
- Verbindungspfade zwischen der Arktis und den mittleren Breiten (1)
- WAAM (1)
- Wellen-Teilchen Wechselwirkungen (1)
- Wismut (1)
- X-ray (1)
- X-ray absorption (1)
- X-ray refraction (1)
- Zufällige Stochastische Irrfahrt (1)
- Zufällige Umgebungen (1)
- absorption (1)
- actuators (1)
- adaptation and mitigation (1)
- additive manufacturing (1)
- aggregation (1)
- amphiphilic side chains (1)
- and governance (1)
- anomalous (or non-Fickian) diffusion (1)
- anomalous heat conduction (1)
- arctic (1)
- astroparticle physics (1)
- astrophysical plasmas (1)
- asynchronous design (1)
- atmosphere (1)
- axial next nearest neighbour Ising chains (1)
- background (1)
- barrier escape (1)
- basis-sets (1)
- binaries: general (1)
- biophysics (1)
- bismuth (1)
- blade (1)
- blended learning (1)
- built-in potential (1)
- bulk-heterojunction solar cells (1)
- bumps (1)
- capacitance spectroscopy (1)
- carrier density (1)
- celestial mechanics (1)
- charge (1)
- charge carrier density (1)
- charge carrier extraction (1)
- charge collection (1)
- charge injection across hybrid interfaces (1)
- charge storage and transport (1)
- charge transport layers (1)
- charge-transfer (1)
- charge-transfer excitations (1)
- chemische Oberflächen-Modifikationen (1)
- chimera states (1)
- circumstellar matter (1)
- climatology (1)
- coma (1)
- comets (1)
- computed tomography (1)
- conductivity (1)
- conformational and hydrodynamic characteristics (1)
- conjugated polymers (1)
- convolutional neural networks (1)
- copper iodide (1)
- creep (1)
- critical adsorption (1)
- crossover dynamics (1)
- crystal (1)
- data assimilation (1)
- deep learning (1)
- delay faults (1)
- density (1)
- dependent velocity (1)
- design for Testability (1)
- dielectric (1)
- dielectrophoresis (1)
- diffraction (1)
- diffusing diffusivity (1)
- dislocations (1)
- driven (1)
- driving force (1)
- dust (1)
- dynamical systems (1)
- dynamo (1)
- ecology and biodiversity (1)
- electret (1)
- electret polymers (1)
- electro-electrets (1)
- electron flux (1)
- electron localization (1)
- electronic structure (1)
- electrons (1)
- electrostatics (1)
- elevated-temperature effects on the operation of dielectric-elastomer (1)
- empirical modeling (1)
- enacted PCK (1)
- energetic disorders (1)
- energy-level alignments (1)
- experiment (1)
- extrusion (1)
- ferroelectricity and piezoelectricity in polymers (1)
- field experience (1)
- films (1)
- first passage (1)
- fluorescence microscopy (1)
- fluorination (1)
- formal specification (1)
- formal verification (1)
- formation (1)
- fractal (1)
- fractional dynamic equations (1)
- fullerenes (1)
- functional materials (1)
- fungus (1)
- galaxies (1)
- gamma rays (1)
- gamma rays: (1)
- gamma rays: diffuse (1)
- gas (1)
- gas chromatography (1)
- genomic DNA conformation (1)
- geometric Brownian motion (1)
- graphene (1)
- hole (1)
- human behaviour (1)
- humidity (1)
- hybrid manufacturing (1)
- hybrid material (1)
- hybrid metal oxides (1)
- hybrid synthesis (1)
- hydrodynamics (1)
- impedance spectroscopy (1)
- individual (1)
- inquiry based learning (1)
- instabilities (1)
- instructional (1)
- instructional explanation (1)
- interfacial recombination (1)
- inversion (1)
- ion mobility spectrometry (1)
- iron (1)
- iron cyanides (1)
- kinetic-theory (1)
- learning environment (1)
- light photocontrol (1)
- low (1)
- low donor content (1)
- machine learning (1)
- magnetic beads (1)
- magnetic fields (1)
- magnetism (1)
- magnetosphere (1)
- manipulation (1)
- mass (1)
- mathematical modeling (1)
- mathematische Modellierung (1)
- matrix composites (1)
- mechanobiology (1)
- metal (1)
- meteorology (1)
- methane localization (1)
- methods: observational (1)
- mhd turbulence (1)
- microstructure-property relations (1)
- mobility (1)
- modelling (1)
- models (1)
- modular logic programs (1)
- mold (1)
- molecular brushes (1)
- molecular crystals (1)
- molecular hydrodynamics and (1)
- molecular overcrowding (1)
- molecular weight (1)
- molecules (1)
- motion (1)
- motivation (1)
- nano-electrodes (1)
- natural resources (biological and non-biological) (1)
- nebulae: general (1)
- networks (1)
- neutron (1)
- nichtstrahlende Verluste (1)
- non-Langevin reduction factors (1)
- non-gaussianity (1)
- non-integer dimension (1)
- nonergodicity (1)
- nonradiative losses (1)
- optics (1)
- option pricing (1)
- organic interfaces (1)
- p-type (1)
- parallel immobilization of biomolecules (1)
- parallele Immobilisierung von Biomolekülen (1)
- parameter (1)
- particle acceleration (1)
- phase transitions (1)
- phase-transition boundary (1)
- photo-chemical pathways (1)
- photochemistry (1)
- photoexcited hole transfer (1)
- photoisomerization (1)
- piezoelectrets (1)
- planetary (1)
- planetary nebulae: individual: SwSt1 (1)
- planets and satellites: rings (1)
- plasma flows (1)
- policies (1)
- politics (1)
- poly(vinylidenefluoride-trifluoroethylene) P(VDF-TrFE) (1)
- polyelectrolytes (1)
- polymer ferroelectrets (1)
- polymer solar cells (1)
- polypropylene (1)
- polystyrene nano-spheres (1)
- populations (1)
- pore orientation (1)
- power conversion efficiency (1)
- power spectral analysis (1)
- practicum (1)
- preferred orientation (1)
- printed electroacoustic thin-film transducers (1)
- printing (1)
- professional knowledge (1)
- quality (1)
- quantum (1)
- quantum correlations (1)
- quasi-particles (1)
- recombination order (1)
- resetting (1)
- residual stress (1)
- resonant inelastic X-ray scattering (1)
- resonant inelastic X-ray scattering; (1)
- ring current electrons (1)
- scattering (1)
- scattering resonances (1)
- school internship (1)
- screen (1)
- segmentations (1)
- sensors and actuators (1)
- shock waves (1)
- silver (1)
- simulations (1)
- single-molecule biosensor (1)
- single-object detection (1)
- soft X-ray (1)
- soft X-ray absorption (1)
- soft electro-active materials (1)
- soft matter (1)
- solvation (1)
- spectrometry (1)
- spectroscopy (1)
- spektrale Leistungsdichte (1)
- spin texture (1)
- spin-crossover (1)
- star formation (1)
- stars (1)
- stars: AGB and post-AGB (1)
- stars: abundances (1)
- stars: evolution (1)
- stars: fundamental parameters (1)
- stars: horizontal branch (1)
- stars: late-type (1)
- stars: massive (1)
- stars: rotation (1)
- stars: solar-type (1)
- stars: variables: general (1)
- stellar content (1)
- stochastic dynamics (1)
- stochastic processes (1)
- stress exponent (1)
- structure (1)
- structures (1)
- stuck-at faults (1)
- superdiffusion and (1)
- supernova remnant (1)
- surface chemical treatment (1)
- surface recombination (1)
- synchronization (1)
- synthesis (1)
- telegrapher's equation (1)
- telluride (1)
- tellurium (1)
- temperature (1)
- thermal stimulation of (1)
- thermally enhanced actuators (1)
- thermoelectrics (1)
- thick junctions (1)
- timing resilient design (1)
- tissue growth (1)
- tranfer excited-state (1)
- transcrystalline polypropylene (1)
- transition metal complexes (1)
- transkristallines Polypropylen (1)
- transparent conductors (1)
- vibrational spectroscopy (1)
- water-interface (1)
- water-methane films (1)
- wave-particle interactions (1)
- weak ergodicity breaking (1)
- work function (1)
- x-ray-absorption (1)
- zufälligen Diffusivität (1)
Institute
- Institut für Physik und Astronomie (183) (remove)
Corona and the climate
(2020)
In the present study, we employ the angle-resolved photoemission spectroscopy (ARPES) technique to study the electronic structure of topological states of matter. In particular, the so-called topological crystalline insulators (TCIs) Pb1-xSnxSe and Pb1-xSnxTe, and the Mn-doped Z2 topological insulators (TIs) Bi2Te3 and Bi2Se3. The Z2 class of strong topological insulators is protected by time-reversal symmetry and is characterized by an odd number of metallic Dirac type surface states in the surface Brillouin zone. The topological crystalline insulators on the other hand are protected by the individual crystal symmetries and exhibit an even number of Dirac cones.
The topological properties of the lead tin chalcogenides topological crystalline insulators can be tuned by temperature and composition. Here, we demonstrate that Bi-doping of the Pb1-xSnxSe(111) epilayers induces a quantum phase transition from a topological crystalline insulator to a Z2 topological insulator. This occurs because Bi-doping lifts the fourfold valley degeneracy in the bulk. As a consequence a gap appears at ⌈¯, while the three Dirac cones at the M̅ points of the surface Brillouin zone remain intact. We interpret this new phase transition is caused by lattice distortion. Our findings extend the topological phase diagram enormously and make strong topological insulators switchable by distortions or electric field. In contrast, the bulk Bi doping of epitaxial Pb1-xSnxTe(111) films induces a giant Rashba splitting at the surface that can be tuned by the doping level. Tight binding calculations identify their origin as Fermi level pinning by trap states at the surface.
Magnetically doped topological insulators enable the quantum anomalous Hall effect (QAHE) which provide quantized edge states for lossless charge transport applications. The edge states are hosted by a magnetic energy gap at the Dirac point which has not been experimentally observed to date. Our low temperature ARPES studies unambiguously reveal the magnetic gap of Mn-doped Bi2Te3. Our analysis shows a five times larger gap size below the Tc than theoretically predicted. We assign this enhancement to a remarkable structure modification induced by Mn doping. Instead of a disordered impurity system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3quintuple layers is formed. This enhances the wave-function overlap and gives rise to a large magnetic gap. Mn-doped Bi2Se3 forms similar heterostructure, but only a nonmagnetic gap is observed in this system. This correlates with the difference in magnetic anisotropy due to the much larger spin-orbit interaction in Bi2Te3 compared to Bi2Se3. These findings provide crucial insights for pushing lossless transport in topological insulators towards room-temperature applications.
We present an efficient technique for control of synchrony in a globally coupled ensemble by pulsatile action. We assume that we can observe the collective oscillation and can stimulate all elements of the ensemble simultaneously. We pay special attention to the minimization of intervention into the system. The key idea is to stimulate only at the most sensitive phase. To find this phase, we implement an adaptive feedback control. Estimating the instantaneous phase of the collective mode on the fly, we achieve efficient suppression using a few pulses per oscillatory cycle. We discuss the possible relevance of the results for neuroscience, namely, for the development of advanced algorithms for deep brain stimulation, a medical technique used to treat Parkinson's disease.
We consider the emerging dynamics of a separable continuous time random walk (CTRW) in the case when the random walker is biased by a velocity field in a uniformly growing domain. Concrete examples for such domains include growing biological cells or lipid vesicles, biofilms and tissues, but also macroscopic systems such as expanding aquifers during rainy periods, or the expanding Universe. The CTRW in this study can be subdiffusive, normal diffusive or superdiffusive, including the particular case of a Lévy flight. We first consider the case when the velocity field is absent. In the subdiffusive case, we reveal an interesting time dependence of the kurtosis of the particle probability density function. In particular, for a suitable parameter choice, we find that the propagator, which is fat tailed at short times, may cross over to a Gaussian-like propagator. We subsequently incorporate the effect of the velocity field and derive a bi-fractional diffusion-advection equation encoding the time evolution of the particle distribution. We apply this equation to study the mixing kinetics of two diffusing pulses, whose peaks move towards each other under the action of velocity fields acting in opposite directions. This deterministic motion of the peaks, together with the diffusive spreading of each pulse, tends to increase particle mixing, thereby counteracting the peak separation induced by the domain growth. As a result of this competition, different regimes of mixing arise. In the case of Lévy flights, apart from the non-mixing regime, one has two different mixing regimes in the long-time limit, depending on the exact parameter choice: in one of these regimes, mixing is mainly driven by diffusive spreading, while in the other mixing is controlled by the velocity fields acting on each pulse. Possible implications for encounter–controlled reactions in real systems are discussed.
We consider the emerging dynamics of a separable continuous time random walk (CTRW) in the case when the random walker is biased by a velocity field in a uniformly growing domain. Concrete examples for such domains include growing biological cells or lipid vesicles, biofilms and tissues, but also macroscopic systems such as expanding aquifers during rainy periods, or the expanding Universe. The CTRW in this study can be subdiffusive, normal diffusive or superdiffusive, including the particular case of a Lévy flight. We first consider the case when the velocity field is absent. In the subdiffusive case, we reveal an interesting time dependence of the kurtosis of the particle probability density function. In particular, for a suitable parameter choice, we find that the propagator, which is fat tailed at short times, may cross over to a Gaussian-like propagator. We subsequently incorporate the effect of the velocity field and derive a bi-fractional diffusion-advection equation encoding the time evolution of the particle distribution. We apply this equation to study the mixing kinetics of two diffusing pulses, whose peaks move towards each other under the action of velocity fields acting in opposite directions. This deterministic motion of the peaks, together with the diffusive spreading of each pulse, tends to increase particle mixing, thereby counteracting the peak separation induced by the domain growth. As a result of this competition, different regimes of mixing arise. In the case of Lévy flights, apart from the non-mixing regime, one has two different mixing regimes in the long-time limit, depending on the exact parameter choice: in one of these regimes, mixing is mainly driven by diffusive spreading, while in the other mixing is controlled by the velocity fields acting on each pulse. Possible implications for encounter–controlled reactions in real systems are discussed.
Quasiuniversal relations between the tidal deformability and the quadrupole moment of neutron stars are predicted by theoretical computations, but have not been measured experimentally. We simulate 120 binary neutron star sources and find that Advanced LIGO and Advanced Virgo at design sensitivity could find possible deviations from predicted relations if the neutron stars are highly spinning. A network of envisaged third generation detectors will even allow extracting such relations, providing new tests of general relativity and nuclear physics predictions.
We present a diffusion-based simulation and theoretical models for explanation of the photoluminescence (PL) emission intensity in semiconductor nanoplatelets. It is shown that the shape of the PL intensity curves can be reproduced by the interplay of recombination, diffusion and trapping of excitons. The emission intensity at short times is purely exponential and is defined by recombination. At long times, it is governed by the release of excitons from surface traps and is characterized by a power-law tail. We show that the crossover from one limit to another is controlled by diffusion properties. This intermediate region exhibits a rich behaviour depending on the value of diffusivity. The proposed approach reproduces all the features of experimental curves measured for different nanoplatelet systems.
A comet is a highly dynamic object, undergoing a permanent state of change. These changes have to be carefully classified and considered according to their intrinsic temporal and spatial scales. The Rosetta mission has, through its contiguous in-situ and remote sensing coverage of comet 67P/Churyumov-Gerasimenko (hereafter 67P) over the time span of August 2014 to September 2016, monitored the emergence, culmination, and winding down of the gas and dust comae. This provided an unprecedented data set and has spurred a large effort to connect in-situ and remote sensing measurements to the surface. In this review, we address our current understanding of cometary activity and the challenges involved when linking comae data to the surface. We give the current state of research by describing what we know about the physical processes involved from the surface to a few tens of kilometres above it with respect to the gas and dust emission from cometary nuclei. Further, we describe how complex multidimensional cometary gas and dust models have developed from the Halley encounter of 1986 to today. This includes the study of inhomogeneous outgassing and determination of the gas and dust production rates. Additionally, the different approaches used and results obtained to link coma data to the surface will be discussed. We discuss forward and inversion models and we describe the limitations of the respective approaches. The current literature suggests that there does not seem to be a single uniform process behind cometary activity. Rather, activity seems to be the consequence of a variety of erosion processes, including the sublimation of both water ice and more volatile material, but possibly also more exotic processes such as fracture and cliff erosion under thermal and mechanical stress, sub-surface heat storage, and a complex interplay of these processes. Seasons and the nucleus shape are key factors for the distribution and temporal evolution of activity and imply that the heliocentric evolution of activity can be highly individual for every comet, and generalisations can be misleading.
Bacterial chemotaxis-a fundamental example of directional navigation in the living world-is key to many biological processes, including the spreading of bacterial infections. Many bacterial species were recently reported to exhibit several distinct swimming modes-the flagella may, for example, push the cell body or wrap around it. How do the different run modes shape the chemotaxis strategy of a multimode swimmer? Here, we investigate chemotactic motion of the soil bacterium Pseudomonas putida as a model organism. By simultaneously tracking the position of the cell body and the configuration of its flagella, we demonstrate that individual run modes show different chemotactic responses in nutrition gradients and, thus, constitute distinct behavioral states. On the basis of an active particle model, we demonstrate that switching between multiple run states that differ in their speed and responsiveness provides the basis for robust and efficient chemotaxis in complex natural habitats.
Bacterial chemotaxis-a fundamental example of directional navigation in the living world-is key to many biological processes, including the spreading of bacterial infections. Many bacterial species were recently reported to exhibit several distinct swimming modes-the flagella may, for example, push the cell body or wrap around it. How do the different run modes shape the chemotaxis strategy of a multimode swimmer? Here, we investigate chemotactic motion of the soil bacterium Pseudomonas putida as a model organism. By simultaneously tracking the position of the cell body and the configuration of its flagella, we demonstrate that individual run modes show different chemotactic responses in nutrition gradients and, thus, constitute distinct behavioral states. On the basis of an active particle model, we demonstrate that switching between multiple run states that differ in their speed and responsiveness provides the basis for robust and efficient chemotaxis in complex natural habitats.
The contamination of barley by molds on the field or in storage leads to the spoilage of grain and the production of mycotoxins, which causes major economic losses in malting facilities and breweries. Therefore, on-site detection of hidden fungus contaminations in grain storages based on the detection of volatile marker compounds is of high interest. In this work, the volatile metabolites of 10 different fungus species are identified by gas chromatography (GC) combined with two complementary mass spectrometric methods, namely, electron impact (EI) and chemical ionization at atmospheric pressure (APCI)-mass spectrometry (MS). The APCI source utilizes soft X-radiation, which enables the selective protonation of the volatile metabolites largely without side reactions. Nearly 80 volatile or semivolatile compounds from different substance classes, namely, alcohols, aldehydes, ketones, carboxylic acids, esters, substituted aromatic compounds, alkenes, terpenes, oxidized terpenes, sesquiterpenes, and oxidized sesquiterpenes, could be identified. The profiles of volatile and semivolatile metabolites of the different fungus species are characteristic of them and allow their safe differentiation. The application of the same GC parameters and APCI source allows a simple method transfer from MS to ion mobility spectrometry (IMS), which permits on-site analyses of grain stores. Characterization of IMS yields limits of detection very similar to those of APCI-MS. Accordingly, more than 90% of the volatile metabolites found by APCI-MS were also detected in IMS. In addition to different fungus genera, different species of one fungus genus could also be differentiated by GC-IMS.
The performance of the recently commissioned spectrometer PEAXIS for resonant inelastic soft X-ray scattering (RIXS) and X-ray photoelectron spectroscopy and its hosting beamline U41-PEAXIS at the BESSY II synchrotron are characterized. The beamline provides linearly polarized light from 180 eV to 1600 eV allowing for RIXS measurements in the range 200-1200 eV. The monochromator optics can be operated in different configurations to provide either high flux with up to 10(12) photons s(-1) within the focal spot at the sample or high energy resolution with a full width at half maximum of <40 meV at an incident photon energy of similar to 400 eV. The measured total energy resolution of the RIXS spectrometer is in very good agreement with theoretically predicted values obtained by ray-tracing simulations. PEAXIS features a 5 m-long RIXS spectrometer arm that can be continuously rotated about the sample position by 106 degrees within the horizontal photon scattering plane, thus enabling the study of momentum-transfer-dependent excitations. Selected scientific examples are presented to demonstrate the instrument capabilities, including measurements of excitations in single-crystalline NiO and in liquid acetone employing a fluid cell sample manipulator. Planned upgrades of the beamline and the RIXS spectrometer to further increase the energy resolution to similar to 100 meV at 1000 eV incident photon energy are discussed.
The performance of the recently commissioned spectrometer PEAXIS for resonant inelastic soft X-ray scattering (RIXS) and X-ray photoelectron spectroscopy and its hosting beamline U41-PEAXIS at the BESSY II synchrotron are characterized. The beamline provides linearly polarized light from 180 eV to 1600 eV allowing for RIXS measurements in the range 200-1200 eV. The monochromator optics can be operated in different configurations to provide either high flux with up to 10(12) photons s(-1) within the focal spot at the sample or high energy resolution with a full width at half maximum of <40 meV at an incident photon energy of similar to 400 eV. The measured total energy resolution of the RIXS spectrometer is in very good agreement with theoretically predicted values obtained by ray-tracing simulations. PEAXIS features a 5 m-long RIXS spectrometer arm that can be continuously rotated about the sample position by 106 degrees within the horizontal photon scattering plane, thus enabling the study of momentum-transfer-dependent excitations. Selected scientific examples are presented to demonstrate the instrument capabilities, including measurements of excitations in single-crystalline NiO and in liquid acetone employing a fluid cell sample manipulator. Planned upgrades of the beamline and the RIXS spectrometer to further increase the energy resolution to similar to 100 meV at 1000 eV incident photon energy are discussed.
What is the optimal distribution of two types of crystalline phases on the surface of icosahedral shells, such as of many viral capsids? We here investigate the distribution of a thin layer of soft material on a crystalline convex icosahedral shell. We demonstrate how the shapes of spherical viruses can be understood from the perspective of elasticity theory of thin two-component shells. We develop a theory of shape transformations of an icosahedral shell upon addition of a softer, but still crystalline, material onto its surface. We show how the soft component "invades" the regions with the highest elastic energy and stress imposed by the 12 topological defects on the surface. We explore the phase diagram as a function of the surface fraction of the soft material, the shell size, and the incommensurability of the elastic moduli of the rigid and soft phases. We find that, as expected, progressive filling of the rigid shell by the soft phase starts from the most deformed regions of the icosahedron. With a progressively increasing soft-phase coverage, the spherical segments of domes are filled first (12 vertices of the shell), then the cylindrical segments connecting the domes (30 edges) are invaded, and, ultimately, the 20 flat faces of the icosahedral shell tend to be occupied by the soft material. We present a detailed theoretical investigation of the first two stages of this invasion process and develop a model of morphological changes of the cone structure that permits noncircular cross sections. In conclusion, we discuss the biological relevance of some structures predicted from our calculations, in particular for the shape of viral capsids.
Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier.
We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.
We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.
We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.
The unidentified very-high-energy (VHE; E > 0.1 TeV) gamma -ray source, HESS J1826-130, was discovered with the High Energy Stereoscopic System (HESS) in the Galactic plane. The analysis of 215 h of HESS data has revealed a steady gamma -ray flux from HESS J1826-130, which appears extended with a half-width of 0.21 degrees +/- 0.02 <br /> (stat)degrees <br /> stat degrees +/- 0.05 <br /> (sys)degrees sys degrees . The source spectrum is best fit with either a power-law function with a spectral index Gamma = 1.78 +/- 0.10(stat) +/- 0.20(sys) and an exponential cut-off at 15.2 <br /> (+5.5)(-3.2) -3.2+5.5 TeV, or a broken power-law with Gamma (1) = 1.96 +/- 0.06(stat) +/- 0.20(sys), Gamma (2) = 3.59 +/- 0.69(stat) +/- 0.20(sys) for energies below and above E-br = 11.2 +/- 2.7 TeV, respectively. The VHE flux from HESS J1826-130 is contaminated by the extended emission of the bright, nearby pulsar wind nebula, HESS J1825-137, particularly at the low end of the energy spectrum. Leptonic scenarios for the origin of HESS J1826-130 VHE emission related to PSR J1826-1256 are confronted by our spectral and morphological analysis. In a hadronic framework, taking into account the properties of dense gas regions surrounding HESS J1826-130, the source spectrum would imply an astrophysical object capable of accelerating the parent particle population up to greater than or similar to 200 TeV. Our results are also discussed in a multiwavelength context, accounting for both the presence of nearby supernova remnants, molecular clouds, and counterparts detected in radio, X-rays, and TeV energies.