Gold Open-Access
Refine
Document Type
- Article (204)
- Review (3)
- Other (2)
- Monograph/Edited Volume (1)
Is part of the Bibliography
- yes (210)
Keywords
- diffusion (13)
- Reflexion (4)
- chemotaxis (4)
- anomalous diffusion (3)
- electrons (3)
- magnetosphere (3)
- model (3)
- perovskite solar cells (3)
- synchronization (3)
- Atlantic meridional overturning circulation (2)
- Kuramoto model (2)
- Lehrkräftebildung (2)
- Levy walks (2)
- Reflexivität (2)
- Ti-6Al-4V (2)
- X-ray (2)
- X-ray computed tomography (CT) (2)
- additive manufacturing (2)
- cell migration (2)
- correlations (2)
- coupled rotators (2)
- diffraction (2)
- first-passage time (2)
- fractional Brownian motion (2)
- geometric Brownian motion (2)
- global surface warming (2)
- hysteresis (2)
- impact (2)
- infrared thermography (2)
- mid-temperature transition (2)
- networks (2)
- noisy systems (2)
- numerical relativity (2)
- ocean heat uptake (2)
- organic solar cells (2)
- oscillations (2)
- quantum thermodynamics (2)
- random diffusivity (2)
- residual stress (2)
- selective laser melting (SLM) (2)
- specific surface area (2)
- stochastic processes (2)
- synchronization transition (2)
- transient chaos (2)
- 2D perovskites (1)
- 3D tomography (1)
- AG (1)
- ANFO (1)
- ARTOF (1)
- ASR-sensitive aggregate (1)
- Absorption (1)
- Adam-Delbruck scenario (1)
- Amazon rainforest (1)
- Antibiotics (1)
- Arctic clouds (1)
- Astroparticle physics (1)
- Astrophysics (1)
- Auger–Meitner (1)
- BL Lacertae objects: individual (1)
- Bacterial biofilms (1)
- Biofilms (1)
- Biological Physics (1)
- Biological defense mechanisms (1)
- Black– Scholes model (1)
- Boltzmann distribution (1)
- Bragg peak (1)
- Brownian motion (1)
- CH3NH3SnI3 (1)
- CZTSe (1)
- Catalysis (1)
- Central asia (1)
- Chebyshev inequality (1)
- Chimera (1)
- Convolutional neural networks (1)
- Cosmogenic nuclides (1)
- Coster–Kronig (1)
- CryoSat-2 (1)
- Cu-Zn disorder (1)
- Cu2ZnSnSe4 (1)
- Cystic fibrosis (1)
- D. discoideum (1)
- DNA (1)
- Dictyostelium discoideum (1)
- Dielectric Relaxation Spectroscopy (DRS) (1)
- Differential Scanning Calorimetry (DSC) (1)
- Donor-Acceptor (DA) interface (1)
- Drude model (1)
- E.coli (1)
- EBSD (1)
- Electronic properties and materials (1)
- Equilibrium-line altitudes (1)
- European storm-time model (1)
- F-region dynamo currents (1)
- FLASH (1)
- Feedback (1)
- Fiber-reinforced concrete (1)
- Flims (1)
- Fokker-Planck equation (1)
- Fokker– Planck equation (1)
- Fortbildung (1)
- GRACE-FO (1)
- Glaciation (1)
- Gold@polydopamine (1)
- Greenland (1)
- HTL (1)
- Hexagonal grid (1)
- Holocene (1)
- Hong-Ou-Mandel effect (1)
- Hurricane Sandy (1)
- ISOS-L-1I protocol (1)
- Inter-hemispheric (1)
- Interdisciplinary Physics (1)
- Kuramoto (1)
- Künstliche Intelligenz (1)
- L-Asterisk (1)
- LLG equation (1)
- Lasers (1)
- Lattice dynamics (1)
- Levy flights (1)
- Lyapunov exponent (1)
- Magnetism (1)
- Maschinelles Lernen (1)
- NEXAFS (1)
- NTCM (1)
- Nanoreactor (1)
- Natural Language Processing (1)
- Network (1)
- Ornstein–Uhlenbeck process (1)
- P(VDF-TFE) copolymer (1)
- Perovskite solar cell (1)
- Perovskites (1)
- Phonons (1)
- Photothermal conversion (1)
- Plasma Physics (1)
- Platform magnetometers (1)
- Professionalisierung (1)
- Pseudo-Voigt fit function (1)
- Pseudomonas aeruginosa (1)
- PyTorch (1)
- Python (1)
- Raman imaging (1)
- Raman spectroscopy (1)
- Referendariat (1)
- Reflection (1)
- Reflection Skills (1)
- Reflexionskompetenz (1)
- Reflexivity (1)
- Resolved and unresolved sources as a function of wavelength (1)
- SCAPS-1D (1)
- SERS (1)
- SPR (1)
- Sammelband (1)
- Sinai diffusion (1)
- Sputum (1)
- Statistical Physics (1)
- Stern-Gerlach effect (1)
- Structural health monitoring (1)
- Sun (1)
- Tagung (1)
- Teacher Education (1)
- Thermal effects (1)
- Thermodynamic properties (1)
- Thin films (1)
- Topological matter (1)
- Ultrafast X-ray diffraction (1)
- Unterrichtsanalyse (1)
- WAAM (1)
- X-ray and (1)
- X-ray computed (1)
- X-ray imaging (1)
- X-ray probe (1)
- X-ray refraction; (1)
- XCT (1)
- actin (1)
- actin dynamics (1)
- actin polymerization (1)
- activator–inhibitor models (1)
- active matter (1)
- active particles (1)
- adaptation and mitigation (1)
- additive (1)
- additive manufacturing (AM) (1)
- aggregation (1)
- alkali-silica reaction (ASR) (1)
- amoeboid motility (1)
- amphiphilic side chains (1)
- analyzer-based imaging (1)
- and governance (1)
- and surface diffusion (1)
- anisotropic fiber orientation (1)
- anomalous (or non-Fickian) diffusion (1)
- anomalous heat conduction (1)
- applications (1)
- approximate methods (1)
- artificial intelligence (1)
- astronomy (1)
- asymmetric Levy flights (1)
- autocorrelation (1)
- autocorrelation function (1)
- automated image processing (1)
- azobenzene (1)
- bacterial swimming strategies (1)
- beam splitter (1)
- bifurcation theory (1)
- binary neutron stars (1)
- biohybrid microsystems (1)
- block copolymer films (1)
- bridges (1)
- brownian motion (1)
- bulk (1)
- cancer diagnosis (1)
- cascading regime (1)
- cell motility (1)
- cell polarity (1)
- cell-cell (1)
- cesium lead halides (1)
- chains (1)
- chalcogenide (1)
- channel (1)
- chaos (1)
- charge injection across hybrid interfaces (1)
- chemical (1)
- chimera (1)
- chirality (1)
- cirrus clouds (1)
- climate (1)
- climate change (1)
- climate impacts (1)
- climate trends (1)
- climate variability (1)
- clustering (1)
- collective dynamics (1)
- collective motion (1)
- coloured and quantum noise (1)
- complementarity (1)
- complex (1)
- complex networks (1)
- complex systems (1)
- components (1)
- computed tomography (1)
- concrete (1)
- conformational and hydrodynamic characteristics (1)
- consecutive disasters (1)
- consequences (1)
- continuous time random walk (1)
- contraction (1)
- control (1)
- corona (1)
- coronal mass ejections (CMEs) (1)
- correlated noise (1)
- cosmology: cosmic background radiation (1)
- cosmology: cosmological parameters (1)
- cosmology: distance scale (1)
- costs (1)
- coupling (1)
- covariance (1)
- crack (1)
- cross layer chip (1)
- crystal orientation (1)
- crystalline phases (1)
- damage quantification (1)
- dark matter (1)
- data processing (1)
- defect detection (1)
- delay differential equation (1)
- density (1)
- deposition (1)
- dermis (1)
- detection (1)
- diaspora (1)
- dielectric properties (1)
- diffraction enhanced imaging (1)
- diffraction-elastic constants (1)
- dimensional reduction (1)
- dispersion (1)
- dispersion force (1)
- distortion (1)
- domino effect (1)
- donor (1)
- doubly transient chaos (1)
- droughts (1)
- dynamical systems (1)
- dynamics (1)
- early warning indicators (1)
- ecology and biodiversity (1)
- economic ripple resonance (1)
- economic ripples (1)
- econophysics (1)
- efficiency (1)
- electro-fused zirconia (1)
- electrochemistry (1)
- electron lifetimes (1)
- electron spectroscopy (1)
- electron-transfer (1)
- ellipsometry (1)
- energy (1)
- energy-level alignments (1)
- ensemble and time averaged mean squared displacement (1)
- entanglement (1)
- entropy production (1)
- enzymatic sensors (1)
- epidermis (1)
- equation of state; (1)
- exact results (1)
- exaction (1)
- excitonic materials (1)
- expanding medium (1)
- exploit (1)
- explosives (1)
- extremal values (1)
- extreme weather (1)
- fastest first-passage time of N walkers (1)
- ferroelectric polymers (1)
- fiber optic sensors (1)
- fiber-electrophoresis chip (1)
- field-aligned currents (1)
- film (1)
- finite-size effects (1)
- first passage (1)
- first passage time (1)
- first-arrival density (1)
- first-hitting time (1)
- first-passage (1)
- first-passage times (1)
- first-reaction time (1)
- flagellum (1)
- flares (1)
- flexible (1)
- flow network (1)
- fluorescence (1)
- fluorinated organic spacer (1)
- functional theory (1)
- galaxies: high-redshift (1)
- gamma-rays: general (1)
- gas phase electron spectroscopy (1)
- geomagnetic storms (1)
- global jets (1)
- gravitational waves (1)
- gravitational-wave astronomy (1)
- green solvents (1)
- guided self assembly (1)
- healing (1)
- heat-treatment (1)
- helical magnetic fields (1)
- heterojunction silicon solar cells (1)
- human behaviour (1)
- hybrid functional (1)
- hybrid manufacturing (1)
- hybrid metal oxides (1)
- hydrodynamic model (1)
- hyperbolic attractor (1)
- ice clouds (1)
- image registration (1)
- immunosensors (1)
- impacts (1)
- imprinted electrodes (1)
- in situ monitoring (1)
- influence of weak magnetic fields on living systems (1)
- information (1)
- information theory (1)
- inorganic perovskites (1)
- instabilities (1)
- instability (1)
- interactions (1)
- interface engineering (1)
- interfaces (1)
- interferometry (1)
- intermolecular force (1)
- international migration (1)
- inverse analysis (1)
- ion channels (1)
- ion optics (1)
- ionosphere (1)
- iteration method (1)
- keratocytle-like motility (1)
- kesterite (1)
- kink-like instability (1)
- large-deviation statistic (1)
- laser powder bed fusion (L-PBF) (1)
- laser-based additive manufacturing (1)
- leakage scheme (1)
- lidar (1)
- literature review (1)
- local equilibrium (1)
- loss propagation (1)
- machine learning (1)
- magnetic fields (1)
- magnetic microstructures (1)
- magnetic nanoparticles (1)
- magnetisation (1)
- magnetohydrodynamics (MHD) (1)
- magnetostriction (1)
- manufacturing (AM) (1)
- mass conservation (1)
- maximum and range (1)
- maximum entropy analysis (1)
- mean-field model (1)
- mechanical properties (1)
- melting slm (1)
- memory effects (1)
- memory kernel (1)
- metal optics (1)
- micro computed tomography (XCT) (1)
- microcracking (1)
- microfluidic paper analytic device (mu PAD) (1)
- microtransport and -assembly (1)
- migration (1)
- migration transition (1)
- modeling (1)
- models (1)
- modes of (1)
- molecular brushes (1)
- molecular dynamics (1)
- molecular hydrodynamics and (1)
- molecular imprinted polymers (1)
- molecular overcrowding (1)
- monitoring (1)
- multi-messenger astrophysics (1)
- multichannel (1)
- mushroom instability (1)
- myosin II (1)
- nanofiber (1)
- nanoscale heat transfer (1)
- natural disasters (1)
- natural language processing (1)
- natural resources (biological and non-biological) (1)
- negative thermal expansion (1)
- network dynamics (1)
- neural (1)
- neutrinos (1)
- neutron (1)
- neutron diffraction (1)
- neutron stars (1)
- neutrophils (1)
- non-Gaussian (1)
- non-Gaussianity (1)
- non-contact heat transfer (1)
- non-destructive evaluation (1)
- non-exponential relaxation (1)
- non-exponential statistics (1)
- non-geminate recombination (1)
- non-halogenated solvents (1)
- non-radiative recombination (1)
- nonlinear waves (1)
- nucleobases (1)
- open quantum systems (1)
- open-circuit voltage decay (1)
- optical tomography (1)
- optics (1)
- option pricing (1)
- organic interfaces (1)
- organic solar cell (1)
- origins (1)
- overdamped brownian systems (1)
- parameter inference (1)
- particle-in-cell simulations (1)
- pattern formation (1)
- patterning glass microfiber (1)
- pause hiatus (1)
- pedagogical content knowledge (PCK) (1)
- pedagogical reasoning (1)
- phase field model (1)
- phase purity (1)
- phase transition (1)
- photo-isomerization kinetics (1)
- photo-sensitive surfactant (1)
- photoelectron (1)
- photoluminescence quenching (1)
- photostability (1)
- photovoltaics (1)
- picosecond ultrasonics (1)
- piezoelectric polymers (1)
- pitch angle (1)
- pitch angle distributions (1)
- policies (1)
- politics (1)
- poly (acrylic acid, sodium salt) (1)
- polymerase chain reaction (PCR) (1)
- porosity (1)
- power spectral density (1)
- power spectrum (1)
- prediction (1)
- probabilistic inference (1)
- probability density function (1)
- process (1)
- process monitoring (1)
- processing (1)
- professionalization (1)
- projections (1)
- pump-probe (1)
- purification (1)
- pyroelectric polymers (1)
- quantum batteries (1)
- quantum mechanics (1)
- quantum phase transition (1)
- quasi-Fermi level splitting (1)
- radiation belts (1)
- random-walk (1)
- reaction cascade (1)
- reaction-diffusion models (1)
- recollimation shocks (1)
- recombination order (1)
- refined consensus model (RCM) (1)
- reflexion (1)
- relative total electron content (1)
- relativistic jets (1)
- repercussion resonance (1)
- residual stress analysis (1)
- return migration (1)
- ring current (1)
- ring current model (1)
- rotational diffusion (1)
- run and tumble (1)
- science teaching (1)
- search efficiency (1)
- self-organisation (1)
- seperation (1)
- shell-like geometries (1)
- shifts (1)
- signal processing (1)
- simulation model (1)
- single trajectories (1)
- single-trajectory analysis (1)
- solar coronal mass ejections (1)
- solar storm (1)
- soliton (1)
- solubility test (1)
- solvent vapor annealing (1)
- space-charge effects (1)
- space-dependent diffusivity (1)
- spacing (1)
- spatial (1)
- spatial localization (1)
- special quasirandom structure (1)
- spin (1)
- spin-dependent forces (1)
- spontaneous parametric down-conversion (1)
- stars: binaries (1)
- stars: neutron (1)
- stationary stochastic process (1)
- steel and concrete structures (1)
- stellar coronal mass ejections (1)
- stochastic dynamics (1)
- stochastic resetting (1)
- stochastic thermodynamics (1)
- strain gauges (1)
- strain sensors (1)
- strain-free lattice (1)
- stretching (1)
- sulfur (1)
- superalloys (1)
- supply chains (1)
- supply network (1)
- surface reconstruction (1)
- surface-roughened (1)
- susceptibility (1)
- synchrotron X-ray diffraction (1)
- synchrotron x-ray refraction radiography (SXRR) (1)
- synthesis (1)
- systems subjected to parameter drift (1)
- tandem solar cells (1)
- teaching practice (1)
- temperature dependence (1)
- temperature fluctuation (1)
- texture (1)
- the Weibel instability (1)
- thermal expansion (1)
- thermodynamic control (1)
- thermodynamic length (1)
- thermodynamics (1)
- thin films (1)
- thiouracil (1)
- time (1)
- time-averaged mean squared displacement (1)
- time-series analysis (1)
- tipping cascade (1)
- tipping interactions (1)
- tomography (XCT) (1)
- transfer dynamics (1)
- transit migration (1)
- transversal instabilities (1)
- traveling waves (1)
- ultrafast photoacoustics (1)
- ultrafast x-ray diffraction (1)
- vacuum fields (1)
- van alien probes (1)
- van allen probes (RBSP) (1)
- verb (1)
- vinylidenefluoride (VDF)-based polymers (1)
- viscoelastic effects and anomalous diffusion (1)
- viscosity (1)
- weather extremes (1)
- x-ray photoemission (1)
- zebrafish (1)
- иперболический аттрактор (1)
- оллективная динамика (1)
- синхронизация (1)
Institute
- Institut für Physik und Astronomie (210) (remove)
We characterize finite-time thermodynamic processes of multidimensional quadratic overdamped systems.
Analytic expressions are provided for heat, work, and dissipation for any evolution of the system covariance matrix.
The Bures-Wasserstein metric between covariance matrices naturally emerges as the local quantifier of dissipation.
General principles of how to apply these geometric tools to identify optimal protocols are discussed.
Focusing on the relevant slow-driving limit, we show how these results can be used to analyze cases in which the experimental control over the system is partial.
We perform numerical studies of a thermally driven, overdamped particle in a random quenched force field, known as the Sinai model. We compare the unbounded motion on an infinite 1-dimensional domain to the motion in bounded domains with reflecting boundaries and show that the unbounded motion is at every time close to the equilibrium state of a finite system of growing size. This is due to time scale separation: inside wells of the random potential, there is relatively fast equilibration, while the motion across major potential barriers is ultraslow. Quantities studied by us are the time dependent mean squared displacement, the time dependent mean energy of an ensemble of particles, and the time dependent entropy of the probability distribution. Using a very fast numerical algorithm, we can explore times up top 10(17) steps and thereby also study finite-time crossover phenomena.
Leptonic nonthermal emission from supernova remnants evolving in the circumstellar magnetic field
(2022)
The very-high-energy (VHE; E > 100 GeV) gamma-ray emission observed from a number of supernova remnants (SNRs) indicates particle acceleration to high energies at the shock of the remnants and a potentially significant contribution to Galactic cosmic rays. It is extremely difficult to determine whether protons (through hadronic interactions and subsequent pion decay) or electrons (through inverse Compton scattering on ambient photon fields) are responsible for this emission. For a successful diagnostic, a good understanding of the spatial and energy distribution of the underlying particle population is crucial. Most SNRs are created in core-collapse explosions and expand into the wind bubble of their progenitor stars. This circumstellar medium features a complex spatial distribution of gas and magnetic field which naturally strongly affects the resulting particle population. In this work, we conduct a detailed study of the spectro-spatial evolution of the electrons accelerated at the forward shock of core-collapse SNRs and their nonthermal radiation, using the RATPaC code that is designed for the time- and spatially dependent treatment of particle acceleration at SNR shocks. We focus on the impact of the spatially inhomogeneous magnetic field through the efficiency of diffusion and synchrotron cooling. It is demonstrated that the structure of the circumstellar magnetic field can leave strong signatures in the spectrum and morphology of the resulting nonthermal emission.
Magnetic reconnection is a multi-faceted process of energy conversion in astrophysical, space and laboratory plasmas that operates at microscopic scales but has macroscopic drivers and consequences.
Solar flares present a key laboratory for its study, leaving imprints of the microscopic physics in radiation spectra and allowing the macroscopic evolution to be imaged, yet a full observational characterization remains elusive.
Here we combine high resolution imaging and spectral observations of a confined solar flare at multiple wavelengths with data-constrained magnetohydrodynamic modeling to study the dynamics of the flare plasma from the current sheet to the plasmoid scale. The analysis suggests that the flare resulted from the interaction of a twisted magnetic flux rope surrounding a filament with nearby magnetic loops whose feet are anchored in chromospheric fibrils. Bright cusp-shaped structures represent the region around a reconnecting separator or quasi-separator (hyperbolic flux tube).
The fast reconnection, which is relevant for other astrophysical environments, revealed plasmoids in the current sheet and separatrices and associated unresolved turbulent motions.
Solar flares provide wide range of observational details about fundamental processes involved. Here, the authors show evidence for magnetic reconnection in a strong confined solar flare displaying all four reconnection flows with plasmoids in the current sheet and the separatrices.
The simultaneous detection of gravitational waves and light from the binary neutron star merger GW170817 led to independent measurements of distance and redshift, providing a direct estimate of the Hubble constant H-0 that does not rely on a cosmic distance ladder, nor assumes a specific cosmological model.
By using gravitational waves as "standard sirens", this approach holds promise to arbitrate the existing tension between the H-0 value inferred from the cosmic microwave background and those obtained from local measurements.
However, the known degeneracy in the gravitational-wave analysis between distance and inclination of the source led to a H-0 value from GW170817 that was not precise enough to resolve the existing tension.
In this review, we summarize recent works exploiting the viewing-angle dependence of the electromagnetic signal, namely the associated short gamma-ray burst and kilonova, to constrain the system inclination and improve on H-0.
We outline the key ingredients of the different methods, summarize the results obtained in the aftermath of GW170817 and discuss the possible systematics introduced by each of these methods.
In the last years, electron density profile functions characterized by a linear dependence on the scale height showed good results when approximating the topside ionosphere. The performance above 800 km, however, is not yet well investigated.
This study investigates the capability of the semi-Epstein functions to represent electron density profiles from the peak height up to 20,000 km. Electron density observations recorded by the Van Allen Probes were used to resolve the scale height dependence in the plasmasphere.
It was found that the linear dependence of the scale height in the topside ionosphere cannot be directly used to extrapolate profiles above 800 km.
We find that the dependence of scale heights on altitude is quadratic in the plasmasphere. A statistical model of the scale heights is therefore proposed. After combining the topside ionosphere and plasmasphere by a unified model, we have obtained good estimations not only in the profile shapes, but also in the Total Electron Content magnitude and distributions when compared to actual measurements from 2013, 2014, 2016 and 2017.
Our investigation shows that Van Allen Probes can be merged to radio-occultation data to properly represent the upper ionosphere and plasmasphere by means of a semi-Epstein function.
The determination of the spin state of iron-bearing compounds at high pressure and temperature is crucial for our understanding of chemical and physical properties of the deep Earth. Studies on the relationship between the coordination of iron and its electronic spin structure in iron-bearing oxides, silicates, carbonates, iron alloys, and other minerals found in the Earth's mantle and core are scarce because of the technical challenges to simultaneously probe the sample at high pressures and temperatures. We used the unique properties of a pulsed and highly brilliant x-ray free electron laser (XFEL) beam at the High Energy Density (HED) instrument of the European XFEL to x-ray heat and probe samples contained in a diamond anvil cell. We heated and probed with the same x-ray pulse train and simultaneously measured x-ray emission and x-ray diffraction of an FeCO3 sample at a pressure of 51 GPa with up to melting temperatures. We collected spin state sensitive Fe K beta(1,3) fluorescence spectra and detected the sample's structural changes via diffraction, observing the inverse volume collapse across the spin transition. During x-ray heating, the carbonate transforms into orthorhombic Fe4C3O12 and iron oxides. Incipient melting was also observed. This approach to collect information about the electronic state and structural changes from samples contained in a diamond anvil cell at melting temperatures and above will considerably improve our understanding of the structure and dynamics of planetary and exoplanetary interiors.
Characterization of binding interactions of SARS-CoV-2 spike protein and DNA-peptide nanostructures
(2022)
Binding interactions of the spike proteins of the severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) to a peptide fragment derived from the human angiotensin converting enzyme 2 (hACE2) receptor are investigated.
The peptide is employed as capture moiety in enzyme linked immunosorbent assays (ELISA) and quantitative binding interaction measurements that are based on fluorescence proximity sensing (switchSENSE).
In both techniques, the peptide is presented on an oligovalent DNA nanostructure, in order to assess the impact of mono- versus trivalent binding modes.
As the analyte, the spike protein and several of its subunits are tested as well as inactivated SARS-CoV-2 and pseudo viruses. While binding of the peptide to the full-length spike protein can be observed, the subunits RBD and S1 do not exhibit binding in the employed concentrations.
Variations of the amino acid sequence of the recombinant full-length spike proteins furthermore influence binding behavior. The peptide was coupled to DNA nanostructures that form a geometric complement to the trimeric structure of the spike protein binding sites.
An increase in binding strength for trimeric peptide presentation compared to single peptide presentation could be generally observed in ELISA and was quantified in switchSENSE measurements. Binding to inactivated wild type viruses could be shown as well as qualitatively different binding behavior of the Alpha and Beta variants compared to the wild type virus strain in pseudo virus models.
The time instant-the first-passage time (FPT)-when a diffusive particle (e.g., a ligand such as oxygen or a signalling protein) for the first time reaches an immobile target located on the surface of a bounded three-dimensional domain (e.g., a hemoglobin molecule or the cellular nucleus) is a decisive characteristic time-scale in diverse biophysical and biochemical processes, as well as in intermediate stages of various inter- and intra-cellular signal transduction pathways. Adam and Delbruck put forth the reduction-of-dimensionality concept, according to which a ligand first binds non-specifically to any point of the surface on which the target is placed and then diffuses along this surface until it locates the target. In this work, we analyse the efficiency of such a scenario and confront it with the efficiency of a direct search process, in which the target is approached directly from the bulk and not aided by surface diffusion. We consider two situations: (i) a single ligand is launched from a fixed or a random position and searches for the target, and (ii) the case of 'amplified' signals when N ligands start either from the same point or from random positions, and the search terminates when the fastest of them arrives to the target. For such settings, we go beyond the conventional analyses, which compare only the mean values of the corresponding FPTs. Instead, we calculate the full probability density function of FPTs for both scenarios and study its integral characteristic-the 'survival' probability of a target up to time t. On this basis, we examine how the efficiencies of both scenarios are controlled by a variety of parameters and single out realistic conditions in which the reduction-of-dimensionality scenario outperforms the direct search.
We study the first-arrival (first-hitting) dynamics and efficiency of a one-dimensional random search model performing asymmetric Levy flights by leveraging the Fokker-Planck equation with a delta-sink and an asymmetric space-fractional derivative operator with stable index alpha and asymmetry (skewness) parameter beta.
We find exact analytical results for the probability density of first-arrival times and the search efficiency, and we analyse their behaviour within the limits of short and long times.
We find that when the starting point of the searcher is to the right of the target, random search by Brownian motion is more efficient than Levy flights with beta <= 0 (with a rightward bias) for short initial distances, while for beta>0 (with a leftward bias) Levy flights with alpha -> 1 are more efficient.
When increasing the initial distance of the searcher to the target, Levy flight search (except for alpha=1 with beta=0) is more efficient than the Brownian search. Moreover, the asymmetry in jumps leads to essentially higher efficiency of the Levy search compared to symmetric Levy flights at both short and long distances, and the effect is more pronounced for stable indices alpha close to unity.