530 Physik
Refine
Has Fulltext
- yes (114)
Year of publication
Document Type
- Postprint (114) (remove)
Language
- English (114)
Is part of the Bibliography
- yes (114) (remove)
Keywords
- diffusion (16)
- anomalous diffusion (11)
- films (3)
- transport (3)
- Phonons (2)
- Thermal effects (2)
- brushes (2)
- complexes (2)
- dynamics (2)
- first passage time (2)
- fractional Brownian motion (2)
- impact (2)
- nonergodicity (2)
- photovoltaics (2)
- random diffusivity (2)
- stochastic processes (2)
- superstatistics (2)
- 2D perovskites (1)
- 3 body recombination (1)
- 47A52 (1)
- 65R20 (1)
- 65R32 (1)
- 78A46 (1)
- AG (1)
- Amazon rainforest (1)
- Anisotropy (1)
- Atlantic meridional overturning circulation (1)
- Auger electron spectroscopy (1)
- Auger–Meitner (1)
- BESSY II. (1)
- BL Lacertae objects: individual (1)
- Bose-Einstein condensates (BECs) (1)
- Bragg peak (1)
- Brownian motion (1)
- Brownian yet non-Gaussian diffusion (1)
- C-asterisk-algebra (1)
- CU (1)
- Chebyshev inequality (1)
- Complementarity (1)
- Coster–Kronig (1)
- Crystal lattices (1)
- DFT (1)
- Debye screening (1)
- Donor-Acceptor (DA) interface (1)
- E. coli (1)
- FLASH (1)
- Femtosecond lasers (1)
- Greenland (1)
- Heterostructures (1)
- Hong-Ou-Mandel effect (1)
- ISOS-L-1I protocol (1)
- Kuramoto model (1)
- Langevin equation (1)
- Lasers (1)
- Lattice dynamics (1)
- Levy walks (1)
- MO (1)
- Magnetism (1)
- Mode function (1)
- NEXAFS (1)
- Ornstein–Uhlenbeck process (1)
- Ott–Antonsen equation (1)
- Perovskites (1)
- Photoexcitations (1)
- Quantum optics (1)
- Resolved and unresolved sources as a function of wavelength (1)
- SIO₂ (1)
- STM (1)
- Shockley-Queisser model (1)
- Strain measurement (1)
- Thermodynamic properties (1)
- Thin films (1)
- Ultrafast X-ray diffraction (1)
- Ultrafast X-rays (1)
- Vacuum fields (1)
- X-ray (1)
- X-ray absorption (1)
- X-ray emission (1)
- X-ray photoelectron spectroscopy (1)
- aerosol size distribution (1)
- ageing (1)
- alignment (1)
- anionic polymerizations (1)
- approximate methods (1)
- aspect ratio (1)
- atomic force microscopy (AFM) (1)
- atomic-force; nano-objects (1)
- attosecond phenomena (1)
- autoregressive models (1)
- azobenzene (1)
- bacteria (1)
- bacterial swimming strategies (1)
- bandgap (1)
- behavior (1)
- biological physics (1)
- cambridge cb4 0wf (1)
- cambs (1)
- cesium lead halides (1)
- chains (1)
- channel (1)
- charge localisation (1)
- chemotaxis (1)
- chimera (1)
- chimera states (1)
- chromophore orientations (1)
- climate (1)
- cluster model (1)
- co-monomer content (1)
- codifference (1)
- coefficient (1)
- coefficients (1)
- collapse (1)
- collective dynamics (1)
- command surfaces (1)
- commutator subgroup (1)
- complementarity (1)
- complex networks (1)
- composites (1)
- confinement (1)
- consequences (1)
- continuation (1)
- continuous time random walk (1)
- control (1)
- costs (1)
- coupled oscillators (1)
- coupled rotators (1)
- covariance (1)
- critical avalanche dynamics (1)
- critical phenomena (1)
- crystal orientation (1)
- crystalline (1)
- cycle decomposition (1)
- cylindrical geometry (1)
- data assimilation (1)
- decarbonization (1)
- democratic form (1)
- deployment (1)
- design concepts (1)
- diffusing diffusivity (1)
- dilute aqueous-solutions (1)
- dimension independent bound (1)
- diselenide (1)
- donor (1)
- droughts (1)
- drug-delivery (1)
- dynamics simulation (1)
- efficiency (1)
- elastomers (1)
- electromagnetic radiation (1)
- electron-transfer (1)
- electronic-structure (1)
- electrostatic interactions (1)
- energy (1)
- energy-system (1)
- england (1)
- ensemble and time averaged mean squared displacement (1)
- entanglement (1)
- entropy production (1)
- equation approach (1)
- ether methacrylates (1)
- exact results (1)
- excitonic materials (1)
- expanding medium (1)
- exploit (1)
- extremal values (1)
- fastest first-passage time of N walkers (1)
- fill factor losses (1)
- filter (1)
- financial time series (1)
- finite-size effects (1)
- first-passage (1)
- first-passage time (1)
- first-passage time distribution (1)
- first-reaction time (1)
- flagellum (1)
- fluorinated organic spacer (1)
- forced symmetry breaking (1)
- fractional dynamics (1)
- free shear layers (1)
- galaxies: high-redshift (1)
- gamma-rays: general (1)
- gas (1)
- gene regulatory networks (1)
- general relativity (1)
- generalised langevin equation (1)
- genomic DNA conformation (1)
- geomagnetic observatory data (1)
- geomagnetic storm drivers (1)
- geometric Brownian motion (1)
- glass (1)
- global surface warming (1)
- gradients (1)
- grafted polymers (1)
- gravity (1)
- ground based gamma ray astronomy (1)
- harmonic traps (1)
- heteroatoms (1)
- heterojunction silicon solar cells (1)
- high dimensional (1)
- historical geomagnetic storms (1)
- hydrogels (1)
- hysteresis (1)
- inorganic perovskites (1)
- instability (1)
- instability control (1)
- integral equation (1)
- integration (1)
- interfaces (1)
- inverse ill-posed problem (1)
- inverse scattering (1)
- iron(II) (1)
- iterative regularization (1)
- l-edge xas (1)
- large-deviation statistic (1)
- laser pulses (1)
- laser remote sensing (1)
- levelized cost (1)
- light modulator (1)
- light-induced deformation (1)
- linearized gravity (1)
- lipid bilayer membrane dynamics (1)
- living cells (1)
- localisation (1)
- locality (1)
- low-dimensional models (1)
- magnetostriction (1)
- maximum and range (1)
- mean versus most probable reaction times (1)
- membrane (1)
- membrane channel (1)
- memory and delay (1)
- metal halide perovskites (1)
- metal nanoparticles (1)
- metal species (1)
- mhd turbulence (1)
- microscopy (1)
- milton rd (1)
- mixed boundary conditions (1)
- model (1)
- models (1)
- molecular bottle brushes (1)
- molecular-structure (1)
- monte-carlo (1)
- motivation (1)
- n-isopropylacrylamide (1)
- nanoscale heat transfer (1)
- narrow escape problem (1)
- negative thermal expansion (1)
- nematic liquid crystals (1)
- networks (1)
- neuronal connectivity (1)
- neuronal networks (1)
- next generation Cherenkov telescopes (1)
- noisy systems (1)
- non-Gaussian diffusion (1)
- non-Gaussianity (1)
- nonfullerene acceptors (1)
- nonlinear (1)
- nonlinear dynamical systems (1)
- nonlocally coupled phase oscillators (1)
- nonradiative voltage losses (1)
- nucleobases (1)
- numerical simulations (1)
- observables (1)
- ocean heat uptake (1)
- oligo(ethylene glycol) methacrylate (1)
- one-dimensional Bose gas (1)
- optical manipulation (1)
- optical near-field (1)
- organic solar cell (1)
- organic solar cells (1)
- origins (1)
- osmotic-pressure (1)
- oxygen (1)
- parameter inference (1)
- partial synchronization (1)
- particles (1)
- perovskite solar cells (1)
- ph-responsive microgels (1)
- phase purity (1)
- phase transition (1)
- phase-transitions (1)
- phonon modes (1)
- photochemistry (1)
- photocontrol (1)
- photoelectron (1)
- photofragmentation (1)
- photoluminescence (1)
- photon recycling (1)
- photoresponsive surfactants (1)
- photosensitive surfactants (1)
- photostability (1)
- physics education (1)
- picosecond ultrasonics (1)
- polyelectrolyte adsorption (1)
- polymer (1)
- porous carbon materials (1)
- posttranslational protein translocation (1)
- power spectral analysis (1)
- power spectral density (1)
- power spectrum (1)
- power-system (1)
- pp-wave solutions (1)
- pre-service teachers (1)
- prediction (1)
- pressures (1)
- probability density function (1)
- probe (1)
- projections (1)
- protein interactions (1)
- protein search (1)
- quantum mechanics (1)
- quasi-Fermi level (1)
- quasi-steady-state photoinduced absorptions (1)
- radiative limit (1)
- raman (1)
- random walk (1)
- random-walk (1)
- random-walks (1)
- reaction cascade (1)
- reanalysis (1)
- recombination (1)
- recombinations (1)
- rectification (1)
- reflecting boundary conditions (1)
- repertory grid (1)
- resonant inelastic X-ray scattering; (1)
- royal soc chemistry (1)
- run and tumble (1)
- rutile-type (1)
- scattering (1)
- science park (1)
- seperation (1)
- sequence-controlled polymers (1)
- shear layers (1)
- shell-like geometries (1)
- silicon (1)
- simulations (1)
- single chain folding (1)
- single trajectories (1)
- single trajectory analysis (1)
- single-particle tracking (1)
- single-stranded-dna (1)
- single-trajectory analysis (1)
- soft X-ray beamline (1)
- soft X-ray spectroscopy (1)
- solar coronal mass ejections (1)
- solar storm (1)
- solid-state nanopores (1)
- soliton (1)
- solvatochromic fluorophore (1)
- space-dependent diffusivity (1)
- special holonomy (1)
- spectra (1)
- spin-state (1)
- splitting (1)
- spontaneous parametric down-conversion (1)
- stability (1)
- stability and accuracy (1)
- star formation (1)
- stationary stochastic process (1)
- stellar coronal mass ejections (1)
- stochastic models (1)
- stochastic resetting (1)
- stochastic time series (1)
- storage (1)
- structured polynucleotides (1)
- subdiffusion (1)
- sulfur (1)
- supervised machine learning (1)
- surface (1)
- surface functionalization (1)
- surface-relief gratings (1)
- swelling behavior (1)
- synchronization (1)
- synchronization transition (1)
- table-top sources (1)
- tandem solar cells (1)
- temperature (1)
- temperature dependence (1)
- thermodynamics (1)
- thermoresponsive polymers (1)
- thin films (1)
- thiouracil (1)
- thomas graham house (1)
- time (1)
- time averaging (1)
- time series analysis (1)
- time-averaged mean squared displacement (1)
- to-coil transition (1)
- tracking (1)
- transfer dynamics (1)
- transitive action (1)
- transmission (1)
- transversal instabilities (1)
- traveling waves (1)
- travelling waves (1)
- truncated power-law correlated noise (1)
- turbulence control (1)
- ultrafast dynamics (1)
- ultrafast molecular dynamics (1)
- ultrafast photoacoustics (1)
- ultrafast x-ray diffraction (1)
- vacuum fields (1)
- voltage losses (1)
- water (1)
- wind (1)
- x-ray free-electron lasers (1)
- x-ray spectroscopies and phenomena (1)
Institute
It is quite generally assumed that the overdamped Langevin equation provides a quantitative description of the dynamics of a classical Brownian particle in the long time limit. We establish and investigate a paradigm anomalous diffusion process governed by an underdamped Langevin equation with an explicit time dependence of the system temperature and thus the diffusion and damping coefficients. We show that for this underdamped scaled Brownian motion (UDSBM) the overdamped limit fails to describe the long time behaviour of the system and may practically even not exist at all for a certain range of the parameter values. Thus persistent inertial effects play a non-negligible role even at significantly long times. From this study a general questions on the applicability of the overdamped limit to describe the long time motion of an anomalously diffusing particle arises, with profound consequences for the relevance of overdamped anomalous diffusion models. We elucidate our results in view of analytical and simulations results for the anomalous diffusion of particles in free cooling granular gases.
What are the physical laws of the mutual interactions of objects bound to cell membranes, such as various membrane proteins or elongated virus particles? To rationalise this, we here investigate by extensive computer simulations mutual interactions of rod-like particles adsorbed on the surface of responsive elastic two-dimensional sheets. Specifically, we quantify sheet deformations as a response to adhesion of such filamentous particles. We demonstrate that tip-to-tip contacts of rods are favoured for relatively soft sheets, while side-by-side contacts are preferred for stiffer elastic substrates. These attractive orientation-dependent substrate-mediated interactions between the rod-like particles on responsive sheets can drive their aggregation and self-assembly. The optimal orientation of the membrane-bound rods is established via responding to the elastic energy profiles created around the particles. We unveil the phase diagramme of attractive–repulsive rod–rod interactions in the plane of their separation and mutual orientation. Applications of our results to other systems featuring membrane-associated particles are also discussed.
We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore.
Derivatization of fullerene (C60) with branched aliphatic chains softens C60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 °C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 ± 0.1%) in comparison with another compound, 10 (PCE: 0.5 ± 0.1%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices.
The gravitational field of a laser pulse of finite lifetime, is investigated in the framework of linearized gravity. Although the effects are very small, they may be of fundamental physical interest. It is shown that the gravitational field of a linearly polarized light pulse is modulated as the norm of the corresponding electric field strength, while no modulations arise for circular polarization. In general, the gravitational field is independent of the polarization direction. It is shown that all physical effects are confined to spherical shells expanding with the speed of light, and that these shells are imprints of the spacetime events representing emission and absorption of the pulse. Nearby test particles at rest are attracted towards the pulse trajectory by the gravitational field due to the emission of the pulse, and they are repelled from the pulse trajectory by the gravitational field due to its absorption. Examples are given for the size of the attractive effect. It is recovered that massless test particles do not experience any physical effect if they are co-propagating with the pulse, and that the acceleration of massless test particles counter-propagating with respect to the pulse is four times stronger than for massive particles at rest. The similarities between the gravitational effect of a laser pulse and Newtonian gravity in two dimensions are pointed out. The spacetime curvature close to the pulse is compared to that induced by gravitational waves from astronomical sources.
Temperature-memory polymers remember the temperature, where they were deformed recently, enabled by broad thermal transitions. In this study, we explored a series of crosslinked poly[ethylene-co-(vinyl acetate)] networks (cPEVAs) comprising crystallizable polyethylene (PE) controlling units exhibiting a pronounced temperature-memory effect (TME) between 16 and 99 °C related to a broad melting transition (∼100 °C). The nanostructural changes in such cPEVAs during programming and activation of the TME were analyzed via in situ X-ray scattering and specific annealing experiments. Different contributions to the mechanism of memorizing high or low deformation temperatures (Tdeform) were observed in cPEVA, which can be associated to the average PE crystal sizes. At high deformation temperatures (>50 °C), newly formed PE crystals, which are established during cooling when fixing the temporary shape, dominated the TME mechanism. In contrast, at low Tdeform (<50 °C), corresponding to a cold drawing scenario, the deformation led preferably to a disruption of existing large crystals into smaller ones, which then fix the temporary shape upon cooling. The observed mechanism of memorizing a deformation temperature might enable the prediction of the TME behavior and the knowledge based design of other TMPs with crystallizable controlling units.
Recent experiments show that transcription factors (TFs) indeed use the facilitated diffusion mechanism to locate their target sequences on DNA in living bacteria cells: TFs alternate between sliding motion along DNA and relocation events through the cytoplasm. From simulations and theoretical analysis we study the TF-sliding motion for a large section of the DNA-sequence of a common E. coli strain, based on the two-state TF-model with a fast-sliding search state and a recognition state enabling target detection. For the probability to detect the target before dissociating from DNA the TF-search times self-consistently depend heavily on whether or not an auxiliary operator (an accessible sequence similar to the main operator) is present in the genome section. Importantly, within our model the extent to which the interconversion rates between search and recognition states depend on the underlying nucleotide sequence is varied. A moderate dependence maximises the capability to distinguish between the main operator and similar sequences. Moreover, these auxiliary operators serve as starting points for DNA looping with the main operator, yielding a spectrum of target detection times spanning several orders of magnitude. Auxiliary operators are shown to act as funnels facilitating target detection by TFs.
Stochastic Wilson
(2015)
We consider a simple Markovian class of the stochastic Wilson–Cowan type models of neuronal network dynamics, which incorporates stochastic delay caused by the existence of a refractory period of neurons. From the point of view of the dynamics of the individual elements, we are dealing with a network of non-Markovian stochastic two-state oscillators with memory, which are coupled globally in a mean-field fashion. This interrelation of a higher-dimensional Markovian and lower-dimensional non-Markovian dynamics is discussed in its relevance to the general problem of the network dynamics of complex elements possessing memory. The simplest model of this class is provided by a three-state Markovian neuron with one refractory state, which causes firing delay with an exponentially decaying memory within the two-state reduced model. This basic model is used to study critical avalanche dynamics (the noise sustained criticality) in a balanced feedforward network consisting of the excitatory and inhibitory neurons. Such avalanches emerge due to the network size dependent noise (mesoscopic noise). Numerical simulations reveal an intermediate power law in the distribution of avalanche sizes with the critical exponent around −1.16. We show that this power law is robust upon a variation of the refractory time over several orders of magnitude. However, the avalanche time distribution is biexponential. It does not reflect any genuine power law dependence.
We define and study in detail utraslow scaled Brownian motion (USBM) characterized by a time dependent diffusion coefficient of the form . For unconfined motion the mean squared displacement (MSD) of USBM exhibits an ultraslow, logarithmic growth as function of time, in contrast to the conventional scaled Brownian motion. In a harmonic potential the MSD of USBM does not saturate but asymptotically decays inverse-proportionally to time, reflecting the highly non-stationary character of the process. We show that the process is weakly non-ergodic in the sense that the time averaged MSD does not converge to the regular MSD even at long times, and for unconfined motion combines a linear lag time dependence with a logarithmic term. The weakly non-ergodic behaviour is quantified in terms of the ergodicity breaking parameter. The USBM process is also shown to be ageing: observables of the system depend on the time gap between initiation of the test particle and start of the measurement of its motion. Our analytical results are shown to agree excellently with extensive computer simulations.
Molecular motors pulling cargos in the viscoelastic cytosol: how power strokes beat subdiffusion
(2014)
The discovery of anomalous diffusion of larger biopolymers and submicron tracers such as endogenous granules, organelles, or virus capsids in living cells, attributed to the viscoelastic nature of the cytoplasm, provokes the question whether this complex environment equally impacts the active intracellular transport of submicron cargos by molecular motors such as kinesins: does the passive anomalous diffusion of free cargo always imply its anomalously slow active transport by motors, the mean transport distance along microtubule growing sublinearly rather than linearly in time? Here we analyze this question within the widely used two-state Brownian ratchet model of kinesin motors based on the continuous-state diffusion along microtubules driven by a flashing binding potential, where the cargo particle is elastically attached to the motor. Depending on the cargo size, the loading force, the amplitude of the binding potential, the turnover frequency of the molecular motor enzyme, and the linker stiffness we demonstrate that the motor transport may turn out either normal or anomalous, as indeed measured experimentally. We show how a highly efficient normal active transport mediated by motors may emerge despite the passive anomalous diffusion of the cargo, and study the intricate effects of the elastic linker. Under different, well specified conditions the microtubule-based motor transport becomes anomalously slow and thus significantly less efficient.