TY  - JOUR
A1  - Abdalla, Hassan E.
A1  - Aharonian, Felix A.
A1  - Benkhali, F. Ait
A1  - Angüner, Ekrem Oǧuzhan
A1  - Arakawa, M.
A1  - Arcaro, C.
A1  - Armand, C.
A1  - Arrieta, M.
A1  - Backes, M.
A1  - Barnard, M.
A1  - Becherini, Y.
A1  - Tjus, J. Becker
A1  - Berge, D.
A1  - Bernloehr, K.
A1  - Blackwell, R.
A1  - Bottcher, M.
A1  - Boisson, C.
A1  - Bolmont, J.
A1  - Bonnefoy, S.
A1  - Bordas, Pol
A1  - Bregeon, J.
A1  - Brun, F.
A1  - Brun, P.
A1  - Bryan, M.
A1  - Buechele, M.
A1  - Bulik, T.
A1  - Bylund, T.
A1  - Capasso, M.
A1  - Caroff, S.
A1  - Carosi, A.
A1  - Casanova, Sabrina
A1  - Cerruti, M.
A1  - Chakraborty, N.
A1  - Chand, T.
A1  - Chandra, S.
A1  - Chaves, R. C. G.
A1  - Chen, A.
A1  - Colafrancesco, S.
A1  - Condon, B.
A1  - Davids, I. D.
A1  - Deil, C.
A1  - Devin, J.
A1  - deWilt, P.
A1  - Dirson, L.
A1  - Djannati-Atai, A.
A1  - Dmytriiev, A.
A1  - Donath, A.
A1  - Doroshenko, V
A1  - Dyks, J.
A1  - Egberts, Kathrin
A1  - Emery, G.
A1  - Ernenwein, J-P
A1  - Eschbach, S.
A1  - Fegan, S.
A1  - Fiasson, A.
A1  - Fontaine, G.
A1  - Funk, S.
A1  - Fuessling, M.
A1  - Gabici, S.
A1  - Gallant, Y. A.
A1  - Gate, F.
A1  - Giavitto, G.
A1  - Glawion, D.
A1  - Glicenstein, J. F.
A1  - Gottschall, D.
A1  - Grondin, M-H
A1  - Hahn, J.
A1  - Haupt, M.
A1  - Heinzelmann, G.
A1  - Henri, G.
A1  - Hermann, G.
A1  - Hinton, James Anthony
A1  - Hofmann, W.
A1  - Hoischen, Clemens
A1  - Holch, Tim Lukas
A1  - Holler, M.
A1  - Horns, D.
A1  - Huber, D.
A1  - Iwasaki, H.
A1  - Jacholkowska, A.
A1  - Jamrozy, M.
A1  - Jankowsky, D.
A1  - Jankowsky, F.
A1  - Jouvin, L.
A1  - Jung-Richardt, I
A1  - Kastendieck, M. A.
A1  - Katarzynski, K.
A1  - Katsuragawa, M.
A1  - Katz, U.
A1  - Kerszberg, D.
A1  - Khangulyan, D.
A1  - Khelifi, B.
A1  - King, J.
A1  - Klepser, S.
A1  - Kluzniak, W.
A1  - Komin, Nu
A1  - Kosack, K.
A1  - Kraus, M.
A1  - Lamanna, G.
A1  - Lau, J.
A1  - Lefaucheur, J.
A1  - Lemiere, A.
A1  - Lemoine-Goumard, M.
A1  - Lenain, J-P
A1  - Leser, Eva
A1  - Lohse, T.
A1  - Lopez-Coto, R.
A1  - Lypova, I
A1  - Malyshev, D.
A1  - Marandon, V
A1  - Marcowith, Alexandre
A1  - Mariaud, C.
A1  - Marti-Devesa, G.
A1  - Marx, R.
A1  - Maurin, G.
A1  - Meintjes, P. J.
A1  - Mitchell, A. M. W.
A1  - Moderski, R.
A1  - Mohamed, M.
A1  - Mohrmann, L.
A1  - Moore, C.
A1  - Moulin, Emmanuel
A1  - Murach, T.
A1  - Nakashima, S.
A1  - de Naurois, M.
A1  - Ndiyavala, H.
A1  - Niederwanger, F.
A1  - Niemiec, J.
A1  - Oakes, L.
A1  - Odaka, H.
A1  - Ohm, S.
A1  - Ostrowski, M.
A1  - Oya, I
A1  - Panter, M.
A1  - Parsons, R. D.
A1  - Perennes, C.
A1  - Petrucci, P-O
A1  - Peyaud, B.
A1  - Piel, Q.
A1  - Pita, S.
A1  - Poireau, V
A1  - Noel, A. Priyana
A1  - Prokhorov, D. A.
A1  - Prokoph, H.
A1  - Puehlhofer, G.
A1  - Punch, M.
A1  - Quirrenbach, A.
A1  - Raab, S.
A1  - Rauth, R.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Renaud, M.
A1  - Rieger, F.
A1  - Rinchiuso, L.
A1  - Romoli, C.
A1  - Rowell, G.
A1  - Rudak, B.
A1  - Ruiz-Velasco, E.
A1  - Sahakian, V
A1  - Saito, S.
A1  - Sanchez, David M.
A1  - Santangelo, A.
A1  - Sasaki, M.
A1  - Schlickeiser, R.
A1  - Schussler, F.
A1  - Schulz, A.
A1  - Schutte, H.
A1  - Schwanke, U.
A1  - Schwemmer, S.
A1  - Seglar-Arroyo, M.
A1  - Senniappan, M.
A1  - Seyffert, A. S.
A1  - Shafi, N.
A1  - Shilon, I
A1  - Shiningayamwe, K.
A1  - Simoni, R.
A1  - Sinha, A.
A1  - Sol, H.
A1  - Specovius, A.
A1  - Spir-Jacob, M.
A1  - Stawarz, L.
A1  - Steenkamp, R.
A1  - Stegmann, Christian
A1  - Steppa, Constantin Beverly
A1  - Takahashi, T.
A1  - Tavernet, J-P
A1  - Tavernier, T.
A1  - Taylor, A. M.
A1  - Terrier, R.
A1  - Tibaldo, L.
A1  - Tiziani, D.
A1  - Tluczykont, M.
A1  - Trichard, C.
A1  - Tsirou, M.
A1  - Tsuji, N.
A1  - Tuffs, R.
A1  - Uchiyama, Y.
A1  - van der Walt, D. J.
A1  - van Eldik, C.
A1  - van Rensburg, C.
A1  - van Soelen, B.
A1  - Vasileiadis, G.
A1  - Veh, J.
A1  - Venter, C.
A1  - Vincent, P.
A1  - Vink, J.
A1  - Voisin, F.
A1  - Voelk, H. J.
A1  - Vuillaume, T.
A1  - Wadiasingh, Z.
A1  - Wagner, S. J.
A1  - Wagner, R. M.
A1  - White, R.
A1  - Wierzcholska, A.
A1  - Yang, R.
A1  - Yoneda, H.
A1  - Zaborov, D.
A1  - Zacharias, M.
A1  - Zanin, R.
A1  - Zdziarski, A. A.
A1  - Zech, Alraune
A1  - Zefi, F.
A1  - Ziegler, A.
A1  - Zorn, J.
A1  - Zywucka, N.
T1  - Particle transport within the pulsar wind nebula HESS J1825-137
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. We present a detailed view of the pulsar wind nebula (PWN) HESS J1825-137. We aim to constrain the mechanisms dominating the particle transport within the nebula, accounting for its anomalously large size and spectral characteristics. Aims. The nebula was studied using a deep exposure from over 12 years of H.E.S.S. I operation, together with data from H.E.S.S. II that improve the low-energy sensitivity. Enhanced energy-dependent morphological and spatially resolved spectral analyses probe the very high energy (VHE, E > 0.1 TeV) gamma-ray properties of the nebula. Methods. The nebula emission is revealed to extend out to 1.5 degrees from the pulsar, similar to 1.5 times farther than previously seen, making HESS J1825-137, with an intrinsic diameter of similar to 100 pc, potentially the largest gamma-ray PWN currently known. Characterising the strongly energy-dependent morphology of the nebula enables us to constrain the particle transport mechanisms. A dependence of the nebula extent with energy of R proportional to E alpha with alpha = -0.29 +/- 0.04(stat) +/- 0.05(sys) disfavours a pure diffusion scenario for particle transport within the nebula. The total gamma-ray flux of the nebula above 1 TeV is found to be (1.12 +/- 0.03(stat) +/- 0.25(sys)) +/- 10(-11) cm(-2) s(-1), corresponding to similar to 64% of the flux of the Crab nebula. Results. HESS J1825-137 is a PWN with clearly energy-dependent morphology at VHE gamma-ray energies. This source is used as a laboratory to investigate particle transport within intermediate-age PWNe. Based on deep observations of this highly spatially extended PWN, we produce a spectral map of the region that provides insights into the spectral variation within the nebula.
KW  - gamma rays: general
KW  - acceleration of particles
KW  - convection
KW  - diffusion
KW  - pulsars: general
Y1  - 2019
U6  - https://doi.org/10.1051/0004-6361/201834335
SN  - 1432-0746
VL  - 621
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Beta, Carsten
T1  - To turn or not to turn?
JF  - NEW JOURNAL OF PHYSICS
N2  - Bacteria typically swim in straight runs, interruped by sudden turning events. In particular, some species are limited to a reversal in the swimming direction as the only turning maneuver at their disposal. In a recent article, Grossmann et al (2016 New J. Phys. 18 043009) introduce a theoretical framework to analyze the diffusive properties of active particles following this type of run-and-reverse pattern. Based on a stochastic clock model to mimic the regulatory pathway that triggers reversal events, they show that a run-and-reverse swimmer can optimize its diffusive spreading by tuning the reversal rate according to the level of rotational noise. With their approach, they open up promising new perspectives of how to incorporate the dynamics of intracellular signaling into coarse-grained active particle descriptions.
KW  - bacterial swimming
KW  - random walks
KW  - diffusion
KW  - stochastic models
Y1  - 2016
U6  - https://doi.org/10.1088/1367-2630/18/5/051003
SN  - 1367-2630
VL  - 18
SP  - 1
EP  - 17
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Cai, Gaochao
A1  - Tötzke, Christian
A1  - Kaestner, Anders
A1  - Ahmed, Mutez Ali
T1  - Quantification of root water uptake and redistribution using neutron imaging: a review and future directions
JF  - The plant journal
N2  - Quantifying root water uptake is essential to understanding plant water use and responses to different environmental conditions. However, non-destructive measurement of water transport and related hydraulics in the soil-root system remains a challenge. 
Neutron imaging, with its high sensitivity to hydrogen, has become an unparalleled tool to visualize and quantify root water uptake in vivo. In combination with isotopes (e.g., deuterated water) and a diffusion-convection model, root water uptake and hydraulic redistribution in root and soil can be quantified. 
Here, we review recent advances in utilizing neutron imaging to visualize and quantify root water uptake, hydraulic redistribution in roots and soil, and root hydraulic properties of different plant species. 
Under uniform soil moisture distributions, neutron radiographic studies have shown that water uptake was not uniform along the root and depended on both root type and age. For both tap (e.g., lupine [Lupinus albus L.]) and fibrous (e.g., maize [Zea mays L.]) root systems, water was mainly taken up through lateral roots. In mature maize, the location of water uptake shifted from seminal roots and their laterals to crown/nodal roots and their laterals. 
Under non-uniform soil moisture distributions, part of the water taken up during the daytime maintained the growth of crown/nodal roots in the upper, drier soil layers. Ultra-fast neutron tomography provides new insights into 3D water movement in soil and roots. We discuss the limitations of using neutron imaging and propose future directions to utilize neutron imaging to advance our understanding of root water uptake and soil-root interactions.
KW  - attenuation coefficient
KW  - convection
KW  - diffusion
KW  - radiography
KW  - root hydraulics
KW  - root water uptake
KW  - tomography
Y1  - 2022
U6  - https://doi.org/10.1111/tpj.15839
SN  - 0960-7412
SN  - 1365-313X
VL  - 111
IS  - 2
SP  - 348
EP  - 359
PB  - Wiley-Blackwell
CY  - Oxford [u.a.]
ER  - 
TY  - JOUR
A1  - Chechkin, Aleksei V.
A1  - Lenz, F.
A1  - Klages, Rainer
T1  - Normal and anomalous fluctuation relations for gaussian stochastic dynamics
JF  - Journal of statistical mechanics: theory and experiment
N2  - We study transient work fluctuation relations (FRs) for Gaussian stochastic systems generating anomalous diffusion. For this purpose we use a Langevin approach by employing two different types of additive noise: (i) internal noise where the fluctuation dissipation relation of the second kind (FDR II) holds, and (ii) external noise without FDR II. For internal noise we demonstrate that the existence of FDR II implies the existence of the fluctuation dissipation relation of the first kind (FDR I), which in turn leads to conventional (normal) forms of transient work FRs. For systems driven by external noise we obtain violations of normal FRs, which we call anomalous FRs. We derive them in the long-time limit and demonstrate the existence of logarithmic factors in FRs for intermediate times. We also outline possible experimental verifications.
KW  - stochastic particle dynamics (theory)
KW  - fluctuations (theory)
KW  - stochastic processes (theory)
KW  - diffusion
Y1  - 2012
U6  - https://doi.org/10.1088/1742-5468/2012/11/L11001
SN  - 1742-5468
IS  - 4
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Chen, Xuhui
A1  - Pohl, Martin
A1  - Bottcher, Markus
A1  - Gao, Shan
T1  - Particle diffusion and localized acceleration in inhomogeneous AGN jets - II. Stochastic variation
JF  - Monthly notices of the Royal Astronomical Society
N2  - We study the stochastic variation of blazar emission under a 2D spatially resolved leptonic jet model we previously developed. Random events of particle acceleration and injection in small zones within the emission region are assumed to be responsible for flux variations. In addition to producing spectral energy distributions that describe the observed flux of Mrk 421, we further analyse the timing properties of the simulated light curves, such as the power spectral density (PSD) at different bands, flux-flux correlations, aswell as the cross-correlation function between X-rays and TeV gamma-rays. We find spectral breaks in the PSD at a time-scale comparable to the dominant characteristic time-scale in the system, which is usually the predefined decay time-scale of an acceleration event. Cooling imposes a delay, and so PSDs taken at lower energy bands in each emission component (synchrotron or inverse Compton) generally break at longer time-scales. The flux-flux correlation between X-rays and TeV gamma-rays can be either quadratic or linear, depending on whether or not there are large variation of the injection into the particle acceleration process. When the relationship is quadratic, the TeV flares lag the X-ray flares, and the optical and GeV flares are large enough to be comparable to the ones in X-ray. When the relationship is linear, the lags are insignificant, and the optical and GeV flares are small.
KW  - acceleration of particles
KW  - diffusion
KW  - radiation mechanisms: non-thermal
KW  - galaxies: active
KW  - BL Lacertae objects: individual: Mrk 421
KW  - galaxies: jets
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw528
SN  - 0035-8711
SN  - 1365-2966
VL  - 458
SP  - 3260
EP  - 3271
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Chen, Xuhui
A1  - Pohl, Martin
A1  - Böttcher, Markus
T1  - Particle diffusion and localized acceleration in inhomogeneous AGN jets - I. Steady-state spectra
JF  - Monthly notices of the Royal Astronomical Society
N2  - We study the acceleration, transport, and emission of particles in relativistic jets. Localized stochastic particle acceleration, spatial diffusion, and synchrotron as well as synchrotron self-Compton (SSC) emission are considered in a leptonic model. To account for inhomogeneity, we use a 2D axisymmetric cylindrical geometry for both relativistic electrons and magnetic field. In this first phase of our work, we focus on steady-state spectra that develop from a time-dependent model. We demonstrate that small isolated acceleration region in a much larger emission volume are sufficient to accelerate particles to high energy. Diffusive escape from these small regions provides a natural explanation for the spectral form of the jet emission. The location of the acceleration regions within the jet is found to affect the cooling break of the spectrum in this diffusive model. Diffusion-caused energy-dependent inhomogeneity in the jets predicts that the SSC spectrum is harder than the synchrotron spectrum. There can also be a spectral hardening towards the high-energy section of the synchrotron spectrum, if particle escape is relatively slow. These two spectral hardening effects indicate that the jet inhomogeneity might be a natural explanation for the unexpected hard. gamma-ray spectra observed in some blazars.
KW  - acceleration of particles
KW  - diffusion
KW  - radiation mechanisms: non-thermal
KW  - galaxies:active
KW  - galaxies: jets
Y1  - 2015
U6  - https://doi.org/10.1093/mnras/stu2438
SN  - 0035-8711
SN  - 1365-2966
VL  - 447
IS  - 1
SP  - 530
EP  - 544
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Ergodicity breaking, ageing, and confinement in generalized diffusion processes with position and time dependent diffusivity
JF  - Journal of statistical mechanics: theory and experiment
N2  - We study generalized anomalous diffusion processes whose diffusion coefficient D(x, t) similar to D-0x(alpha)t(beta) depends on both the position x of the test particle and the process time t. This process thus combines the features of scaled Brownian motion and heterogeneous diffusion parent processes. We compute the ensemble and time averaged mean squared displacements of this generalized diffusion process. The scaling exponent of the ensemble averaged mean squared displacement is shown to be the product of the critical exponents of the parent processes, and describes both subdiffusive and superdiffusive systems. We quantify the amplitude fluctuations of the time averaged mean squared displacement as function of the length of the time series and the lag time. In particular, we observe a weak ergodicity breaking of this generalized diffusion process: even in the long time limit the ensemble and time averaged mean squared displacements are strictly disparate. When we start to observe this process some time after its initiation we observe distinct features of ageing. We derive a universal ageing factor for the time averaged mean squared displacement containing all information on the ageing time and the measurement time. External confinement is shown to alter the magnitudes and statistics of the ensemble and time averaged mean squared displacements.
KW  - diffusion
Y1  - 2015
U6  - https://doi.org/10.1088/1742-5468/2015/05/P05010
SN  - 1742-5468
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Vinod, Deepak
A1  - Aghion, Erez
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Time averaging, ageing and delay analysis of financial time series
JF  - New journal of physics
N2  - We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black–Scholes–Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics.
KW  - time averaging
KW  - diffusion
KW  - geometric Brownian motion
KW  - financial time series
Y1  - 2017
U6  - https://doi.org/10.1088/1367-2630/aa7199
SN  - 1367-2630
VL  - 19
SP  - 1
EP  - 11
PB  - IOP
CY  - London
ER  - 
TY  - GEN
A1  - Cherstvy, Andrey G.
A1  - Vinod, Deepak
A1  - Aghion, Erez
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Time averaging, ageing and delay analysis of financial time series
N2  - We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black–Scholes–Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 347 
KW  - diffusion
KW  - financial time series
KW  - geometric Brownian motion
KW  - time averaging
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-400541
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Vinod, Deepak
A1  - Aghion, Erez
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Time averaging, ageing and delay analysis of financial time series
JF  - New journal of physics : the open-access journal for physics
N2  - We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black-Scholes-Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics.
KW  - time averaging
KW  - diffusion
KW  - geometric Brownian motion
KW  - financial time series
Y1  - 2017
U6  - https://doi.org/10.1088/1367-2630/aa7199
SN  - 1367-2630
VL  - 19
SP  - 135
EP  - 147
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Dal Bianco, Andrea
A1  - Wischke, Christian
A1  - Zhou, Shuo
A1  - Lendlein, Andreas
T1  - Controlling surface properties and permeability of polyglycerol network films
JF  - Polymers for advanced technologies
N2  - While branched polyglycerol (PG)-based molecules are well established as hydrophilic particles, the capacity of utilizing PG in bulk materials and opportunities arising by their further surface functionalization have only recently been considered. Here we investigated how the mold used in PG network synthesis may affect surface composition and how the permeability of substances through PG can be controlled by altering network structure, i.e. introducing 20mol% oligoethylene glycol (OEG) bifunctional spacer molecules. Overall, PG-based bulk network materials were shown to be tailorable, hydrophilic, low swelling and relatively stiff polyether-based materials, with low impact of salt onto material properties. Based on these features, but also on the principal capacity of free hydroxyl groups to be used for functionalization reactions, these materials may be an interesting platform for medical and technical applications, e.g. as diffusion-rate controlling membrane in aqueous environment. Copyright (c) 2016 John Wiley & Sons, Ltd.
KW  - polyglycerol
KW  - surface properties
KW  - diffusion
KW  - network structure
Y1  - 2017
U6  - https://doi.org/10.1002/pat.3917
SN  - 1042-7147
SN  - 1099-1581
VL  - 28
SP  - 1263
EP  - 1268
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Doerries, Timo J.
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Apparent anomalous diffusion and non-Gaussian distributions in a simple mobile-immobile transport model with Poissonian switching
JF  - Interface : journal of the Royal Society
N2  - We analyse mobile-immobile transport of particles that switch between the mobile and immobile phases with finite rates. Despite this seemingly simple assumption of Poissonian switching, we unveil a rich transport dynamics including significant transient anomalous diffusion and non-Gaussian displacement distributions. Our discussion is based on experimental parameters for tau proteins in neuronal cells, but the results obtained here are expected to be of relevance for a broad class of processes in complex systems. Specifically, we obtain that, when the mean binding time is significantly longer than the mean mobile time, transient anomalous diffusion is observed at short and intermediate time scales, with a strong dependence on the fraction of initially mobile and immobile particles. We unveil a Laplace distribution of particle displacements at relevant intermediate time scales. For any initial fraction of mobile particles, the respective mean squared displacement (MSD) displays a plateau. Moreover, we demonstrate a short-time cubic time dependence of the MSD for immobile tracers when initially all particles are immobile.
KW  - diffusion
KW  - mobile-immobile model
KW  - tau proteins
Y1  - 2022
U6  - https://doi.org/10.1098/rsif.2022.0233
SN  - 1742-5689
SN  - 1742-5662
VL  - 19
IS  - 192
PB  - Royal Society
CY  - London
ER  - 
TY  - JOUR
A1  - Dunsing, Valentin
A1  - Petrich, Annett
A1  - Chiantia, Salvatore
T1  - Multicolor fluorescence fluctuation spectroscopy in living cells via spectral detection
JF  - eLife
N2  - Signaling pathways in biological systems rely on specific interactions between multiple biomolecules. Fluorescence fluctuation spectroscopy provides a powerful toolbox to quantify such interactions directly in living cells. Cross-correlation analysis of spectrally separated fluctuations provides information about intermolecular interactions but is usually limited to two fluorophore species. Here, we present scanning fluorescence spectral correlation spectroscopy (SFSCS), a versatile approach that can be implemented on commercial confocal microscopes, allowing the investigation of interactions between multiple protein species at the plasma membrane. We demonstrate that SFSCS enables cross-talk-free cross-correlation, diffusion, and oligomerization analysis of up to four protein species labeled with strongly overlapping fluorophores. As an example, we investigate the interactions of influenza A virus (IAV) matrix protein 2 with two cellular host factors simultaneously. We furthermore apply raster spectral image correlation spectroscopy for the simultaneous analysis of up to four species and determine the stoichiometry of ternary IAV polymerase complexes in the cell nucleus.
KW  - fluorescence
KW  - optical microscopy
KW  - virus assembly
KW  - protein-protein
KW  - interactions
KW  - diffusion
KW  - Viruses
Y1  - 2021
U6  - https://doi.org/10.7554/eLife.69687
SN  - 2050-084X
VL  - 10
PB  - eLife Sciences Publications
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Gallego-Llorente, Marcos
A1  - Sarah, Connell
A1  - Jones, Eppie R.
A1  - Merrett, Deborah C.
A1  - Jeon, Y.
A1  - Eriksson, Anders
A1  - Siska, Veronika
A1  - Gamba, Cristina
A1  - Meiklejohn, Christopher
A1  - Beyer, Robert
A1  - Jeon, Sungwon
A1  - Cho, Yun Sung
A1  - Hofreiter, Michael
A1  - Bhak, Jong
A1  - Manica, Andrea
A1  - Pinhasi, Ron
T1  - The genetics of an early Neolithic pastoralist from the Zagros, Iran
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The agricultural transition profoundly changed human societies. We sequenced and analysed the first genome (1.39x) of an early Neolithic woman from Ganj Dareh, in the Zagros Mountains of Iran, a site with early evidence for an economy based on goat herding, ca. 10,000 BP. We show that Western Iran was inhabited by a population genetically most similar to hunter-gatherers from the Caucasus, but distinct from the Neolithic Anatolian people who later brought food production into Europe. The inhabitants of Ganj Dareh made little direct genetic contribution to modern European populations, suggesting those of the Central Zagros were somewhat isolated from other populations of the Fertile Crescent. Runs of homozygosity are of a similar length to those from Neolithic farmers, and shorter than those of Caucasus and Western Hunter-Gatherers, suggesting that the inhabitants of Ganj Dareh did not undergo the large population bottleneck suffered by their northern neighbours. While some degree of cultural diffusion between Anatolia, Western Iran and other neighbouring regions is possible, the genetic dissimilarity between early Anatolian farmers and the inhabitants of Ganj Dareh supports a model in which Neolithic societies in these areas were distinct.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 952 
KW  - whole-genome association
KW  - ancient
KW  - domestication
KW  - agriculture
KW  - mountains
KW  - diffusion
KW  - migration
KW  - admixture
KW  - patterns
KW  - sequence
KW  - archaeology
KW  - biological anthropology
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-439355
SN  - 1866-8372
IS  - 952
ER  - 
TY  - GEN
A1  - Granado, Felipe Le Vot
A1  - Abad, Enrique
A1  - Metzler, Ralf
A1  - Yuste, Santos B.
T1  - Continuous time random walk in a velocity field
BT  - role of domain growth, Galilei-invariant advection-diffusion, and kinetics of particle mixing
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - 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.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1005 
KW  - diffusion
KW  - expanding medium
KW  - continuous time random walk
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-479997
SN  - 1866-8372
IS  - 1005
SP  - 28
ER  - 
TY  - JOUR
A1  - Granado, Felipe Le Vot
A1  - Abad, Enrique
A1  - Metzler, Ralf
A1  - Yuste, Santos B.
T1  - Continuous time random walk in a velocity field
BT  - role of domain growth, Galilei-invariant advection-diffusion, and kinetics of particle mixing
JF  - New Journal of Physics
N2  - 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.
KW  - diffusion
KW  - expanding medium
KW  - continuous time random walk
Y1  - 2020
U6  - https://doi.org/10.1088/1367-2630/ab9ae2
SN  - 1367-2630
VL  - 22
PB  - Dt. Physikalische Ges.
CY  - Bad Honnef
ER  - 
TY  - GEN
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
T1  - Distribution of first-reaction times with target regions on boundaries of shell-like domains
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - We study the probability density function (PDF) of the first-reaction times between a diffusive ligand and a membrane-bound, immobile imperfect target region in a restricted 'onion-shell' geometry bounded by two nested membranes of arbitrary shapes. For such a setting, encountered in diverse molecular signal transduction pathways or in the narrow escape problem with additional steric constraints, we derive an exact spectral form of the PDF, as well as present its approximate form calculated by help of the so-called self-consistent approximation. For a particular case when the nested domains are concentric spheres, we get a fully explicit form of the approximated PDF, assess the accuracy of this approximation, and discuss various facets of the obtained distributions. Our results can be straightforwardly applied to describe the PDF of the terminal reaction event in multi-stage signal transduction processes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1255 
KW  - diffusion
KW  - first-passage time
KW  - first-reaction time
KW  - shell-like geometries
KW  - approximate methods
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-557542
SN  - 1866-8372
SP  - 1
EP  - 23
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
T1  - Distribution of first-reaction times with target regions on boundaries of shell-like domains
JF  - New Journal of Physics (NJP)
N2  - We study the probability density function (PDF) of the first-reaction times between a diffusive ligand and a membrane-bound, immobile imperfect target region in a restricted 'onion-shell' geometry bounded by two nested membranes of arbitrary shapes. For such a setting, encountered in diverse molecular signal transduction pathways or in the narrow escape problem with additional steric constraints, we derive an exact spectral form of the PDF, as well as present its approximate form calculated by help of the so-called self-consistent approximation. For a particular case when the nested domains are concentric spheres, we get a fully explicit form of the approximated PDF, assess the accuracy of this approximation, and discuss various facets of the obtained distributions. Our results can be straightforwardly applied to describe the PDF of the terminal reaction event in multi-stage signal transduction processes.
KW  - diffusion
KW  - first-passage time
KW  - first-reaction time
KW  - shell-like geometries
KW  - approximate methods
Y1  - 2021
U6  - https://doi.org/10.1088/1367-2630/ac4282
SN  - 1367-2630
VL  - 2021
SP  - 1
EP  - 23
PB  - IOP Publishing
CY  - London
ET  - 23
ER  - 
TY  - JOUR
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
T1  - A molecular relay race: sequential first-passage events to the terminal reaction centre in a cascade of diffusion controlled processes
JF  - New Journal of Physics (NJP)
N2  - We consider a sequential cascade of molecular first-reaction events towards a terminal reaction centre in which each reaction step is controlled by diffusive motion of the particles. The model studied here represents a typical reaction setting encountered in diverse molecular biology systems, in which, e.g. a signal transduction proceeds via a series of consecutive 'messengers': the first messenger has to find its respective immobile target site triggering a launch of the second messenger, the second messenger seeks its own target site and provokes a launch of the third messenger and so on, resembling a relay race in human competitions. For such a molecular relay race taking place in infinite one-, two- and three-dimensional systems, we find exact expressions for the probability density function of the time instant of the terminal reaction event, conditioned on preceding successful reaction events on an ordered array of target sites. The obtained expressions pertain to the most general conditions: number of intermediate stages and the corresponding diffusion coefficients, the sizes of the target sites, the distances between them, as well as their reactivities are arbitrary.
KW  - diffusion
KW  - reaction cascade
KW  - first passage time
Y1  - 2021
U6  - https://doi.org/10.1088/1367-2630/ac1e42
SN  - 1367-2630
VL  - 23
PB  - IOP - Institute of Physics Publishing
CY  - Bristol
ER  - 
TY  - GEN
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
T1  - From single-particle stochastic kinetics to macroscopic reaction rates
BT  - fastest first-passage time of N random walkers
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - We consider the first-passage problem for N identical independent particles that are initially released uniformly in a finite domain Ω and then diffuse toward a reactive area Γ, which can be part of the outer boundary of Ω or a reaction centre in the interior of Ω. For both cases of perfect and partial reactions, we obtain the explicit formulas for the first two moments of the fastest first-passage time (fFPT), i.e., the time when the first out of the N particles reacts with Γ. Moreover, we investigate the full probability density of the fFPT. We discuss a significant role of the initial condition in the scaling of the average fFPT with the particle number N, namely, a much stronger dependence (1/N and 1/N² for partially and perfectly reactive targets, respectively), in contrast to the well known inverse-logarithmic behaviour found when all particles are released from the same fixed point. We combine analytic solutions with scaling arguments and stochastic simulations to rationalise our results, which open new perspectives for studying the relevance of multiple searchers in various situations of molecular reactions, in particular, in living cells.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1018 
KW  - diffusion
KW  - first-passage
KW  - fastest first-passage time of N walkers
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-484059
SN  - 1866-8372
IS  - 1018
ER  - 
TY  - JOUR
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
T1  - From single-particle stochastic kinetics to macroscopic reaction rates
BT  - fastest first-passage time of N random walkers
JF  - New Journal of Physics
N2  - We consider the first-passage problem for N identical independent particles that are initially released uniformly in a finite domain Ω and then diffuse toward a reactive area Γ, which can be part of the outer boundary of Ω or a reaction centre in the interior of Ω. For both cases of perfect and partial reactions, we obtain the explicit formulas for the first two moments of the fastest first-passage time (fFPT), i.e., the time when the first out of the N particles reacts with Γ. Moreover, we investigate the full probability density of the fFPT. We discuss a significant role of the initial condition in the scaling of the average fFPT with the particle number N, namely, a much stronger dependence (1/N and 1/N² for partially and perfectly reactive targets, respectively), in contrast to the well known inverse-logarithmic behaviour found when all particles are released from the same fixed point. We combine analytic solutions with scaling arguments and stochastic simulations to rationalise our results, which open new perspectives for studying the relevance of multiple searchers in various situations of molecular reactions, in particular, in living cells.
KW  - diffusion
KW  - first-passage
KW  - fastest first-passage time of N walkers
Y1  - 2020
U6  - https://doi.org/10.1088/1367-2630/abb1de
SN  - 1367-2630
VL  - 22
PB  - Dt. Physikalische Ges.
CY  - Bad Honnef
ER  - 
TY  - GEN
A1  - Grebenkov, Denis S.
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
T1  - A molecular relay race: sequential first-passage events to the terminal reaction centre in a cascade of diffusion controlled processes
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - We consider a sequential cascade of molecular first-reaction events towards a terminal reaction centre in which each reaction step is controlled by diffusive motion of the particles. The model studied here represents a typical reaction setting encountered in diverse molecular biology systems, in which, e.g. a signal transduction proceeds via a series of consecutive 'messengers': the first messenger has to find its respective immobile target site triggering a launch of the second messenger, the second messenger seeks its own target site and provokes a launch of the third messenger and so on, resembling a relay race in human competitions. For such a molecular relay race taking place in infinite one-, two- and three-dimensional systems, we find exact expressions for the probability density function of the time instant of the terminal reaction event, conditioned on preceding successful reaction events on an ordered array of target sites. The obtained expressions pertain to the most general conditions: number of intermediate stages and the corresponding diffusion coefficients, the sizes of the target sites, the distances between them, as well as their reactivities are arbitrary.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1159 
KW  - diffusion
KW  - reaction cascade
KW  - first passage time
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-521942
SN  - 1866-8372
ER  - 
TY  - JOUR
A1  - Grebenkov, Denis S.
A1  - Sposini, Vittoria
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
A1  - Seno, Flavio
T1  - Exact distributions of the maximum and range of random diffusivity processes
JF  - New Journal of Physics
N2  - We study the extremal properties of a stochastic process xt defined by the Langevin equation ẋₜ =√2Dₜ ξₜ, in which ξt is a Gaussian white noise with zero mean and Dₜ is a stochastic‘diffusivity’, defined as a functional of independent Brownian motion Bₜ.We focus on threechoices for the random diffusivity Dₜ: cut-off Brownian motion, Dₜt ∼ Θ(Bₜ), where Θ(x) is the Heaviside step function; geometric Brownian motion, Dₜ ∼ exp(−Bₜ); and a superdiffusive process based on squared Brownian motion, Dₜ ∼ B²ₜ. For these cases we derive exact expressions for the probability density functions of the maximal positive displacement and of the range of the process xₜ on the time interval ₜ ∈ (0, T).We discuss the asymptotic behaviours of the associated probability density functions, compare these against the behaviour of the corresponding properties of standard Brownian motion with constant diffusivity (Dₜ = D0) and also analyse the typical behaviour of the probability density functions which is observed for a majority of realisations of the stochastic diffusivity process.
KW  - random diffusivity
KW  - extremal values
KW  - maximum and range
KW  - diffusion
KW  - Brownian motion
Y1  - 2021
U6  - https://doi.org/10.1088/1367-2630/abd313
SN  - 1367-2630
VL  - 23
PB  - Dt. Physikalische Ges.
CY  - Bad Honnef
ER  - 
TY  - GEN
A1  - Grebenkov, Denis S.
A1  - Sposini, Vittoria
A1  - Metzler, Ralf
A1  - Oshanin, Gleb
A1  - Seno, Flavio
T1  - Exact distributions of the maximum and range of random diffusivity processes
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - We study the extremal properties of a stochastic process xt defined by the Langevin equation ẋₜ =√2Dₜ ξₜ, in which ξt is a Gaussian white noise with zero mean and Dₜ is a stochastic‘diffusivity’, defined as a functional of independent Brownian motion Bₜ.We focus on threechoices for the random diffusivity Dₜ: cut-off Brownian motion, Dₜt ∼ Θ(Bₜ), where Θ(x) is the Heaviside step function; geometric Brownian motion, Dₜ ∼ exp(−Bₜ); and a superdiffusive process based on squared Brownian motion, Dₜ ∼ B²ₜ. For these cases we derive exact expressions for the probability density functions of the maximal positive displacement and of the range of the process xₜ on the time interval ₜ ∈ (0, T).We discuss the asymptotic behaviours of the associated probability density functions, compare these against the behaviour of the corresponding properties of standard Brownian motion with constant diffusivity (Dₜ = D0) and also analyse the typical behaviour of the probability density functions which is observed for a majority of realisations of the stochastic diffusivity process.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1142 
KW  - random diffusivity
KW  - extremal values
KW  - maximum and range
KW  - diffusion
KW  - Brownian motion
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-503976
SN  - 1866-8372
IS  - 1142
ER  - 
TY  - THES
A1  - Grätz, Fabio M.
T1  - Nonlinear diffusion in granular gases and dense planetary rings
N2  - Small moonlets or moons embedded in dense planetary rings create S-shaped density modulations called propellers if their masses are smaller than a certain threshold, alternatively they create a circumferential gap in the disk if the embedded body’s mass exceeds this threshold (Spahn and Sremčević, 2000). The gravitational perturber scatters the ring particles, depletes the disk’s density, and, thus, clears a gap, whereas counteracting viscous diffusion of the ring material has the tendency to close the created gap, thereby forming a propeller. Propeller objects were predicted by Spahn and Sremčević (2000) and Sremčević et al. (2002) and were later discovered by the Cassini space probe (Tiscareno et al., 2006, Sremčević et al., 2007, Tiscareno et al., 2008, and Tiscareno et al., 2010). The ring moons Pan and Daphnis are massive enough to maintain the circumferential Encke and Keeler gaps in Saturn’s A ring and were detected by Showalter (1991) and Porco (2005) in Voyager and Cassini images, respectively. In this thesis, a nonlinear axisymmetric diffusion model is developed to describe radial density profiles of circumferential gaps in planetary rings created by embedded moons (Grätz et al., 2018). The model accounts for the gravitational scattering of the ring particles by the embedded moon and for the counteracting viscous diffusion of the ring matter back into the gap. With test particle simulations it is shown that the scattering of the ring particles passing the moon is larger for small impact parameters than estimated by Goldreich and Tremaine (1980). This is especially significant for the modeling of the Keeler gap. The model is applied to the Encke and Keeler gaps with the aim to estimate the shear viscosity of the ring in their vicinities. In addition, the model is used to analyze whether tiny icy moons whose dimensions lie below Cassini’s resolution capabilities would be able to cause the poorly understood gap structure of the C ring and the Cassini Division. One of the most intriguing facets of Saturn’s rings are the extremely sharp edges of the Encke and Keeler gaps: UVIS-scans of their gap edges show that the optical depth drops from order unity to zero over a range of far less than 100 m, a spatial scale comparable to the ring’s vertical extent. This occurs despite the fact that the range over which a moon transfers angular momentum onto the ring material is much larger. Borderies et al. (1982, 1989) have shown that this striking feature is likely related to the local reversal of the usually outward-directed viscous transport of angular momentum in strongly perturbed regions. We have revised the Borderies et al. (1989) model using a granular flow model to define the shear and bulk viscosities, ν and ζ, in order to incorporate the angular momentum flux reversal effect into the axisymmetric diffusion model for circumferential gaps presented in this thesis (Grätz et al., 2019). The sharp Encke and Keeler gap edges are modeled and conclusions regarding the shear and bulk viscosities of the ring are discussed. Finally, we explore the question of whether the radial density profile of the central and outer A ring, recently measured by Tiscareno and Harris (2018) in the highest resolution to date, and in particular, the sharp outer A ring edge can be modeled consistently from the balance of gravitational scattering by several outer moons and the mass and momentum transport. To this aim, the developed model is extended to account for the inward drifts caused by multiple discrete and overlapping resonances with multiple outer satellites and is then used to hydrodynamically simulate the normalized surface mass density profile of the A ring. This section of the thesis is based on studies by Tajeddine et al. (2017a) who recently discussed the common misconception that the 7:6 resonance with Janus alone maintains the outer A ring edge, showing that the combined effort of several resonances with several outer moons is required to confine the A ring as observed by the Cassini spacecraft.
KW  - celestial mechanics
KW  - diffusion
KW  - hydrodynamics
KW  - planets and satellites: rings
KW  - scattering
Y1  - 2020
ER  - 
TY  - JOUR
A1  - Grätz, Fabio M.
A1  - Seiss, Martin
A1  - Spahn, Frank
T1  - Formation of moon-induced gaps in dense planetary rings
BT  - application to the rings of saturn
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We develop an axisymmetric diffusion model to describe radial density profiles in the vicinity of tiny moons embedded in planetary rings. Our diffusion model accounts for the gravitational scattering of the ring particles by an embedded moon and for the viscous diffusion of the ring matter back into the gap. With test particle simulations, we show that the scattering of the ring particles passing the moon is larger for small impact parameters than estimated by Goldreich & Tremaine and Namouni. This is significant for modeling the Keeler gap. We apply our model to the gaps of the moons Pan and Daphnis embedded in the outer A ring of Saturn with the aim to estimate the shear viscosity of the ring in the vicinity of the Encke and Keeler gap. In addition, we analyze whether tiny icy moons whose dimensions lie below Cassini's resolution capabilities would be able to explain the gap structure of the C ring and the Cassini division.
KW  - diffusion
KW  - planets and satellites: rings
KW  - scattering
Y1  - 2018
U6  - https://doi.org/10.3847/1538-4357/aace00
SN  - 0004-637X
SN  - 1538-4357
VL  - 862
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Grätz, Fabio M.
A1  - Seiß, Martin
A1  - Schmidt, Jürgen
A1  - Colwell, Joshua
A1  - Spahn, Frank
T1  - Sharp Gap Edges in Dense Planetary Rings
BT  - an Axisymmetric Diffusion Model
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - One of the most intriguing facets of Saturn's rings are the sharp edges of gaps in the rings where the surface density abruptly drops to zero. This is despite of the fact that the range over which a moon transfers angular momentum onto the ring material is much larger. Recent UVIS-scans of the edges of the Encke and Keeler gap show that this drop occurs over a range approximately equal to the rings' thickness. Borderies et al. show that this striking feature is likely related to the local reversal of the usually outward directed viscous transport of angular momentum in strongly perturbed regions. In this article we revise the Borderies et al. model using a granular flow model to define the shear and bulk viscosities, ν and ζ, and incorporate the angular momentum flux reversal effect into the axisymmetric diffusion model we developed for gaps in dense planetary rings. Finally, we apply our model to the Encke and Keeler division in order to estimate the shear and bulk viscosities in the vicinity of both gaps
KW  - celestial mechanics
KW  - diffusion
KW  - hydrodynamics
KW  - planets and satellites: rings
KW  - scattering
Y1  - 2019
U6  - https://doi.org/10.3847/1538-4357/ab007e
SN  - 0004-637X
SN  - 1538-4357
VL  - 872
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Guggenberger, Tobias
A1  - Chechkin, Aleksei
A1  - Metzler, Ralf
T1  - Absence of stationary states and non-Boltzmann distributions of fractional Brownian motion in shallow external potentials
JF  - New journal of physics : the open-access journal for physics
N2  - We study the diffusive motion of a particle in a subharmonic potential of the form U(x) = |x|( c ) (0 < c < 2) driven by long-range correlated, stationary fractional Gaussian noise xi ( alpha )(t) with 0 < alpha <= 2. In the absence of the potential the particle exhibits free fractional Brownian motion with anomalous diffusion exponent alpha. While for an harmonic external potential the dynamics converges to a Gaussian stationary state, from extensive numerical analysis we here demonstrate that stationary states for shallower than harmonic potentials exist only as long as the relation c > 2(1 - 1/alpha) holds. We analyse the motion in terms of the mean squared displacement and (when it exists) the stationary probability density function. Moreover we discuss analogies of non-stationarity of Levy flights in shallow external potentials.
KW  - diffusion
KW  - Boltzmann distribution
KW  - fractional Brownian motion
Y1  - 2022
U6  - https://doi.org/10.1088/1367-2630/ac7b3c
SN  - 1367-2630
VL  - 24
IS  - 7
PB  - Dt. Physikalische Ges.
CY  - [Bad Honnef]
ER  - 
TY  - THES
A1  - Hennig, Theresa
T1  - Uranium migration in the Opalinus Clay quantified on the host rock scale with reactive transport simulations
T1  - Uranmigration im Opalinuston quantifiziert für die Wirtsgesteinsskala mit reaktiven Transportsimulationen
N2  - Humankind and their environment need to be protected from the harmful effects of spent nuclear fuel, and therefore disposal in deep geological formations is favoured worldwide. Suitability of potential host rocks is evaluated, among others, by the retention capacity with respect to radionuclides. Safety assessments are based on the quantification of radionuclide migration lengths with numerical simulations as experiments cannot cover the required temporal (1 Ma) and spatial scales (>100 m). 

Aim of the present thesis is to assess the migration of uranium, a geochemically complex radionuclide, in the potential host rock Opalinus Clay. Radionuclide migration in clay formations is governed by diffusion due to their low permeability and retarded by sorption. Both processes highly depend on pore water geochemistry and mineralogy that vary between different facies. Diffusion is quantified with the single-component (SC) approach using one diffusion coefficient for all species and the process-based multi-component (MC) option. With this, each species is assigned its own diffusion coefficient and the interaction with the diffuse double layer is taken into account. Sorption is integrated via a bottom-up approach using mechanistic surface complexation models and cation exchange. Therefore, reactive transport simulations are conducted with the geochemical code PHREEQC to quantify uranium migration, i.e. diffusion and sorption, as a function of mineralogical and geochemical heterogeneities on the host rock scale.

Sorption processes are facies dependent. Migration lengths vary between the Opalinus Clay facies by up to 10 m. Thereby, the geochemistry of the pore water, in particular the partial pressure of carbon dioxide (pCO2), is more decisive for the sorption capacity than the amount of clay minerals. Nevertheless, higher clay mineral quantities compensate geochemical variations. Consequently, sorption processes must be quantified as a function of pore water geochemistry in contact with the mineral assemblage. 

Uranium diffusion in the Opalinus Clay is facies independent. Speciation is dominated by aqueous ternary complexes of U(VI) with calcium and carbonate. Differences in the migration lengths between SC and MC diffusion are with +/-5 m negligible. Further, the application of the MC approach highly depends on the quality and availability of the underlying data. Therefore, diffusion processes can be adequately quantified with the SC approach using experimentally determined diffusion coefficients.

The hydrogeological system governs pore water geochemistry within the formation rather than the mineralogy. Diffusive exchange with the adjacent aquifers established geochemical gradients over geological time scales that can enhance migration by up to 25 m. Consequently, uranium sorption processes must be quantified following the identified priority: pCO2 > hydrogeology > mineralogy.  

The presented research provides a workflow and orientation for other potential disposal sites with similar pore water geochemistry due to the identified mechanisms and dependencies. With a maximum migration length of 70 m, the retention capacity of the Opalinus Clay with respect to uranium is sufficient to fulfill the German legal minimum requirement of a thickness of at least 100 m.
N2  - Zum Schutz von Mensch und Umwelt vor den schädlichen Auswirkungen abgebrannter Brennelemente, wird weltweit die Endlagerung in tiefen geologischen Formationen favorisiert. Daher ist das Rückhaltevermögen potenzieller Wirtsgesteine gegenüber Radionukliden ein wichtiges Kriterium. Sicherheitsbewertungen basieren auf der Quantifizierung der Migration mit numerischen Simulationen, da Experimente die erforderlichen zeitlichen (1 Ma) und räumlichen Skalen (>100 m) nicht abdecken können. 

Ziel der Dissertation ist es, die Migration des geochemisch komplexen Radionuklids Uran im potenziellen Wirtsgestein Opalinuston zu bewerten. In Tonformationen wird die Radionuklidmigration aufgrund der geringen Durchlässigkeit von Diffusion bestimmt und durch Sorption verzögert. Beide Prozesse hängen stark von der Porenwassergeochemie und Mineralogie ab, die zwischen verschiedenen Fazies variieren. Die Diffusion wird mit dem Einkomponenten- (SC) und Mehrkomponentenansatz (MC) quantifiziert. Nach dem SC-Ansatz wird ein Diffusionskoeffizient für alle Spezies verwendet, wohingegen mit der MC-Option individuelle Werte zugewiesen und die Interaktion mit der diffusen Doppelschicht berücksichtigt wird. Die Sorption ist mit Hilfe mechanistischer Oberflächenkomplexierungsmodelle und Kationenaustausch integriert. Die Durchführung reaktiver Transportsimulationen mit dem Code PHREEQC ermöglicht die Quantifizierung der Uranmigration, d. h. Diffusion und Sorption, in Abhängigkeit der Mineralogie und Porenwassergeochemie für die Wirtsgesteinsskala.

Sorptionsprozesse sind faziesabhängig. Die Migrationslängen variieren um bis zu 10 m zwischen den Fazies aufgrund von Unterschieden in der Porenwassergeochemie. Dabei ist insbesondere der Partialdruck des Kohlendioxids (pCO2) entscheidender für die Sorptionskapazität als die Menge an Tonmineralen. Allerdings kompensieren höhere Tonmineralmengen geochemische Schwankungen. Folglich müssen Sorptionsprozesse in Abhängigkeit der Porenwassergeochemie quantifiziert werden. 

Urandiffusion ist faziesunabhängig. Die Speziation wird durch aquatische ternäre Komplexe von U(VI) mit Kalzium und Karbonat dominiert. Die Unterschiede in den Migrationslängen zwischen SC- und MC-Diffusion sind mit +/-5 m vernachlässigbar. Die Anwendung des MC-Ansatzes hängt stark von der Qualität und Verfügbarkeit der zugrunde liegenden Daten ab. Diffusionsprozesse können also mit dem SC-Ansatz unter Verwendung experimentell ermittelter Diffusionskoeffizienten quantifiziert werden.

Haupteinflussfaktor auf die Porenwassergeochemie ist das hydrogeologische System und nicht die Mineralogie. Der diffusive Austausch mit den angrenzenden Aquiferen hat über geologische Zeiträume geochemische Gradienten geschaffen, die die Migration um bis zu 25 m verlängern können. Folglich müssen Sorptionsprozesse nach der identifizierten Priorität quantifiziert werden: pCO2 > Hydrogeologie > Mineralogie.  

Die ermittelten Abhängigkeiten dienen als Orientierung für andere potenzielle Endlagerstandorte mit ähnlicher Porenwassergeochemie. Mit einer maximalen Migration von 70 m reicht das Rückhaltevermögen des Opalinustons gegenüber Uran aus, um die deutsche gesetzliche Mindestanforderung von 100 m Mächtigkeit zu erfüllen.
KW  - uranium
KW  - Opalinus Clay
KW  - PHREEQC
KW  - diffusion
KW  - sorption
KW  - nuclear waste disposal
KW  - reactive transport simulation
KW  - host rock scale
KW  - Opalinuston
KW  - PHREEQC
KW  - Diffusion
KW  - Wirtsgesteinsskala
KW  - Endlagerung nuklearer Abfälle
KW  - reaktive Transportsimulation
KW  - Sorption
KW  - Uran
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-552700
ER  - 
TY  - JOUR
A1  - Hennig, Theresa
A1  - Kühn, Michael
T1  - Potential uranium migration within the geochemical gradient of the opalinus clay system at the Mont Terri
JF  - Minerals
N2  - Transport properties of potential host rocks for nuclear waste disposal are typically determined in laboratory or in-situ experiments under geochemically controlled and constant conditions. Such a homogeneous assumption is no longer applicable on the host rock scale as can be seen from the pore water profiles of the potential host rock Opalinus Clay at Mont Terri (Switzerland). The embedding aquifers are the hydro-geological boundaries, that established gradients in the 210 m thick low permeable section through diffusive exchange over millions of years. Present-day pore water profiles were confirmed by a data-driven as well as by a conceptual scenario. Based on the modelled profiles, the influence of the geochemical gradient on uranium migration was quantified by comparing the distances after one million years with results of common homogeneous models. Considering the heterogeneous system, uranium migrated up to 24 m farther through the formation depending on the source term position within the gradient and on the partial pressure of carbon dioxide pCO2 of the system. Migration lengths were almost equal for single- and multicomponent diffusion. Differences can predominantly be attributed to changes in the sorption capacity, whereby pCO2 governs how strong uranium migration is affected by the geochemical gradient. Thus, the governing parameters for uranium migration in the Opalinus Clay can be ordered in descending priority: pCO2, geochemical gradients, mineralogical heterogeneity.</p>
KW  - PHREEQC
KW  - reactive transport
KW  - sorption
KW  - diffusion
KW  - repository far-field
KW  - hydro-geological system
Y1  - 2021
U6  - https://doi.org/10.3390/min11101087
SN  - 2075-163X
VL  - 11
IS  - 10
PB  - MDPI
CY  - Basel
ER  - 
TY  - THES
A1  - Klumpp, Stefan
T1  - Movements of molecular motors : diffusion and directed walks
N2  - Bewegungen von prozessiven molekularen Motoren des Zytoskeletts sind durch ein Wechselspiel von gerichteter Bewegung entlang von Filamenten und Diffusion in der umgebenden Lösung gekennzeichnet. Diese eigentümlichen Bewegungen werden in der vorliegenden Arbeit untersucht, indem sie als Random Walks auf einem Gitter modelliert werden. Ein weiterer Gegenstand der Untersuchung sind Effekte von Wechselwirkungen zwischen den Motoren auf diese Bewegungen.   Im einzelnen werden vier Transportphänomene untersucht:  (i) Random Walks von einzelnen Motoren in Kompartimenten verschiedener Geometrien,  (ii) stationäre Konzentrationsprofile, die sich in geschlossenen Kompartimenten infolge dieser Bewegungen einstellen, (iii) randinduzierte Phasenübergänge in offenen röhrenartigen Kompartimenten, die an Motorenreservoirs gekoppelt sind, und  (iv) der Einfluß von kooperativen Effekten bei der Motor-Filament-Bindung auf die Bewegung. Alle diese Phänomene sind experimentell zugänglich, und mögliche experimentelle Realisierungen werden diskutiert.
N2  - Movements of processive cytoskeletal motors are characterized by an interplay between directed motion along filament and diffusion in the surrounding solution. In the present work, these peculiar movements are studied by modeling them as random walks on a lattice. An additional subject of our studies is the effect of motor-motor interactions on these movements.   In detail, four transport phenomena are studied:  (i) Random walks of single motors in compartments of various geometries,  (ii) stationary concentration profiles which build up as a result of these movements in closed compartments,  (iii) boundary-induced phase transitions in open tube-like compartments coupled to reservoirs of motors, and  (iv) the influence of cooperative effects in motor-filament binding on the movements. All these phenomena are experimentally accessible and possible experimental realizations are discussed.
KW  - molekulare Motoren
KW  - aktive Prozesse
KW  - Diffusion
KW  - Random Walks
KW  - Gittermodelle
KW  - Phasenübergänge
KW  - Staus
KW  - kooperative Phänomene
KW  - molecular motors
KW  - active processes
KW  - diffusion
KW  - random walks
KW  - lattice models
KW  - phase transitions
KW  - traffic jams
KW  - cooperative phenomena
Y1  - 2003
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-0000806
ER  - 
TY  - GEN
A1  - Li, Yongge
A1  - Mei, Ruoxing
A1  - Xu, Yong
A1  - Kurths, Jürgen
A1  - Duan, Jinqiao
A1  - Metzler, Ralf
T1  - Particle dynamics and transport enhancement in a confined channel with position-dependent diffusivity
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - This work focuses on the dynamics of particles in a confined geometry with position-dependent diffusivity, where the confinement is modelled by a periodic channel consisting of unit cells connected by narrow passage ways. We consider three functional forms for the diffusivity, corresponding to the scenarios of a constant (D ₀), as well as a low (D ₘ) and a high (D d) mobility diffusion in cell centre of the longitudinally symmetric cells. Due to the interaction among the diffusivity, channel shape and external force, the system exhibits complex and interesting phenomena. By calculating the probability density function, mean velocity and mean first exit time with the Itô calculus form, we find that in the absence of external forces the diffusivity D d will redistribute particles near the channel wall, while the diffusivity D ₘ will trap them near the cell centre. The superposition of external forces will break their static distributions. Besides, our results demonstrate that for the diffusivity D d, a high dependence on the x coordinate (parallel with the central channel line) will improve the mean velocity of the particles. In contrast, for the diffusivity D ₘ, a weak dependence on the x coordinate will dramatically accelerate the moving speed. In addition, it shows that a large external force can weaken the influences of different diffusivities; inversely, for a small external force, the types of diffusivity affect significantly the particle dynamics. In practice, one can apply these results to achieve a prominent enhancement of the particle transport in two- or three-dimensional channels by modulating the local tracer diffusivity via an engineered gel of varying porosity or by adding a cold tube to cool down the diffusivity along the central line, which may be a relevant effect in engineering applications. Effects of different stochastic calculi in the evaluation of the underlying multiplicative stochastic equation for different physical scenarios are discussed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 974 
KW  - diffusion
KW  - channel
KW  - space-dependent diffusivity
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-474542
SN  - 1866-8372
IS  - 974
ER  - 
TY  - JOUR
A1  - Li, Yongge
A1  - Mei, Ruoxing
A1  - Xu, Yong
A1  - Kurths, Jürgen
A1  - Duan, Jinqiao
A1  - Metzler, Ralf
T1  - Particle dynamics and transport enhancement in a confined channel with position-dependent diffusivity
JF  - New Journal of Physics
N2  - This work focuses on the dynamics of particles in a confined geometry with position-dependent diffusivity, where the confinement is modelled by a periodic channel consisting of unit cells connected by narrow passage ways. We consider three functional forms for the diffusivity, corresponding to the scenarios of a constant (D ₀), as well as a low (D ₘ) and a high (D d) mobility diffusion in cell centre of the longitudinally symmetric cells. Due to the interaction among the diffusivity, channel shape and external force, the system exhibits complex and interesting phenomena. By calculating the probability density function, mean velocity and mean first exit time with the Itô calculus form, we find that in the absence of external forces the diffusivity D d will redistribute particles near the channel wall, while the diffusivity D ₘ will trap them near the cell centre. The superposition of external forces will break their static distributions. Besides, our results demonstrate that for the diffusivity D d, a high dependence on the x coordinate (parallel with the central channel line) will improve the mean velocity of the particles. In contrast, for the diffusivity D ₘ, a weak dependence on the x coordinate will dramatically accelerate the moving speed. In addition, it shows that a large external force can weaken the influences of different diffusivities; inversely, for a small external force, the types of diffusivity affect significantly the particle dynamics. In practice, one can apply these results to achieve a prominent enhancement of the particle transport in two- or three-dimensional channels by modulating the local tracer diffusivity via an engineered gel of varying porosity or by adding a cold tube to cool down the diffusivity along the central line, which may be a relevant effect in engineering applications. Effects of different stochastic calculi in the evaluation of the underlying multiplicative stochastic equation for different physical scenarios are discussed.
KW  - diffusion
KW  - channel
KW  - space-dependent diffusivity
Y1  - 2020
U6  - https://doi.org/10.1088/1367-2630/ab81b9
SN  - 1367-2630
VL  - 22
PB  - Dt. Physikalische Ges.
CY  - Bad Honnef
ER  - 
TY  - JOUR
A1  - Magdziarz, Marcin
A1  - Metzler, Ralf
A1  - Szczotka, Wladyslaw
A1  - Zebrowski, Piotr
T1  - Correlated continuous-time random walks-scaling limits and Langevin picture
JF  - Journal of statistical mechanics: theory and experiment
N2  - In this paper we analyze correlated continuous-time random walks introduced recently by Tejedor and Metzler (2010 J. Phys. A: Math. Theor. 43 082002). We obtain the Langevin equations associated with this process and the corresponding scaling limits of their solutions. We prove that the limit processes are self-similar and display anomalous dynamics. Moreover, we extend the model to include external forces. Our results are confirmed by Monte Carlo simulations.
KW  - stochastic processes (theory)
KW  - diffusion
Y1  - 2012
U6  - https://doi.org/10.1088/1742-5468/2012/04/P04010
SN  - 1742-5468
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - GEN
A1  - Makwana, Kirit D.
A1  - Yan, Huirong
T1  - Properties of magnetohydrodynamic modes in compressively driven plasma turbulence
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - We study properties of magnetohydrodynamic (MHD) eigenmodes by decomposing the data of MHD simulations into linear MHD modes-namely, the Alfven, slow magnetosonic, and fast magnetosonic modes. We drive turbulence with a mixture of solenoidal and compressive driving while varying the Alfven Mach number (M-A), plasma beta, and the sonic Mach number from subsonic to transsonic. We find that the proportion of fast and slow modes in the mode mixture increases with increasing compressive forcing. This proportion of the magnetosonic modes can also become the dominant fraction in the mode mixture. The anisotropy of the modes is analyzed by means of their structure functions. The Alfven-mode anisotropy is consistent with the Goldreich-Sridhar theory. We find a transition from weak to strong Alfvenic turbulence as we go from low to high M-A. The slow-mode properties are similar to the Alfven mode. On the other hand, the isotropic nature of fast modes is verified in the cases where the fast mode is a significant fraction of the mode mixture. The fast-mode behavior does not show any transition in going from low to high M-A. We find indications that there is some interaction between the different modes, and the properties of the dominant mode can affect the properties of the weaker modes. This work identifies the conditions under which magnetosonic modes can be a major fraction of turbulent astrophysical plasmas, including the regime of weak turbulence. Important astrophysical implications for cosmic-ray transport and magnetic reconnection are discussed.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1225 
KW  - mhd turbulence
KW  - star formation
KW  - simulations
KW  - Anisotropy
KW  - diffusion
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-531607
SN  - 1866-8372
VL  - 10
IS  - 3
PB  - American Physical Society (APS)
CY  - College Park
ER  - 
TY  - THES
A1  - Mulansky, Mario
T1  - Chaotic diffusion in nonlinear Hamiltonian systems
T1  - Chaotische Diffusion in nichtlinearen Hamiltonschen Systemen
N2  - This work investigates diffusion in nonlinear Hamiltonian systems. The diffusion, more precisely subdiffusion, in such systems is induced by the intrinsic chaotic behavior of trajectories and thus is called chaotic diffusion''. Its properties are studied on the example of one- or two-dimensional lattices of harmonic or nonlinear oscillators with nearest neighbor couplings. The fundamental observation is the spreading of energy for localized initial conditions. Methods of quantifying this spreading behavior are presented, including a new quantity called excitation time. This new quantity allows for a more precise analysis of the spreading than traditional methods. Furthermore, the nonlinear diffusion equation is introduced as a phenomenologic description of the spreading process and a number of predictions on the density dependence of the spreading are drawn from this equation. Two mathematical techniques for analyzing nonlinear Hamiltonian systems are introduced. The first one is based on a scaling analysis of the Hamiltonian equations and the results are related to similar scaling properties of the NDE. From this relation, exact spreading predictions are deduced. Secondly, the microscopic dynamics at the edge of spreading states are thoroughly analyzed, which again suggests a scaling behavior that can be related to the NDE. Such a microscopic treatment of chaotically spreading states in nonlinear Hamiltonian systems has not been done before and the results present a new technique of connecting microscopic dynamics with macroscopic descriptions like the nonlinear diffusion equation. All theoretical results are supported by heavy numerical simulations, partly obtained on one of Europe's fastest supercomputers located in Bologna, Italy. In the end, the highly interesting case of harmonic oscillators with random frequencies and nonlinear coupling is studied, which resembles to some extent the famous Discrete Anderson Nonlinear Schroedinger Equation. For this model, a deviation from the widely believed power-law spreading is observed in numerical experiments. Some ideas on a theoretical explanation for this deviation are presented, but a conclusive theory could not be found due to the complicated phase space structure in this case. Nevertheless, it is hoped that the techniques and results presented in this work will help to eventually understand this controversely discussed case as well.
N2  - Diese Arbeit beschäftigt sich mit dem Phänomen der Diffusion in nichtlinearen Systemen. Unter Diffusion versteht man normalerweise die zufallsmä\ss ige Bewegung von Partikeln durch den stochastischen Einfluss einer thermodynamisch beschreibbaren Umgebung. Dieser Prozess ist mathematisch beschrieben durch die Diffusionsgleichung. In dieser Arbeit werden jedoch abgeschlossene Systeme ohne Einfluss der Umgebung betrachtet. Dennoch wird eine Art von Diffusion, üblicherweise bezeichnet als Subdiffusion, beobachtet. Die Ursache dafür liegt im chaotischen Verhalten des Systems. Vereinfacht gesagt, erzeugt das Chaos eine intrinsische Pseudo-Zufälligkeit, die zu einem gewissen Grad mit dem Einfluss einer thermodynamischen Umgebung vergleichbar ist und somit auch diffusives Verhalten provoziert. Zur quantitativen Beschreibung dieses subdiffusiven Prozesses wird eine Verallgemeinerung der Diffusionsgleichung herangezogen, die Nichtlineare Diffusionsgleichung. Desweiteren wird die mikroskopische Dynamik des Systems mit analytischen Methoden untersucht, und Schlussfolgerungen für den makroskopischen Diffusionsprozess abgeleitet. Die Technik der Verbindung von mikroskopischer Dynamik und makroskopischen Beobachtungen, die in dieser Arbeit entwickelt wird und detailliert beschrieben ist, führt zu einem tieferen Verständnis von hochdimensionalen chaotischen Systemen. Die mit mathematischen Mitteln abgeleiteten Ergebnisse sind darüber hinaus durch ausführliche Simulationen verifiziert, welche teilweise auf einem der leistungsfähigsten Supercomputer Europas durchgeführt wurden, dem sp6 in Bologna, Italien. Desweiteren können die in dieser Arbeit vorgestellten Erkenntnisse und Techniken mit Sicherheit auch in anderen Fällen bei der Untersuchung chaotischer Systeme Anwendung finden.
KW  - Chaos
KW  - Diffusion
KW  - Thermalisierung
KW  - Energieausbreitung
KW  - chaos
KW  - diffusion
KW  - thermalization
KW  - energy spreading
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-63180
ER  - 
TY  - JOUR
A1  - Mutothya, Nicholas Mwilu
A1  - Xu, Yong
A1  - Li, Yongge
A1  - Metzler, Ralf
T1  - Characterising stochastic motion in heterogeneous media driven by coloured non-Gaussian noise
JF  - Journal of physics : A, Mathematical and theoretical
N2  - We study the stochastic motion of a test particle in a heterogeneous medium in terms of a position dependent diffusion coefficient mimicking measured deterministic diffusivity gradients in biological cells or the inherent heterogeneity of geophysical systems. Compared to previous studies we here investigate the effect of the interplay of anomalous diffusion effected by position dependent diffusion coefficients and coloured non-Gaussian noise. The latter is chosen to be distributed according to Tsallis' q-distribution, representing a popular example for a non-extensive statistic. We obtain the ensemble and time averaged mean squared displacements for this generalised process and establish its non-ergodic properties as well as analyse the non-Gaussian nature of the associated displacement distribution. We consider both non-stratified and stratified environments.
KW  - diffusion
KW  - anomalous diffusion
KW  - non-extensive statistics
KW  - coloured
KW  - noise
KW  - heterogeneous diffusion process
Y1  - 2021
U6  - https://doi.org/10.1088/1751-8121/abfba6
SN  - 1751-8113
SN  - 1751-8121
VL  - 54
IS  - 29
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Mutothya, Nicholas Mwilu
A1  - Xu, Yong
A1  - Li, Yongge
A1  - Metzler, Ralf
A1  - Mutua, Nicholas Muthama
T1  - First passage dynamics of stochastic motion in heterogeneous media driven by correlated white Gaussian and coloured non-Gaussian noises
JF  - Journal of physics. Complexity
N2  - We study the first passage dynamics for a diffusing particle experiencing a spatially varying diffusion coefficient while driven by correlated additive Gaussian white noise and multiplicative coloured non-Gaussian noise. We consider three functional forms for position dependence of the diffusion coefficient: power-law, exponential, and logarithmic. The coloured non-Gaussian noise is distributed according to Tsallis' q-distribution. Tracks of the non-Markovian systems are numerically simulated by using the fourth-order Runge-Kutta algorithm and the first passage times (FPTs) are recorded. The FPT density is determined along with the mean FPT (MFPT). Effects of the noise intensity and self-correlation of the multiplicative noise, the intensity of the additive noise, the cross-correlation strength, and the non-extensivity parameter on the MFPT are discussed.
KW  - first passage
KW  - diffusion
KW  - non-Gaussian
KW  - correlated noise
Y1  - 2021
U6  - https://doi.org/10.1088/2632-072X/ac35b5
SN  - 2632-072X
VL  - 2
PB  - IOP Publishing
CY  - Bristol
ER  - 
TY  - GEN
A1  - Münch, Thomas
A1  - Kipfstuhl, Sepp
A1  - Freitag, Johannes
A1  - Meyer, Hanno
A1  - Laepple, Thomas
T1  - Regional climate signal vs. local noise
BT  - a two-dimensional view of water isotopes in Antarctic firn at Kohnen Station, Dronning Maud Land
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - In low-accumulation regions, the reliability of delta O-18-derived temperature signals from ice cores within the Holocene is unclear, primarily due to the small climate changes relative to the intrinsic noise of the isotopic signal. In order to learn about the representativity of single ice cores and to optimise future ice-core-based climate reconstructions, we studied the stable-water isotope composition of firn at Kohnen Station, Dronning Maud Land, Antarctica. Analysing delta O-18 in two 50m long snow trenches allowed us to create an unprecedented, two-dimensional image characterising the isotopic variations from the centimetre to the 100-metre scale. Our results show seasonal layering of the isotopic composition but also high horizontal isotopic variability caused by local stratigraphic noise. Based on the horizontal and vertical structure of the isotopic variations, we derive a statistical noise model which successfully explains the trench data. The model further allows one to determine an upper bound for the reliability of climate reconstructions conducted in our study region at seasonal to annual resolution, depending on the number and the spacing of the cores taken.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 500 
KW  - ice-core records
KW  - past 2 kyr
KW  - temperature variability
KW  - accumulation rates
KW  - East Antarctica
KW  - stable-isotopes
KW  - surface snow
KW  - time-series
KW  - diffusion
KW  - Greenland
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-408385
SN  - 1866-8372
IS  - 500
ER  - 
TY  - GEN
A1  - Münch, Thomas
A1  - Kipfstuhl, Sepp
A1  - Freitag, Johannes
A1  - Meyer, Hanno
A1  - Laepple, Thomas
T1  - Constraints on post-depositional isotope modifications in East Antarctic firn from analysing temporal changes of isotope profiles
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - The isotopic composition of water in ice sheets is extensively used to infer past climate changes. In low-accumulation regions their interpretation is, however, challenged by poorly constrained effects that may influence the initial isotope signal during and after deposition of the snow. This is reflected in snow-pit isotope data from Kohnen Station, Antarctica, which exhibit a seasonal cycle but also strong interannual variations that contradict local temperature observations. These inconsistencies persist even after averaging many profiles and are thus not explained by local stratigraphic noise. Previous studies have suggested that post-depositional processes may significantly influence the isotopic composition of East Antarctic firn. Here, we investigate the importance of post-depositional processes within the open-porous firn (greater than or similar to 10 cm depth) at Kohnen Station by separating spatial from temporal variability. To this end, we analyse 22 isotope profiles obtained from two snow trenches and examine the temporal isotope modifications by comparing the new data with published trench data extracted 2 years earlier. The initial isotope profiles undergo changes over time due to downward advection, firn diffusion and densification in magnitudes consistent with independent estimates. Beyond that, we find further modifications of the original isotope record to be unlikely or small in magnitude (<< 1 parts per thousand RMSD). These results show that the discrepancy between local temperatures and isotopes most likely originates from spatially coherent processes prior to or during deposition, such as precipitation intermittency or systematic isotope modifications acting on drifting or loose surface snow.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 662 
KW  - Dronning Maud Land
KW  - near-surface snow
KW  - Ice core records
KW  - Kohnen Station
KW  - stable isotopes
KW  - water isotopes
KW  - polar firn
KW  - climate
KW  - diffusion
KW  - precipitation
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-418763
SN  - 1866-8372
IS  - 662
ER  - 
TY  - JOUR
A1  - Palyulin, Vladimir V.
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Space-fractional Fokker-Planck equation and optimization of random search processes in the presence of an external bias
JF  - Journal of statistical mechanics: theory and experiment
N2  - Based on the space-fractional Fokker-Planck equation with a delta-sink term, we study the efficiency of random search processes based on Levy flights with power-law distributed jump lengths in the presence of an external drift, for instance, an underwater current, an airflow, or simply the preference of the searcher based on prior experience. While Levy flights turn out to be efficient search processes when the target is upstream relative to the starting point, in the downstream scenario, regular Brownian motion turns out to be advantageous. This is caused by the occurrence of leapovers of Levy flights, due to which Levy flights typically overshoot a point or small interval. Studying the solution of the fractional Fokker-Planck equation, we establish criteria when the combination of the external stream and the initial distance between the starting point and the target favours Levy flights over the regular Brownian search. Contrary to the common belief that Levy flights with a Levy index alpha = 1 (i.e. Cauchy flights) are optimal for sparse targets, we find that the optimal value for alpha may range in the entire interval (1, 2) and explicitly include Brownian motion as the most efficient search strategy overall.
KW  - driven diffusive systems (theory)
KW  - fluctuations (theory)
KW  - stochastic processes (theory)
KW  - diffusion
Y1  - 2014
U6  - https://doi.org/10.1088/1742-5468/2014/11/P11031
SN  - 1742-5468
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Palyulin, Vladimir V.
A1  - Metzler, Ralf
T1  - How a finite potential barrier decreases the mean first-passage time
JF  - Journal of statistical mechanics: theory and experiment
N2  - We consider the mean first-passage time of a random walker moving in a potential landscape on a finite interval, the starting and end points being at different potentials. From analytical calculations and Monte Carlo simulations we demonstrate that the mean first-passage time for a piecewise linear curve between these two points is minimized by the introduction of a potential barrier. Due to thermal fluctuations, this barrier may be crossed. It turns out that the corresponding expense for this activation is less severe than the gain from an increased slope towards the end point. In particular, the resulting mean first-passage time is shorter than for a linear potential drop between the two points.
KW  - diffusion
Y1  - 2012
U6  - https://doi.org/10.1088/1742-5468/2012/03/L03001
SN  - 1742-5468
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Pohlenz, Philipp
A1  - Niedermeier, Frank
T1  - The Bologna Process and the harmonisation of higher education systems in other world regions
BT  - a case from Southeast Asia
JF  - Innovation : the European journal of social sciences
N2  - The Bologna Process has inspired harmonisation strategies for higher education systems in other parts of the world. However, developments in other contexts are not much under review in the European debate. The present article describes the case of Southeast Asia and the attempt to promote harmonisation of its higher education systems. It further compares the processes in ASEAN and the European Higher Education Area to then discuss open questions for future comparative research. To do so the authors re-contextualise data from a study in ASEAN against the background of future research needs in the field of higher education harmonisation.
KW  - ASEAN
KW  - Bologna Process
KW  - European Higher Education Area
KW  - higher education
KW  - quality assurance
KW  - harmonisation
KW  - regionalisation
KW  - diffusion
KW  - mobility
Y1  - 2019
U6  - https://doi.org/10.1080/13511610.2019.1637248
SN  - 1351-1610
SN  - 1469-8412
VL  - 32
IS  - 4
SP  - 481
EP  - 494
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Prokopovic, Vladimir Z.
A1  - Duschl, Claus
A1  - Volodkin, Dmitry
T1  - Hyaluronic Acid/Poly-l-Lysine Multilayers as Reservoirs for Storage and Release of Small Charged Molecules
JF  - Macromolecular bioscience
N2  - Polyelectrolyte multilayer films are nowadays very attractive for bioapplications due to their tunable properties and ability to control cellular response. Here we demonstrate that multilayers made of hyaluronic acid and poly-l-lysine act as high-capacity reservoirs for small charged molecules. Strong accumulation within the film is explained by electrostatically driven binding to free charges of polyelectrolytes. Binding and release mechanisms are discussed based on charge balance and polymer dynamics in the film. Our results show that transport of molecules through the film-solution interface limits the release rate. The multilayers might serve as an effective platform for drug delivery and tissue engineering due to high potential for drug loading and controlled release.
KW  - diffusion
KW  - drug delivery
KW  - dye
KW  - release mechanism
Y1  - 2015
U6  - https://doi.org/10.1002/mabi.201500093
SN  - 1616-5187
SN  - 1616-5195
VL  - 15
IS  - 10
SP  - 1357
EP  - 1363
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Prokopovic, Vladimir Z.
A1  - Vikulina, Anna S.
A1  - Sustr, David
A1  - Duschl, Claus
A1  - Volodkin, Dmitry
T1  - Biodegradation-Resistant Multilayers Coated with Gold Nanoparticles. Toward a Tailor-made Artificial Extracellular Matrix
JF  - Journal of colloid and interface science
N2  - Polymer multicomponent coatings such as multilayers mimic an extracellular, matrix (ECM) that attracts significant attention for the use of the multilayers as functional supports for advanced cell culture and tissue engineering. Herein, biodegradation and molecular transport in hyaluronan/polylysine multilayers coated with gold nanoparticles were described. Nanoparticle coating acts as a semipermeable barrier that governs molecular transport into/from the multilayers, and makes them biodegradation-resistant. Model protein lysozyme (mimics of ECM-soluble signals) diffuses into the multilayers as fast- and, slow-diffusing populations existing in an equilibrium,. Such a. composite system may have high potential to be exploited as degradation-resistant drug-delivery platforms suitable for cell-based applications.
KW  - hyaluronic acid
KW  - polylysine
KW  - diffusion
KW  - semipermeable
KW  - fluorescence recovery after photobleaching
KW  - layer-by-layer
KW  - enzymatic degradation
KW  - cell adhesion
Y1  - 2016
U6  - https://doi.org/10.1021/acsami.6b10095
SN  - 1944-8244
VL  - 8
SP  - 24345
EP  - 24349
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - BOOK
A1  - Schmiedgen, Jan
A1  - Rhinow, Holger
A1  - Köppen, Eva
A1  - Meinel, Christoph
T1  - Parts without a whole?
BT  - The current state of Design Thinking practice in organizations
N2  - This explorative study gives a descriptive overview of what organizations do and experience when they say they practice design thinking. It looks at how the concept has been appropriated in organizations and also describes patterns of design thinking adoption. The authors use a mixed-method research design fed by two sources: questionnaire data and semi-structured personal expert interviews. The study proceeds in six parts: (1) design thinking¹s entry points into organizations; (2) understandings of the descriptor; (3) its fields of application and organizational localization; (4) its perceived impact; (5) reasons for its discontinuation or failure; and (6) attempts to measure its success. In conclusion the report challenges managers to be more conscious of their current design thinking practice. The authors suggest a co-evolution of the concept¹s introduction with innovation capability building and the respective changes in leadership approaches. It is argued that this might help in unfolding design thinking¹s hidden potentials as well as preventing unintended side-effects such as discontented teams or the dwindling authority of managers.
N2  - Diese explorative Studie gibt einen deskriptiven Überblick, was Organisationen tun und zu erleben, wenn sie sagen, sie üben Design Thinking. Es untersucht, wie das Konzept in Organisationen angeeignet und beschreibt auch Muster der Design Thinking Annahme. Die Autoren verwenden eine von zwei Quellen gespeist Mixed-Verfahren Forschungsdesign: Fragebogendaten und semi-strukturierten persönlichen Experteninterviews. Die Studie läuft in sechs Teile: Einstiegspunkte (1) Design-Denken in Organisationen; (2) Verständnis des Deskriptors; (3) ihre Anwendungsgebiete und organisatorische Lokalisierung;(4) dessen empfundenen Auswirkungen; (5) Gründe für ihre Einstellung oder Misserfolg; und (6) versucht, den Erfolg zu messen. Abschließend fordert der Bericht-Manager mehr bewusst ihre aktuellen Design Thinking der Praxis zu sein. Die Autoren schlagen eine Ko-Evolution von Einführung des Konzepts mit Innovationsfähigkeit Gebäude und den jeweiligen Führungswechsel Ansätze. Es wird argumentiert, dass dies in der Entfaltung versteckte Potentiale Design Denken wie auch zur Verhinderung unbeabsichtigten Nebenwirkungen, wie unzufrieden Teams oder die schwindende Autorität von Managern zu helfen.
T3  - Technische Berichte des Hasso-Plattner-Instituts für Digital Engineering an der Universität Potsdam - 97 
KW  - design thinking
KW  - innovation
KW  - innovation management
KW  - innovation capabilities
KW  - organizational change
KW  - change management
KW  - management
KW  - adoption
KW  - diffusion
KW  - study
KW  - leadership
KW  - Design Thinking
KW  - Innovation
KW  - Innovationsmanagement
KW  - Organisationsveränderung
KW  - Change Management
KW  - Management
KW  - Innovationsmethode
KW  - Studie
KW  - Leadership
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-79969
SN  - 978-3-86956-334-3
SN  - 1613-5652
SN  - 2191-1665
IS  - 97
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Schwarzl, Maria
A1  - Godec, Aljaz
A1  - Oshanin, Gleb
A1  - Metzler, Ralf
T1  - A single predator charging a herd of prey: effects of self volume and predator-prey decision-making
JF  - Journal of physics : A, Mathematical and theoretical
N2  - We study the degree of success of a single predator hunting a herd of prey on a two-dimensional square lattice landscape. We explicitly consider the self volume of the prey restraining their dynamics on the lattice. The movement of both predator and prey is chosen to include an intelligent, decision making step based on their respective sighting ranges, the radius in which they can detect the other species (prey cannot recognise each other besides the self volume interaction): after spotting each other the motion of prey and predator turns from a nearest neighbour random walk into directed escape or chase, respectively. We consider a large range of prey densities and sighting ranges and compute the mean first passage time for a predator to catch a prey as well as characterise the effective dynamics of the hunted prey. We find that the prey's sighting range dominates their life expectancy and the predator profits more from a bad eyesight of the prey than from his own good eye sight. We characterise the dynamics in terms of the mean distance between the predator and the nearest prey. It turns out that effectively the dynamics of this distance coordinate can be captured in terms of a simple Ornstein–Uhlenbeck picture. Reducing the many-body problem to a simple two-body problem by imagining predator and nearest prey to be connected by an effective Hookean bond, all features of the model such as prey density and sighting ranges merge into the effective binding constant.
KW  - first passage process
KW  - diffusion
KW  - predator-prey model
Y1  - 2016
U6  - https://doi.org/10.1088/1751-8113/49/22/225601
SN  - 1751-8113
SN  - 1751-8121
VL  - 49
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Seiß, Martin
A1  - Albers, Nicole
A1  - Sremčević, Miodrag
A1  - Schmidt, Jürgen
A1  - Salo, Heikki
A1  - Seiler, Michael
A1  - Hoffmann, Holger
A1  - Spahn, Frank
T1  - Hydrodynamic Simulations of Moonlet-induced Propellers in Saturn's Rings
BT  - Application to Bleriot
JF  - The astronomical journal
N2  - One of the biggest successes of the Cassini mission is the detection of small moons (moonlets) embedded in Saturns rings that cause S-shaped density structures in their close vicinity, called propellers. Here, we present isothermal hydrodynamic simulations of moonlet-induced propellers in Saturn's A ring that denote a further development of the original model. We find excellent agreement between these new hydrodynamic and corresponding N-body simulations. Furthermore, the hydrodynamic simulations confirm the predicted scaling laws and the analytical solution for the density in the propeller gaps. Finally, this mean field approach allows us to simulate the pattern of the giant propeller Blériot, which is too large to be modeled by direct N-body simulations. Our results are compared to two stellar occultation observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS), which intersect the propeller Blériot. Best fits to the UVIS optical depth profiles are achieved for a Hill radius of 590 m, which implies a moonlet diameter of about 860 m. Furthermore, the model favors a kinematic shear viscosity of the surrounding ring material of ν0 = 340 cm2 s−1, a dispersion velocity in the range of 0.3 cm s−1 < c0 < 1.5 cm s−1, and a fairly high bulk viscosity 7 < ξ0/ν0 < 17. These large transport values might be overestimated by our isothermal ring model and should be reviewed by an extended model including thermal fluctuations.
KW  - diffusion
KW  - hydrodynamics
KW  - planets and satellites: rings
Y1  - 2018
U6  - https://doi.org/10.3847/1538-3881/aaed44
SN  - 0004-6256
SN  - 1538-3881
VL  - 157
IS  - 1
PB  - IOP Publishing Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Shin, Jaeoh
A1  - Cherstvy, Andrey G.
A1  - Kim, Won Kyu
A1  - Metzler, Ralf
T1  - Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles
JF  - New journal of physics : the open-access journal for physics
N2  - We study the dynamics of polymer chains in a bath of self-propelled particles (SPP) by extensive Langevin dynamics simulations in a two-dimensional model system. Specifically, we analyse the polymer looping properties versus the SPP activity and investigate how the presence of the active particles alters the chain conformational statistics. We find that SPPs tend to extend flexible polymer chains, while they rather compactify stiffer semiflexible polymers, in agreement with previous results. Here we show that higher activities of SPPs yield a higher effective temperature of the bath and thus facilitate the looping kinetics of a passive polymer chain. We explicitly compute the looping probability and looping time in a wide range of the model parameters. We also analyse the motion of a monomeric tracer particle and the polymer's centre of mass in the presence of the active particles in terms of the time averaged mean squared displacement, revealing a giant diffusivity enhancement for the polymer chain via SPP pooling. Our results are applicable to rationalising the dimensions and looping kinetics of biopolymers at constantly fluctuating and often actively driven conditions inside biological cells or in suspensions of active colloidal particles or bacteria cells.
KW  - diffusion
KW  - active transport
KW  - polymers
Y1  - 2015
U6  - https://doi.org/10.1088/1367-2630/17/11/113008
SN  - 1367-2630
VL  - 17
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Shoaee, Safa
A1  - Sanna, Anna Laura
A1  - Sforazzini, Giuseppe
T1  - Elucidating charge generation in green-solvent processed organic solar cells
JF  - Molecules : a journal of synthetic chemistry and natural product chemistry / Molecular Diversity Preservation International
N2  - Organic solar cells have the potential to become the cheapest form of electricity. Rapid increase in the power conversion efficiency of organic solar cells (OSCs) has been achieved with the development of non-fullerene small-molecule acceptors. Next generation photovoltaics based upon environmentally benign "green solvent" processing of organic semiconductors promise a step-change in the adaptability and versatility of solar technologies and promote sustainable development. However, high-performing OSCs are still processed by halogenated (non-environmentally friendly) solvents, so hindering their large-scale manufacture. In this perspective, we discuss the recent progress in developing highly efficient OSCs processed from eco-compatible solvents, and highlight research challenges that should be addressed for the future development of high power conversion efficiencies devices.
KW  - organic solar cells
KW  - green solvents
KW  - non-halogenated solvents
KW  - exaction
KW  - diffusion
KW  - photoluminescence quenching
Y1  - 2021
U6  - https://doi.org/10.3390/molecules26247439
SN  - 1420-3049
VL  - 26
IS  - 24
PB  - MDPI
CY  - Basel
ER  -