@phdthesis{SvirejevaHopkins2004, author = {Svirejeva-Hopkins, Anastasia}, title = {Urbanised territories as a specific component of the global carbon cycle}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001512}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {Wir betrachten folgende Teile: die zus{\"a}tzlichen Kohlenstoff(C)-emissionen, welche aus der Umwandlung von nat{\"u}rlichem Umland durch Stadtwachstum resultieren, und die {\"A}nderung des C-Flusses durch 'urbanisierte' {\"O}kosysteme, soweit atmosph{\"a}risches C durch diese in umliegende nat{\"u}rliche {\"O}kosysteme entlang der Kette \“Atmosph{\"a}re -> Vegetation -> abgestorbene organische Substanzen\” gepumpt wird: d.h. C-Export; f{\"u}r den Zeitraum von 1980 bis 2050. Als Szenario nutzen wir Prognosen der regionalen Stadtbev{\"o}lkerung, welche durch ein 'Hybridmodell' generiert werden f{\"u}r acht Regionen. Alle Sch{\"a}tzungen der C-Fl{\"u}sse basieren auf zwei Modellen: das Regression Modell und das sogenannte G-Modell. Die Siedlungsfl{\"a}che, welche mit dem Wachstum der Stadtbev{\"o}lkerung zunimmt, wird in 'Gr{\"u}nfl{\"a}chen' (Parks, usw.), Geb{\"a}udefl{\"a}chen und informell st{\"a}dtisch genutzte Fl{\"a}chen (Slums, illegale Lagerpl{\"a}tze, usw.) unterteilt. Es werden j{\"a}hrlich die regionale und globale Dynamik der C-Emissionen und des C-Exports sowie die C-Gesamtbilanz berechnet. Dabei liefern beide Modelle qualitativ {\"a}hnliche Ergebnisse, jedoch gibt es einige quantitative Unterschiede. Im ersten Modell erreicht die globale Jahresemission f{\"u}r die Dekade 2020-2030 resultierend aus der Landnutzungs{\"a}nderung ein Maximum von 205 Mt/a. Die maximalen Beitr{\"a}ge zur globalen Emission werden durch China, die asiatische und die pazifische Region erbracht. Im zweiten Modell erh{\"o}ht sich die j{\"a}hrliche globale Emission von 1.12 GtC/a f{\"u}r 1980 auf 1.25 GtC/a f{\"u}r 2005 (1Gt = 109 t). Danach beginnt eine Reduzierung. Vergleichen wir das Emissionmaximum mit der Emission durch Abholzung im Jahre 1980 (1.36 GtC/a), k{\"o}nnen wir konstatieren, daß die Urbanisierung damit in vergleichbarer Gr{\"o}sse zur Emission beitr{\"a}gt. Bezogen auf die globale Dynamik des j{\"a}hrlichen C-Exports durch Urbanisierung beobachten wir ein monotones Wachstum bis zum nahezu dreifachen Wert von 24 MtC/a f{\"u}r 1980 auf 66 MtC/a f{\"u}r 2050 im ersten Modell, bzw. im zweiten Modell von 249 MtC/a f{\"u}r 1980 auf 505 MtC/a f{\"u}r 2050. Damit ist im zweiten Fall die Transportleistung der Siedlungsgebiete mit dem C-Transport durch Fl{\"u}sse in die Ozeane (196 .. 537 MtC/a) vergleichbar. Bei der Absch{\"a}tzung der Gesamtbilanz finden wir, daß die Urbanisierung die Bilanz in Richtung zu einer 'Senke' verschiebt. Entsprechend dem zweiten Modell beginnt sich die C-Gesamtbilanz (nach ann{\"a}hernder Konstanz) ab dem Jahre 2000 mit einer fast konstanten Rate zu verringern. Wenn das Maximum im Jahre 2000 bei 905MtC/a liegt, f{\"a}llt dieser Wert anschliessend bis zum Jahre 2050 auf 118 MtC/a. Bei Extrapolation dieser Dynamik in die Zukunft k{\"o}nnen wir annehmen, daß am Ende des 21. Jahrhunderts die \“urbane\” C-Gesamtbilanz Null bzw. negative Werte erreicht.}, language = {en} } @article{JayVazdaCruzEckertetal.2020, author = {Jay, Raphael M. and Vaz da Cruz, Vinicius and Eckert, Sebastian and Fondell, Mattis and Mitzner, Rolf and F{\"o}hlisch, Alexander}, title = {Probing solute-solvent interactions of transition metal complexes using L-edge absorption spectroscopy}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {124}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {27}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.0c00638}, pages = {5636 -- 5645}, year = {2020}, abstract = {In order to tailor solution-phase chemical reactions involving transition metal complexes, it is critical to understand how their valence electronic charge distributions are affected by the solution environment. Here, solute-solvent interactions of a solvatochromic mixed-ligand iron complex were investigated using X-ray absorption spectroscopy at the transition metal L-2,L-3-edge. Due to the selectivity of the corresponding core excitations to the iron 3d orbitals, the method grants direct access to the valence electronic structure around the iron center and its response to interactions with the solvent environment. A linear increase of the total L-2,L-3-edge absorption cross section as a function of the solvent Lewis acidity is revealed. The effect is caused by relative changes in different metal-ligand-bonding channels, which preserve local charge densities while increasing the density of unoccupied states around the iron center. These conclusions are corroborated by a combination of molecular dynamics and spectrum simulations based on time-dependent density functional theory. The simulations reproduce the spectral trends observed in the X-ray but also optical absorption experiments. Our results underscore the importance of solute-solvent interactions when aiming for an accurate description of the valence electronic structure of solvated transition metal complexes and demonstrate how L-2,L-3-edge absorption spectroscopy can aid in understanding the impact of the solution environment on intramolecular covalency and the electronic charge distribution.}, language = {en} } @article{CervantesShpritsAseevetal.2019, author = {Cervantes, Sebastian and Shprits, Yuri Y. and Aseev, Nikita and Drozdov, Alexander and Castillo Tibocha, Angelica Maria and Stolle, Claudia}, title = {Identifying radiation belt electron source and loss processes by assimilating spacecraft data in a three-dimensional diffusion model}, series = {Journal of geophysical research : Space physics}, volume = {125}, journal = {Journal of geophysical research : Space physics}, number = {1}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1029/2019JA027514}, pages = {16}, year = {2019}, abstract = {Data assimilation aims to blend incomplete and inaccurate data with physics-based dynamical models. In the Earth's radiation belts, it is used to reconstruct electron phase space density, and it has become an increasingly important tool in validating our current understanding of radiation belt dynamics, identifying new physical processes, and predicting the near-Earth hazardous radiation environment. In this study, we perform reanalysis of the sparse measurements from four spacecraft using the three-dimensional Versatile Electron Radiation Belt diffusion model and a split-operator Kalman filter over a 6-month period from 1 October 2012 to 1 April 2013. In comparison to previous works, our 3-D model accounts for more physical processes, namely, mixed pitch angle-energy diffusion, scattering by Electromagnetic Ion Cyclotron waves, and magnetopause shadowing. We describe how data assimilation, by means of the innovation vector, can be used to account for missing physics in the model. We use this method to identify the radial distances from the Earth and the geomagnetic conditions where our model is inconsistent with the measured phase space density for different values of the invariants mu and K. As a result, the Kalman filter adjusts the predictions in order to match the observations, and we interpret this as evidence of where and when additional source or loss processes are active. The current work demonstrates that 3-D data assimilation provides a comprehensive picture of the radiation belt electrons and is a crucial step toward performing reanalysis using measurements from ongoing and future missions.}, language = {en} } @article{AwadMetzler2022, author = {Awad, Emad and Metzler, Ralf}, title = {Closed-form multi-dimensional solutions and asymptotic behaviours for subdiffusive processes with crossovers: II. Accelerating case}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {55}, journal = {Journal of physics : A, Mathematical and theoretical}, number = {20}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8121/ac5a90}, pages = {29}, year = {2022}, abstract = {Anomalous diffusion with a power-law time dependence vertical bar R vertical bar(2)(t) similar or equal to t(alpha i) of the mean squared displacement occurs quite ubiquitously in numerous complex systems. Often, this anomalous diffusion is characterised by crossovers between regimes with different anomalous diffusion exponents alpha(i). Here we consider the case when such a crossover occurs from a first regime with alpha(1) to a second regime with alpha(2) such that alpha(2) > alpha(1), i.e., accelerating anomalous diffusion. A widely used framework to describe such crossovers in a one-dimensional setting is the bi-fractional diffusion equation of the so-called modified type, involving two time-fractional derivatives defined in the Riemann-Liouville sense. We here generalise this bi-fractional diffusion equation to higher dimensions and derive its multidimensional propagator (Green's function) for the general case when also a space fractional derivative is present, taking into consideration long-ranged jumps (Levy flights). We derive the asymptotic behaviours for this propagator in both the short- and long-time as well the short- and long-distance regimes. Finally, we also calculate the mean squared displacement, skewness and kurtosis in all dimensions, demonstrating that in the general case the non-Gaussian shape of the probability density function changes.}, language = {en} }