TY - JOUR A1 - Nkenke, Emeka A1 - Zachow, Stefan A1 - Benz, Michaela A1 - Maier, Tobias A1 - Veit, Klaus A1 - Kramer, Manuel A1 - Benz, St. A1 - Häusler, Gerd A1 - Neukam, Friedrich A1 - Lell, Michael T1 - Fusion of computed tomography data and optical 3D images of the dentition for streak artefact correction in the simulation of orthognathic surgery JF - Journal of Dento-Maxillofacial Radiology Y1 - 2004 U6 - https://doi.org/10.1259/dmfr/27071199 VL - 33 SP - 226 EP - 232 ER - TY - JOUR A1 - Reimers, Jeffrey R. A1 - Biczysko, Malgorzata A1 - Bruce, Douglas A1 - Coker, David F. A1 - Frankcombe, Terry J. A1 - Hashimoto, Hideki A1 - Hauer, Jürgen A1 - Jankowiak, Ryszard A1 - Kramer, Tobias A1 - Linnanto, Juha A1 - Mamedov, Fikret A1 - Müh, Frank A1 - Rätsep, Margus A1 - Renger, Thomas A1 - Styring, Stenbjörn A1 - Wan, Jian A1 - Wang, Zhuan A1 - Wang-Otomo, Zheng-Yu A1 - Weng, Yu-Xiang A1 - Yang, Chunhong A1 - Zhang, Jian-Ping A1 - Freiberg, Arvi A1 - Krausz, Elmars T1 - Challenges facing an understanding of the nature of low-energy excited states in photosynthesis JF - BBA Bioenergetics N2 - While the majority of the photochemical states and pathways related to the biological capture of solar energy are now well understood and provide paradigms for artificial device design, additional low-energy states have been discovered in many systems with obscure origins and significance. However, as low-energy states are naively expected to be critical to function, these observations pose important challenges. A review of known properties of low energy states covering eight photochemical systems, and options for their interpretation, are presented. A concerted experimental and theoretical research strategy is suggested and outlined, this being aimed at providing a fully comprehensive understanding. Y1 - 2016 U6 - https://doi.org/10.1016/j.bbabio.2016.06.010 VL - 1857 IS - 9 SP - 1627 EP - 1640 ER - TY - JOUR A1 - Kramer, Tobias A1 - Läuter, Matthias A1 - Rubin, Martin A1 - Altwegg, Kathrin T1 - Seasonal changes of the volatile density in the coma and on the surface of comet 67P/Churyumov-Gerasimenko JF - Monthly Notices of the Royal Astronomical Society N2 - Starting from several monthly data sets of Rosetta’s COmetary Pressure Sensor we reconstruct the gas density in the coma around comet 67P/Churyumov-Gerasimenko. The underlying inverse gas model is constructed by fitting ten thousands of measurements to thousands of potential gas sources distributed across the entire nucleus surface. The ensuing self-consistent solution for the entire coma density and surface activity reproduces the temporal and spatial variations seen in the data for monthly periods with Pearson correlation coefficients of 0.93 and higher. For different seasonal illumination conditions before and after perihelion we observe a systematic shift of gas sources on the nucleus. Y1 - 2017 U6 - https://doi.org/10.1093/mnras/stx866 VL - 469 SP - S20 EP - S28 ER - TY - JOUR A1 - Kramer, Tobias A1 - Noack, Matthias A1 - Baum, Daniel A1 - Hege, Hans-Christian A1 - Heller, Eric J. T1 - Dust and gas emission from cometary nuclei: the case of comet 67P/Churyumov-Gerasimenko JF - Advances in Physics: X N2 - Comets display with decreasing solar distance an increased emission of gas and dust particles, leading to the formation of the coma and tail. Spacecraft missions provide insight in the temporal and spatial variations of the dust and gas sources located on the cometary nucleus. For the case of comet 67P/Churyumov-Gerasimenko (67P/C-G), the long-term obser- vations from the Rosetta mission point to a homogeneous dust emission across the entire illuminated surface. Despite the homogeneous initial dis- tribution, a collimation in jet-like structures becomes visible. We propose that this observation is linked directly to the complex shape of the nucleus and projects concave topographical features into the dust coma. To test this hypothesis, we put forward a gas-dust description of 67P/C-G, where gravitational and gas forces are accurately determined from the surface mesh and the rotation of the nucleus is fully incorporated. The emerging jet-like structures persist for a wide range of gas-dust interactions and show a dust velocity dependent bending. Y1 - 2018 U6 - https://doi.org/10.1080/23746149.2017.1404436 VL - 3 IS - 1 SP - 1404436 ER - TY - JOUR A1 - Kreisbeck, Christoph A1 - Kramer, Tobias A1 - Molina, Rafael T1 - Time-dependent wave packet simulations of transport through Aharanov–Bohm rings with an embedded quantum dot JF - Journal of Physics: Condensed Matter N2 - We have performed time-dependent wave packet simulations of realistic Aharonov-Bohm (AB) devices with a quantum dot embedded in one of the arms of the interferometer. The AB ring can function as a measurement device for the intrinsic transmission phase through the quantum dot, however, care has to be taken in analyzing the influence of scattering processes in the junctions of the interferometer arms. We consider a harmonic quantum dot and show how the Darwin–Fock spectrum emerges as a unique pattern in the interference fringes of the AB oscillations. Y1 - 2017 U6 - https://doi.org/10.1088/1361-648X/aa605d VL - 29 IS - 15 SP - 155301 ER - TY - JOUR A1 - Kramer, Tobias A1 - Rodriguez, Mirta A1 - Zelinskyi, Yaroslav T1 - Modeling of Transient Absorption Spectra in Exciton Charge-Transfer Systems JF - Journal of Physical Chemistry B N2 - Time-resolved spectroscopy provides the main tool for analyzing the dynamics of excitonic energy transfer in light-harvesting complexes. To infer time-scales and effective coupling parameters from experimental data requires to develop numerical exact theoretical models. The finite duration of the laser-molecule interactions and the reorganization process during the exciton migration affect the location and strength of spectroscopic signals. We show that the non-perturbative hierarchical equations of motion (HEOM) method captures these processes in a model exciton system, including the charge transfer state. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcb.6b09858 VL - 121 SP - 463 EP - 470 ER - TY - JOUR A1 - Kramer, Tobias A1 - Rodriguez, Mirta T1 - Two-dimensional electronic spectra of the photosynthetic apparatus of green sulfur bacteria JF - Scientific Reports N2 - Advances in time resolved spectroscopy have provided new insight into the energy transmission in natural photosynthetic complexes. Novel theoretical tools and models are being developed in order to explain the experimental results. We provide a model calculation for the two-dimensional electronic spectra of Cholorobaculum tepidum which correctly describes the main features and transfer time scales found in recent experiments. From our calculation one can infer the coupling of the antenna chlorosome with the environment and the coupling between the chlorosome and the Fenna-Matthews-Olson complex. We show that environment assisted transport between the subunits is the required mechanism to reproduce the experimental two-dimensional electronic spectra. Y1 - 2017 U6 - https://doi.org/10.1038/srep45245 VL - 7 SP - 45245 ER - TY - JOUR A1 - Kramer, Tobias A1 - Noack, Matthias A1 - Baum, Daniel A1 - Hege, Hans-Christian A1 - Heller, Eric J. T1 - Homogeneous dust emission and jet structure near active cometary nuclei: the case of 67P/Churyumov-Gerasimenko N2 - We compute trajectories of dust grains starting from a homogeneous surface activity-profile on a irregularly shaped cometary nucleus. Despite the initially homogeneous dust distribution a collimation in jet-like structures becomes visible. The fine structure is caused by concave topographical features with similar bundles of normal vectors. The model incorporates accurately determined gravitational forces, rotation of the nucleus, and gas-dust interaction. Jet-like dust structures are obtained for a wide range of gas-dust interactions. For the comet 67P/Churyumov-Gerasimenko, we derive the global dust distribution around the nucleus and find several areas of agreement between the homogeneous dust emission model and the Rosetta observation of dust jets, including velocity-dependent bending of trajectories. Y1 - 2015 ER - TY - JOUR A1 - Kramer, Tobias A1 - Kreisbeck, Christoph A1 - Riha, Christian A1 - Chiatti, Olivio A1 - Buchholz, Sven A1 - Wieck, Andreas A1 - Reuter, Dirk A1 - Fischer, Saskia T1 - Thermal energy and charge currents in multi-terminal nanorings JF - AIP Advances N2 - We study in experiment and theory thermal energy and charge transfer close to the quantum limit in a ballistic nanodevice, consisting of multiply connected one-dimensional electron waveguides. The fabricated device is based on an AlGaAs/GaAs heterostructure and is covered by a global top-gate to steer the thermal energy and charge transfer in the presence of a temperature gradient, which is established by a heating current. The estimate of the heat transfer by means of thermal noise measurements shows the device acting as a switch for charge and thermal energy transfer. The wave-packet simulations are based on the multi-terminal Landauer-Büttiker approach and confirm the experimental finding of a mode-dependent redistribution of the thermal energy current, if a scatterer breaks the device symmetry. Y1 - 2016 U6 - https://doi.org/10.1063/1.4953812 VL - 6 SP - 065306 ER - TY - JOUR A1 - Kramer, Tobias A1 - Noack, Matthias T1 - On the origin of inner coma structures observed by Rosetta during a diurnal rotation of comet 67P/Churyumov-Gerasimenko JF - The Astrophysical Journal Letters N2 - The Rosetta probe around comet 67P/Churyumov–Gerasimenko (67P) reveals an anisotropic dust distribution of the inner coma with jet-like structures. The physical processes leading to jet formation are under debate, with most models for cometary activity focusing on localized emission sources, such as cliffs or terraced regions. Here we suggest, by correlating high-resolution simulations of the dust environment around 67P with observations, that the anisotropy and the background dust density of 67P originate from dust released across the entire sunlit surface of the nucleus rather than from few isolated sources. We trace back trajectories from coma regions with high local dust density in space to the non-spherical nucleus and identify two mechanisms of jet formation: areas with local concavity in either two dimensions or only one. Pits and craters are examples of the first case; the neck region of the bi-lobed nucleus of 67P is an example of the latter case. The conjunction of multiple sources, in addition to dust released from all other sunlit areas, results in a high correlation coefficient (~0.8) of the predictions with observations during a complete diurnal rotation period of 67P. Y1 - 2016 U6 - https://doi.org/10.3847/2041-8205/823/1/L11 VL - 823 IS - 1 SP - L11 ER -