727 research outputs found
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Efficient Intramolecular Singlet Fission in Spiro-Linked Heterodimers [research data]
No full textWe investigate intramolecular singlet fission (iSF) of spiro-linked azaacene heterodimers by time-resolved spectroscopy and quantum chemical calculations. Combining two different azaacenes through a nonconjugated linker using condensation chemistry furnishes azaacene heterodimers. Compared to their homodimers, iSF quantum yields are improved at an extended absorption range. The driving force of iSF, the energy difference between the S1 state and the correlated triplet pair 1(TT), is tuned by the nature of the heterodimers. iSF is exothermic in all of the herein studied molecules. The overall quantum yield for triplet exciton formation reaches approximately 174%. This novel concept exploits large energy differences between singlet electronic states in combination with spatially fixed chromophores, which achieves efficient heterogeneous iSF, if the through-space interaction between the chromophores is minimal
A Minimalistic, Synthetic Cell-Inspired Metamaterial for Enabling Reversible Strain-Stiffening [data]
No full textStrain-stiffening, i.e. the nonlinear stiffening of a material in response to a strain, is an intrinsic feature of many biological systems, including skin, blood vessels, and single cells. To avoid a mismatch in mechanical properties, synthetic materials in contact with such biological systems should also be strain-stiffening. Conventional strain-stiffening materials are either highly dependent on the applied strain-rate, or only available for a limited stiffness regime. Both aspects limit the applicability of these materials. In contrast, living cells employ a dynamic strain-stiffening mechanism that is based on the cross-linking of cytoskeletal fibers in response to external stress. This strain-stiffening of the cytoskeleton is mimicked in a mechanical metamaterial by a minimalistic structure consisting of parallel slats connected to backbones. Herein, it is demonstrated experimentally that the structures can be adapted such that the strain required for stiffening, the final stiffness, as well as the degree of stiffening can be tuned, particularly by combining several strain-stiffening elements. These properties make the structure promising for the development of devices that should resemble the mechanical properties of human soft tissues, e.g., skin-integrated flexible electronics and blood vessel grafts
Refining and validating change requests from a crowd to derive requirements [data]
No full text[Context/Motivation] Integrating user feedback into software development enhances system acceptance, decreases the likelihood of project failure and strengthens customer loyalty. Moreover, user feedback plays an important role in software evolution, because it can be the basis for deriving requirements.
[Problems] However, to be able to derive requirements from feedback, the feedback must contain actionable change requests, that is contain detailed information regarding a change to the application. Furthermore, requirements engineers must know how many users support the change request.
[Principal ideas] To address these challenges, we propose an approach that uses structured questions to transform non-actionable change requests into actionable and validate the change requests to assess their support among the users. We evaluate the approach in the large-scale research project SMART-AGE with over 200 older adults, aged 67 and older.
[Contribution] We contribute a set of templates for our questions and our process, and we evaluate the approach’s feasibility, effectiveness and user satisfaction, resulting in very positive outcomes.</p
Stabilization of Acenes: “Geländer”-Pentacenes [data]
No full textWe report soluble tetrakis-biphenyl substituted pentacenes comprised of sp2 carbons and synthesized from pentacene-5,7,12,14-tetraone. Intramolecular Yamamoto coupling of two tetrakis(chlorobiphenylyl)pentacenes yields helical, doubly wrapped pentacenes, in which the quaterphenylene units solubilize the pentacenes and shield their central anthracene units to an unprecedented degree. The criss-cross-bridged pentacenes resist (photo)oxidation, Diels-Alder reactions and are much less reactive than TIPS-ethynylated pentacene. Extension of this concept might provide access to the larger acenes
Excited States Dynamics at Pentacene/Perfluoropentacene Interfaces: A Femtosecond Time-Resolved Second Harmonic Generation Study [research data]
No full textUnderstanding the dynamics of excited states after optical excitation at donor-acceptor (D/A) interfaces is of paramount importance for improving the efficiency and performance of optoelectronic devices. Here, we studied the ultrafast excited state dynamics after optical excitation at interfaces between the electron donor (D) pentacene (PEN) and the electron acceptor (A) perfuoropentacene (PFP) as well as within the single compounds (PEN and PFP) using femtosecond (fs) time-resolved second harmonic generation (SHG). In the single compounds singlet fission is observed on a time scale of around 200 fs. In the bilayer systems a huge SHG intensity rise is observed due to the creation of charge transfer states at the interface and accordingly to formation of a local electric field within tens of picoseconds. The local electric field and therefore the SHG signal intensity from the interface of PEN/PFP bilayer is much more intense compared to the PFP/PEN system because the PFP and PEN intermixing at the PEN/PFP interface is higher. Accordingly a population of defect states on a time scale of 55±12 ps has been proposed for PEN/PFP. Our study provides important insights into D/A charge transfer properties, which is needed for the understanding of the interfacial photophysics of pentacene-based organic compounds
Polarization-Dependent Strong and Weak Light- Matter Coupling in Aligned Perylene Diimide Thin-Films [data]
No full textUnderlying data for figures in the paper "Polarization-Dependent Strong and Weak Light- Matter Coupling in Aligned Perylene Diimide Thin-Films
Motional Narrowing Effects in the Excited State Spin Populations of Mn-Doped Hybrid Perovskites [Research Data]
No full textSpin-orbit coupling in the electronic states of solution-processed hybrid metal halide perovskites forms complex spin-textures in the band structures and allows for optical manipulation of excited state spin-polarizations. Here, we report that motional narrowing acts on the photoexcited spin-polarization in CH3NH3PbBr3 thin films, which are doped at percentage-level with Mn2+ ions. Using ultrafast circularly polarized broadband transient absorption spectroscopy at cryogenic temperatures, we investigate the spin population dynamics in our doped hybrid perovskites and find that spin relaxation lifetimes are increased by a factor of three compared to undoped materials. Using quantitative analysis of the photoexcitation cooling processes, we reveal increased carrier scattering rates in the doped perovskites as the fundamental mechanism driving spin-polarization maintaining motional narrowing. Our work reports transition-metal doping of hybrid perovskites as a concept to extend spin lifetimes of hybrid perovskites
Code and Workflow for Checking Image Arrival Times in fMRI Neurofeedback Experiments
No full textDataset containing SOP & code for replicating measurements of image arrival times in an fMRI setup
Simulation-based Inference for Model Parameterization on Analog Neuromorphic Hardware [data]
No full textThis data is presented in the paper "Simulation-based Inference for Model Parameterization on Analog Neuromorphic Hardware"
Supplementary Material zu: Geomorphological Diversity and Habitat Variability. A Model of Late Palaeolithic Catchment Composition in Northern Bavaria / Geomorphologische Diversität und Habitatvariabilität. Ein Modell der spätpaläolithischen Catchment in Nordbayern
No full textDue to the lack of adequate data, the environmental and bioeconomic framework of archaeological sites often cannot be investigated. This situation is visible with the Late Palaeolithic in Southern Germany, which is typically represented by surface collections that do not provide ecological information. In this paper, we analyse the topographic composition of site-catchments of Late Palaeolithic sites in Northern Bavaria (Germany). We use a geomorphology-driven approach, which employs the close relationship between local topography and abiotic conditions relevant to plant growth. This way it is
possible to model potential regional physiotope diversity and habitat patterning. This methodology allows the analysis of site-environment relationships in cases, when traditional proxies, like palynological or faunal data are lacking or do not provide an adequate spatial extent and resolution. In this paper, site catchment analysis and physiotope diversity estimation for Late Palaeolithic sites in the study area highlight the relevance of relatively specialized landscapes, which provide comparably wet conditions. This indicates the focus of Late Glacial foragers on the exploitation on bioresources associated with wetland and floodplain environments in the study area