@inproceedings{45741, author = {{Alberternst, B. and Steinhoff, Lena and Eggert, A. and Giesler, M.}}, booktitle = {{2021 AMA Winter Academic Conference Proceedings, St. Petersburg}}, location = {{St. Petersburg}}, title = {{{Consumer Solidarity: A Social-System Perspective on the Glue that Holds Society Together}}}, year = {{2021}}, } @article{43493, abstract = {{We consider a measure given as the continuum limit of a one-dimensional Ising model with long-range translationally invariant interactions. Mathematically, the measure can be described by a self-interacting Poisson driven jump process. We prove a correlation inequality, estimating the magnetic susceptibility of this model, which holds for small norm of the interaction function. The bound on the magnetic susceptibility has applications in quantum field theory and can be used to prove existence of ground states for the spin boson model.}}, author = {{Hasler, David and Hinrichs, Benjamin and Siebert, Oliver}}, issn = {{0304-4149}}, journal = {{Stochastic Processes and their Applications}}, pages = {{60--79}}, publisher = {{Elsevier BV}}, title = {{{Correlation bound for a one-dimensional continuous long-range Ising model}}}, doi = {{10.1016/j.spa.2021.12.010}}, volume = {{146}}, year = {{2021}}, } @article{43465, abstract = {{We show the existence of ground states in the massless spin boson model without any infrared regularization. Our proof is non-perturbative and relies on a compactness argument. It works for arbitrary values of the coupling constant under the hypothesis that the second derivative of the ground state energy as a function of a constant external magnetic field is bounded.}}, author = {{Hasler, David and Hinrichs, Benjamin and Siebert, Oliver}}, issn = {{0010-3616}}, journal = {{Communications in Mathematical Physics}}, number = {{1}}, pages = {{419--433}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{On Existence of Ground States in the Spin Boson Model}}}, doi = {{10.1007/s00220-021-04185-w}}, volume = {{388}}, year = {{2021}}, } @article{26077, abstract = {{Nonlinear SU(1,1) interferometers are fruitful and promising tools for spectral engineering and precise measurements with phase sensitivity below the classical bound. Such interferometers have been successfully realized in bulk and fiber-based configurations. However, rapidly developing integrated technologies provide higher efficiencies, smaller footprints, and pave the way to quantum-enhanced on-chip interferometry. In this work, we theoretically realised an integrated architecture of the multimode SU(1,1) interferometer which can be applied to various integrated platforms. The presented interferometer includes a polarization converter between two photon sources and utilizes a continuous-wave (CW) pump. Based on the potassium titanyl phosphate (KTP) platform, we show that this configuration results in almost perfect destructive interference at the output and supersensitivity regions below the classical limit. In addition, we discuss the fundamental difference between single-mode and highly multimode SU(1,1) interferometers in the properties of phase sensitivity and its limits. Finally, we explore how to improve the phase sensitivity by filtering the output radiation and using different seeding states in different modes with various detection strategies.}}, author = {{Ferreri, Alessandro and Santandrea, Matteo and Stefszky, Michael and Luo, Kai Hong and Herrmann, Harald and Silberhorn, Christine and Sharapova, Polina R.}}, issn = {{2521-327X}}, journal = {{Quantum}}, title = {{{Spectrally multimode integrated SU(1,1) interferometer}}}, doi = {{10.22331/q-2021-05-27-461}}, year = {{2021}}, } @inproceedings{39027, abstract = {{We experimentally investigate the generation of continuous-wave optical squeezing from a titanium-indiffused lithium niobate waveguide resonator at low and high frequencies. The device promises integration with different platform chips for more complex optical systems.}}, author = {{Domeneguetti, Renato R. and Conradi, Hauke and Kleinert, Moritz and Kießler, Christian and Stefszky, Michael and Herrmann, Harald and Silberhorn, Christine and Andersen, Ulrik L. and Neergaard-Nielsen, Jonas Schou and Gehring, Tobias}}, booktitle = {{2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference}}, keywords = {{Optical systems, Polymer waveguides, Quantum key distribution, Quantum light sources, Squeezed states, Waveguides}}, pages = {{eb_4_1}}, publisher = {{Optica Publishing Group}}, title = {{{Nonlinear waveguides for integrated quantum light source}}}, year = {{2021}}, } @article{26218, author = {{Santandrea, Matteo and Stefszky, Michael and Silberhorn, Christine}}, issn = {{2040-8978}}, journal = {{Journal of Optics}}, title = {{{General analytic theory of classical collinear three-wave mixing in a monolithic cavity}}}, doi = {{10.1088/2040-8986/ac0b90}}, year = {{2021}}, } @inproceedings{24159, abstract = {{The online fitting of a microscopic traffic simulation model to reconstruct the current state of a real traffic area can be challenging depending on the provided data. This paper presents a novel method based on limited data from sensors positioned at specific locations and guarantees a general accordance of reality and simulation in terms of multimodal road traffic counts and vehicle speeds. In these considerations, the actual purpose of research is of particular importance. Here, the research aims at improving the traffic flow by controlling the Traffic Light Systems (TLS) of the examined area which is why the current traffic state and the route choices of individual road users are the matter of interest. An integer optimization problem is derived to fit the current simulation to the latest field measurements. The concept can be transferred to any road traffic network and results in an observation of the current multimodal traffic state matching at the given sensor position. First case studies show promosing results in terms of deviations between reality and simulation.}}, author = {{Malena, Kevin and Link, Christopher and Mertin, Sven and Gausemeier, Sandra and Trächtler, Ansgar}}, booktitle = {{VEHITS 2021 Proceedings of the 7th International Conference on Vehicle Technology and Intelligent Transport Systems}}, isbn = {{978-989-758-513-5}}, keywords = {{Microscopic Traffic Simulation, Online State Estimation, Mixed Road Users, Sensor Fusion, Integer Programming, Route Choice, Vehicle2Infrastructure}}, location = {{Online Streaming}}, pages = {{386--395}}, publisher = {{SCITEPRESS}}, title = {{{Online State Estimation for Microscopic Traffic Simulations using Multiple Data Sources*}}}, volume = {{7}}, year = {{2021}}, } @inproceedings{24166, abstract = {{This paper deals with a novel method for the online fitting of a microscopic traffic simulation model to the current state of a real world traffic area. The traffic state estimation is based on limited data of different measurement sources and guarantees general accordance of reality and simulation in terms of multimodal road traffic counts and vehicle speeds. The research is embedded in the challenge of improving the traffic by controlling the traffic light systems (TLS) of the examined area. Therefore, the current traffic state and the predicted route choices of individual road users are the matter of interest. The concept is generally transferable to any road traffic system. To give an impression of the accuracy and potential of the approach, the validation and first application results are presented.}}, author = {{Malena, Kevin and Link, Christopher and Mertin, Sven and Gausemeier, Sandra and Trächtler, Ansgar}}, booktitle = {{2021 IEEE Transportation Electrification Conference & Expo (ITEC)}}, isbn = {{978-1-7281-7584-3}}, publisher = {{IEEE}}, title = {{{Validation of an Online State Estimation Concept for Microscopic Traffic Simulations◆}}}, doi = {{10.1109/itec51675.2021.9490087}}, year = {{2021}}, } @article{63848, author = {{Elbwart, Katharina}}, journal = {{Praxis Englisch}}, pages = {{44--46}}, title = {{{Welcome to Miami, bienvenido a Miami - Showcasing Florida to teach linguistic and cultural diversity in the EFL classroom}}}, volume = {{1}}, year = {{2021}}, } @article{63847, author = {{Elbwart, Katharina}}, journal = {{Praxis Englisch}}, pages = {{44--46}}, title = {{{Speaking Singlish - A legacy of Singapore's colonialism}}}, volume = {{4}}, year = {{2021}}, } @article{36077, author = {{Hoppe, Thomas and Müller, Jens and Wittek, Katharina and Weinrich, Arndt}}, journal = {{iStR}}, title = {{{Eine ökonomische Einordnung des öffentlichen Country-by-Country Reporting in der EU}}}, year = {{2021}}, } @inbook{37533, author = {{Dopheide, Fredericke and Freitag, Christine and Koch, Lea and Struchholz, Caroline}}, booktitle = {{Impulse zu Methoden in der deutschsprachigen Civic Engagement-Forschung}}, editor = {{Gerholz, Karl-Heinz}}, pages = {{15--32}}, title = {{{Gesellschaftliche Wirkprozesse des Civic Engagement qualitativ erforschen}}}, year = {{2021}}, } @article{64052, abstract = {{Abstract Estuaries are key ecosystems with unique biodiversity and are of high economic importance. Along the estuaries, variations in environmental parameters, such as salinity and light penetration, can modify the characteristics of dissolved organic matter (DOM). Nevertheless, there is still limited information about the atomic-level transformations of DOM in this ecosystem. Solid-state NMR spectroscopy provides unique insights into the nature of functional groups in DOM. A major limitation of this technique is its lack of sensivity, which results in experimental time of tens of hours for the acquisition of 13C NMR spectra and generally precludes the observation of 15N nuclei for DOM. We show here how the sensitivity of solid-state NMR experiments on DOM of Seine estuary can be enhanced using dynamic nuclear polarization (DNP) under magic-angle spinning. This technique allows the acquisition of 13C NMR spectra of these samples in few minutes, instead of hours for conventional solid-state NMR. Both conventional and DNP-enhanced 13C NMR spectra indicate that the 13C local environments in DOM are not strongly modified along the Seine estuary. Furthermore, the sensitivity gain provided by the DNP allows the detection of 15N NMR signal of DOM, in spite of the low nitrogen content. These spectra reveal that the majority of nitrogen is in the amide form in these DOM samples and show an increased disorder around these amide groups near the mouth of the Seine.}}, author = {{Venel, Florian and Nagashima, Hiroki and Rankin, Andrew G. M. and Anquetil, Christelle and Klimavicius, Vytautas and Gutmann, Torsten and Buntkowsky, Gerd and Derenne, Sylvie and Lafon, Olivier and Huguet, Arnaud and Pourpoint, Frédérique}}, issn = {{1439-4235; 1439-7641}}, journal = {{Chemphyschem}}, keywords = {{dynamic nuclear polarization, 13C, 15N, dissolved organic matter, Seine estuary}}, number = {{18}}, pages = {{1907–1913}}, publisher = {{John Wiley & Sons, Ltd}}, title = {{{Characterization of Functional Groups in Estuarine Dissolved Organic Matter by DNP-enhanced 15N and 13C Solid-State NMR}}}, doi = {{10.1002/cphc.202100334}}, volume = {{22}}, year = {{2021}}, } @article{64051, abstract = {{The efficiency of dynamic nuclear polarization (DNP) enhanced 19F MAS NMR spectroscopy without 19F-containing solvents and matrices, which transport polarization via 19F–19F spin diffusion, is demonstrated. By preventing solvent and matrix signals respectively masking the corresponding resonances, this enables the detection of fluorinated target molecules in nanomolar amounts. As model compound, 1,3,5-tris(2-fluoro-2-methylpropionylamino)benzene (F-BTA) is investigated in a frozen 1,1,2,2-tetrachloroethane (TCE) solution and incorporated into a matrix of isotactic polypropylene (i-PP). While the polarizing agent is homogeneously dissolved within the frozen solution, for the i-PP/F-BTA blend, it is distributed via the incipient wetness impregnation (IWI) technique. For the frozen solutions with an F-BTA concentration of 187.5 mM an εon/off of 260 was obtained. For F-BTA concentrations of 10 and 2.5 mM the sensitivity trend suggests even higher DNP gains. The substantial enhancements could be achieved by direct polarization transfer over distances up to at least 20 Å, derived from a simple geometric model assuming a homogeneous solution, engaging a large part of the sample volume. Cross-polarization (CP) to 13C nuclei allowed selection of the NMR spectroscopic resonances of the minority species in the i-PP/F-BTA blend suppressing the otherwise dominating resonances of the IWI solvent and the polymer matrix. The possibility of exciting 19F via DNP directly and of transferring the polarization to other heteronuclei within close proximity enables spatial spectral editing to clear up spectra otherwise crowded by matrix and solvent signals. We thus expect direct polarization transfer techniques for DNP enhanced NMR spectroscopy to become more important in the future.}}, author = {{van der Zwan, Kasper P. and Riedel, Wiebke and Aussenac, Fabien and Reiter, Christian and Kreger, Klaus and Schmidt, Hans-Werner and Risse, Thomas and Gutmann, Torsten and Senker, Jürgen}}, issn = {{1932-7447}}, journal = {{Journal of Physical Chemistry C}}, number = {{13}}, pages = {{7287–7296}}, publisher = {{American Chemical Society}}, title = {{{19F MAS DNP for Probing Molecules in Nanomolar Concentrations: Direct Polarization as Key for Solid-State NMR Spectra without Solvent and Matrix Signals}}}, doi = {{10.1021/acs.jpcc.1c01167}}, volume = {{125}}, year = {{2021}}, } @article{64046, abstract = {{The synthesis of a novel immobilized Wilkinson’s catalyst [SiO2∼PvPy-Wilk] is presented. The support material of this catalyst consists of silica particles that are modified with polymer brushes carrying pyridyl moieties that enable the coordination of Wilkinson’s catalyst. The synthesis of this catalyst is monitored by 1D and 2D multinuclear solid-state NMR techniques to confirm the success of the immobilization. The [SiO2∼PvPy-Wilk] catalyst is then tested in the hydrogenation of styrene, and its reusability is inspected showing that significant structural changes after several reaction cycles yield an activation of the catalyst. Finally, the catalyst is tested in PHIP experiments giving rise to about 200-fold enhancement of the signals of the hydrogenation product ethylbenzene.}}, author = {{Srour, Mohamad and Hadjiali, Sara and Brunnengräber, Kai and Weidler, Heiko and Xu, Yeping and Breitzke, Hergen and Gutmann, Torsten and Buntkowsky, Gerd}}, issn = {{1932-7447}}, journal = {{Journal of Physical Chemistry C}}, number = {{13}}, pages = {{7178–7187}}, publisher = {{American Chemical Society}}, title = {{{A Novel Wilkinson’s Type Silica Supported Polymer Catalyst: Insights from Solid-State NMR and Hyperpolarization Techniques}}}, doi = {{10.1021/acs.jpcc.1c00112}}, volume = {{125}}, year = {{2021}}, } @article{64032, abstract = {{Ruthenium nanoparticles (Ru NPs) stabilized by bis-diphenylphosphinobutane (dppb) and surface-saturated with hydrogen have been exposed to gaseous 15NH3 and studied using solid-state 15N CP MAS NMR. Three signals have been observed at 24.5, −12 and −42 ppm (reference external liquid ammonia) which are assigned to chemisorbed ammonia species RuNHx. Sample exposure to vacuum or aging leads to conversion of the 24.5 ppm species into the other ones, a process which is reversed by re-exposure to hydrogen gas. Exposure to a mixture of 15NH3 and 13CO leads to the formation of surface bound urea as demonstrated by 15N and 13C CP MAS NMR. To understand the surface reactions of ammonia and the 15N NMR results, quantum chemical calculations of the structures, energies and 15N chemical shifts of ammonia species on Ru6 and Ru55 model clusters have been performed. The calculations indicate that under the experimental conditions applied, the fractions of RuNH3 and RuNH2 species are similar, independent of the H2 pressure. No RuN and RuNH species are formed which are calculated to resonate at a lower field than the signals observed experimentally. However, the 15N chemical shifts of RuNH2 depend on the number of neighboring surface hydrogens and hence on the H2 pressure. Thus, the signal at 24.5 ppm is assigned to RuNH2 in a neighborhood rich in surface hydrogens. RuNH2 depleted in neighboring surface hydrogens and RuNH3 resonated both in a similar chemical shift range to which the signals at −12 and −42 belong. A change of the hydrogen pressure then leads to interconversion of hydrogen-rich and hydrogen-poor neighborhoods of RuNH2 but does not alter the fractions of RuNH3 and RuNH2 according to the calculated stability diagram. Nevertheless, dissociation of RuNH3 into RuNH2 and surface hydrogen is expected to take place during the initial ammonia adsorption process and at low H2 pressures and high temperatures. Finally, some preliminary quantum chemical calculations suggest stepwise binding of two NH2 groups to adsorbed CO leading to surface bound urea where the oxygen is coordinated to Ru.}}, author = {{Rothermel, Niels and Limbach, Hans-Heinrich and Del Rosal, Iker and Poteau, Romuald and Mencia, Gabriel and Chaudret, Bruno and Buntkowsky, Gerd and Gutmann, Torsten}}, issn = {{2044-4753}}, journal = {{Catalysis Science & Technology}}, number = {{13}}, pages = {{4509–4520}}, publisher = {{The Royal Society of Chemistry}}, title = {{{Surface reactions of ammonia on ruthenium nanoparticles revealed by 15N and 13C solid-state NMR}}}, doi = {{10.1039/D0CY02476G}}, volume = {{11}}, year = {{2021}}, } @article{64025, abstract = {{Dirhodium(II) complexes such as [Rh2(TFA)4] bound to a functionalized mesoporous SBA-15 carrier material have proven to be valuable candidates for heterogeneous catalysis in the field of pharmaceutical synthesis. However, the mechanistic steps of immobilization by linker molecules containing carboxyl or amine functionalities remain the subject of discussion. Here we present a theoretical study of possible mechanistic binding pathways for the [Rh2(TFA)4] complex through model representations of synthetically investigated linkers, namely n-butylamine and n-butyric acid. Experimentally proposed intermediates of the immobilization process are investigated and analyzed by density functional theory calculations to gain insights into structural properties and the influence of solvation. An evaluation of the thermodynamic data for all identified intermediates allowed distinguishing between two possible reaction pathways that are characterized by a first axial complexation of either n-butyric acid or n-butylamine. In agreement with results from NMR spectroscopy, singly or doubly n-butylamine-fixated complexes were found to present possible immobilization products. Initial binding through a carboxy-functionalized linker is proposed as the most favorable reaction pathway for the formation of the mixed linker pattern [Rh2(TFA)3]·(n-butylamine)·(n-butyrate). The linkers n-butyric acid and n-butyrate, respectively, are found to exhibit an unaltered binding affinity to the dirhodium complex despite their protonation states, indicating invariance to the acidic environment unlike an immobilization by n-butylamine. These results present a theoretical framework for the rationalization of observed product distributions while also providing inspiration and guidance for the preparation of functionalized heterogeneous SBA-15/dirhodium catalyst systems.}}, author = {{Pietruschka, Dennis S. and Kumari, Bharti and Buntkowsky, Gerd and Gutmann, Torsten and Mollenhauer, Doreen}}, journal = {{Inorganic Chemistry}}, number = {{9}}, pages = {{6239–6248}}, publisher = {{American Chemical Society}}, title = {{{Mechanism of Heterogenization of Dirhodium Catalysts: Insights from DFT Calculations}}}, doi = {{10.1021/acs.inorgchem.0c03712}}, volume = {{60}}, year = {{2021}}, } @article{64027, abstract = {{The biorelevant PyFALGEA oligopeptide ligand, which is selective towards the epidermal growth factor receptor (EGFR), has been successfully employed as a substrate in magnetic resonance signal amplification by reversible exchange (SABRE) experiments. It is demonstrated that PyFALGEA and the iridium catalyst IMes form a PyFALGEA:IMes molecular complex. The interaction between PyFALGEA:IMes and H-2 results in a ternary SABRE complex. Selective 1D EXSY experiments reveal that this complex is labile, which is an essential condition for successful hyperpolarization by SABRE. Polarization transfer from parahydrogen to PyFALGEA is observed leading to significant enhancement of the H-1 NMR signals of PyFALGEA. Different iridium catalysts and peptides are inspected to discuss the influence of their molecular structures on the efficiency of hyperpolarization. It is observed that PyFALGEA oligopeptide hyperpolarization is more efficient when an iridium catalyst with a sterically less demanding NHC ligand system such as IMesBn is employed. Experiments with shorter analogues of PyFALGEA, that is, PyLGEA and PyEA, show that the bulky phenylalanine from the PyFALGEA oligopeptide causes steric hindrance in the SABRE complex, which hampers hyperpolarization with IMes. Finally, a single-scan H-1 NMR SABRE experiment of PyFALGEA with IMesBn revealed a unique pattern of NMR lines in the hydride region, which can be treated as a fingerprint of this important oligopeptide.}}, author = {{Ratajczyk, T. and Buntkowsky, G. and Gutmann, Torsten and Fedorczyk, B. and Mames, A. and Pietrzak, M. and Puzio, Z. and Szkudlarek, P. G.}}, journal = {{ChemBioChem}}, number = {{5}}, pages = {{855–860}}, title = {{{Magnetic Resonance Signal Amplification by Reversible Exchange of Selective PyFALGEA Oligopeptide Ligands Towards Epidermal Growth Factor Receptors}}}, doi = {{10.1002/cbic.202000711}}, volume = {{22}}, year = {{2021}}, } @article{64022, abstract = {{High-field dynamic nuclear polarization is a powerful tool for the structural characterization of species on the surface of porous materials or nanoparticles. For these studies the main source of polarization are radical-containing solutions which are added by post-synthesis impregnation of the sample. Although this strategy is very efficient for a wide variety of materials, the presence of the solvent may influence the chemistry of functional species of interest. Here we address the development of a comprehensive strategy for solvent-free DNP enhanced NMR characterization of functional (target) species on the surface of mesoporous silica (SBA-15). The strategy includes the partial functionalization of the silica surface with Carboxy-Proxyl nitroxide radicals and target Fmoc-Glycine functional groups. As a proof of principle, we have observed for the first time DNP signal enhancements, using the solvent-free approach, for 13C1H CPMAS signals corresponding to organic functionalities on the silica surface. DNP enhancements of up to 3.4 were observed for 13C1H CPMAS, corresponding to an experimental time save of about 12 times. This observation opens the possibility for the DNP-NMR study of surface functional groups without the need of a solvent, allowing, for example, the characterization of catalytic reactions occurring on the surface of mesoporous systems of interest. For 29Si with direct polarization NMR, up to 8-fold DNP enhancements were obtained. This 29Si signal enhancement is considerably higher than the obtained with similar approaches reported in literature. Finally, from DNP enhancement profiles we conclude that cross-effect is probably the dominant polarization transfer mechanism.}}, author = {{Oliveira, Marcos and Herr, Kevin and Brodrecht, Martin and Haro-Mares, Nadia B. and Wissel, Till and Klimavicius, Vytautas and Breitzke, Hergen and Gutmann, Torsten and Buntkowsky, Gerd}}, journal = {{Physical Chemistry Chemical Physics}}, number = {{22}}, pages = {{12559–12568}}, publisher = {{The Royal Society of Chemistry}}, title = {{{Solvent-free dynamic nuclear polarization enhancements in organically modified mesoporous silica}}}, doi = {{10.1039/D1CP00985K}}, volume = {{23}}, year = {{2021}}, } @article{64016, abstract = {{Bacterial cellulose (BC) combined with organo-bridged porous silica nanoparticles offers potential opportunities to develop smart hybrid materials such as advanced drug delivery nanosystems. This work reports the preparation of bacterial cellulose membrane (BCM) and their modification by in situ methodology with the organo-bridged precursor 1,4-bis(triethoxysilyl)benzene (BTEB). BTEB was successfully incorporated into the BCM, and spherical hybrid silica nanoparticles with heterogeneous particle size (30–100 nm) and probably porous structure were formed and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared–attenuated total reflectance (FTIR-ATR), thermogravimetric analysis (TGA), and solid state nuclear magnetic resonance (NMR). We further combined solid-state NMR with dynamic nuclear polarization (DNP) to achieve sensitivity enhancement and to selectively enhance the NMR signal of the hydrophobic BTEB moieties on the BCM surface. This allowed us to get more detailed structural information about the BTEB–BCM multicomponent material.}}, author = {{Monteiro, Andreia S. and Oliveira, Marcos and Santagneli, Silvia and Carcel, Carole and Gutmann, Torsten and Buntkowsky, Gerd and Man, Michel Wong Chi and Barud, Hernane S. and Ribeiro, Sidney J. L.}}, issn = {{1932-7447}}, journal = {{Journal of Physical Chemistry C}}, number = {{8}}, pages = {{4498–4508}}, publisher = {{American Chemical Society}}, title = {{{Modification of Bacterial Cellulose Membrane with 1,4-Bis(triethoxysilyl)benzene: A Thorough Physical–Chemical Characterization Study}}}, doi = {{10.1021/acs.jpcc.0c09837}}, volume = {{125}}, year = {{2021}}, }