TY - INPR A1 - Huber, Bernhard A1 - Pres, Sebastian A1 - Wittmann, Emanuel A1 - Dietrich, Lysanne A1 - Lüttig, Julian A1 - Fersch, Daniel A1 - Krauss, Enno A1 - Friedrich, Daniel A1 - Kern, Johannes A1 - Lisinetskii, Victor A1 - Hensen, Matthias A1 - Hecht, Bert A1 - Bratschitsch, Rudolf A1 - Riedle, Eberhard A1 - Brixner, Tobias T1 - Space- and time-resolved UV-to-NIR surface spectroscopy and 2D nanoscopy at 1 MHz repetition rate N2 - We describe a setup for time-resolved photoemission electron microscopy (TRPEEM) with aberration correction enabling 3 nm spatial resolution and sub-20 fs temporal resolution. The latter is realized by our development of a widely tunable (215–970 nm) noncollinear optical parametric amplifier (NOPA) at 1 MHz repetition rate. We discuss several exemplary applications. Efficient photoemission from plasmonic Au nanoresonators is investigated with phase-coherent pulse pairs from an actively stabilized interferometer. More complex excitation fields are created with a liquid-crystal-based pulse shaper enabling amplitude and phase shaping of NOPA pulses with spectral components from 600 to 800 nm. With this system we demonstrate spectroscopy within a single plasmonic nanoslit resonator by spectral amplitude shaping and investigate the local field dynamics with coherent two-dimensional (2D) spectroscopy at the nanometer length scale (“2D nanoscopy”). We show that the local response varies across a distance as small as 33 nm in our sample. Further, we report two-color pump–probe experiments using two independent NOPA beamlines. We extract local variations of the excited-state dynamics of a monolayered 2D material (WSe2) that we correlate with low-energy electron microscopy (LEEM) and reflectivity (LEER) measurements. Finally, we demonstrate the in-situ sample preparation capabilities for organic thin films and their characterization via spatially resolved electron diffraction and dark-field LEEM. KW - Photoemission electron microscopy PEEM KW - Low energy electron microscopy LEEM KW - Spatially resolved 2D spectroscopy KW - Two-color pump-probe spectroscopy KW - Time-resolved photoemission electron microscopy Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-191906 SN - 0034-6748 N1 - This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Review of Scientific Instruments 90, 113103 (2019); https://doi.org/10.1063/1.5115322 and may be found at https://doi.org/10.1063/1.5115322. ER - TY - THES A1 - Koch, Daniel Friedrich T1 - Wirksame Begrenzung von Staatsverschuldung unter Berücksichtigung (polit-)ökonomischer und ethischer Aspekte T1 - Limitation of public debt N2 - In den letzten Jahrzehnten griff die Staatsverschuldung in den meisten westlichen Staaten um sich wie ein wucherndes Krebsgeschwür. Die Ereignisse im Zuge der Euro-Krise haben ein Schlaglicht auf die Gefahren dieser Entwicklung geworfen. Diese Arbeit untersucht die Frage, wie sich Staatsverschuldung wirksam begrenzen lässt, wann dies nötig ist und welche Komponenten dafür berücksichtigt werden sollten. Sie betrachtet verschiedene Ansätze zur Begrenzung von Staatsverschuldung, evaluiert sie, und versucht aus ihren Stärken und Schwächen eine verbesserte Begrenzungsregel abzuleiten. Schließlich untermauert sie die gesellschaftliche Akzeptanz und Relevanz ihres Vorschlags, indem sie die Notwendigkeit und die mögliche Ausgestaltung einer Begrenzungsregel nicht nur unter Effizienzgesichtspunkten betrachtet, sondern auch eine normative Untersuchung vornimmt. Die erarbeiteten Evaluierungskriterien und Vorschläge sollen gleichermaßen mit ethischen und ökonomischen Anforderungen vereinbar sein. Es wird gezeigt, dass Staatsverschuldung aus Effizienzgründen wie auch aus ethischen Überlegungen begrenzt werden sollte. Sie zeigt, dass es ohne ein entsprechendes Reglement immer wieder zu einem staatsverschuldungsförderndem Politikversagen kommt. Andererseits teilt diese Arbeit aber nicht den weit verbreiteten Defätismus, dass der Kampf gegen die ansteigende Verschuldung aussichtslos sei. Vielmehr wird ein Vorschlag erarbeitet, wie sich dieses Politikversagen aushebeln und solide Staatsfinanzen erzwingen lassen. Neben einer Reihe kleinerer Aspekte werden folgende vier zentralen Ergebnisse erarbeitet: 1. Es wird erstmals ein umfassender Kriterienkatalog entwickelt, der alle relevanten Theoriebereiche abdeckt, die systematische Evaluierung verschiedener Budgetregeln ermöglicht und als Schema für die Entwicklung neuer Budgetregeln dienen kann. Dieser Katalog in Form einer Kriterienmatrix operationalisiert die Erkenntnisse der volkswirtschaftlichen Forschung zu Charakter, Wirkung und Ursachen von Staatsverschuldung. Erstmals werden in dieser Arbeit die unterschiedlichen Theoriestränge innerhalb eines Kriterienkataloges verknüpft. Denn nur so kann ein vollständiges Bild gezeichnet werden, nur so kann ein Prüfschema Anspruch auf Vollständigkeit erheben, und nur so können Begrenzungskonzepte entwickelt werden, die auch erfolgversprechend sind. Die hier ausgearbeitete Kriterienmatrix schließt damit gleich zwei Lücken, indem sie bisher isolierte Erkenntnisse vereint und diese gleich in ein Analyseinstrument umwandelt, das Ausgangspunkt für weitere Diskussion sein kann. 2. Literatur und politische Praxis halten eine Vielzahl von Vorschlägen zur Begrenzung von Staatsverschuldung bereit. Diese werden jedoch kaum verglichen und gegeneinander abgewogen. Dies mag auch an dem Fehlen eines geeigneten Analyseinstruments liegen. Dadurch gehen aber wertvolle Erkenntnisse verloren, die sich aus dem Abgleich von Stärken und Schwächen ergeben. Diese Arbeit nutzt den hier neu entwickelten Analyserahmen, um den Vergleich und die Evaluation verschiedener Budgetregeln vorzunehmen. Dabei werden systematisch Vor- und Nachteile der verschiedenen Konzepte herausgearbeitet. Dieser Vergleich ist nicht nur für sich genommen interessant und lange überfällig, sondern kann auch für die Weiterentwicklung der Diskussion wertvoll sein. So zeigen sich in der, alle relevanten Theorien umfassenden Kriterienmatrix, blinde Flecken, die allen Ansätzen gemein sind. 3. Ausgehend von der Kriterienmatrix und den Ergebnissen der Evaluierungen entwickelt diese Arbeit eine verbesserte Begrenzungsregel: die qualifizierte Lastenbremse. Diese basiert auf der Kriterienmatrix und den zuvor durchgeführten Evaluierungen. Dank dieser Analyse können einerseits die jeweils besten Elemente aus den bestehen Konzepten übernommen, bzw. durch Modifikationen optimiert werden, andererseits können die zuvor identifizierten Lücken durch neue Vorschläge geschlossen werden. Im Kern wird vorgeschlagen, die anderweitig eingeführten Ansätze des strukturellen Schuldenverbotes mit bestimmten Ausnahmen beizubehalten, und durch die hier neu entwickelten Konzepte der Staatsbilanz und der unabhängigen Kontrollinstanz mit Sanktionsrechten zu erweitern. Dieser Vorschlag erfüllt alle zuvor erarbeiteten Kriterien, d.h. er berücksichtig als einziger alle relevanten theoretischen Erkenntnisse zur Staatsverschuldung. Die qualifizierte Lastenbremse umfasst explizite und implizite Staatsverschuldung und begrenzt deren Anstieg nachhaltig. Dabei wahrt sie jedoch auch die nötige Flexibilität. Vor allem aber schlägt sie mehrere Sicherheitsmechanismen vor, welche die Wirksamkeit der Regel im politischen Alltag gewährleisten. So wird den Erkenntnissen der Neuen Politischen Ökonomie Rechnung getragen. 4. Schließlich bleibt diese Arbeit nicht dabei stehen, einen Vorschlag zu entwickeln, der allen ökonomischen Kriterien gerecht wird. Sie begnügt sich nicht damit, festzustellen, dass es effizient und wohlfahrtssteigernd wäre, wenn ihre Vorschläge umgesetzt würden. Sie geht einen Schritt weiter, wirft einen Blick über den Tellerrand der Volkswirtschaftslehre hinaus und fragt auch nach der Legitimität und dem ethischen Wert des Vorschlags. Dies geht von der Erkenntnis aus, dass eine solch tiefgreifende Maßnahme wie eine wirksame Schuldenbremse auch das normative Empfinden der Bürger widerspiegeln muss und dass die gesellschaftliche Relevanz und Durchsetzbarkeit einer Regel von einer Legitimität abhängt, die auf Effizienz und Ethik gleichermaßen fußt. Unbewusst wird diese Auffassung in weiten Teilen der Ökonomie geteilt, was sich daran zeigt, dass viele Arbeiten zur Staatsschuldbegrenzung auf Gerechtigkeitsaspekte und moralische Verpflichtungen Bezug nehmen. Sie kranken jedoch daran, dass ihre Annahme der ethischen Fragwürdigkeit von Staatsverschuldung unbegründet bleibt. Dadurch stehen sie auf wackeligen Füßen. Diese Lücke wird hier geschlossen. Eine Analyse auf Basis der katholischen Soziallehre belegt die Zielkongruenz von normativen und ökonomischen Anforderungen an die Fiskalpolitik. Es wird gezeigt, dass die hier vorgeschlagene Begrenzung von Staatsverschuldung nicht nur ökonomisch, sondern auch ethisch geboten ist. Unterm Strich lässt sich festhalten, dass diese Arbeit den weit verbreiteten Fatalismus im Bezug auf Politik und Staatsverschuldung nicht teilt. Ja, es stimmt, dass der politische Wettbewerb oft unerfreuliche fiskalpolitische Ergebnisse hervorbringt. Ja, es stimmt, dass die Entwicklung der Staatsfinanzen besorgniserregend ist. Ja, es besteht dringender Handlungsbedarf. Aber nein, diese Entwicklung ist nicht alternativlos. Nein, der Kampf gegen die Staatsverschuldung ist nicht aussichtslos. Und nein, die westlichen Demokratien sind nicht zwangsläufig dazu verdammt, immer weiter in die Schuldenfalle zu rutschen. Staatsverschuldung lässt sich wirksam begrenzen und es gibt Mechanismen, mit denen das Politikversagen umgangen werden kann. Das Ringen um bessere Regeln ist die Mühe wert. Für eine wirksame Begrenzung von Staatsverschuldung einzutreten ist das Gebot der ökonomischen Vernunft, wie auch ethische Verpflichtung. N2 - Public debt has turned into a major political and economical problem. This thesis studies possibilities of limiting the rise of public debt. It not only evaluates the classical economic theory, but also incorporates findings of the theory of political economics. Alongside it conducts a thorough study of the ethical aspects of public debt. The key findings are a new approach to the limitation of public debt, a catalogue of criteria for every limitation rule to fulfill, and an evaluation of existing budget rules. KW - Öffentliche Schulden KW - Beschränkung KW - Politische Ökonomie KW - Ethik KW - Christliche Sozialethik KW - Katholische Soziallehre KW - ökonomische Theorie der Verfassung KW - Public Debt Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-67383 ER - TY - JOUR A1 - Lüftner, Daniel A1 - Milko, Matus A1 - Huppmann, Sophia A1 - Scholz, Markus A1 - Ngyuen, Nam A1 - Wießner, Michael A1 - Schöll, Achim A1 - Reinert, Friedrich A1 - Puschnig, Peter T1 - CuPc/Au(1 1 0): Determination of the azimuthal alignment by a combination of angle-resolved photoemission and density functional theory JF - Journal of Electron Spectroscopy and Related Phenomena N2 - Here we report on a combined experimental and theoretical study on the structural and electronic properties of a monolayer of Copper-Phthalocyanine (CuPc) on the Au(1 1 0) surface. Low-energy electron diffraction reveals a commensurate overlayer unit cell containing one adsorbate species. The azimuthal alignment of the CuPc molecule is revealed by comparing experimental constant binding energy (kxky)-maps using angle-resolved photoelectron spectroscopy with theoretical momentum maps of the free molecule's highest occupied molecular orbital (HOMO). This structural information is confirmed by total energy calculations within the framework of van-der-Waals corrected density functional theory. The electronic structure is further analyzed by computing the molecule-projected density of states, using both a semi-local and a hybrid exchange-correlation functional. In agreement with experiment, the HOMO is located about 1.2 eV below the Fermi-level, while there is no significant charge transfer into the molecule and the CuPc LUMO remains unoccupied on the Au(1 1 0) surface. KW - density functional theory KW - angle-resolved photoemission spectroscopy KW - organic molecule KW - organic–metal interface Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-120986 SN - 0368-2048 VL - 195 ER - TY - JOUR A1 - Reiter, Theresa A1 - Gensler, Daniel A1 - Ritter, Oliver A1 - Weiss, Ingo A1 - Geistert, Wolfgang A1 - Kaufmann, Ralf A1 - Hoffmeister, Sabine A1 - Friedrich, Michael T. A1 - Wintzheimer, Stefan A1 - Düring, Markus A1 - Nordbeck, Peter A1 - Jakob, Peter M. A1 - Ladd, Mark E. A1 - Quick, Harald H. A1 - Bauer, Wolfgang R. T1 - Direct cooling of the catheter tip increases safety for CMR-guided electrophysiological procedures JF - Journal of Cardiovascular Magnetic Resonance N2 - Background: One of the safety concerns when performing electrophysiological (EP) procedures under magnetic resonance (MR) guidance is the risk of passive tissue heating due to the EP catheter being exposed to the radiofrequency (RF) field of the RF transmitting body coil. Ablation procedures that use catheters with irrigated tips are well established therapeutic options for the treatment of cardiac arrhythmias and when used in a modified mode might offer an additional system for suppressing passive catheter heating. Methods: A two-step approach was chosen. Firstly, tests on passive catheter heating were performed in a 1.5 T Avanto system (Siemens Healthcare Sector, Erlangen, Germany) using a ASTM Phantom in order to determine a possible maximum temperature rise. Secondly, a phantom was designed for simulation of the interface between blood and the vascular wall. The MR-RF induced temperature rise was simulated by catheter tip heating via a standard ablation generator. Power levels from 1 to 6 W were selected. Ablation duration was 120 s with no tip irrigation during the first 60 s and irrigation at rates from 2 ml/min to 35 ml/min for the remaining 60 s (Biotronik Qiona Pump, Berlin, Germany). The temperature was measured with fluoroscopic sensors (Luxtron, Santa Barbara, CA, USA) at a distance of 0 mm, 2 mm, 4 mm, and 6 mm from the catheter tip. Results: A maximum temperature rise of 22.4 degrees C at the catheter tip was documented in the MR scanner. This temperature rise is equivalent to the heating effect of an ablator's power output of 6 W at a contact force of the weight of 90 g (0.883 N). The catheter tip irrigation was able to limit the temperature rise to less than 2 degrees C for the majority of examined power levels, and for all examined power levels the residual temperature rise was less than 8 degrees C. Conclusion: Up to a maximum of 22.4 degrees C, the temperature rise at the tissue surface can be entirely suppressed by using the catheter's own irrigation system. The irrigated tip system can be used to increase MR safety of EP catheters by suppressing the effects of unwanted passive catheter heating due to RF exposure from the MR scanner. KW - EP Procedures KW - radiofrequency ablation KW - contact force KW - lesion size KW - MRI KW - temperature KW - tissue KW - wires KW - model KW - ablation KW - safety KW - catheter tip KW - MR guidance Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-134927 VL - 14 IS - 12 ER - TY - JOUR A1 - He, Jiang A1 - Rauch, Florian A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Ribbeck, Tatjana A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Marder, Todd B. T1 - N-Heterocyclic Olefins as Electron Donors in Combination with Triarylborane Acceptors: Synthesis, Optical and Electronic Properties of D-π-A Compounds JF - Chemistry - A European Journal N2 - N‐heterocyclic olefins (NHOs), relatives of N‐heterocyclic carbenes (NHCs), exhibit high nucleophilicity and soft Lewis basic character. To investigate their π‐electron donating ability, NHOs were attached to triarylborane π‐acceptors (A) giving donor (D)–π–A compounds 1–3. In addition, an enamine π‐donor analogue (4) was synthesized for comparison. UV–visible absorption studies show a larger red shift for the NHO‐containing boranes than for the enamine analogue, a relative of cyclic (alkyl)(amino) carbenes (CAACs). Solvent‐dependent emission studies indicate that 1–4 have moderate intramolecular charge‐transfer (ICT) behavior. Electrochemical investigations reveal that the NHO‐containing boranes have extremely low reversible oxidation potentials (e.g., for 3, \(E^{ox}_{1/2}\) =−0.40 V vs. ferrocene/ferrocenium, Fc/Fc\(^+\), in THF). Time‐dependent (TD) DFT calculations show that the HOMOs of 1–3 are much more destabilized than that of the enamine‐containing 4, which confirms the stronger donating ability of NHOs. KW - donor-acceptor systems KW - electrochemistry KW - photophysical prosperties KW - N-heterocyclic olefins KW - triarylboranes Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204690 VL - 25 ER - TY - JOUR A1 - Benoit, Joshua B. A1 - Adelman, Zach N. A1 - Reinhardt, Klaus A1 - Dolan, Amanda A1 - Poelchau, Monica A1 - Jennings, Emily C. A1 - Szuter, Elise M. A1 - Hagan, Richard W. A1 - Gujar, Hemant A1 - Shukla, Jayendra Nath A1 - Zhu, Fang A1 - Mohan, M. A1 - Nelson, David R. A1 - Rosendale, Andrew J. A1 - Derst, Christian A1 - Resnik, Valentina A1 - Wernig, Sebastian A1 - Menegazzi, Pamela A1 - Wegener, Christian A1 - Peschel, Nicolai A1 - Hendershot, Jacob M. A1 - Blenau, Wolfgang A1 - Predel, Reinhard A1 - Johnston, Paul R. A1 - Ioannidis, Panagiotis A1 - Waterhouse, Robert M. A1 - Nauen, Ralf A1 - Schorn, Corinna A1 - Ott, Mark-Christoph A1 - Maiwald, Frank A1 - Johnston, J. Spencer A1 - Gondhalekar, Ameya D. A1 - Scharf, Michael E. A1 - Raje, Kapil R. A1 - Hottel, Benjamin A. A1 - Armisén, David A1 - Crumière, Antonin Jean Johan A1 - Refki, Peter Nagui A1 - Santos, Maria Emilia A1 - Sghaier, Essia A1 - Viala, Sèverine A1 - Khila, Abderrahman A1 - Ahn, Seung-Joon A1 - Childers, Christopher A1 - Lee, Chien-Yueh A1 - Lin, Han A1 - Hughes, Daniel S.T. A1 - Duncan, Elizabeth J. A1 - Murali, Shwetha C. A1 - Qu, Jiaxin A1 - Dugan, Shannon A1 - Lee, Sandra L. A1 - Chao, Hsu A1 - Dinh, Huyen A1 - Han, Yi A1 - Doddapaneni, Harshavardhan A1 - Worley, Kim C. A1 - Muzny, Donna M. A1 - Wheeler, David A1 - Panfilio, Kristen A. A1 - Jentzsch, Iris M. Vargas A1 - Jentzsch, IMV A1 - Vargo, Edward L. A1 - Booth, Warren A1 - Friedrich, Markus A1 - Weirauch, Matthew T. A1 - Anderson, Michelle A.E. A1 - Jones, Jeffery W. A1 - Mittapalli, Omprakash A1 - Zhao, Chaoyang A1 - Zhou, Jing-Jiang A1 - Evans, Jay D. A1 - Attardo, Geoffrey M. A1 - Robertson, Hugh M. A1 - Zdobnov, Evgeny M. A1 - Ribeiro, Jose M.C. A1 - Gibbs, Richard A. A1 - Werren, John H. A1 - Palli, Subba R. A1 - Schal, Coby A1 - Richards, Stephen T1 - Unique features of a global human ectoparasite identified through sequencing of the bed bug genome JF - Nature Communications N2 - The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host–symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human–bed bug and symbiont–bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as a human ectoparasite. KW - human ectoparasite KW - bed bug KW - Cimex lectularius KW - genome Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-166221 VL - 7 IS - 10165 ER - TY - JOUR A1 - Ferger, Matthias A1 - Ban, Željka A1 - Krošl, Ivona A1 - Tomić, Sanja A1 - Dietrich, Lena A1 - Lorenzen, Sabine A1 - Rauch, Florian A1 - Sieh, Daniel A1 - Friedrich, Alexandra A1 - Griesbeck, Stefanie A1 - Kenđel, Adriana A1 - Miljanić, Snežana A1 - Piantanida, Ivo A1 - Marder, Todd B. T1 - Bis(phenylethynyl)arene Linkers in Tetracationic Bis-triarylborane Chromophores Control Fluorimetric and Raman Sensing of Various DNAs and RNAs JF - Chemistry-A European Journal N2 - We report four new luminescent tetracationic bis-triarylborane DNA and RNA sensors that show high binding affinities, in several cases even in the nanomolar range. Three of the compounds contain substituted, highly emissive and structurally flexible bis(2,6-dimethylphenyl-4-ethynyl)arene linkers (3: arene=5,5′-2,2′-bithiophene; 4: arene=1,4-benzene; 5: arene=9,10-anthracene) between the two boryl moieties and serve as efficient dual Raman and fluorescence chromophores. The shorter analogue 6 employs 9,10-anthracene as the linker and demonstrates the importance of an adequate linker length with a certain level of flexibility by exhibiting generally lower binding affinities than 3–5. Pronounced aggregation–deaggregation processes are observed in fluorimetric titration experiments with DNA for compounds 3 and 5. Molecular modelling of complexes of 5 with AT-DNA, suggest the minor groove as the dominant binding site for monomeric 5, but demonstrate that dimers of 5 can also be accommodated. Strong SERS responses for 3–5 versus a very weak response for 6, particularly the strong signals from anthracene itself observed for 5 but not for 6, demonstrate the importance of triple bonds for strong Raman activity in molecules of this compound class. The energy of the characteristic stretching vibration of the C≡C bonds is significantly dependent on the aromatic moiety between the triple bonds. The insertion of aromatic moieties between two C≡C bonds thus offers an alternative design for dual Raman and fluorescence chromophores, applicable in multiplex biological Raman imaging. KW - boranes KW - Raman probes KW - molecular modelling KW - fluorescent probes KW - DNA/RNA sensors Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256717 VL - 27 IS - 16 ER - TY - JOUR A1 - Merz, Julia A1 - Dietz, Maximilian A1 - Vonhausen, Yvonne A1 - Wöber, Frederik A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Moos, Michael A1 - Holzapfel, Marco A1 - Lambert, Christoph A1 - Marder, Todd B. T1 - Synthesis, Photophysical and Electronic Properties of New Red-to-NIR Emitting Donor-Acceptor Pyrene Derivatives JF - Chemistry - A European Journal N2 - We synthesized new pyrene derivatives with strong bis(para ‐methoxyphenyl)amine donors at the 2,7‐positions and n ‐azaacene acceptors at the K‐region of pyrene. The compounds possess a strong intramolecular charge transfer, leading to unusual properties such as emission in the red to NIR region (700 nm), which has not been reported before for monomeric pyrenes. Detailed photophysical studies reveal very long intrinsic lifetimes of >100 ns for the new compounds, which is typical for 2,7‐substituted pyrenes but not for K‐region substituted pyrenes. The incorporation of strong donors and acceptors leads to very low reduction and oxidation potentials, and spectroelectrochemical studies show that the compounds are on the borderline between localized Robin‐Day class‐II and delocalized Robin‐Day class‐III species. KW - orylation KW - K-region KW - luminescence KW - polycyclic aromatic hydrocarbons KW - redox Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-207486 VL - 26 IS - 2 ER - TY - JOUR A1 - Tufarelli, Tommaso A1 - Friedrich, Daniel A1 - Groß, Heiko A1 - Hamm, Joachim A1 - Hess, Ortwin A1 - Hecht, Bert T1 - Single quantum emitter Dicke enhancement JF - Physical Review Research N2 - Coupling N identical emitters to the same field mode is a well-established method to enhance light-matter interaction. However, the resulting √N boost of the coupling strength comes at the cost of a “linearized” (effectively semiclassical) dynamics. Here, we instead demonstrate a new approach for enhancing the coupling constant of a single quantum emitter, while retaining the nonlinear character of the light-matter interaction. We consider a single quantum emitter with N nearly degenerate transitions that are collectively coupled to the same field mode. We show that in such conditions an effective Jaynes-Cummings model emerges with a boosted coupling constant of order √N. The validity and consequences of our general conclusions are analytically demonstrated for the instructive case N=2. We further observe that our system can closely match the spectral line shapes and photon autocorrelation functions typical of Jaynes-Cummings physics, proving that quantum optical nonlinearities are retained. Our findings match up very well with recent broadband plasmonic nanoresonator strong-coupling experiments and will, therefore, facilitate the control and detection of single-photon nonlinearities at ambient conditions. KW - Cavity quantum electrodynamics KW - Collective effects in quantum optics KW - Quantum optics with artificial atoms KW - Superradiance & subradiance Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-261459 VL - 3 ER - TY - JOUR A1 - Rauch, Florian A1 - Endres, Peter A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Hähnel, Martin A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Ji, Lei A1 - Marder, Todd B. T1 - An Iterative Divergent Approach to Conjugated Starburst Borane Dendrimers JF - Chemistry – A European Journal N2 - Using a new divergent approach, conjugated triarylborane dendrimers were synthesized up to the 2nd generation. The synthetic strategy consists of three steps: 1) functionalization, via iridium catalyzed C−H borylation; 2) activation, via fluorination of the generated boronate ester with K[HF\(_{2}\)] or [N(nBu\(_{4}\))][HF\(_{2}\)]; and 3) expansion, via reaction of the trifluoroborate salts with aryl Grignard reagents. The concept was also shown to be viable for a convergent approach. All but one of the conjugated borane dendrimers exhibit multiple, distinct and reversible reduction potentials, making them potentially interesting materials for applications in molecular accumulators. Based on their photophysical properties, the 1st generation dendrimers exhibit good conjugation over the whole system. However, the conjugation does not increase further upon expansion to the 2nd generation, but the molar extinction coefficients increase linearly with the number of triarylborane subunits, suggesting a potential application as photonic antennas. KW - density functional calculations KW - electron storage KW - luminescence KW - redox KW - triarylborane Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218345 VL - 26 IS - 57 SP - 12951 EP - 12963 ER - TY - JOUR A1 - Rauch, Florian A1 - Fuchs, Sonja A1 - Friedrich, Alexandra A1 - Sieh, Daniel A1 - Krummenacher, Ivo A1 - Braunschweig, Holger A1 - Finze, Maik A1 - Marder, Todd B. T1 - Highly Stable, Readily Reducible, Fluorescent, Trifluoromethylated 9‐Borafluorenes JF - Chemistry – A European Journal N2 - Three different perfluoroalkylated borafluorenes (\(^{F}\)Bf) were prepared and their electronic and photophysical properties were investigated. The systems have four trifluoromethyl moieties on the borafluorene moiety as well as two trifluoromethyl groups at the ortho positions of their exo‐aryl moieties. They differ with regard to the para substituents on their exo‐aryl moieties, being a proton \(^{F}\)Xyl\(^{F}\)Bf, \(^{F}\)Xyl: 2,6‐bis(trifluoromethyl)phenyl), a trifluoromethyl group (\(^{F}\)Mes\(^{F}\)Bf, \(^{F}\)Mes: 2,4,6‐tris(trifluoromethyl)phenyl) or a dimethylamino group (p‐NMe\(_{2}\)‐\(^{F}\)Xyl\(^{F}\)Bf, p‐NMe\(_{2}\)‐\(^{F}\)Xyl: 4‐(dimethylamino)‐2,6‐bis(trifluoromethyl)phenyl), respectively. All derivatives exhibit extraordinarily low reduction potentials, comparable to those of perylenediimides. The most electron‐deficient derivative \(^{F}\)Mes\(^{F}\)Bf was also chemically reduced and its radical anion isolated and characterized. Furthermore, all compounds exhibit very long fluorescent lifetimes of about 250 ns up to 1.6 μs; however, the underlying mechanisms responsible for this differ. The donor‐substituted derivative p‐NMe\(_{2}\)‐\(^{F}\)Xyl\(^{F}\)Bf exhibits thermally activated delayed fluorescence (TADF) from a charge‐transfer (CT) state, whereas the \(^{F}\)Mes\(^{F}\)Bf and FXylFBf borafluorenes exhibit only weakly allowed locally excited (LE) transitions due to their symmetry and low transition‐dipole moments. KW - borafluorenes KW - boron KW - EPR spectroscopy KW - fluorescence KW - heterocycles Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218390 VL - 26 IS - 56 SP - 12794 EP - 12808 ER - TY - JOUR A1 - Friedrich, Maximilian U. A1 - Schneider, Erich A1 - Buerklein, Miriam A1 - Taeger, Johannes A1 - Hartig, Johannes A1 - Volkmann, Jens A1 - Peach, Robert A1 - Zeller, Daniel T1 - Smartphone video nystagmography using convolutional neural networks: ConVNG JF - Journal of Neurology N2 - Background Eye movement abnormalities are commonplace in neurological disorders. However, unaided eye movement assessments lack granularity. Although videooculography (VOG) improves diagnostic accuracy, resource intensiveness precludes its broad use. To bridge this care gap, we here validate a framework for smartphone video-based nystagmography capitalizing on recent computer vision advances. Methods A convolutional neural network was fine-tuned for pupil tracking using > 550 annotated frames: ConVNG. In a cross-sectional approach, slow-phase velocity of optokinetic nystagmus was calculated in 10 subjects using ConVNG and VOG. Equivalence of accuracy and precision was assessed using the “two one-sample t-test” (TOST) and Bayesian interval-null approaches. ConVNG was systematically compared to OpenFace and MediaPipe as computer vision (CV) benchmarks for gaze estimation. Results ConVNG tracking accuracy reached 9–15% of an average pupil diameter. In a fully independent clinical video dataset, ConVNG robustly detected pupil keypoints (median prediction confidence 0.85). SPV measurement accuracy was equivalent to VOG (TOST p < 0.017; Bayes factors (BF) > 24). ConVNG, but not MediaPipe, achieved equivalence to VOG in all SPV calculations. Median precision was 0.30°/s for ConVNG, 0.7°/s for MediaPipe and 0.12°/s for VOG. ConVNG precision was significantly higher than MediaPipe in vertical planes, but both algorithms’ precision was inferior to VOG. Conclusions ConVNG enables offline smartphone video nystagmography with an accuracy comparable to VOG and significantly higher precision than MediaPipe, a benchmark computer vision application for gaze estimation. This serves as a blueprint for highly accessible tools with potential to accelerate progress toward precise and personalized Medicine. KW - digital medicine KW - nystagmus KW - eye movement disorders KW - videooculography KW - computer vision KW - telemedicine KW - precision medicine Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-324526 VL - 270 IS - 5 ER -