Synthese substituierter Acene und Untersuchung ihrer Struktur-Eigenschaftsbeziehungen

Diese Arbeit befasst sich mit der Synthese 2,3-dialkylsubstituierter Anthracenderivate, die mittels Suzuki-Miyaura-Kreuzkupplung an 2,3-Dibromanthracen sowie alternativ über die Reduktion der entsprechenden Anthrachinone realisiert wurde. Die auf diese Weise synthetisierten Monomere wurden durch UV-Bestrahlung in Lösung mittels einer photochemisch erlaubten [4+4]-Cycloaddition in ihre kovalenten Dimere überführt. Nach Isolation der Dimere wurden aus den erhaltenen Isomerenverhältnissen Aussagen über im Reaktionsübergangszustand wirkende, attraktive London-Dispersionswechselwirkungen abgeleitet. Mithilfe von NOE-Spektroskopie und Röntgendiffraktometrie konnte zudem ein tiefergehender Einblick in die strukturellen Eigenschaften der Verbindungsklasse der Dianthracene erhalten werden. In einem weiteren Projekt wurden neuartige Vertreter von tetrafluorsubstituierten Pentacenderivaten durch thermische Umsetzung geeigneter Vorstufen mit 1,2,4,5-Tetrazindicarbonsäuredimethylester in einer Sequenz aus Diels-Alder- und retro-Diels-Alder-Reaktionen synthetisiert. Fluorpentacene sind aufgrund ihrer n-Typ-Halbleitungseigenschaften für den Bau elektronischer Bauteile, beispielsweise organischer Feldeffekttransistoren (OFETs) von Interesse, des Weiteren kann Singulett-Spaltung an ihnen untersucht werden. Die entsprechenden Verbindungen wurden eingehend in Lösung sowie im Festkörper charakterisiert und ihr Verhalten nach Oxidation zu den Radikalkationen beziehungsweise Dikationen in Lösung untersucht. Die erhaltenen Ergebnisse wurden mit quantenchemischen Rechnungen auf DFT-Niveau korreliert. Es konnte gezeigt werden, dass die mit der Modifikation des Substitutionsmusters einhergehende Veränderung des Kristallpackungsmotivs maßgeblichen Einfluss auf die thermische Stabilität der untersuchten Tetrafluorpentacene hat

Mapping Per- and Polyfluoroalkyl Substances (PFAS) in South Carolina Surface Waters: Are there Hotspots?

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals used in consumer products for their unique chemical properties. PFAS compounds are resistant to water, oil, heat, and grease, making them useful for a wide variety of everyday items such as non-stick cooking pans, food packaging, electronics, carpets, upholstery, paints, adhesives, and personal care products.1 The resilient nature of PFAS has made these compounds immensely popular with consumers but has since been considered a potential environmental and public health hazard for their ability to bioaccumulate and for their stability in the environment. More than 6000 PFAS have been discovered in the environment to date, but this number continues to grow.2 We collected surface waters from 37 locations across the State of South Carolina and applied a new Total Organic Fluorine (TOF) method created in our lab to capture all PFAS compounds. This method combines the extraction technique Extractable Organic Fluorine (EOF) and Combustion Ion Chromatography (CIC) to measure PFAS hotspots.3 Results show that 36 of these samples contain TOF levels remarkably higher than U.S. Environmental Protection Agency’s new proposed regulatory limits of 4 parts-per-trillion for perfluorooctanoic acid (PFOA) and 4 parts-per-trillion for perfluorooctane sulfonate (PFOS).

Scattering laser light on cold atoms: multiple scattering signals from single-atom responses

We deduce the coherent backscattering signal from two distant laser-driven atoms using single-atom equations. In contrast to the standard master equation treatment, this new approach is suitable for the generalization to a large number of atomic scatterers.Comment: 4 pages, 2 figure

Sparsity Invariant CNNs

In this paper, we consider convolutional neural networks operating on sparse inputs with an application to depth upsampling from sparse laser scan data. First, we show that traditional convolutional networks perform poorly when applied to sparse data even when the location of missing data is provided to the network. To overcome this problem, we propose a simple yet effective sparse convolution layer which explicitly considers the location of missing data during the convolution operation. We demonstrate the benefits of the proposed network architecture in synthetic and real experiments with respect to various baseline approaches. Compared to dense baselines, the proposed sparse convolution network generalizes well to novel datasets and is invariant to the level of sparsity in the data. For our evaluation, we derive a novel dataset from the KITTI benchmark, comprising 93k depth annotated RGB images. Our dataset allows for training and evaluating depth upsampling and depth prediction techniques in challenging real-world settings and will be made available upon publication

The growing American health penalty: International trends in the employment of older workers with poor health

Many countries have reduced the generosity of sickness and disability programs while making them more activating – yet few studies have examined how employment rates have subsequently changed. We present estimates of how employment rates of older workers with poor health in 13 high-income countries changed 2004–7 to 2012–15 using HRS/SHARE/ELSA data. We find that those in poor health in the USA have experienced a unique deterioration: they have not only seen a widening gap to the employment rates of those with good health, but their employment rates fell per se. We find only for Sweden (and possibly England) signs that the health employment gap shrank, with rising employment but stable gaps elsewhere. We then examine possible explanations for the development in the USA: we find no evidence it links to labor market trends, but possible links to the USA's lack of disability benefit reform and wider economic trends

Inelastic Multiple Scattering of Interacting Bosons in Weak Random Potentials

We develop a diagrammatic scattering theory for interacting bosons in a three-dimensional, weakly disordered potential. We show how collisional energy transfer between the bosons induces the thermalization of the inelastic single-particle current which, after only few collision events, dominates over the elastic contribution described by the Gross-Pitaevskii ansatz.Comment: 5 pages, 3 figures, very close to published versio