Experimentelle und theoretische Untersuchungen zu Diorgano-Xenon(II)-Verbindungen

Mit der röntgenographischen Charakterisierung von Xe(C6F5)2 auf Basis von Röntgenpulverdaten gelingt erstmalig der direkte Nachweis einer Xenon-Verbindung mit zwei Xenon-Kohlenstoff-Bindungen. Auf dem Weg der Fluorid-katalysierten Reaktion von Xenondifluorid mit Trimethylarylsilanen können neue, bisher nicht beschriebene Verbindungen der Typen Xe(ArF)2 und ArFXeF (ArF = (2,3,5,6 F4C6H), (2,3,4,6 F4C6H), (2,3,4,5 F4C6H), (2,4,6 F3C6H2), (2,6 F2C6H3)) dargestellt werden, die auf Basis von 129Xe- und 19F-NMR-Daten charakterisiert werden. Die bei den Untersuchungen mit abnehmendem Fluorierungsgrad des Aromaten beobachtete Deaktivierung des Trimethylarylsilans läßt die Synthese der 2,6-Difluorphenyl-Verbindung auf diesem Weg nur mit geringer Ausbeute, die der Monofluor- und Phenyl-Xenon-Verbindungen nicht zu. Die Fluorid-katalysierte Reaktion von Xenondifluorid mit 1,4-Bis(trimethylsilyl)(2,3,5,6-tetrafluorbenzol) führt zu Hinweisen auf die Bildung von Verbindungen mit (Xe-C6F4-Xe)n-Einheiten. Jedoch gelingt es nicht, die Zusammensetzung der entstehenden Xenon-haltigen Produktgemische in zur weiteren Analyse ausreichendem Maße durch die Reaktionsparameter zu beeinflussen. Die exemplarische Untersuchung der Reaktion von (CH3)3Si(2,3,5,6-F4C6H) mit [(CH3)4N]F mit dem Ziel des Nachweises eines Trialkylarylsilicates, als das bei den Arylierungs-Reaktionen postulierte reaktive Intermediat, führt zu dem indirekten Nachweis von [(CH3)4N][(CH3)3Si(F)(2,3,5,6-F4C6H)]. Untersuchungen der Phenylierungseigenschaften von F3SiC6H5 gegenüber Xenondifluorid ergeben NMR-spektroskopische Hinweise auf die Bildung einer neuen, nicht-fluorierten Xenon-Verbindung, deren Eigenschaften die Vermutung nahelegen, daß es sich um [(C6H5)Xe] + handelt. Durch die Reaktion von [(2,6-F2C6H3)Xe][BF4] mit [(CH3)4N]F gelingt die Synthese der neuen Xenon-Verbindung (2,6-F2C6H3)XeF, deren NMR-spektroskopischen und chemischen Eigenschaften aufgeklärt werden. Dabei zeigt sich, daß (2,6-F2C6H3)XeF gegenüber Silanen unter Austausch des terminalen Fluor-Atoms zu neuen Verbindungen des Typs (2,6-F2C6H3)XeX (X = OCOCF3, Cl, Br, NCO, CN, C6F5, (2,3,5,6 F4C6H), (2,6 F2C6H3)) reagiert. (2,6-Difluorphenyl)xenonbromid repräsentiert die erste stabile Xenon(II)-Brom-Verbindung, (2,6-F2C6H3)XeNCO das erste Xenonisocyanat, (2,6-F2C6H3)Xe(C6F5) die erste unsymmetrisch substituierte Xenon-Aryl-Verbindung. Die Reaktionen von (2,6-Difluorphenyl)xenonfluorid mit (CH3)3SiI und (CH3)3SiN3 lassen anhand der Reaktionsprodukte auf die intermediäre Bildung von (2,6-F2C6H3)XeI, bzw. 2,6-F2C6H3)XeN3 schließen. Die NMR-spektroskopischen Ergebnisse der Reaktion von 1,4 Bis(trimethylsilyl)(2,3,5,6-tetrafluorbenzol) gegenüber (2,6-Difluorphenyl)xenonfluorid deuten auf die Bildung von 1,4-Bis(2,6-difluorphenyl)xenon)(2,3,5,6-tetrafluorbenzol) hin. Die Bildung von 1,3-F2-2-(CF3)C6H3 bei der Reaktion von (2,6-F2C6H3)XeF mit (CH3)3SiCF3 ist Anzeichen für das intermediäre Auftreten von (2,6 Difluorphenyl)trifluormethylxenon. Die Reaktion von [(CH3)4N][F5Si(C6H5)] mit (2,6-Difluorphenyl)xenonfluorid führt zum NMR-spektroskopischen Nachweis einer Xenon-Verbindung, deren Eigenschaften auf die Bildung von (2,6-Difluorphenyl)phenylxenon schließen lassen. Durch Vergleich der aus der röntgenographischen Charakterisierung von Xe(C6F5)2 gewonnenen experimentellen mit berechneten Strukturdaten wird gezeigt, daß die Dichtefunktional-Methodik B3LYP zusammen mit dem korrelations-konsistenten, quasirelativistischen triple-zeta Basissatz SDB-cc-pVTZ zur Vorhersage von Minimalstrukturen Xenon-haltiger Moleküle geeignet ist. Aufgrund der auf diesem theoretischen Level durchgeführten quantenmechanischen Berechnungen werden Vorhersagen von strukturellen, thermodynamischen und elektronischen Eigenschaften der im Rahmen dieser Arbeit synthetisierten Verbindungen getroffen, die in gutem Einklang mit den experimentell ermittelten stehen. Aufgrund von erstmalig zur Verbindungsklasse der Xenon-Kohlenstoff-Verbindungen durchgeführten Berechnungen der Elektronenlokalisationsfunktion gelingt es, Charakteristika unterschiedlicher Xenon-Element-Bindungen zu ermitteln

Aus der Arbeit der Naturschutzstation Südharz

Am 1. September 1991 wurde die Naturschutzstation Südharz als nachgeordnete Einrichtung der Oberen Naturschutzbehörde der Bezirksregierung Halle gegründet. Ihren Sitz hat sie im Landkreis Mansfelder Land in Wippra. Momentan sind in der Naturschutzstation ein Leiter, vier von den Forstämtern Pölsfeld, Roßla und Wippra delegierte Waldarbeiter, zwei Zivildienstleistende und ein Mitarbeiter im Rahmen einer Arbeitsbeschaffungsmaßnahme tätig. Vier Studenten absolvierten bisher Praktika

From Simulation Data to Test Cases for Fully Automated Driving and ADAS

Part 3: Practical Applications International audience Within this paper we present a new concept on deriving test cases from simulation data and outline challenging tasks when testing and validating fully automated driving functions and Advanced Driver Assistance Systems (ADAS). Open questions on topics like virtual simulation and identification of relevant situations for consistent testing of fully automated vehicles are given. Well known criticality metrics are assessed and discussed with regard to their potential to test fully automated vehicles and ADAS. Upon our knowledge most of them are not applicable to identify relevant traffic situations which are of importance for fully automated driving and ADAS. To overcome this limitation, we present a concept including filtering and rating of potentially relevant situations. Identified situations are described in a formal, abstract and human readable way. Finally, a situation catalogue is built up and linked to system requirements to derive test cases using a Domain Specific Language (DSL). Document type: Part of book or chapter of boo

Long-lived quantum memory enabling atom-photon entanglement over 101 km telecom fiber

Long-distance entanglement distribution is the key task for quantum networks, enabling applications such as secure communication and distributed quantum computing. Here we report on novel developments extending the reach for sharing entanglement between a single $^{87}$Rb atom and a single photon over long optical fibers. To maintain a high fidelity during the long flight times through such fibers, the coherence time of the single atom is prolonged to 7 ms by applying a long-lived qubit encoding. In addition, the attenuation in the fibers is minimized by converting the photon's wavelength to the telecom S-Band via polarization-preserving quantum frequency conversion. This enables to observe entanglement between the atomic quantum memory and the emitted photon after passing 101 km of optical fiber with a fidelity better than 70.8$\pm$2.4%. The fidelity, however, is no longer reduced due to loss of coherence of the atom or photon but in the current setup rather due to detector dark counts, showing the suitability of our platform to realize city-to-city scale quantum network links.Comment: 11 pages, 8 figures, comments are welcom

Delayed Fluorescence by Triplet–Triplet Annihilation from Columnar Liquid Crystal Films

Delayed fluorescence (DF) by triplet–triplet annihilation (TTA) is observed in solutions of a benzoperylene-imidoester mesogen that shows a hexagonal columnar mesophase at room temperature in the neat state. A similar benzoperylene-imide with a slightly smaller HOMO–LUMO gap, that also is hexagonal columnar liquid crystalline at room temperature, does not show DF in solution, and mixtures of the two mesogens show no DF in solution either, because of collisional quenching of the excited triplet states on the imidoester by the imide. In contrast, DF by TTA from the imide but not from the imidoester is observed in condensed films of such mixtures, even though neat films of either single material are not displaying DF. In contrast to the DF from the monomeric imidoester in solution, DF of the imide occurs from dimeric aggregates in the blend films, assisted by the imidoester. Thus, the close contact of intimately stacked molecules of the two different species in the columnar mesophase leads to a unique mesophase-assisted aggregate DF. This constitutes the first observation of DF by TTA from the columnar liquid crystalline state. If the imide is dispersed in films of polybromostyrene, which provides an external heavy-atom effect facilitating triplet formation, DF is also observed. Organic light-emitting diodes (OLEDs) devices incorporating these liquid crystal molecules demonstrated high external quantum efficiency (EQE). On the basis of the literature and to the best of our knowledge, the EQE reported is the highest among nondoped solution-processed OLED devices using a columnar liquid crystal molecule as the emitting layer

Entangling single atoms over 33 km telecom fibre

Quantum networks promise to provide the infrastructure for many disruptive applications, such as efcient long-distance quantum communication and distributed quantum computing1,2 . Central to these networks is the ability to distribute entanglement between distant nodes using photonic channels. Initially developed for quantum teleportation3,4 and loophole-free tests of Bell’s inequality5,6 , recently, entanglement distribution has also been achieved over telecom fbres and analysed retrospectively7,8 . Yet, to fully use entanglement over long-distance quantum network links it is mandatory to know it is available at the nodes before the entangled state decays. Here we demonstrate heralded entanglement between two independently trapped single rubidium atoms generated over fbre links with a length up to 33 km. For this, we generate atom–photon entanglement in two nodes located in buildings 400 m line-of-sight apart and to overcome high-attenuation losses in the fbres convert the photons to telecom wavelength using polarization-preserving quantum frequency conversion9 . The long fbres guide the photons to a Bell-state measurement setup in which a successful photonic projection measurement heralds the entanglement of the atoms10. Our results show the feasibility of entanglement distribution over telecom fbre links useful, for example, for device-independent quantum key distribution11–13 and quantum repeater protocols. The presented work represents an important step towards the realization of large-scale quantum network links

An unusual plank-shaped nematogen with a graphene nanoribbon core

A [12]phenacene exclusively decorated with four lateral hexylester substituents self-assembles into a nematic liquid crystal glass on cooling after melting at high temperature. This uniaxial nematic organization of a plank-shaped nanographene is unprecedented and in strong contrast to the common design rules for liquid crystals. Highly birefringent samples emitting polarized fluorescence can be obtained in homogeneously planar or twisted waveguiding configurations that are stable against crystallization at and below room temperature and up to 100 °C

Characterizing Antimicrobial Resistance in Clinically Relevant Bacteria Isolated at the Human/Animal/Environment Interface Using Whole-Genome Sequencing in Austria

This article belongs to the Collection Feature Papers in Molecular Microbiology.Antimicrobial resistance (AMR) is a public health issue attributed to the misuse of antibiotics in human and veterinary medicine. Since AMR surveillance requires a One Health approach, we sampled nine interconnected compartments at a hydrological open-air lab (HOAL) in Austria to obtain six bacterial species included in the WHO priority list of antibiotic-resistant bacteria (ARB). Whole genome sequencing-based typing included core genome multilocus sequence typing (cgMLST). Genetic and phenotypic characterization of AMR was performed for all isolates. Eighty-nine clinically-relevant bacteria were obtained from eight compartments including 49 E. coli, 27 E. faecalis, 7 K. pneumoniae and 6 E. faecium. Clusters of isolates from the same species obtained in different sample collection dates were detected. Of the isolates, 29.2% were resistant to at least one antimicrobial. E. coli and E. faecalis isolates from different compartments had acquired antimicrobial resistance genes (ARGs) associated with veterinary drugs such as aminoglycosides and tetracyclines, some of which were carried in conjugative and mobilizable plasmids. Three multidrug resistant (MDR) E. coli isolates were found in samples from field drainage and wastewater. Early detection of ARGs and ARB in natural and farm-related environments can identify hotspots of AMR and help prevent its emergence and dissemination along the food/feed chain.This research was partially funded by the European Union’s Horizon 2020 Research and Innovation program, grant agreement No 773830: One Health European Joint Program.info:eu-repo/semantics/publishedVersio

Mobile Air Quality Studies (MAQS) - an international project

Due to an increasing awareness of the potential hazardousness of air pollutants, new laws, rules and guidelines have recently been implemented globally. In this respect, numerous studies have addressed traffic-related exposure to particulate matter using stationary technology so far. By contrast, only few studies used the advanced technology of mobile exposure analysis. The Mobile Air Quality Study (MAQS) addresses the issue of air pollutant exposure by combining advanced high-granularity spatial-temporal analysis with vehicle-mounted, person-mounted and roadside sensors. The MAQS-platform will be used by international collaborators in order 1) to assess air pollutant exposure in relation to road structure, 2) to assess air pollutant exposure in relation to traffic density, 3) to assess air pollutant exposure in relation to weather conditions, 4) to compare exposure within vehicles between front and back seat (children) positions, and 5) to evaluate "traffic zone"- exposure in relation to non-"traffic zone"-exposure. Primarily, the MAQS-platform will focus on particulate matter. With the establishment of advanced mobile analysis tools, it is planed to extend the analysis to other pollutants including including NO2, SO2, nanoparticles, and ozone

Carbohydrate binding module-fused antibodies improve the performance of cellulose-based lateral flow immunoassays

Since the pandemic outbreak of Covid-19 in December 2019, several lateral flow assay (LFA) devices were developed to enable the constant monitoring of regional and global infection processes. Additionally, innumerable lateral flow test devices are frequently used for determination of different clinical parameters, food safety, and environmental factors. Since common LFAs rely on non-biodegradable nitrocellulose membranes, we focused on their replacement by cellulose-composed, biodegradable papers. We report the development of cellulose paper-based lateral flow immunoassays using a carbohydrate-binding module-fused to detection antibodies. Studies regarding the protein binding capacity and potential protein wash-off effects on cellulose paper demonstrated a 2.7-fold protein binding capacity of CBM-fused antibody fragments compared to the sole antibody fragment. Furthermore, this strategy improved the spatial retention of CBM-fused detection antibodies to the test area, which resulted in an enhanced sensitivity and improved overall LFA-performance compared to the naked detection antibody. CBM-assisted antibodies were validated by implementation into two model lateral flow test devices (pregnancy detection and the detection of SARS-CoV-2 specific antibodies). The CBM-assisted pregnancy LFA demonstrated sensitive detection of human gonadotropin (hCG) in synthetic urine and the CBM-assisted Covid-19 antibody LFA was able to detect SARS-CoV-2 specific antibodies present in serum. Our findings pave the way to the more frequent use of cellulose-based papers instead of nitrocellulose in LFA devices and thus potentially improve the sustainability in the field of POC diagnostics