Advanced chemical investigations of the volatile element flerovium (Fl, Z=114)

The chemical and physical properties of transactinide elements are strongly influenced by relativistic effects. The determination of chemical properties of element 114 (flerovium, Fl) is a topic of high interest. Early atomic calculations indicated that Fl could be chemically inert. Recent relativistic calculations confirm that it should be more inert than its lighter homolog Pb, but nevertheless predict it to have a distinct metallic character. Experimental studies on Fl are challenging, due to its low production rates and relatively short half-lives. First chemistry experiments could not clarify the chemical properties due to limited statistics and inconsistent results. Therefore advanced studies on Fl were conducted at GSI, Darmstadt using TASCA. Prior to further investigations, several improvements to the experimental set-up were performed, mainly to optimize the overall efficiency and transportation time. This was assessed in multiple experiments with short-lived Hg and Pb isotopes. After the preparatory experiments, two successful Fl studies were performed at TASCA. Several radioactive decays of Fl were observed. In this thesis the details, methods and results of the experiments are discussed.Die Bestimmung der chemischen Eigenschaften von Flerovium (Fl, Z=114) ist sowohl für die theoretische als auch für die experimentelle Forschung von großem Interesse. Aufgrund der relativistischen Stabilisierung der quasi-geschlossenen Elektronenschalenkonfiguration von Fl sagten frühe theoretische Berechnungen voraus, dass Fl chemisch inert sei. Neuere realtivistische Berechnungen besagen ebenfalls ein weniger reaktives Verhalten als sein leichteres Homolog Pb, es soll aber dennoch einen ausgeprägten metallischen Charakter aufweisen. Experimentelle Studien zu Fl sind aufgrund der geringen Produktionsraten und der relativ kurzen Halbwertszeiten eine Herausforderung. Erste Experimente konnten aufgrund von widersprüchlichen Schlussfol- gerungen keine eindeutige Klärung herbeiführen. Aus diesem Grund, wurden an der GSI in Darmstadt verbesserte Experimente an TASCA durchgeführt. Zunächst wurde der Versuchsaufbau optimiert um die chemische Effizienz zu maximieren und die Transportzeit zu minimieren. Die Optimierungen wurden anhand von kurzlebigen Isotopen von Hg und Pb getestet. Nach den vorbereitenden Experimenten, wurden zwei erfolgreiche Fl-Studien an TASCA durchgeführt. Es wurden mehrere radioaktive Zerfälle von Fl beobachtet. In dieser Arbeit werden die Details, Methoden und Ergebnisse der Experimente diskutiert

Incidence, Risk Factors and Outcome of Suspected Central Venous Catheter-related Infections in Critically Ill COVID-19 Patients: A Multicenter Retrospective Cohort Study

BACKGROUND: Aims of this study were to investigate the prevalence and incidence of catheter-related infection, identify risk factors and determine the relation of catheter-related infection with mortality in critically ill COVID-19 patients. METHODS: This was a retrospective cohort study of central venous catheters (CVCs) in critically ill COVID-19 patients. Eligible CVC insertions required an indwelling time of at least 48 hours and were identified using a full-admission electronic healthrecord database. Risk factors were identified using logistic regression. Differences in survival rates at day 28 of follow-up were assessed using a log-rank test and proportional hazard model. RESULTS: In 538 patients, a total of 914 CVCs were included. Prevalence and incidence of suspected catheter-related infection were 7.9% and 9.4 infections per 1000 catheter indwelling days, respectively. Prone ventilation for more than five days was associated with increased risk of suspected catheter-related infection; odds ratio: 5.05 (95 CI: 2.12 - 11.0). Risk of death was significantly higher in patients with suspected catheter-related infection; hazard ratio: 1.78 (95% CI: 1.25 - 2.53). CONCLUSION: This study shows that in critically ill patients with COVID-19 prevalence and incidence of suspected catheter-related infection is high, prone ventilation is a risk factor and mortality is higher in case of catheter-related infection