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It has been found in recent measurements that the singlet-to-triplet exciton ratio in organic light-emitting diodes (OLEDs) is larger than expected from spin degeneracy, and that singlet excitons form at a larger rate than triplets. We employed the technique of optically detected magnetic resonance to measure the spin-dependent exciton formation rates in films of a polymer and corresponding monomer, and explore the relation between the formation rates and the actual singlet-to-triplet ratio measured previously in OLEDs. We found that the spin-dependent exciton formation rates can indeed quantitatively explain the observed exciton yields, and that singlet formation rates and yields are significantly enhanced only in polymer OLEDs, but not in OLEDs made from the corresponding monomer
Im Vergleich zu Umfragen an Wahrscheinlichkeitsstichproben bieten Umfragen an Access-Panels, die auf Nicht-Wahrscheinlichkeitsstichproben basieren, unbestreitbare wirtschaftliche Vorteile. Diese Vorteile gehen jedoch mit unvermeidbaren Qualitätseinbußen einher, die auch dann bestehen bleiben, wenn Erstere sehr niedrige Responseraten haben. Daher müssen die wirtschaftlichen Vorteile und die methodischen Einschränkungen gegeneinander abgewogen werden. Es wird argumentiert, dass diese Abwägung anhand normativer Festlegungen erfolgen muss. Unter Anwendung der hier vorgeschlagenen Maßstäbe kommt der Beitrag zu dem Schluss, dass die Qualitätsansprüche an über Massenmedien verbreitete Meinungsumfragen höher sein sollten als für rein (sozial)wissenschaftliche Zwecke.
Pulp Science?
(2023)
Since COVID-19 became a pandemic, many studies are being conducted to get a better understanding of the disease itself and its spread. One crucial indicator is the prevalence of SARS-CoV-2 infections. Since this measure is an important foundation for political decisions, its estimate must be reliable and unbiased. This paper presents reasons for biases in prevalence estimates due to unit nonresponse in typical studies. Since it is difficult to avoid bias in situations with mostly unknown nonresponse mechanisms, we propose the maximum amount of bias as one measure to assess the uncertainty due to nonresponse. An interactive web application is presented that calculates the limits of such a conservative unit nonresponse confidence interval (CUNCI).