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  1. Abstract

    We report the identification of metastable isomeric states of$$^{228}$$228Ac at 6.28 keV, 6.67 keV and 20.19 keV, with lifetimes of an order of 100 ns. These states are produced by the$$\beta $$β-decay of$$^{228}$$228Ra, a component of the$$^{232}$$232Th decay chain, with$$\beta $$βQ-values of 39.52 keV, 39.13 keV and 25.61 keV, respectively. Due to the low Q-value of$$^{228}$$228Ra as well as the relative abundance of$$^{232}$$232Th and their progeny in low background experiments, these observations potentially impact the low-energy background modeling of dark matter search experiments.

  2. Public Speaking Anxiety (PSA) and Foreign Language Anxiety (FLA) afflict most English Language Learners (ELLs) during a presentation. However, few tools are available to help multicultural learners clearly identify which type of anxiety they are feeling. In this paper, we present a field study conducted in real language classrooms. We developed machine learning models based on features of electrodermal activity (EDA) to predict non-verbal behaviors manifested as PSA and FLA. The students were labeled with the anxiety categories both PSA and FLA, PSA more, FLA more, or no anxiety. To classify the ELLs into their respective anxiety categories, prominent EDAmore »features were employed that supported the predictions of anxiety sources. These results may encourage both ELLs and instructors to be aware of the origins of anxiety subtypes and develop a customized practice for public speaking in a foreign language.« less
  3. Free, publicly-accessible full text available August 1, 2022