Eastward enlargements of the European Union, transitional arrangements and self-employment.

When the European Union expanded eastward in 2004 and 2007 to accession the so-called EU8 and EU2 countries, respectively, the incumbent member states imposed temporary restrictions on the employment of EU8 and EU2 nationals. Self-employed individuals were exempted from these transitional arrangements, prompting concerns that self-employment could be used as a means to evade the restrictions on labour market access. If the transitional arrangements led to an increase in EU8 and EU2 nationals' self-employment rates, as previous research suggests, then their removal should have led to a corresponding decrease.

The impact of repeated mass antigen testing for COVID-19 on the prevalence of the disease.

In the absence of effective vaccination, mass testing and quarantining of positive cases and their contacts could help to mitigate pandemics and allow economies to stay open. We investigate the effects of repeated mass testing on the COVID-19 pandemic caused by the SARS-CoV-2 virus, using data from the first ever nationwide rapid antigen testing implemented in Slovakia in autumn 2020. After the first round of testing, only districts above an ex ante unknown threshold of test positivity were re-tested.

Sperm motility and lipid composition in internally fertilizing ocellate river stingray Potamotrygon motoro.

All extant groups of Elasmobranches have internal fertilization and the structure of the male reproductive organs is very specific: sperm passes from the internal organs via the cloaca, but the male copulating organ (clasper) is distant from the cloaca. This suggests that sperm can contact the surrounding medium before fertilization. Because of this involvement with the environment, external signaling in sperm motility activation could occur in these species even though their fertilization mode is internal.