Updating the occurrences of Pterois miles in the Mediterranean Sea, with considerations on thermal boundaries and future range expansion

Here we present an update of the Mediterranean distribution of the lionfish Pterois miles, based on a comprehensive list of geo-referenced occurrences up to October 2019. New data were provided by multiple reporting tools and citizen science initiatives. Our findings suggest that well established populations of P. miles exist in the Levantine Sea, in the southern and central Aegean Sea, as well as in the Greek Ionian Sea, whilst so far, only a few individuals were reported from Tunisia and southern Sicily (Italy). We also argue about the future expansion of this invasive species in the Mediterranean region and about the role of climate change by projecting the limits of winter isotherms under different climate change scenarios. Under the assumption that the mean winter sea surface temperature is the main limiting factor of the range expansion of the species (i.e. 15.3oC winter isotherm), P. miles could substantially expand in the Mediterranean Sea, except the coolest northernmost regions, under future climatic scenarios. These results were discussed in comparison to published outcomes of species distribution modelling

A first-overtone RR Lyrae star with cyclic period changes

A detailed light curve analysis is presented for a first-overtone RR Lyrae star, MACHO* J050918.712-695015.31, based on MACHO and OGLE-III observations. As a foreground object of the Large Magellanic Cloud, it gives an extraordinary opportunity to study an almost continuous, 12-year long dataset of a relatively bright (V~15.0 mag) RRc star with rapid period change. Cyclic period modulation is suggested by the O-C method, where the cycle length is about 8 years. With the available unique dataset, we could draw strong limits on other light curve changes that may be associated to the period modulation. We could exclude both multiple periodicity and amplitude modulation unambiguously. Any theoretical model should reproduce the observed lack of photometric modulations. Simple arguments are also given for possible hydromagnetic effects.Comment: 6 pages, 6 figures, accepted for publication in MNRA

Are there any abnormal returns for early moving companies? An event study analysis of Greek companies

This study examines the phenomenon of the early moving companies. 50 Greek companies of high capitalisation enlisted in the Athens Stock Exchange are tested as to whether their intention to merge with or acquire another company in the South-Eastern European region provides them with positive abnormal returns. The methodology and model used is the Event studies method and the Market Model. There were 109 events examined, an event being the day when the intention to invest was known to the public. Results show neither positive nor negative abnormal returns for the sample companies, being in partial agreement with the literature.early movers; abnormal returns; market models; early moving companies; Greece; high capitalisation; Athens stock exchange; mergers; acquisitions; M&A; South-Eastern Europe; event studies; investments.

The Saffman–Taylor problem and several sets of remarkable integral identities

Publication status: PublishedFunder: Research Committee of Academy of AthensThe methodology based on the so‐called global relation, introduced by the first author, has recently led to the derivation of a novel nonlinear integral‐differential equation characterizing the classical problem of the Saffman–Taylor fingers with nonzero surface tension. In the particular case of zero surface tension, this equation is satisfied by the explicit solution obtained by Saffman and Taylor. Here, first, for the case of zero surface tension, we present a new nonlinear integrodifferential equation characterizing the Saffman–Taylor fingers. Then, by using the explicit Saffman–Taylor solution valid for the particular case of zero surface tension, we show that the above equations give rise to sets of remarkable integral trigonometric identities