... HI tidal tails, bridges and clouds . by B rbel Koribalski (CASS) . Neutral hydrogen gas (HI) is abundant in most galaxies, but it is also found well outside their stellar envelopes where it contributes to the intergalactic medium. Prominent nearby examples of intergalactic gas include the Magellanic Stream and extended HI bridges in the M 81 group of galaxies. ... We are currently writing a review paper on "HI tidal tails, bridges and clouds". ... today * ATNF | ...

metrologia The leap second: its history and possible future R. A. Nelson, D. D. McCarthy , S. Malys, J. Levine, B. Guinot, H. F. Fliegel , R. L. Beard and T. R. Bartholome w Abstract. This paper reviews the theoretica l motivatio n for the leap second in the context of the historica l evolutio n of time measurement . Th e periodic insertio n of a leap second step into th e scale of Coordinate d Universal Time (UTC) necessitates frequent changes in comple x timekeepin g systems an d is currentl y th e