Flamingos,salt lakes and volcanoes: hunting for evidence of past climate change on the high Altiplano of Bolivia

Hidden within the vast Bolivian Altiplano are archives of past climate change in the form of remarkable carbonate rocks surrounding lakes long since disappeared. Beyond the Salar de Uyuni, the largest salt flat in the world, lies a relatively untouched realm of volcanoes and salt lakes. Ancient shorelines from intervals in the Altiplano history, when large lakes were more abundant, may hold important information about a time when the climate in this region was punctuated by much wetter phases before present day aridity took a hold. Previous studies in this region have reconstructed robust chronological timelines for such events and highlight two large lake phases over the last 18 thousand years (the Tauca and Coipasa lake phases); however higher resolution climate data are scarce. Current studies on climate proxies from smaller lakes in southern Bolivia may shed light on some of these higher resolution climate events including El Niño–Southern Oscillation (ENSO) events. Laminated tufa found around the palaeoshorelines of the West Lípez Lakes is one such proxy, and can be analysed to investigate the potential roles of annual versus shorter‐term climatic variation in the evolving Altiplano climate at the time.     

Note on the energy scale of the Michigan OSO III ion chamber

The energy scale of the Michigan OSO III soft X-ray ion chamber has been assessed by using realistic theoretical X-ray spectra. Multiplicative factors by which the data may be corrected are proposed. The factors are only slightly temperature-dependent. A test of the proposed energy scale indicates it is still somewhat uncertain.Now at the University of Arizona, Tucson, Arizona.     

Binaries and multiple systems among the young stars

Binary formation is the dominant mode of star formation in the nearby Taurus and Ophiuchus star forming regions. I describe very briefly our present understanding of multiplicity among the youngest stars, the evolution and structure of their circumstellar disks, and their potential as sites of planetary system formation.     

An empirical model for the beams of radio pulsars

Motivated by recent results on the location of the radio emission in pulsar magnetospheres, we have developed a model which can account for the large diversity found in the average profile shapes of pulsars. At the centre of our model lies the idea that radio emission at a particular frequency arises from a wide range of altitudes above the surface of the star, and that it is confined to a region close to the last open field lines. We assert that the radial height range over which emission occurs is responsible for the complex average pulse shapes rather than the transverse (longitudinal) range proposed in most current models. By implementing an abrupt change in the height range to discriminate between young, short-period, highly energetic pulsars and their older counterparts, we obtain the observed transition between the simple and complex average pulse profiles observed in each group respectively. Monte Carlo simulations are used to demonstrate the match of our model to real observations.