Active tectonics of the Hellenic subduction zone

This thesis is remarkable for the wide range of the techniques and observations used and for its insights, which cross several disciplines. It begins by solving a famous puzzle of the ancient world, which is what was responsible for the tsunami that destroyed settlements in the eastern Mediterranean in 365 AD. By radiocarbon dating of preserved marine organisms, Shaw demonstrates that the whole of western Crete was lifted out of the sea by up to 10 metres in a massive earthquake at that time, which occured on a previously unknown fault. The author shows that the resulting tsunami would have the characteristics described by ancient writers, and uses modern GPS measurements and coastiline geomorphology to show that the strain build-up near Crete requires such a tsunami-earthquake about every 6.000 years - a major insight into Mediterranean tsunami hazard. A detailed seismological study of earthquakes in the Cretan arc over the last 50 years reveals other important features of its behaviour that were previously unknown. Finally, she provides fundamental insights into the limitations of radiocarbon dating marine organisms, relating to how they secrete carbon into their skeletons. The thesis resulted in three major papers in top journals

Resolving discrete pulsar spin-down states with current and future instrumentation

An understanding of pulsar timing noise offers the potential to improve the timing precision of a large number of pulsars as well as facilitating our understanding of pulsar magnetospheres. For some sources, timing noise is attributable to a pulsar switching between two different spin-down rates $(\dot{\nu})$. Such transitions may be common but difficult to resolve using current techniques. In this work, we use simulations of $\dot{\nu}$-variable pulsars to investigate the likelihood of resolving individual $\dot{\nu}$ transitions. We inject step-changes in the value of $\dot{\nu}$ with a wide range of amplitudes and switching timescales. We then attempt to redetect these transitions using standard pulsar timing techniques. The pulse arrival-time precision and the observing cadence are varied. Limits on $\dot{\nu}$ detectability based on the effects such transitions have on the timing residuals are derived. With the typical cadences and timing precision of current timing programs, we find we are insensitive to a large region of $\Delta \dot{\nu}$ parameter space which encompasses small, short timescale switches. We find, where the rotation and emission states are correlated, that using changes to the pulse shape to estimate $\dot{\nu}$ transition epochs, can improve detectability in certain scenarios. The effects of cadence on $\Delta \dot{\nu}$ detectability are discussed and we make comparisons with a known population of intermittent and mode-switching pulsars. We conclude that for short timescale, small switches, cadence should not be compromised when new generations of ultra-sensitive radio telescopes are online.Comment: 19 pages, 11 figure

"Differing Prospects For Women and Men: Young Old-Age, Old Old-Age, and Elder Care"

Although elderly men and women share many of the same problems as they age, their lives are likely to follow different courses. Women are more likely than men to live into old old-age and are more likely to spend part of their young old-age caring for husbands or parents. By providing this unpaid care women might enter retirement earlier, rather than prolonging their working lives. Because they live longer, but are less likely than men to live with someone who will care for them, women are also more likely than men to require paid care either at home or in a nursing home. Proposals to reduce government spending on Social Security, Medicare, and Medicaid will thus have different implications for women and men. This paper evaluates changes in these programs, and describes alternative and innovative ways of providing and paying for eldercare in other countries as well as in the United States.

Variations in propagation delay times for line ten (TV) based time transfers

Variation in the propagation delay for a 30 km TV (Line Ten) radio link was evaluated for a series of 30 independent measurements. Time marks from TV Channel 5 WTTG in Washington, D.C. were simultaneously measured at the Johns Hopkins University Applied Physics Laboratory and at the United States Naval Observatory against each stations' local cesium standard clocks. Differences in the stations' cesium clocks were determined by portable cesium clock transfers. Thirty independent timing determinations were made. The root mean square deviation in the propagation delay calculated from the timing determinations was 11 ns. The variations seen in the propagation delays are believed to be caused by environmental factors and by errors in the portable clock timing measurements. In correlating the propagation delay variations with local weather conditions, only a moderate dependence on air temperature and absolute humidity was found