Since the previous Symposium, several exciting new developments and advances have occurred in the field of frequency standards and metrology. These include the first results on the long-tenn stability of a millisecond Pulsar, for which data 14 integrated over several years now show a stability of around 10- . Improvements in the understanding of various biases in Cesium beam standards promise accuracies in the low 14s for primary standards and in the low 13s for short commercial tubes, for which long tenn stabilities in low 14s have already been shown to be obtainable by accuracy improvement. Beams using optical pumping for state selection and for detection have been operated with excellent results, and more are being realized. Other new frequency standards which have appeared include a macroscopic rf trap with Mercury ions, which perfonns in the low 15s in one day, the sub millimeter metastable Magnesium beam, which has shown a short tenn stability 19 in the low 12s in one second and promises an accuracy of 10- , and the cold Hydrogen masers, which have such high stabilities that they cannot be measured with existing local oscillators. Prospects for future developments include laser manipulation of neutrals and spectroscopy of single ions at rest in a trap. Both these groups of techniques have great potential for unprecedented accuracy and short-and long-tenn stability, and new superior frequency standards are expected to be realizable in this way in the not too distant future.

An innovative study of the relationship between Andrea Mantegna and Giovanni Bellini, two masters of the Italian Renaissance Andrea Mantegna (c. 1431-1506) and Giovanni Bellini (active c. 1459; died 1516) each produced groundbreaking paintings, marked by pictorial and technical innovations, that are among the masterpieces of the Italian Renaissance. Exploring the fruitful dynamic between Mantegna's inventive compositional approach and interest in classical antiquity and Bellini's passion for landscape painting, this fascinating volume examines how these two artists, who were also brothers-in-law, influenced and responded to each other's work. Full of new insights and captivating juxtapositions-including comparisons of each of the artist's depictions of the Agony in the Garden and the Presentation to the Temple-this study reveals that neither Mantegna's nor Bellini's achievements can be fully understood in isolation and that their continuous creative exchanges shaped the work of both. Published by National Gallery Company/Distributed by Yale University Press Exhibition Schedule: National Gallery, London (10/01/18-01/27/19) Gemaldegalerie, Berlin (03/01/19-06/30/19)