And then they took away the pigeon holes

Supermassive Black Holes Then and Now

Supermassive black holes have been a prime candidate for the probable energy sources of quasars, the most energetic objects in the universe, since the discovery of quasars. Over the last decade local surveys have suggested tha t quasars are present in most galaxies in the present universe [1,2]. The demographics of these objects are so fundamental to an est imate of their merger rate tha t we r...

Primordial Black Holes: Do They Exist and Are They Useful?

Recent developments in the study of primordial black holes (PBHs) are reviewed, with particular emphasis on their formation and evaporation. It is still not clear whether PBHs formed but, if they did, they could provide a unique probe of the early Universe, gravitational collapse, high energy physics and quantum gravity. Indeed their study may place interesting constraints on the physics releva...

Ecology. Oh the locusts sang, then they dropped dead.

Pigeon holes of memory: the life and times of Dr John Mackenzie (1803–1886)

CHRISTINA BYAM SHAW (ed.), Pigeon holes of memory: the life and times of Dr John Mackenzie (1803-1886), London, Constable, 1988, 8vo, pp. 443, illus., £20.00. John Mackenzie was born in northern Scotland in 1803. He studied medicine in Edinburgh, graduating in 1824. As part of his education he walked the wards of the London Hospital. He practised in the army and in Edinburgh and, after the chol...

Decisions for Others Become Less Impulsive the Further Away They Are on the Family Tree

BACKGROUND People tend to prefer a smaller immediate reward to a larger but delayed reward. Although this discounting of future rewards is often associated with impulsivity, it is not necessarily irrational. Instead it has been suggested that it reflects the decision maker's greater interest in the 'me now' than the 'me in 10 years', such that the concern for our future self is about the same a...