I read with interest Anne MacGregor’s letter in the January 2013 issue of the Journal describing the removal of an unusually shaped intrauterine system (IUS) and asking if others have had similar experiences. A couple of years ago I too was alarmed as I removed an IUS through a slightly tight cervical os and noted an odd shape. On closer inspection the device was removed intact, but as in Dr Ma...

We provide a theory of the spread and decline of violence in a structured population. Engaging in violence towards a particular target group of individuals shapes the attitudes of individuals in the perpetrating group. We focus on situations where violence has private costs and provides local benefits to the perpetrating group only socially. The free rider problem is overcome when individuals f...

Scheme includes an easy-to-use and powerful macro mechanism for extending the programming language with new expression and definition forms. Using macros, a Scheme programmer can define a new notation for a specific problem domain and can then state algorithms in this language. Thus, Scheme programmers can formulate layers of abstraction whose expressive power greatly surpasses that of ordinary...

this paper presents an e-ring shaped printed monopole antenna for uwb applications with dual notched bands performance. in order to generate single frequency band notch function, we applied a u-ring shaped monopole antenna, and by inserting a rectangular ring in the centre of it an e-ring shaped radiating patch created and a dual band-notch function can be achieved. the measured bandwidth of th...