We focused on how repeat collaborations in projects for inventions affect performance. Repeat collaborations have two contradictory aspects. A positive aspect is team development or experience, and a negative aspect is team degeneration or decline. Since both contradicting phenomena are observed, inventors have a dilemma as to whether they should keep collaborating in a team or not. The dilemma...

By international standards the economy of South Africa is extremely energy intensive with only a few countries having higher intensities. SA’s primary energy use per unit of GDP is amongst the highest in the world The high energy and electricity intensity of the economy partly reflects SA’s resource endowments (in particular the abundance of coal) but is also a function of the historical under-...

This paper considers some fundamental questions concerning marginally trapped surfaces, or apparent horizons, in Cauchy data sets for the Einstein equation. An area estimate for outermost marginally trapped surfaces is proved. The proof makes use of an existence result for marginal surfaces, in the presence of barriers, curvature estimates, together with a novel surgery construction for margina...