No abstract

The regioselective double hydrophosphination of alkynes mediated by rhodium catalysts is presented. The distinctive stereoelectronic properties of the NHC ligand prevent the catalyst deactivation by diphosphine coordination thereby allowing for the closing of a productive catalytic cycle.

We discuss a previously unpublished description of electromagnetism outlined by Richard P Feynman in the 1960s in five handwritten pages, recently uncovered among his papers, and partly developed in later lectures. Though similar to the existing approaches deriving electromagnetism from special relativity, the present one extends a long way towards the derivation of Maxwell’s equations with minimal physical assumptions. In particular, without postulating Coulomb’s law, homogeneous Maxwell’s equations are written down by following a route different from the standard one, i.e. first introducing electromagnetic potentials in order to write down a relativistic invariant action, which is just the inverse approach to the usual one. Also, Feynman’s derivation of the Lorentz force exclusively follows from its linearity in the charge velocity and from relativistic invariance. Going further, i.e. adding the inhomogeneous Maxwell’s equations, requires some more physical input, and can be done by just following conventional lines, hence this task was not pursued here. Despite its incompleteness, this way of proceeding is of great historical and epistemological significance. We also comment about its possible relevance to didactics, as an interesting supplement to usual treatments. ‘One man’s assumption is another man’s conclusion’ [] —R. P. Feynman.

No abstract

No abstract

We give a detailed description of the energy balance equation for a stand-alone hybrid solar-wind power generating system. The dimensions of the power generator and the energy capacity of a buffer battery (used as an energy storage system) are chosen to suit a known consumer's profile. Future applications of the mathematical model developed and analogies with a similar hydrodynamic problem are discussed.

No abstract

A ‘sunflower’ system able to concentrate light from the Sun, storing it in a black body for energy application either for household or industrial use, is developed by means of basic physics concepts. A particular application to household water heating, called Planckon, is presented. Given its simplicity, the system can be realized and tested in any high-school or college laboratory, in order to stress the link existing between basic physics concepts and renewable energy resources.