Given a linear form C1X1 + · · · + CnXn, with coefficients in the integers, we characterize exactly the countably infinite abelian groups G for which there exists a permutation f that maps all solutions (α1, . . . , αn) ∈ Gn (with the αi not all equal) to the equation C1X1+ · · ·+CnXn = 0 to non-solutions. This generalises a result of Hegarty about permutations of an abelian group avoiding arit...

Abstract As part of the roundtable, “Ethics and Future Global Food System,” this essay discusses some major challenges we will face in feeding world 2050. A first challenge is nutritional: 690 million people (9 percent world's population) are currently undernourished, while 2.1 billion adults (28 overweight or obese. The current global food system insufficient ensuring that nutritious foods mak...

Destroying Biological Hazards Anthrax. Mad Cow Disease. Biological Weapons. These words have filled headlines, increasing anxiety around the world. The threat of such biological hazards, both natural and man-made, has created unprecedented challenges for public health institutions and hospitals, as well as for national defense. These biohazards demand fast and effective decontamination techniques.