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It took eventually from the turn of the century until 1926 before the extraterrestrial nature of the penetrating radiation was generally accepted.

In the work that culminated with high altitude balloon flights, many important contributions have been forgotten and in particular those of Domenico Pacini, who, in June 1911, demonstrated by studying the decrease of radioactivity with an electroscope immersed in water that the radiation today called "cosmic rays" could not come from the crust of the Earth. This was the first time in which the technique of comparison of undersea measurements with measurements at sea level has been used to obtain a result in fundamental physics; this technique will be used in neutrino experiments of the near future. This article carefully retraces the history of the discovery of cosmic rays and puts the unfolding story in both the political and scientific contexts. With the help of material previously unknown to the history of science, for example the nominations for the Nobel prizes related to cosmic ray research and the relevant internal reports of the Swedish Royal Academy of Science, and letters exchanged between Victor Hess and Pacini, a more complete view of this fascinating discovery is possible.

A nucleation site initiates the birth of a crystal. In most cases, take for example the dust particle in a snowflake, nucleation starts from a heterogenous defect. Homogenous nucleation is more elusive because of the prevalence of defects in any bulk sample. Crystallisation in tiny droplets alleviates this difficulty in a manner that is conceptually simple: subdivide the system into more domains than the number of defects. If the domains greatly outnumber the defects then only the homogenous mechanism can induce nucleation in a defect free compartment.

Such an approach has been used here to investigate nucleation in polyethylene (PE) droplets. At high temperatures, a thin PE film dewets from an unfavourable surface forming tiny droplets, much like water beading up on a waxy leaf (Fig. (b)). The resulting sample geometry is ideal: thousands of droplets ranging in size can be monitored simultaneously with optical microscopy, with a nucleation event easily distinguishable by the rapid growth of the crystal (Fig. (c)). Each droplet becomes an isolated independent nucleation experiment. By investigating thousands of droplets supercooled well below the melting temperature, studies of homogenous nucleation become straightforward. Relating the probability of homogenous nucleation to the size of the droplet, the authors show that nucleation is surface activated. Stated most simply, a droplet with twice the surface area is twice as likely to nucleate, indicating that the perturbation induced by the interface reduces the intrinsic activation barrier to crystal nucleation.

Population dynamics is a venerable and widely applicable subject. Over the last two centuries, many studies provided valuable insights into various phenomena, e.g., the emergence of biodiversity and fitness/extinction, while novelties are continually being discovered. Specifically, recent investigations of three species competing cyclically (e.g., rock-paper-scissors game) revealed rich and complex behaviours, whether the populations are well-mixed or dwelling on one- or two-dimensional lattices. Indeed, the well-mixed system displayed surprising survival probabilities: The species with the slowest consumption rate wins, leading to a popularized headline "Survival of the Weakest." Fascinating properties were also found in systems with spatial structure, including formation of complex patterns and mobility effects. Many aspects can be understood by exploiting techniques from statistical physics and non-linear dynamics.

Our work focuses on four cyclically competing species. Unlike the 3-species case, ours allows final states with coexisting pairs. The reason is simple: Resembling the game of Bridge, the four form two opposing teams of ally-pairs. For each pair, the product of their consumption rates determines if it wins or loses. From a master equation for the full stochastic problem, we derive an approximate set of rate equations (ODE's). Predictions from the latter typically agree well with simulations. Instead of the weakest surviving, our observations support a different maxim: "The prey of the prey of the weakest is the least likely to survive." Intuitively reasonable, this principle also applies to the special 3-species case! Meanwhile, a variety of intriguing extinction probabilities, discovered through simulations, provides numerous challenges for future research.