Games Microbes Play: the Game Theory Behind Cooperative Sucrose Metabolism in Yeast

Understanding the conditions required for the initiation and maintenance of cooperation is a classic problem in evolutionary biology with deep connections to game theory. For a state of cooperation to be stable, it must be a Nash Equilibrium of the corresponding “game.” Such ideas from game theory have had a profound impact in population biology. However, existing ecological systems are difficult to manipulate experimentally and don’t lend themselves to quantitative analysis. We’re studying sucrose metabolism in the yeast S. cerevisiae to quantitatively test models in evolutionary game theory. Yeast digest sucrose using the enzyme invertase in such a way that a majority of the useable product is lost to the environment and consumed by other cells. We demonstrate experimentally that this can result in cooperative sucrose metabolism, and find the conditions under which this cooperative behavior emerges. We’ve developed a simple model that explains the cooperative interaction and predicts the outcome of competition between the “wildtype” cooperator strain and a “cheater” strain that does not produce invertase.

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The Magellanic Clouds and the Dark Halo of the Milky Way

It is expected from current models of hierarchical structure formation that the interaction between the Large and Small Magellanic Clouds (LMC and SMC) and the Milky Way (MW) will have played an important role in the dynamical evolution of the MW's outer parts. However, new high-precision velocities for the clouds using the Hubble Space Telescope are ~100 km/s higher than those used in all theoretical models thus far—the implications of which are very unexpected in light of our previous understanding of the MW-LMC-SMC system. I will discuss these implications as well as ongoing efforts to confirm the new velocities .

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Metrology and Simulation with Small Quantum Systems

Experimental approaches to implementing ideas from quantum information science focus on developing well-understood physical systems that have only a few quantum bits. I will discuss potential applications of these small quantum systems, ranging from high-resolution magnetic field sensing to simulating interesting quantum mechanical systems. By relying upon proven technologies, we can take full advantage of the tremendous experimental advances in preparing, controlling, and measuring isolated mesoscopic and atomic systems made over the past decade.

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Black Holes in the Universe

Black holes are the keystone to the understanding of one of the fundamental forces in Nature: gravity. Indeed, black holes are gravity at its extreme. Binary stellar systems contain black holes a few times more massive than our Sun, while clusters of galaxies host black holes millions of times more massive. In both environments the gas is heated to millions of degrees and emits most strongly in the X-ray part of the electromagnetic spectrum. X-ray observations provide astrophysicists with a wealth of information and mysteries. I will tackle some of the basic questions that arise by observing black holes in the Universe, and will discuss how we are developing simple models aimed at finding the answers.

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The Latest in Neutrino Oscillations: New Results from SNO

All experiments studying neutrinos produced in the sun have observed less than half of the predicted number of electron-flavor neutrinos. This long-standing mystery was solved in 2001 with the spectacular confirmation of solar neutrino oscillations by the Sudbury Neutrino Observatory (SNO). SNO was the first experiment to simultaneously observe the disappearance of electron-flavor solar neutrinos and the appearance of muon- and tau-flavor neutrinos. A new detector system was installed in SNO in 2005 to make the first completely independent test of this exciting discovery. I will present first results from the new SNO data.

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