In this issue: Plant Power, New Light On Uranium Chemistry, Not a Lumpy Universe
---------------------------
Plant Power
Light-harvesting molecules in plants inspire a proposal for more efficient solar cells.
In solar cells, the energy of photons is absorbed by electrons, which become unbound and can generate an electrical current. But the electrons can also quickly recombine, which poses limits on the efficiency of most photoelectric materials. Molecules in plants, on the other hand, can, under certain conditions, convert photons to electrons with near perfect efficiency, and recent results suggest this is the result of quantum-mechanical effects. Researchers in Cambridge (UK) have proposed a model photocell inspired by how plants convert sunlight into useful energy. According to their calculation, their system of three molecules, thanks to quantum effects, could have a 35% higher efficiency than a cell that works based on classical physics only.
* Celestino Creatore (contact author), MA Parker, S Emmott, and AW Chin, “An efficient biologically-inspired photocell enhanced by delocalised quantum states”, Physical Review Letters (expected publication date: Dec 18)
---------------------------
New Light On Uranium Chemistry
The X-ray analysis of uranium oxides calls for a revision of the current thinking on uranium chemistry.
The storage of spent fuel poses one of the most challenging problems to the nuclear industry. Safe disposal, for instance in deep geological repositories, requires a thorough understanding of the possible chemical forms of uranium in a fuel rod: different oxides may have different properties, such as their solubility in water. At the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, a research team has used X-ray techniques to probe several oxides of uranium. The authors were able to study how uranium dioxide – the main component of nuclear fuel rods – transforms into other types of oxides. The results will help predict uranium’s behavior in a number of chemical reactions relevant to long term nuclear-fuel storage.
* Kristina O Kvashnina (contact author), SM Butorin, P Martin, and P Glatzel, “Chemical state of complex uranium oxides”, Physical Review Letters (expected publication date: Dec 17)
---------------------------
Not a Lumpy Universe
Astrophysical observations suggest the expansion of the universe is accelerating – a puzzling fact attributed to the presence of the yet-to-be-deciphered dark energy. But there are alternative theories that do not invoke a new form of energy. A popular one explains the observed expansion rates by assuming the universe is “lumpy”, i.e. its density is not uniform on large scales. But a team of theorists at the University of Texas (Dallas) has now shown a lumpy universe model would be at odds with observations of the speed by which clusters of galaxies grow. Instead, the authors show that some form of dark energy would still be needed to model galaxy-cluster growth.
* Mustapha Ishak (contact author), A Peel, and MA Troxel, “Stringent restriction from the growth of large-scale structure on apparent acceleration in inhomogeneous cosmological models”, Physical Review Letters (expected publication date: Dec 19)
---------------------------
Journal articles and preprints are available to journalists on request.
