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<jats:p>In cleaner fish, punishment of foraging partners who cheat a client benefits punishers by increasing future cooperation.</jats:p>

<jats:title>Recruiting the Components for Cell Division</jats:title> <jats:p> A complete chromosome set must be apportioned to each daughter cell during cell division. A number of molecular mechanisms check that chromosome pairs or homologs are correctly aligned and attached to microtubules just before they separate to the two daughters; their spatial orientation ensures an even inheritance of the genome. One critical component of this system is the protein kinase Bub1. <jats:bold> Kawashima <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="172" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1180189">172</jats:related-article> , see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5962" page="150" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1184770">Javerzat</jats:related-article> </jats:bold> ; published online 19 November) now show that the main substrate for Bub1 kinase activity in fission yeast is the chromatin protein histone H2A. Phosphorylation of H2A recruits the shugoshin proteins to chromatin, and especially to centromeres, where they also act to ensure correct chromosome segregation. This link between Bub1, histone H2A phosphorylation, and shugoshin is conserved in budding yeast and mammalian cells. </jats:p>

<jats:title>Hidden Symmetry Revealed</jats:title> <jats:p> It is not often that an exact theory can describe a many-particle quantum-mechanical system, but one of the few exceptions is the behavior of a string of ferromagnets—an Ising chain—at magnetic field strengths that separate different types of ordering. Its excitations were predicted 20 years ago to be governed by the symmetry group E8, one of the most intriguing objects in mathematics. Now, <jats:bold> Coldea <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="177" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1180085">177</jats:related-article> ) report direct experimental confirmation of this result in a quasi-one-dimensional Ising ferromagnet CoNb <jats:sub>2</jats:sub> O <jats:sub>6</jats:sub> , which they probed by neutron scattering. Two of the eight predicted excitations could be observed. Moreover, the ratio of the two lowest excitations is in quantitative agreement with the so-called “golden ratio” predicted by theory. </jats:p>

<jats:title>Nematic Electronic Order in Iron Superconductors</jats:title> <jats:p> The properties of many high-temperature superconductors vary strongly as the composition of a doping element changes, and at sufficient under- or overdoping, other phases with different types of electronic ordering can form. Chuang et al. (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="181" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1181083">181</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5962" page="155" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183464">Fradkin and Kivelson</jats:related-article> ) use scanning tunneling microscopy techniques to probe the electronic structure of an underdoped compound in the iron superconductor family, Ca(Fe <jats:sub> 1− <jats:italic>x</jats:italic> </jats:sub> Co <jats:sub> <jats:italic>x</jats:italic> </jats:sub> ) <jats:sub>2</jats:sub> As <jats:sub>2</jats:sub> . They observed periodic nanostructures oriented along Fe–Fe bonds that exhibit an electronic ordering related to ordering seen in nematic liquid crystals. </jats:p>

<jats:title>Silicon Microwires as Photocathodes</jats:title> <jats:p> Solar hydrogen generation will require the development of photocathodes with high surface area, durability, and efficiency. Silicon microwire arrays, which allow for greater light penetration, could achieve this goal if the carrier mobilities are sufficiently high so that surface reactions occur before charges recombine. <jats:bold> Boettcher <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="185" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1180783">185</jats:related-article> ) report the electronic properties on positively doped silicon microwire arrays that were grown with copper catalysts and used in a methyl viologen redox system. Although equivalent efficiencies for normal solar fluxes were only 2 to 3%, the high internal efficiencies and low use of the available optical flux suggest that further improvements are possible. </jats:p>

<jats:title>Stars Going Quietly or with a Bang</jats:title> <jats:p> Stars with masses seven to ten times the mass of the Sun, which can burn carbon in their cores at their end of their lives, may end up as oxygen-neon core white dwarfs or explode as core-collapse supernovae. The defining line between these two end products of stellar evolution is not well understood. <jats:bold> Gänsicke <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="188" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1180228">188</jats:related-article> ; published online 12 November) identified two white dwarfs whose photospheric oxygen-to-carbon abundance ratio exceeds unity. Their low carbon abundance and their large quantity of oxygen imply that they are oxygen-neon white dwarfs that lost their hydrogen envelopes. As such, they may have evolved from stars at the borderline between stars that explode as supernova and stars that form white dwarfs. </jats:p>

<jats:title>Smooth Space Pebble</jats:title> <jats:p> In September 2008, on its way to meet comet 67P/Churyumov-Gerasimenko, the Rosetta spacecraft flew by asteroid Steins, a member of a very rare class of asteroids that had never been observed closely by spacecraft. <jats:bold> Keller <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="190" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1179559">190</jats:related-article> ) analyzed the images to generate a reconstruction of the asteroid's shape. Steins is oblate with an effective spherical diameter of 5.3 kilometers, and it lacks small craters, which may have been erased by surface reshaping. Indeed, Steins's shape resembles that of a body that was spun-up by the YORP effect—a torque produced by incident sunlight, which can alter the rotation rate of a small body—that causes material to slide toward the equator. This effect may have produced Steins's distinctive diamond-like shape. </jats:p>

<jats:title>Spin Transitions and Mantle Phases</jats:title> <jats:p> The extreme temperatures and pressures at depth can cause mantle minerals to undergo phase transformations. For example, it is thought that an electronic spin transition that occurs at high pressures in the lower mantle leads to the partitioning of various iron mineral phases. Using a multianvil apparatus to study a synthetic material similar in composition to the lower mantle, <jats:bold> Irifune <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="193" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1181443">193</jats:related-article> , see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5962" page="151" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1184786">Hirose</jats:related-article> </jats:bold> ; published online 3 December) demonstrate that the spin transition occurs at lower pressures, and thus shallower depth, than suggested by earlier studies based on simpler compositions. As verification of the material's applicability in lower mantle studies, its density profile with pressure overlaps very well with those predicted by seismological models. </jats:p>

<jats:title>Cradle of Diversity</jats:title> <jats:p> Is the biological diversity of reefs a result of attracting species that originated elsewhere, or are they particularly important as cradles of evolution? <jats:bold> Kiessling <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="196" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182241">196</jats:related-article> ; see the cover) examine a large database of fossil benthic marine organisms dating back to the Cambrian to test these questions. It seems that reefs, even in comparison to other shallow marine environments, were indeed important during the origination of new species, including ones that migrate elsewhere. </jats:p>

<jats:title>Anti-MicroRNA Antiviral</jats:title> <jats:p> MicroRNAs (miRNAs) are small noncoding RNAs found in eukaryotes and viruses. They are critical regulators of a wide range of cellular processes. The highly conserved miRNA miR-122 is required for infection by hepatitis C virus (HCV), a leading cause of liver disease in humans. Present HCV treatment regimes can have serious side effects and are effective in only 50% of cases. In order to try to tackle HCV infection, <jats:bold> Lanford <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="198" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1178178">198</jats:related-article> , published online 3 December) targeted miR-122 using a complementary locked nucleic acid (LNA) oligonucleotide. Treatment of chimpanzees infected by HCV with the LNA antagonist resulted in a long-term reduction of disease symptoms without the concomitant appearance of resistant strains of the virus. </jats:p>