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<jats:p> A monthly roundup of recent news and projects of <jats:italic>Science</jats:italic> 's publisher, the American Association for the Advancement of Science. </jats:p>

<jats:title>Warming and Melting</jats:title> <jats:p> Mass loss from the ice sheets of Greenland and Antarctica account for a large fraction of global sea-level rise. Part of this loss is because of the effects of warmer air temperatures, and another because of the rising ocean temperatures to which they are being exposed. <jats:bold> Joughin <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="1172" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1226481">1172</jats:related-article> ) review how ocean-ice interactions are impacting ice sheets and discuss the possible ways that exposure of floating ice shelves and grounded ice margins are subject to the influences of warming ocean currents. Estimates of the mass balance of the ice sheets of Greenland and Antarctica have differed greatly—in some cases, not even agreeing about whether there is a net loss or a net gain—making it more difficult to project accurately future sea-level change. <jats:bold> Shepherd <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="1183" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228102">1183</jats:related-article> ) combined data sets produced by satellite altimetry, interferometry, and gravimetry to construct a more robust ice-sheet mass balance for the period between 1992 and 2011. All major regions of the two ice sheets appear to be losing mass, except for East Antarctica. All told, mass loss from the polar ice sheets is contributing about 0.6 millimeters per year (roughly 20% of the total) to the current rate of global sea-level rise. </jats:p>

<jats:title>Building with DNA</jats:title> <jats:p> One route for assembling three-dimensional (3D) DNA nanostructures is to start with a long natural DNA single strand and attach short strands, or “staples,” that cause the entire “origami” structure to fold into a desired shape. <jats:bold> Ke <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="1177" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1227268">1177</jats:related-article> , see the cover; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6111" page="1159" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1229960">Gothelf</jats:related-article> </jats:bold> ) present an alternative approach to 3D assembly that builds upon modular assembly of 2D DNA tiles. One hundred and two distinct shapes were created from four-domain, 32-nucleotide single-stranded DNAs that assembled like children's blocks; each block could bind to four neighboring blocks through specific pairing interactions. Computer design and stepwise assembly allowed assembly of hollow shapes with a variety of internal cavities. </jats:p>

<jats:title>Warming and Melting</jats:title> <jats:p> Mass loss from the ice sheets of Greenland and Antarctica account for a large fraction of global sea-level rise. Part of this loss is because of the effects of warmer air temperatures, and another because of the rising ocean temperatures to which they are being exposed. <jats:bold> Joughin <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="1172" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1226481">1172</jats:related-article> ) review how ocean-ice interactions are impacting ice sheets and discuss the possible ways that exposure of floating ice shelves and grounded ice margins are subject to the influences of warming ocean currents. Estimates of the mass balance of the ice sheets of Greenland and Antarctica have differed greatly—in some cases, not even agreeing about whether there is a net loss or a net gain—making it more difficult to project accurately future sea-level change. <jats:bold> Shepherd <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="1183" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228102">1183</jats:related-article> ) combined data sets produced by satellite altimetry, interferometry, and gravimetry to construct a more robust ice-sheet mass balance for the period between 1992 and 2011. All major regions of the two ice sheets appear to be losing mass, except for East Antarctica. All told, mass loss from the polar ice sheets is contributing about 0.6 millimeters per year (roughly 20% of the total) to the current rate of global sea-level rise. </jats:p>

<jats:title>Glow from the Past</jats:title> <jats:p> Extragalactic background light (EBL) is the integrated radiation from all extragalactic sources in the universe. Foreground emission from our solar system and galaxy makes direct detection of the EBL very difficult. However, it is possible to measure EBL from gamma-ray spectra of distant sources, because gamma-ray photons from these sources interact with the EBL. <jats:bold> Ackermann <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="1190" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1227160">1190</jats:related-article> , published online 1 November; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6111" page="1160" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1231128">Bromm</jats:related-article> </jats:bold> ) report a measurement of the EBL based on an attenuation feature seen in the combined spectra of distant active galaxies detected by the Fermi Gamma-Ray Space Telescope. The result puts constraints on the cosmic history of star formation. </jats:p>

<jats:title>What Do You Know? A Dome</jats:title> <jats:p> The superconducting dome—the appearance of a maximum in the transition temperature as a function of a tuning parameter—has been observed in compounds such as cuprates, pnictides, and heavy fermion materials and is thought of as a signature of unconventional superconductivity. <jats:bold> Ye <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="1193" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1228006">1193</jats:related-article> ) used a liquid gating technique combined with back gating to finely tune the carrier density in the band insulator MoS <jats:sub>2</jats:sub> , which allowed them to observe the formation of a dome. The unexpected finding awaits theoretical explanation but may suggest that the appearance of an optimal carrier density may be a more common occurrence than was previously thought. </jats:p>

<jats:p>An analytical model suggests that the terrestrial and giant planets in the solar system formed moons through a similar process.</jats:p>

<jats:title>Swimming in Iron Pools</jats:title> <jats:p> Because iron is essential for marine phytoplankton growth, its availability limits the primary productivity of the oceans. Iron is typically bioavailable only when present in a dissolved state; however, a large fraction of the total iron in the oceans exists as tiny solid-phase particles ranging in size from a few nanometers to a few micrometers. <jats:bold> von der Heyden <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="1199" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1227504">1199</jats:related-article> ) used high-resolution x-ray microscopy and spectroscopy to characterize the distribution of iron particles along two transects of the Southern Ocean. Analysis of a number of individual particles reveals strong variation in iron oxidation state, particle mineralogy, and substitution of aluminum for iron—all of which control the solubility, and hence bioavailability, of iron. </jats:p>

<jats:title>Modeling the Brain</jats:title> <jats:p> Neurons are pretty complicated cells. They display an endless variety of shapes that sprout highly variable numbers of axons and dendrites; they sport time- and voltage-dependent ion channels along with an impressive array of neurotransmitter receptors; and they connect intimately with near neighbors as well as former neighbors who have since moved away. Simulating a sizeable chunk of brain tissue has recently become achievable, thanks to advances in computer hardware and software. <jats:bold> Eliasmith <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="1202" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1225266">1202</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="6111" page="1156" related-article-type="in-this-issue" vol="338" xlink:href="10.1126/science.1231865">Machens</jats:related-article> </jats:bold> ) present their million-neuron model of the brain and show that it can recognize numerals, remember lists of digits, and write down those lists—tasks that seem effortless for a human but that encompass the triad of perception, cognition, and behavior. </jats:p>

<jats:p>Resistance to a damaging disease of soybean is conferred by a cluster of linked genes present in multiple copies.</jats:p>