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<jats:p>The threshold for mathematical problems being easy or hard to solve can be extremely abrupt.</jats:p>

<jats:p>A pioneering scientist and gold medal Olympian had unflagging energy and broad interests that fueled his research.</jats:p>

<jats:title>Unlikely Planet</jats:title> <jats:p> Most known extrasolar planets orbit stars similar to the Sun. Very few planets have been detected around metal-poor stars whose abundances of elements other than hydrogen and helium are much lower than those of the Sun, or around stars that are at a late stage in their evolution. <jats:bold> Setiawan <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="1642" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1193342">1642</jats:related-article> , published online 18 November) report the detection of a close-in giant planet around a metal-poor star belonging to a group of stars that formed in a satellite galaxy of the Milky Way. The star has gone past the red giant phase of stellar evolution, when stars like the Sun expand up to many times their original size, and so it is unclear why the planet was not engulfed by the star as it expanded. </jats:p>

<jats:title>Spin Control</jats:title> <jats:p> Controlling and manipulating the spin of an electron is a central requirement for applications in spintronics. Some of the challenges researchers are facing include efficient creation of spin currents, minimization of Joule heating, and extending the lifetime of electronic spins, which is especially important for quantum information applications. <jats:bold>Costache and Valenzuela</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1645" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1196228">1645</jats:related-article> ) address the first challenge by designing and fabricating an efficient and simple superconducting-based single-electron transistor that can produce spin current with controlled flow. Key to the design is asymmetric tunneling, which leads to a ratchet effect (or diode-like behavior), allowing the separation of up and down spins. <jats:bold> Jonietz <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="1648" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1195709">1648</jats:related-article> ) use electric currents five orders of magnitude smaller than those used previously in nanostructures to manipulate magnetization in a bulk material, MnSi, pointing the way toward decreased Joule heating in spintronic devices. This so-called spin-torque effect causes the rotation of the skyrmion lattice of spins, characteristic of MnSi, which is detected by neutron scattering. Finally, <jats:bold> McCamey <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="1652" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197931">1652</jats:related-article> ) extend the short lifetime of an electronic spin of a phosphorous dopant by mapping it onto the much longer lived nuclear spin of the atom. Mapping the nuclear spin back onto the electronic spin allows production of a spin memory with a storage time exceeding 100s, which should prove useful for future practical applications. </jats:p>

<jats:title>Spin Control</jats:title> <jats:p> Controlling and manipulating the spin of an electron is a central requirement for applications in spintronics. Some of the challenges researchers are facing include efficient creation of spin currents, minimization of Joule heating, and extending the lifetime of electronic spins, which is especially important for quantum information applications. <jats:bold>Costache and Valenzuela</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1645" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1196228">1645</jats:related-article> ) address the first challenge by designing and fabricating an efficient and simple superconducting-based single-electron transistor that can produce spin current with controlled flow. Key to the design is asymmetric tunneling, which leads to a ratchet effect (or diode-like behavior), allowing the separation of up and down spins. <jats:bold> Jonietz <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="1648" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1195709">1648</jats:related-article> ) use electric currents five orders of magnitude smaller than those used previously in nanostructures to manipulate magnetization in a bulk material, MnSi, pointing the way toward decreased Joule heating in spintronic devices. This so-called spin-torque effect causes the rotation of the skyrmion lattice of spins, characteristic of MnSi, which is detected by neutron scattering. Finally, <jats:bold> McCamey <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="1652" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197931">1652</jats:related-article> ) extend the short lifetime of an electronic spin of a phosphorous dopant by mapping it onto the much longer lived nuclear spin of the atom. Mapping the nuclear spin back onto the electronic spin allows production of a spin memory with a storage time exceeding 100s, which should prove useful for future practical applications. </jats:p>

<jats:title>Spin Control</jats:title> <jats:p> Controlling and manipulating the spin of an electron is a central requirement for applications in spintronics. Some of the challenges researchers are facing include efficient creation of spin currents, minimization of Joule heating, and extending the lifetime of electronic spins, which is especially important for quantum information applications. <jats:bold>Costache and Valenzuela</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1645" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1196228">1645</jats:related-article> ) address the first challenge by designing and fabricating an efficient and simple superconducting-based single-electron transistor that can produce spin current with controlled flow. Key to the design is asymmetric tunneling, which leads to a ratchet effect (or diode-like behavior), allowing the separation of up and down spins. <jats:bold> Jonietz <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="1648" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1195709">1648</jats:related-article> ) use electric currents five orders of magnitude smaller than those used previously in nanostructures to manipulate magnetization in a bulk material, MnSi, pointing the way toward decreased Joule heating in spintronic devices. This so-called spin-torque effect causes the rotation of the skyrmion lattice of spins, characteristic of MnSi, which is detected by neutron scattering. Finally, <jats:bold> McCamey <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="1652" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197931">1652</jats:related-article> ) extend the short lifetime of an electronic spin of a phosphorous dopant by mapping it onto the much longer lived nuclear spin of the atom. Mapping the nuclear spin back onto the electronic spin allows production of a spin memory with a storage time exceeding 100s, which should prove useful for future practical applications. </jats:p>

<jats:title>Better Imaging When Separated</jats:title> <jats:p> A fluorescent probe works better if its absorption and emission wavelengths are well separated; otherwise, the probe tends to reabsorb its own emission. <jats:bold> Ghosh <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="1656" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1196382">1656</jats:related-article> , published online 25 November) found that oxygen doping of semiconducting single-wall carbon nanotubes (SWCNTs) improved the characteristics of these materials as imaging probes in the near-infrared. Exposure of SWCNTs to ozone and then to visible light caused the emission wavelength to be 10 to 15% longer than the absorption wavelength. They imaged these probes and untreated SWCNTs in cultured human cells and found an ∼20-fold improvement in contrast. </jats:p>

<jats:title>A Hot Dipole</jats:title> <jats:p> In a ferroelectric material, there is an alignment of local electric dipole moments that produces a net overall electric polarization. This state is accompanied by a decrease in symmetry, which can be restored by heating above a critical temperature. In contrast, through a combination of theory and experiments, <jats:bold> Božin <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="1660" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1192759">1660</jats:related-article> ) now show that with increasing temperature, rock-salt–structured lead telluride and lead sulfide go through a phase transition from a high symmetry phase to a low symmetry phase with an associated dipole moment. Paradoxically, the dipoles are stabilized in the disordered state at high temperature, even though the undistorted structure has lower internal energy. </jats:p>

<jats:title>Burn, Baby, Burn</jats:title> <jats:p> The atmospheric trace gas, carbon monoxide, has important effects on methane and on ozone, and is important both in atmospheric chemistry and for its indirect influence on climate. Little is known about the abundance and sources of CO prior to the industrial age, or about the importance of anthropogenic activities on its budget. <jats:bold> Wang <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="1663" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197257">1663</jats:related-article> , published online 2 December; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6011" page="1636" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1199809">Prentice</jats:related-article> </jats:bold> ) present a 650-year-long record of CO atmospheric concentration and isotopic composition, using samples from Antarctic ice cores, in order to begin to reconstruct past CO variability and its causes. The concentration of CO decreased by ∼25% from the mid-1300s to the 1600s, and then recovered completely by the late 1800s. Large variations in the degree of biomass burning in the Southern Hemisphere are likely to have been primarily responsible for the observed changes. </jats:p>

<jats:title>Dissecting Nitric Oxide Reductase</jats:title> <jats:p> Bacterial breakdown of nitrogen compounds in soil and the oceans provides the largest emission source of the greenhouse gas, nitrous oxide (N <jats:sub>2</jats:sub> O). A key enzyme in this process is nitric oxide reductase (NOR), which catalyzes the reduction of nitric oxide (NO) to N <jats:sub>2</jats:sub> O. <jats:bold> Hino <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="1666" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1195591">1666</jats:related-article> , published online 25 November; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6011" page="1632" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1200247"> <jats:bold>Moënne-Loccoz and Fee</jats:bold> </jats:related-article> ) now describe the crystal structure of NOR from <jats:italic>Pseudomonas aeruginosa</jats:italic> . Consistent with their evolutionary relatedness, the transmembrane region topology and arrangement of metal centers in NOR are similar to those in cytochrome oxidases, key enzymes in aerobic respiration. </jats:p>