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<jats:title>Controlling Light Propagation</jats:title> <jats:p> Surface plasmons are light-induced collective electronic excitations in a metal that offer the possibility of manufacturing optoelectronic devices at nanometer scale. Before such shrinking can be achieved, the propagation direction and lifetime of the plasmonic excitations have to be controlled (see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="283" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1236154"> <jats:bold>Miroshnichenko and Kivshar</jats:bold> </jats:related-article> ). <jats:bold> Rodríguez-Fortuño <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="328" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1233739">328</jats:related-article> ) show how this is done using polarized light. Alternatively, using an array of metallic nanoantennae (in this case, slits) patterned into a thin gold film, <jats:bold> Lin <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="331" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1233746">331</jats:related-article> ) present a further improvement on current plasmonic coupling schemes that has the potential to encode information contained in both the intensity and polarization of light. </jats:p>

<jats:title>Controlling Light Propagation</jats:title> <jats:p> Surface plasmons are light-induced collective electronic excitations in a metal that offer the possibility of manufacturing optoelectronic devices at nanometer scale. Before such shrinking can be achieved, the propagation direction and lifetime of the plasmonic excitations have to be controlled (see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="283" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1236154"> <jats:bold>Miroshnichenko and Kivshar</jats:bold> </jats:related-article> ). <jats:bold> Rodríguez-Fortuño <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="328" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1233739">328</jats:related-article> ) show how this is done using polarized light. Alternatively, using an array of metallic nanoantennae (in this case, slits) patterned into a thin gold film, <jats:bold> Lin <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="331" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1233746">331</jats:related-article> ) present a further improvement on current plasmonic coupling schemes that has the potential to encode information contained in both the intensity and polarization of light. </jats:p>

<jats:title>Splitting Singlets</jats:title> <jats:p> Solar cell efficiency is limited because light at wavelengths shorter than the cell's absorption threshold does not channel any of its excess energy into the generated electricity. <jats:bold> Congreve <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="334" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1232994">334</jats:related-article> ) have developed a method to harvest the excess energy in carbon-based absorbers through a process termed “singlet fission.” In this process, high-energy photons propel two current carriers, rather than just one, by populating a singlet state that spontaneously divides into a pair of triplet states. Although it works in a functioning organic solar cell, the efficiency needs improving. </jats:p>

<jats:title>Tuning Mesopores</jats:title> <jats:p> Porous materials are of interest for catalysis and filtration because the open channels lend themselves to separating materials or function. <jats:bold> Suteewong <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="337" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1231391">337</jats:related-article> ) report on a method to make branched mesoporous silica nanoparticles that contain cubic (core) and hexagonally structured (branch) parts within one particle. Controlling the extent of the branched structure is achieved by tuning the concentration of additives in a simple, one-pot reaction system. </jats:p>

<jats:title>Southern Change</jats:title> <jats:p> Antarctica has been mostly covered by ice since the inception of large-scale continental glaciation during the Oligocene, which profoundly altered the isotopic and mineralogical records of the sediments surrounding the continent. <jats:bold> Houben <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="341" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1223646">341</jats:related-article> ) found records of the corresponding living systems in the fossil marine dinoflagellate cysts, which revealed that a microplankton ecosystem, similar to the one that exists today, appeared simultaneously with the first major Antarctic glaciation approximately 34 million years ago. </jats:p>

<jats:title>Dissolving Charcoal</jats:title> <jats:p> Biomass burning produces 40 to 250 million tons of charcoal per year worldwide. Much of this is preserved in soils and sediments for thousands of years. However, the estimated production rate of charcoal is significantly larger than that of decomposition, and <jats:bold> Jaffe <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="345" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1231476">345</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="6130" page="287" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1237688">Masiello and Louchouarn</jats:related-article> </jats:bold> ) calculate that a large fraction of the charcoal produced by fires is lost from the land through dissolution and transport to the oceans. </jats:p>

<jats:title>History Matters</jats:title> <jats:p> Fishery-induced mortality is not the sole driver of fish population dynamics, and shifts in population abundance are also subject to ecological impacts. In a meta-analysis, <jats:bold> Neubauer <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="347" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1230441">347</jats:related-article> ) showed how some fish-stock recoveries have been slower than theoretically predicted. They discovered that a species' exploitation history is also an important predictor of recovery. The data indicate that even extreme limitations in harvest pressure may not allow for the timely recovery of collapsed stocks. </jats:p>

<jats:title>Red in Cell and Marrow</jats:title> <jats:p> About one hundred billion new red cells are released every day from the adult human bone marrow—the result of a complex differentiation pathway. <jats:bold> Barde <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="350" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1232398">350</jats:related-article> , published online 14 March) show that an essential step in this process, the elimination of mitochondria from maturing erythroblasts through mitophagy, is controlled through the timely induction of specific members of the large family of KRAB-containing zinc finger proteins (KRAB-ZFPs), which, together with their cofactor KAP1, repress the expression of micro-RNAs targeting the transcripts of mitophagy effector genes. This multilayered and combinatorial regulation system provides a level of modularity that may be shared by other physiological processes. </jats:p>

<jats:title>Sliding Restriction</jats:title> <jats:p> Helicase enzymes access the genetic information stored in double-helical DNA and RNA by opening the individual strands. Pseudo-helicases, including bacterial Type III restriction enzymes, use adenosine triphosphate (ATP) hydrolysis to communicate between two distant restriction sites on the same DNA and excise it only if the DNA is sensed as “foreign.” <jats:bold> Schwarz <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="353" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1231122">353</jats:related-article> ) show that the bacterial Type III restriction enzyme, EcoP15I, undergoes an ATP-dependent conformational switch that promotes sliding along the DNA to allow the enzyme to localize to its target. </jats:p>

<jats:title>Cargo-Motor Interaction</jats:title> <jats:p> Kinesin-1 directs a diverse array of functions within axons by interacting with many proteins. To understand the mechanisms underpinning kinesin-cargo recognition, <jats:bold> Pernigo <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6130" page="356" related-article-type="in-this-issue" vol="340" xlink:href="10.1126/science.1234264">356</jats:related-article> , published online 21 March) solved the crystal structure of the tetratricopeptide repeat of kinesin light chain 2 bound to a W-acidic cargo peptide from SKIP—a critical host determinant in <jats:italic>Salmonella</jats:italic> pathogenesis that controls lysosome positioning. </jats:p>