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<jats:title>Beating the heat by blending</jats:title> <jats:p> Charge carriers move through semiconductor polymers by hopping transport. In principle, these polymers should be more conductive at higher temperatures. In practice, conductivity drops at high temperatures because interchain contacts are disrupted, which limits potential applications. Gumyusenge <jats:italic>et al.</jats:italic> now show that appropriate blending of a semicrystalline conjugated polymer with an insulating polymer that has a high glass-transition temperature creates a morphology that stabilizes a network of semiconductor channels. High charge conductivity was maintained in these materials up to 220°C. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6419" page="1131" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau0759">1131</jats:related-article> </jats:p>

<jats:title>No barriers to growing a row</jats:title> <jats:p> Classical nucleation theory predicts that two-dimensional islands on a surface must reach a critical size before they continue to grow; below that size, they dissolve. Chen <jats:italic>et al.</jats:italic> used phage display to select for short peptides that would bind to molybdenum disulfide (MoS <jats:sub>2</jats:sub> ) (see the Perspective by Kahr and Ward). Hexagonal arrays of these peptides grew epitaxially as dimers but without a size barrier—the critical nuclei size was zero. Although two-dimensional arrays formed, growth occurred one row at time. Classical nucleation theory indeed predicts the absence of a barrier for such one-dimensional growth. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6419" page="1135" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aau4146">1135</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6419" page="1111" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aav7009">1111</jats:related-article> </jats:p>

<jats:title>One program to rule them all</jats:title> <jats:p> Computers can beat humans at increasingly complex games, including chess and Go. However, these programs are typically constructed for a particular game, exploiting its properties, such as the symmetries of the board on which it is played. Silver <jats:italic>et al.</jats:italic> developed a program called AlphaZero, which taught itself to play Go, chess, and shogi (a Japanese version of chess) (see the Editorial, and the Perspective by Campbell). AlphaZero managed to beat state-of-the-art programs specializing in these three games. The ability of AlphaZero to adapt to various game rules is a notable step toward achieving a general game-playing system. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6419" page="1140" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aar6404">1140</jats:related-article> ; see also pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6419" page="1087" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aaw2221">1087</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6419" page="1118" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aav1175">1118</jats:related-article> </jats:p>

<jats:title>Working toward fluoride batteries</jats:title> <jats:p> Owing to the low atomic weight of fluorine, rechargeable fluoride-based batteries could offer very high energy density. However, current batteries need to operate at high temperatures that are required for the molten salt electrolytes. Davis <jats:italic>et al.</jats:italic> push toward batteries that can operate at room temperature, through two advances. One is the development of a room-temperature liquid electrolyte based on a stable tetraalkylammonium salt–fluorinated ether combination. The second is a copper–lanthanum trifluoride core-shell cathode material that demonstrates reversible partial fluorination and defluorination reactions. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6419" page="1144" related-article-type="in-this-issue" vol="362" xlink:href="10.1126/science.aat7070">1144</jats:related-article> </jats:p>