Catálogo de publicaciones - revistas

<jats:title>Room-temperature electron ratchets</jats:title> <jats:p> Conventional diodes rectify current flow by forming a junction between dissimilar conductors; a metal-semiconductor diode that forms a Schottky barrier is one example. In these devices, capacitance limits operating frequency. Custer <jats:italic>et al.</jats:italic> describe a diode made entirely of silicon that can rectify currents up to 40 gigahertz at room temperature. They fabricated silicon nanowires with a cylindrical sawtooth profile that act as ratchets, funneling current preferentially in one direction through specular reflection of quasi-ballistic electrons. </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="6487" page="177" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aay8663">177</jats:related-article> </jats:p>

<jats:title>A window to the embryo</jats:title> <jats:p> Mammalian embryonic development is a complex process, continuously changing in space and time. Q. Huang <jats:italic>et al.</jats:italic> designed an abdominal window to image mouse embryos in utero from embryonic day 9.5 to birth. Using this technique, they visualized dynamic activities during embryonic organ formation, including neurotransmission and cell division in the brain, autophagy in the retina, viral gene delivery, and placental drug transfer. They also tracked diverging fates of human and mouse neural crest cells in interspecies chimeras. </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="6487" page="181" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aba0210">181</jats:related-article> </jats:p>

<jats:title>Ironing out the details of mucosal healing</jats:title> <jats:p> Anemia is a frequent complication of disorders such as inflammatory bowel disease, occurring in part as a result of increased bleeding into the intestine. Bessman <jats:italic>et al.</jats:italic> show that the peptide hormone hepcidin, which regulates systemic iron homeostasis, is required for intestinal repair in a mouse model of inflammatory bowel disease (see the Perspective by Rescigno). This effect was independent of hepatocyte-produced hepcidin and systemic iron levels. Instead, production of hepcidin by conventional dendritic cells was necessary and sufficient to promote local iron sequestration by macrophages, which in turn modulated the makeup of the gut microbiota to one with a more beneficial distribution of species. </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="6487" page="186" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aau6481">186</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6487" page="129" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb2915">129</jats:related-article> </jats:p>

<jats:title>Immersing the impurities</jats:title> <jats:p> In solids, moving electrons can polarize their environment, the ionic crystal lattice, creating quasi particles known as polarons. An analogous phenomenon can be studied in quantum gases by placing impurity atoms into a much denser gas of atoms of a different species. Yan <jats:italic>et al.</jats:italic> studied the behavior of Bose polarons, quasiparticles consisting of impurity atoms of potassium-40 immersed in a Bose gas of sodium-23 atoms. In the vicinity of a quantum critical point, the lifetime of the polarons followed the so-called Planckian scale. </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="6487" page="190" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aax5850">190</jats:related-article> </jats:p>

<jats:title>A South American anthropoid</jats:title> <jats:p> Although there are many primate lineages in the Old World, it is thought that the New World is home to just one group, the platyrrhine monkeys, which appear to have colonized the region during the Eocene. Seiffert <jats:italic>et al.</jats:italic> describe a new primate species on the basis of fossil molars found in the Peruvian Amazon that appears to belong to the Parapithecidae, a group of stem anthropoid primates best known from northern Africa (see the Perspective by Godinot). The fossils appear to be from a well-differentiated lineage, suggesting that this species had been evolving within South America for some time. It is likely that the ancestors of this new species arrived via a transatlantic rafting event when sea levels dropped at the Eocene–Oligocene transition ∼32 to 35 million years ago. </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="6487" page="194" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aba1135">194</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6487" page="136" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb4107">136</jats:related-article> </jats:p>

<jats:title>More than a normal neurotransmitter</jats:title> <jats:p> The molecular mechanisms underlying the persistence of addiction remain largely unclear. Lepack <jats:italic>et al.</jats:italic> found that, with cocaine exposure, there is an intracellular accumulation of dopamine in neurons of a brain region called the ventral tegmental area (see the Perspective by Girault). Dopamine associates with chromatin to initiate a previously unknown form of epigenetic regulation called dopaminylation. This modification has an impact on ventral tegmental area function and, consequently, on dopaminergic action potentials. The result is aberrant dopamine signaling in the ventral striatum during periods of drug seeking. </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="6487" page="197" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaw8806">197</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6487" page="134" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb3533">134</jats:related-article> </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>