Catálogo de publicaciones - revistas

<jats:title>Mediating transcription</jats:title> <jats:p> The Mediator complex is recruited by transcription factors to all protein-coding genes in eukaryotes and helps to assemble the machinery necessary to transcribe the gene. Abdella <jats:italic>et al.</jats:italic> present the cryo–electron microscopy structure of the human Mediator-bound preinitiation complex (Med-PIC). The structure shows how Mediator positions the long, flexible C-terminal domain of RNA polymerase II to be phosphorylated by the kinase CDK7, a crucial step for further processing of the RNA into a mature RNA. Most sites where transcription factors bind to Mediator are flexibly tethered to the complex, allowing the large Med-PIC to assemble at any gene. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6537" page="52" related-article-type="in-this-issue" vol="372">52</jats:related-article> </jats:p>

<jats:title>Burying Mars' ancient water in the crust</jats:title> <jats:p> Mars once had oceans of liquid water on its surface but little of that water remains today in the planet's ice caps and atmosphere. This discrepancy is usually interpreted as loss of water to space, supported by the atmospheric deuterium/hydrogen (D/H) ratio, but this has been difficult to reconcile with other constraints. Scheller <jats:italic>et al.</jats:italic> propose that water could instead have been incorporated into minerals in the planet's crust, which were later buried (see the Perspective by Kurokawa). They simulated the evolution of the D/H ratio and atmospheric loss rates for a range of plausible conditions, finding that 30 to 99% of Mars' initial water was buried in the crust. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6537" page="56" related-article-type="in-this-issue" vol="372">56</jats:related-article> ; see also p. <jats:related-article issue="6537" page="27" related-article-type="in-this-issue" vol="372">27</jats:related-article> </jats:p>

<jats:title>The birth of modern rainforests</jats:title> <jats:p> The origin of modern rainforests can be traced to the aftermath of the bolide impact at the end of the Cretaceous. Carvalho <jats:italic>et al.</jats:italic> used fossilized pollen and leaves to characterize the changes that took place in northern South American forests at this time (see the Perspective by Jacobs and Currano). They not only found changes in species composition but were also able to infer changes in forest structure. Extinctions were widespread, especially among gymnosperms. Angiosperm taxa came to dominate the forests over the 6 million years of recovery, when the flora began to resemble that of modern lowland neotropical forest. The leaf data also imply that the forest canopy evolved from relatively open to closed and layered, leading to increased vertical stratification and a greater diversity of plant growth forms. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6537" page="63" related-article-type="in-this-issue" vol="372">63</jats:related-article> ; see also p. <jats:related-article issue="6537" page="28" related-article-type="in-this-issue" vol="372">28</jats:related-article> </jats:p>

<jats:title>Engineering interface polarization</jats:title> <jats:p> Many properties can emerge at the interface of van der Waals materials created by rotating the layers of a single material or by creating heterointerfaces between different materials. Akamatsu <jats:italic>et al.</jats:italic> formed an interface that intentionally broke in-plane inversion symmetry by combining crystals of tungsten diselenide with threefold rotational symmetry and black phosphorus with twofold rotational symmetry. This interface creates in-plane electronic polarization that results in a spontaneous photovoltaic effect only along the polarization direction. This effect was explained in terms of a shift current mechanism. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6537" page="68" related-article-type="in-this-issue" vol="372">68</jats:related-article> </jats:p>

<jats:title>Nonlinear control of topology</jats:title> <jats:p> Controlling the topological properties of physical systems provides a platform for developing devices and technology that are robust to defects. Xia <jats:italic>et al.</jats:italic> present a photonic platform in which the underlying dynamics are driven and tuned by the interplay among topology, non-Hermiticity, and nonlinearity (see the Perspective by Roztocki and Morandotti). Using photonic lattices consisting of laser-written waveguides that are continuous (“gain”) and sectioned (“loss”) and coupled to an interface defect, they demonstrate the nonlinear control of parity-time symmetry and nonlinearity-induced restoration and/or destruction of non-Hermitian topological states. Such concepts are applicable to a broad spectrum of non-Hermitian systems that have intensity-dependent gain or loss and may enable new approaches for light manipulation. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6537" page="72" related-article-type="in-this-issue" vol="372">72</jats:related-article> ; see also p. <jats:related-article issue="6537" page="32" related-article-type="in-this-issue" vol="372">32</jats:related-article> </jats:p>

<jats:title>Isolating and stabilizing boron</jats:title> <jats:p> Oxidative dehydrogenation of propane can produce propene from shale gas and help to replace petroleum as a propene feedstock. Boron-based catalysts can have high selectivity to propene, but the water by-product can deactivate the catalyst by hydrolyzing boron. Zhou <jats:italic>et al.</jats:italic> synthesized boron-doped silicate zeolites containing isolated boron sites that were stable against hydrolysis. The catalyst could achieve one-pass propane conversions up to ∼44% with selectivities for propene and &gt;80% for ethene. They observed no deactivation after a 210-hour continuous test. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6537" page="76" related-article-type="in-this-issue" vol="372">76</jats:related-article> </jats:p>

<jats:title>A shifting burden</jats:title> <jats:p> In 1962, Rachel Carson's <jats:italic>Silent Spring</jats:italic> was published, and the world was forced to take notice of the unintended impacts of pesticides on wildlife. Since then, there has been a perceived reduction in the amount of pesticides used and a shift in the kinds of pesticides available. Schulz <jats:italic>et al.</jats:italic> looked at the type, amount, and toxicity of pesticides applied over the last 25 years. They found that despite decreasing total amounts applied and decreased impacts on vertebrates, toxicity—in particular to insects and aquatic invertebrates—has increased substantially. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article issue="6537" page="81" related-article-type="in-this-issue" vol="372">81</jats:related-article> </jats:p>