Catálogo de publicaciones - revistas

<jats:p>Entries feature reporting on topics ranging from Ebola to the global COVID-19 pandemic</jats:p>

<jats:title>Magnetic special relativity</jats:title> <jats:p> Magnetic materials have domains, patches of ordered spins that are separated from one another by boundaries called domain walls. These boundaries can be driven by electrical currents, a phenomenon forming the basis of the so-called racetrack memories. The speed of the domain walls has steadily increased as experimenters have perfected these devices. Caretta <jats:italic>et al.</jats:italic> now show experimentally that this speed is fundamentally limited (see the Perspective by Daniels and Stiles). Just as no object can travel faster than the speed of light, the speed of the domain walls saturates to a constant determined only by the properties of the magnetic host material. </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="6523" page="1438" related-article-type="in-this-issue" vol="370" xlink:href="10.1126/science.aba5555">1438</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6523" page="1413" related-article-type="in-this-issue" vol="370" xlink:href="10.1126/science.abe3387">1413</jats:related-article> </jats:p>

<jats:title>Two steps forward—now look back</jats:title> <jats:p> Whether designed computationally or uncovered in activity screening, enzymes repurposed for biocatalysis rarely start at the peak of proficiency. However, directed evolution can in some cases increase catalytic efficiency of a poor enzyme by many orders of magnitude. Otten <jats:italic>et al.</jats:italic> used a suite of biochemical techniques to investigate the origins of rate enhancement in a previously evolved model enzyme. Two conformational states are present in the initial, computationally designed enzyme, but only one is active. Shifting the population toward the active state is one factor in increasing catalytic efficiency during evolution. Single mutations do not greatly increase activity, but the synergistic combination of just two out of 17 substitutions can provide most of the rate enhancement seen in the final, evolved enzyme. </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="6523" page="1442" related-article-type="in-this-issue" vol="370" xlink:href="10.1126/science.abd3623">1442</jats:related-article> </jats:p>

<jats:title>A sound demonstration of Klein tunneling</jats:title> <jats:p> The ability of particles to tunnel through barriers is an important property of quantum mechanical systems, and the extent of the effect is strongly dependent on the properties of the barrier. By contrast, Klein tunneling can exhibit unity transmission that is independent of the width and height of the energy barrier, but direct evidence for this effect remains elusive. Using a phononic system comprising a periodic array of dielectric pillars, Jiang <jats:italic>et al.</jats:italic> provide evidence for the direct observation of Klein tunneling. Near-unity transmission of acoustic excitations was observed across the barrier independently of its width and height. This ability to tune the effect by controlling the size of the junctions and the frequency of incident waves provides a promising platform to explore complex nontrivial physics and applications in signal processing and information communications. </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="6523" page="1447" related-article-type="in-this-issue" vol="370" xlink:href="10.1126/science.abe2011">1447</jats:related-article> </jats:p>

<jats:title>A combined multimessenger analysis</jats:title> <jats:p> Neutron stars are stellar remnants with densities greater than that of an atomic nucleus. The properties of matter under such extreme conditions are poorly understood and inaccessible to terrestrial laboratories. Dietrich <jats:italic>et al.</jats:italic> developed a framework to combine multiple constraints on the masses and radii of neutron stars, including data from gravitational waves, electromagnetic observations, and theoretical nuclear physics calculations. They used this analysis to constrain the neutron-star equation of state and also improved the precision on the gravitational wave (standard siren) measurement of the Hubble constant—the expansion rate of the Universe. </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="6523" page="1450" related-article-type="in-this-issue" vol="370" xlink:href="10.1126/science.abb4317">1450</jats:related-article> </jats:p>