Catálogo de publicaciones - revistas

<jats:title>Niche relocated by muscle contraction</jats:title> <jats:p> Regulation of adult stem cells by their microenvironment, or niche, is essential for tissue homeostasis and for regeneration after injury and during aging. Normal regression of hair follicles during the hair cycle poses a particular challenge for maintaining a functional proximity of stem cells to their niche, especially the specialized mesenchymal cells of the dermal papilla. Using mice as a model organism, Heitman <jats:italic>et al.</jats:italic> demonstrate that the follicle dermal sheath is an active smooth muscle that drives tissue remodeling through coordinated cell contraction, enabling renewed contact between the dermal papilla and hair follicle stem cells during hair follicle regression. This biomechanical mechanism of niche relocation may be utilized in other stem cell niche systems. </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="6474" page="161" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aax9131">161</jats:related-article> </jats:p>

<jats:title>Finding new species</jats:title> <jats:p> Thousands of species have been described, and, although most may agree that many thousand remain undiscovered, identifying new taxa of charismatic vertebrates, like birds, is rare. Rheindt <jats:italic>et al.</jats:italic> describe five new songbird species and five new subspecies found on a single small island near Sulawesi, Indonesia, over a single 6-week expedition (see the Perspective by Kennedy and Fjeldså). They targeted the area because of its geological history and complexity and the historical notes of other explorers. They argue that similar approaches in other regions could also lead to the discovery of new 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="6474" page="167" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aax2146">167</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6474" page="140" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aba3798">140</jats:related-article> </jats:p>

<jats:title>An anti-embrittlement roadmap</jats:title> <jats:p> Hydrogen is important for energy applications such as fuel cells but tends to diffuse into materials and make them more susceptible to fracture. Chen <jats:italic>et al.</jats:italic> tackled the challenge of identifying the exact location of hydrogen atoms in two common steels. The light weight and high mobility of hydrogen creates serious problems with conventional techniques. The authors used cryo-transfer atom probe tomography to show that hydrogen is pinned to various interfaces in the steels. This direct look into hydrogen trapping should help with the development of materials that are more resistant to hydrogen embrittlement. </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="6474" page="171" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaz0122">171</jats:related-article> </jats:p>

<jats:title>Upside-down molecules on a salt surface</jats:title> <jats:p> The quantum states of molecules are usually measured in gas-phase studies to minimize collisions that would blur the spectra. However, for carbon monoxide (CO) molecules adsorbed on a NaCl(100) surface, infrared emission from even high vibrational states can be resolved. In quantum-state resolved spectra, Lau <jats:italic>et al.</jats:italic> found that infrared-laser excitation of a monolayer of CO adsorbed on NaCl(100) forms an isomer in which CO binds to Na <jats:sup>+</jats:sup> through its O atom in an upside-down configuration (see the Perspective by Wu). These results could be understood with a simple vibrationally adiabatic electrostatic theory, making this system convenient for studies of the isomerization chemistry. </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="6474" page="175" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaz3407">175</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6474" page="148" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aba1100">148</jats:related-article> </jats:p>

<jats:title>The “hole” story of water ionization</jats:title> <jats:p> The direct observation of the cationic hole H <jats:sub>2</jats:sub> O <jats:sup>+</jats:sup> that is formed in liquid water after ionization has been a long-standing experimental challenge. Previous attempts using optical and ultraviolet techniques have failed to reveal its key spectroscopic signature during ultrafast transformation into a OH radical. Loh <jats:italic>et al.</jats:italic> address this gap by using intense, ultrafast x-ray pulses from an x-ray free electron laser at ∼530 electron volts. They found compelling evidence for the formation H <jats:sub>2</jats:sub> O <jats:sup>+</jats:sup> and its decay to an OH radical by a proton transfer mechanism and elucidated the other fastest–time scale steps in the early-time dynamics of ionized liquid water. </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="6474" page="179" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaz4740">179</jats:related-article> </jats:p>

<jats:title>Gamma-ray flash from a lightning leader</jats:title> <jats:p> Terrestrial gamma-ray flashes (TGFs) are millisecond pulses of gamma rays produced by thunderstorms. Neubert <jats:italic>et al.</jats:italic> observed a TGF from above, using instruments on the International Space Station. High-speed photometry in optical, ultraviolet, x-ray, and gamma-ray bands allowed them to determine the sequence of events that produced the TGF. Emission from an intracloud lightning leader was followed within a millisecond by the TGF. The subsequent lightning flash produced an electromagnetic pulse, which induced expanding waves of ultraviolet emission in the ionosphere above the thunderstorm, called an elve. The authors conclude that high electric fields produced within the lightning leader generated the TGF. </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="6474" page="183" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aax3872">183</jats:related-article> </jats:p>

<jats:title>Spin and charge go their separate ways</jats:title> <jats:p> Strongly interacting chains of fermions are predicted to exhibit two types of collective excitations: spinons, which carry only spin, and holons, which carry only charge. These excitations move at different velocities. Signatures of this so-called spin-charge separation have been observed in solid-state systems, but obtaining direct dynamical evidence is tricky. With this goal in mind, Vijayan <jats:italic>et al.</jats:italic> perturbed a chain of ultracold interacting fermions housed in a one-dimensional optical lattice by removing one of the atoms. This gave rise to two independent excitations, which the researchers identified as spinons and holons using a quantum gas microscope. </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="6474" page="186" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aay2354">186</jats:related-article> </jats:p>

<jats:title>Reaching a conductance plateau</jats:title> <jats:p> The surface of the iron-based superconductor FeTe <jats:sub>0.55</jats:sub> Se <jats:sub>0.45</jats:sub> satisfies the necessary conditions to support topological superconductivity. Under the application of a magnetic field, vortices with zero-bias peaks that are consistent with Majorana bound states have been observed. Using scanning tunneling spectroscopy, Zhu <jats:italic>et al.</jats:italic> studied the conductance of these states as the tip-sample distance was reduced (see the Perspective by Sau). The researchers found that the value of the conductance increased and eventually saturated. For one of the vortices they studied, the conductance reached a quantized value that is characteristic of the Majorana bound states. </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="6474" page="189" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aax0274">189</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6474" page="145" related-article-type="in-this-issue" vol="367" xlink:href="10.1126/science.aaz9589">145</jats:related-article> </jats:p>