Catálogo de publicaciones - revistas

<jats:title>Filling the terahertz gap</jats:title> <jats:p> Compared with other wavelengths, coherent sources of electromagnetic radiation in the terahertz regime are relatively scarce. Despite a number of applications in security imaging, spectroscopy, and chemical analysis, it has been experimentally challenging to produce such light. Chevalier <jats:italic>et al.</jats:italic> demonstrate an approach involving the excitation of a molecular gas with a quantum cascade laser. They show that they can tune into a broad range of desired wavelengths by carefully selecting the required molecular transition. A compact platform—the size of a shoe box—and widely tunable source of coherent terahertz radiation should find immediate application across a number of fields. </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="6467" page="856" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay8683">856</jats:related-article> </jats:p>

<jats:title>Switching light on-chip</jats:title> <jats:p> The development of practical, reconfigurable photonics requires a platform that can be scaled to large circuits and driven by low-voltage complementary metal-oxide semiconductor (CMOS) electronics. Such a platform requires that switching devices possess a compact footprint, low driving voltages, fast switching, low optical losses, and low power consumption. Haffner <jats:italic>et al.</jats:italic> demonstrate that the combination of opto-electro-mechanical effects with plasmonic devices can provide a platform that meets all the above criteria. The results are promising for developing on-chip integrated optical networks that can be switched by CMOS-level voltages. </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="6467" page="860" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay8645">860</jats:related-article> </jats:p>

<jats:title>A glass that won't break</jats:title> <jats:p> Oxide glasses are important for applications ranging from smartphone screens to window panes. One familiar feature of glass is that it fractures and shatters when rapidly deformed, limiting the number of potential uses. However, Frankberg <jats:italic>et al.</jats:italic> found that they could deform thin films of glassy alumina (Al <jats:sub>2</jats:sub> O <jats:sub>3</jats:sub> ) with high strain rates at room temperature (see the Perspective by Wondraczek). This surprising observation is supported by simulations of the material that show that dense and flawless glassy alumina samples can deform this way. The discovery provides important insight into designing new glasses that might be more fracture resistant. </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="6467" page="864" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aav1254">864</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6467" page="804" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz2127">804</jats:related-article> </jats:p>

<jats:title>Taking electrical control</jats:title> <jats:p> Excitons—bound pairs of electrons and holes in a solid—can, in principle, be used as information carriers. However, their lifetime is limited because the electrons and holes tend to quickly recombine. One way to extend this lifetime is to physically separate electrons and holes—for example, by having them reside in different layers of a van der Waals heterostructure. Jauregui <jats:italic>et al.</jats:italic> used this strategy to form long-lived interlayer excitons in a heterostructure made out of monolayers of molybdenum diselenide (MoSe <jats:sub>2</jats:sub> ) and tungsten diselenide (WSe <jats:sub>2</jats:sub> ). Through electrical control of the layers in the heterostructure, the researchers further increased exciton lifetime and formed and manipulated charged excitons. </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="6467" page="870" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaw4194">870</jats:related-article> </jats:p>

<jats:title>Cross-linking a range of alkyl polymers</jats:title> <jats:p> Some alkyl polymers, such as polyethylene, can be cross-linked by using peroxides or high-energy radiation or through the addition of a radical forming agent. Others, like polypropylene, are likely to undergo chain scission, and this process tends to be uncontrolled in the distribution of the cross-links. Lepage <jats:italic>et al.</jats:italic> developed a widely applicable approach using <jats:italic>bis</jats:italic> -diazirine molecules as cross-linking agents (see the Perspective by de Zwart <jats:italic>et al.</jats:italic> ). These molecules can be thermally or photochemically activated to form carbenes that readily insert into the polymer carbon-hydrogen bonds, thus leading to cross-linking. The <jats:italic>bis</jats:italic> -diazirine is nonexplosive, nonvolatile, and easily activated at relatively mild temperatures and thus could be used to fine-tune the properties of existing polymers through small chemical modifications. </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="6467" page="875" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay6230">875</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6467" page="800" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz7612">800</jats:related-article> </jats:p>

<jats:title>Change in plants as bicarbonate rises</jats:title> <jats:p> Freshwater plants can be broadly divided into two major categories according to their photosynthetic traits: Some use carbon dioxide as their carbon source, whereas others use bicarbonate. Iversen <jats:italic>et al.</jats:italic> found that the relative concentrations of these two inorganic carbon forms in water determine the functional composition of plant communities across freshwater ecosystems (see the Perspective by Marcé and Obrador). They created global maps revealing that community composition is structured by catchment geology and not climate (in contrast to the terrestrial realm, where the trait composition is structured by temperature and rainfall). Anthropogenic influences from land-use change are causing large-scale increases in bicarbonate concentrations in freshwater catchments and are thus leading to wholesale changes in the composition of their aquatic plant communities. </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="6467" page="878" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay5945">878</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6467" page="805" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz9096">805</jats:related-article> </jats:p>

<jats:title>Peptide mimicry breaks the heart</jats:title> <jats:p> Myocarditis, a prolonged chronic inflammation of heart muscle, can eventually progress to inflammatory cardiomyopathy, a serious condition associated with heart failure. Activated T helper (T <jats:sub>H</jats:sub> ) cells that recognize myosin heavy chain 6–derived peptides are thought to play a central role in this pathogenesis. Using a mouse model of myocarditis, Gil-Cruz <jats:italic>et al.</jats:italic> found that cardiac myosin–reactive T <jats:sub>H</jats:sub> cells are initially primed by myosin-peptide mimics derived from commensal <jats:italic>Bacteroides</jats:italic> species in the gut (see the Perspective by Epelman). Unlike heathy controls, human myocarditis patients also showed detectable immune reactivity to both <jats:italic>Bacteroides</jats:italic> and cardiac myosin antigens. Treatment with antibiotics dampened inflammatory responses and prevented lethal heart disease. </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="6467" page="881" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aav3487">881</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6467" page="806" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz4400">806</jats:related-article> </jats:p>

<jats:title>Many factors influence global change</jats:title> <jats:p> Global environmental change is driven by multiple natural and anthropogenic factors. With a focus on global change as it affects soils, Rillig <jats:italic>et al.</jats:italic> point out that nearly all published studies consider just one or two factors at a time (see the Perspective by Manning). In a laboratory experiment, they tested 10 drivers of global change both individually and in combination, at levels ranging from 2 to 10 factors. They found that soil properties, processes, and microbial communities could not be predicted from single-effect responses and that multiple factors in combination produced unsuspected responses. They concluded that single-factor studies remain important for uncovering mechanisms but that global change biology needs to embrace more fully the multitude of drivers impinging on ecosystems. </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="6467" page="886" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay2832">886</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6467" page="801" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz9000">801</jats:related-article> </jats:p>

<jats:title>Magnetic fields can generate spicules</jats:title> <jats:p> Spicules are small jets of plasma from the surface of the Sun that last a few minutes. Around a million are occurring at any moment, even during periods of low solar activity. The mechanism responsible for launching spicules remains unknown, as is their contribution to heating the solar corona. Samanta <jats:italic>et al.</jats:italic> observed emerging spicules and the magnetic fields in the adjacent solar surface. They found that many spicules appear a few minutes after a patch of reverse-polarity magnetic field and that the overlying corona is heated shortly afterward. This result provides evidence that magnetic reconnection can generate spicules, which then transfer energy to the corona. </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="6467" page="890" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaw2796">890</jats:related-article> </jats:p>

<jats:title>Irreversible splitting of light</jats:title> <jats:p> Prisms and dielectric beam splitters tend to be unitary and reversible optical elements, with the quantum properties of the photons largely irrelevant. Kurtscheid <jats:italic>et al.</jats:italic> introduce a method of irreversibly, but coherently, populating a split state with photons by thermalizing the photons into a low-energy ground state by repeated absorption-emission interaction with a fluorescent dye within a double-dimple optical cavity. Generation of such a coherent split state could be used as a precursor step to the quasi-continuous creation of many-body entangled states of light, which could be useful in applications in quantum communication, computing, and simulation. </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="6467" page="894" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay1334">894</jats:related-article> </jats:p>