Catálogo de publicaciones - revistas

<jats:title>A cool route to nanospectroscopy</jats:title> <jats:p> Confining light to a cavity is often used to enhance the interaction between the light and a particle stored within the cavity. Benz <jats:italic>et al.</jats:italic> worked with a self-assembled monolayer of biphenyl-4-thiol molecules sandwiched between a gold film and a gold nanoparticle. They used laser irradiation to move atoms in the nanoparticle and produced a “picocavity” that was stable at cryogenic temperatures. The authors were then able to obtain time-dependent Raman spectra from individual molecules. Such subwavelength cavities that can localize light to volumes well below 1 nm <jats:sup>3</jats:sup> will enable optical experiments on the atomic 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="6313" page="726" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah5243">726</jats:related-article> </jats:p>

<jats:title>Coordinated scission of N–H or O–H bonds</jats:title> <jats:p> Ammonia and water both have well-explored acid-base chemistry at room temperature, revolving around proton exchange. In contrast, radical chemistry involving H-atom exchange is comparatively rare in these molecules in the absence of a high-energy stimulus. Bezdek <jats:italic>et al.</jats:italic> now show that coordination of ammonia or water to a molybdenum complex substantially weakens the N–H or O–H bonds, so much so that heating to 60°C liberates hydrogen (see the Perspective by Hoover). Theoretical and electrochemical analyses reveal the underpinnings of the bond-weakening phenomenon. </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="6313" page="730" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aag0246">730</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6313" page="707" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aaj2332">707</jats:related-article> </jats:p>

<jats:title>Watching as helium goes topsy-turvy</jats:title> <jats:p> Theorists have long pondered the underpinnings of the Fano resonance, a spectral feature that resembles adjacent rightside-up and upside-down peaks. An especially well-studied instance of this feature appears in the electronic spectrum of helium as a transient state undergoes delayed ionization. Two studies have now traced the dynamics of this state in real time. Gruson <jats:italic>et al.</jats:italic> used photoelectron spectroscopy to extract the amplitude and phase of the electron wave packet after inducing its interference with reference wave packets tuned into resonance at variable delays. Kaldun <jats:italic>et al.</jats:italic> used extreme ultraviolet absorption spectroscopy to probe the transient state while variably forcing ionization with a strong near-infrared field. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6313" page="734" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah5188">734</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6313" page="738" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6972">738</jats:related-article> </jats:p>

<jats:title>Watching as helium goes topsy-turvy</jats:title> <jats:p> Theorists have long pondered the underpinnings of the Fano resonance, a spectral feature that resembles adjacent rightside-up and upside-down peaks. An especially well-studied instance of this feature appears in the electronic spectrum of helium as a transient state undergoes delayed ionization. Two studies have now traced the dynamics of this state in real time. Gruson <jats:italic>et al.</jats:italic> used photoelectron spectroscopy to extract the amplitude and phase of the electron wave packet after inducing its interference with reference wave packets tuned into resonance at variable delays. Kaldun <jats:italic>et al.</jats:italic> used extreme ultraviolet absorption spectroscopy to probe the transient state while variably forcing ionization with a strong near-infrared field. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6313" page="734" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah5188">734</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6313" page="738" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6972">738</jats:related-article> </jats:p>

<jats:title>Biological inspiration for reduction</jats:title> <jats:p> Microorganisms have evolved sophisticated enzymatic machinery to reduce perchlorate and nitrate ions. Although the energetics of the pathways are different, the heme-containing active sites of the corresponding reductase enzymes are remarkably similar. Ford <jats:italic>et al.</jats:italic> constructed an inorganic catalyst to mediate these reactions based on these active sites, using a nonheme iron complex. A secondary coordination sphere near the iron center aligned the nitrate or perchlorate oxyanions and formed an iron-oxo complex. Regenerating the catalyst in the presence of protons and electrons released water—a potentially much more sustainable process than reduction strategies that require the use of harsh reagents. </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="6313" page="741" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah6886">741</jats:related-article> </jats:p>

<jats:title>British squirrels infected with leprosy</jats:title> <jats:p> With the exception of armadillos in the Americas, leprosy infections are considered almost exclusively restricted to humans. Avanzi <jats:italic>et al.</jats:italic> examined warty growths on the faces and extremities of red squirrels in the British Isles and found that two species of leprosy-causing organisms were to blame (see the Perspective by Stinear and Brosch). <jats:italic>Mycobacterium leprae</jats:italic> in the southern population of Brownsea Island squirrels originated from a medieval human strain. <jats:italic>M. lepromatosis</jats:italic> was found in red squirrels from elsewhere in the United Kingdom and Ireland. Human leprosy is proving hard to eradicate, despite available drugs. Perhaps other wildlife species are also reservoirs for this stubborn 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="6313" page="744" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah3783">744</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6313" page="702" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aal0145">702</jats:related-article> </jats:p>

<jats:title>Why we are losing sea ice</jats:title> <jats:p> Arctic sea ice is disappearing rapidly, leading to predictions of an ice-free summer in the near future. Simulations of the timing of summer sea-ice loss differ substantially, making it difficult to evaluate the pace of the loss. Notz and Stroeve observed a linear relationship between the monthly-mean September sea-ice area and cumulative CO <jats:sub>2</jats:sub> emissions. This allowed them to predict Arctic summer sea ice directly from the observational record. Interestingly, most models underestimate this loss. </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="6313" page="747" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aag2345">747</jats:related-article> </jats:p>

<jats:title>Global spread of aggressive mycobacteria</jats:title> <jats:p> Many mycobacteria, in addition to those causing leprosy and tuberculosis, are capable of infecting humans. Some can be particularly dangerous in patients suffering from immunosuppression or chronic disease, such as cystic fibrosis (CF). Bryant <jats:italic>et al.</jats:italic> observed clusters of near-identical isolates of drug-resistant <jats:italic>Mycobacterium abscessus</jats:italic> in patients reporting to CF clinics. The similarity of the isolates suggests transmission between patients, rather than environmental acquisition. Although this bacterium is renowned for its environmental resilience, the mechanism for its long-distance transmission among the global CF patient community remains a puzzle. </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="6313" page="751" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aaf8156">751</jats:related-article> </jats:p>

<jats:title>Resolving a ticklish problem</jats:title><jats:p>What is the neural correlate of ticklishness? When Ishiyama and Brecht tickled rats, the animals produced noises and other joyful responses. During the tickling, the authors observed nerve cell activity in deep layers of the somatosensory cortex corresponding to the animals' trunks. Furthermore, microstimulation of this brain region evoked the same behavior. Just as in humans, mood could modulate this neuronal activity. Anxiety-inducing situations suppressed the cells' firing, and the animal could no longer be tickled.</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="6313" page="757" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aah5114">757</jats:related-article></jats:p>

<jats:title>Identifying genes under recent selection</jats:title> <jats:p> Evolutionary analyses aim to identify recent genetic changes that are likely to have been subject to selection. Field <jats:italic>et al.</jats:italic> present a method to identify such changes, the singleton density score, which they applied to over 3000 human genomes. Over the past ∼100 generations (2000 to 3000 years), Europeans are likely to have experienced selection for genetic variants, including those that affect skin and hair pigmentation, as well as height. </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="6313" page="760" related-article-type="in-this-issue" vol="354" xlink:href="10.1126/science.aag0776">760</jats:related-article> </jats:p>