Catálogo de publicaciones - revistas

<jats:title>Watching fermions transition on site</jats:title> <jats:p> Optical lattices are a promising platform for simulating the many-body physics that occurs in solids. In lattices filled with cold bosonic atoms, “quantum microscopy” makes it possible to watch quantum phase transitions as they unravel. Greif <jats:italic>et al.</jats:italic> bring a similar capability to lattices filled with fermions, which are trickier to cool but are a closer match to electrons in a solid. Tuning the interaction between the <jats:sup>6</jats:sup> Li atoms allowed for the observation of transitions from a metallic phase to a band insulator and then to an interaction-dominated Mott insulator phase. </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="6276" page="953" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad9041">953</jats:related-article> </jats:p>

<jats:title>A golden opportunity for graphene</jats:title> <jats:p> Reducing friction can limit wear and improve the energy efficiency of mechanical devices. Graphene is a promising lubricant because the friction between sheets is minuscule under certain circumstances. Kawai <jats:italic>et al.</jats:italic> show that the same ultra-low frictional properties extend to other surfaces. They find ultralow friction when dragging graphene nanoribbons across a gold surface using an atomic force microscope. This discovery sets up the potential for developing nanographene frictionless coatings. </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="6276" page="957" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad3569">957</jats:related-article> </jats:p>

<jats:title>Competition for binaphthyl catalysts</jats:title> <jats:p> The binaphthyl framework has proven extremely effective in biasing a broad range of chemical reactions toward just one of two mirror-image products. The motif was first applied as a ligand in metal catalysis, and more recently as a conjugate base in acid catalysis. Gheewala <jats:italic>et al.</jats:italic> report a class of chiral carbon acids based around a cyclopentadiene framework that are easily accessible from readily available precursors. The compounds are showcased as highly selective catalysts for asymmetric Mukaiyama Mannich and oxocarbenium aldol reactions. </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="6276" page="961" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad0591">961</jats:related-article> </jats:p>

<jats:title>Direct hydrogen peroxide synthesis</jats:title> <jats:p> Hydrogen peroxide is synthesized industrially without direct contact of hydrogen and oxygen in order to achieve high concentrations. For many applications, only dilute aqueous solutions are needed. Freakley <jats:italic>et al.</jats:italic> report an improvement in the direct synthesis of hydrogen peroxide over using palladium-tin alloys. This catalyst still achieves selectivities of &gt;95%, like palladium-gold alloys, but is cheaper and can suppress reactions that decompose the product. </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="6276" page="965" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad5705">965</jats:related-article> </jats:p>

<jats:title>Close-up view of the nuclear periphery</jats:title> <jats:p> Cell biologists would like to be able to visualize complexes inside cells at molecular resolution. Several limitations, however, have prevented the field from realizing this goal. The thickness of most cells precludes cryo-electron tomography, a technique which itself does not provide sufficient contrast. Mahamid <jats:italic>et al.</jats:italic> successfully combined recent advances on both fronts to analyze structures in situ at the periphery of the nucleus. Their images reveal features that inform our understanding of the native organization of nuclear pores and of the nuclear lamina. </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="6276" page="969" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad8857">969</jats:related-article> </jats:p>

<jats:title>Leaf seasonality in Amazon forests</jats:title> <jats:p> Models assume that lower precipitation in tropical forests means less plant-available water and less photosynthesis. Direct measurements in the Amazon, however, show that production remains constant or increases in the dry season. To investigate this mismatch, Wu <jats:italic>et al.</jats:italic> use tower-based cameras to detect the phenology (i.e., the seasonal patterns) of leaf dynamics in tropical tree crowns in Amazonia, Brazil, and relate this to patterns of CO <jats:sub>2</jats:sub> flux. Accounting for age-dependent variation among individual leaves and crowns is necessary for understanding the seasonal dynamics of photosynthesis in the entire ecosystem. Leaf phenology regulates seasonality of the carbon flux in tropical forests across a gradient of climate zones. </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="6276" page="972" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad5068">972</jats:related-article> </jats:p>

<jats:title>Layered versatility atop circadian clocks</jats:title> <jats:p> The circadian clock evolved to allow cells or organisms to anticipate changes in physiological requirements associated with Earth's 24-hour light/dark cycle. Some activities, however, need to occur out of phase with the core clock. Liang <jats:italic>et al.</jats:italic> imaged changes in intracellular concentration of Ca <jats:sup>2+</jats:sup> in populations of neurons in the fruit fly brain. Although the underlying clock was synchronous, the rhythms of Ca <jats:sup>2+</jats:sup> changes corresponded with distinct timing of activities associated with activity of the particular neuronal populations. Proper coordination of these distinct phases required expression of the neuropeptide pigment-dispersing factor and its receptor. </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="6276" page="976" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad3997">976</jats:related-article> </jats:p>

<jats:title>Neurotransmitter uptake one vesicle at a time</jats:title> <jats:p> Despite opposing ionic gradients, synaptic vesicles are able to accumulate neurotransmitters. To resolve the mystery of how this happens, Farsi <jats:italic>et al.</jats:italic> made parallel measurements of pH gradients and membrane potential at the single synaptic vesicle level. Glutamatergic and GABAergic vesicles had different uptake mechanisms, revealing insights into the energetic and ionic coupling of vesicular neurotransmitter transport. </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="6276" page="981" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad8142">981</jats:related-article> </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>