Catálogo de publicaciones - revistas

<jats:p>Ten years ago, the SARS outbreak spurred efforts by the World Health Organization to improve global responses to health threats and crises.</jats:p>

<jats:title>The Thalamus in Fear and Memory</jats:title> <jats:p> The medial prefrontal cortex (mPFC) mediates the cognitive control of many high-level brain functions. However, it is unclear which synaptic projections from the mPFC to subcortical regions are critical for maintaining the proper balance between retention and generalization of fear memory details. Using an array of behavioral, physiological, and anatomical techniques, <jats:bold>Xu and Südhof</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1290" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229534">1290</jats:related-article> ) describe a neural circuit that controls memory generalization and specificity. This circuit involves the nucleus reuniens (NR), a thalamic nucleus of largely unknown function. Optogenetic activation of NR neurons in awake behaving mice revealed the role of the NR in fear memory generalization. </jats:p>

<jats:title>Magnetic Droplet</jats:title> <jats:p> When a solitary wave travels atop the surface of a fluid, its shape generally changes with time, with some of its components traveling at velocities slightly different than others. In nonlinear media, this spreading effect may be countered by a slimming effect stemming from the non-linearity, which generates an object with perfectly preserved shape, called a soliton. Solitons have been observed in fluids, granular media, and other systems. <jats:bold> Mohseni <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1295" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1230155">1295</jats:related-article> ) detected a dissipative soliton (one that also balances gain and dissipation) in a magnetic system, in the form of a magnetic droplet consisting of a core of spins pointing opposite to the external magnetic field. The droplet exhibited peculiar dynamics and could be controlled by electric current. </jats:p>

<jats:title>Flexi-Fibers</jats:title> <jats:p> Glass or metal fibers can show incredible flexibility. <jats:bold> Natalio <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1298" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1216260">1298</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1281" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1235357">Sethmann</jats:related-article> </jats:bold> ) used the protein silicatein-α, which is responsible for the biomineralization of silicates in sponges, to guide the formation of spicules made of calcite. These synthetic spicules could be bent to a high degree because of their inherent elasticity, whilst retaining the ability to guide light. </jats:p>

<jats:title>Surface Molecules Not Quite Desorbing</jats:title> <jats:p> The dynamics of molecules desorbing from or adsorbing on surfaces requires that molecules rapidly gain or lose a large amount or translational and rotational energy to enter or leave the gas phase. An intermediate precursor state has long been invoked in which molecules interact weakly with the surface but translate along it and exchange energy without forming localized surface bonds. <jats:bold> Dell'Angela <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1302" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1231711">1302</jats:related-article> ) found evidence for such a state in changes in x-ray absorption and emission spectra of CO molecules adsorbed on a ruthenium surface after optical excitation rapidly heated the surface. The use of a free electron laser provided high time resolution for x-ray spectroscopy studies. Density function theory and modeling of high temperature states revealed a state that forms from molecules that have not overcome the desorption barrier during heating and that are bonded less strongly than the chemisorbed state. </jats:p>

<jats:title>Under the Sea Floor</jats:title> <jats:p> Microorganisms living in basaltic sea floor buried beneath sediments derive energy from inorganic components from the host rocks that interact with infiltrating seawater, which brings dissolved oxygen and other trace nutrients with it. <jats:bold> Lever <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1305" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229240">1305</jats:related-article> ) directly sampled the subseafloor community off the eastern flank of the Juan de Fuca Ridge in the Pacific Ocean and found evidence for ongoing microbial sulfate reduction and methanogenesis. Multiyear incubation experiments with samples of host rock confirmed the microbial activities measured in situ. </jats:p>

<jats:title>Four-Winged Birds?</jats:title> <jats:p> Recently, nonavialan dinosaurs with feathers on their fore- and hindlimbs have been described. <jats:bold> Zheng <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1309" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1228753">1309</jats:related-article> ) describe eleven basal avialan fossils with clear evidence of feathered hindlimbs. Together these fossils show that early avialans possessed four wings, rather than two. A gradual reduction in hindlimb feathering eventually yielded the two-wing condition in today's birds. Such a transition may have accompanied a locomotory decoupling of the fore- and hindlimbs, which facilitated the development of the forelimbs into flight-capable wings. </jats:p>

<jats:title>Additive Effects</jats:title> <jats:p> Although specific genes involved in animal coloration have been identified, the underlying selection for genetic variation in color-specific adaptation is not well understood. Examining the <jats:italic>Agouti</jats:italic> gene and other loci in the deer mice of Nebraska, where predation selects for light-colored mice in light environments and dark-colored mice in dark environments, <jats:bold> Linnen <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1312" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1233213">1312</jats:related-article> ) find evidence of multiple genetic variants under selection affecting coloration. The light color of Sand Hills mice is not the result of a single large-effect mutation, but is because of many accumulated mutations, each with a smaller phenotypic effect. </jats:p>

<jats:title>Synchronizing Photosynthetic Capacity</jats:title> <jats:p> Coordination of photosynthetic activity with sunlight benefits plant productivity. <jats:bold> Noordally <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1316" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1230397">1316</jats:related-article> ) analyzed how the <jats:italic>Arabidopsis</jats:italic> circadian clock keeps the chloroplasts working in tune with the Sun. SIGMA FACTOR5 (SIG5) is encoded in the cell nucleus and reflects circadian cycles with changes in its own transcript abundance. SIG5 acts, however, in the chloroplast, where it supports photosystem II production. </jats:p>

<jats:title>Coordinating Metabolism</jats:title> <jats:p> Growth factors help to coordinate metabolism with growth in part by stimulating the activity of the protein kinase mTORC1 (mechanistic target of rapamycin complex 1). <jats:bold> Ben-Sahra <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1323" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1228792">1323</jats:related-article> , published online 21 February) and <jats:bold> Robitaille <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6125" page="1320" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1228771">1320</jats:related-article> , published online 21 February) independently identified a key target of mTORC1—carbamolyl-phosphate synthase 2, or CAD, the rate-limiting enzyme for de novo synthesis of pyrimidines. Metabolomic profiling and phosphoproteomic analyses of normal cells and cells lacking signaling by mTORC1 converged on CAD as a key point at which growth-promoting signals also ramp up production of nucleic acids. </jats:p>