Catálogo de publicaciones - revistas

<jats:p>The release of a cytokine from immune cells requires a protein to guide a protease to the cell surface.</jats:p>

<jats:p>A chemist, whose DNA work underlies powerful biochemical and genetic tools, sought to control nuclear arms and foster science communication to policy-makers.</jats:p>

<jats:p>Radiation damage is used to locate proteins embedded in dense DNA in a megavirus.</jats:p>

<jats:title>Why Wait?</jats:title> <jats:p> Tropospheric ozone can be dangerous to human health, can be harmful to vegetation, and is a major contributor to climate warming. Black carbon also has significant negative effects on health and air quality and causes warming of the atmosphere. <jats:bold> Shindell <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="183" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1210026">183</jats:related-article> ) present results of an analysis of emissions, atmospheric processes, and impacts for each of these pollutants. Seven measures were identified that, if rapidly implemented, would significantly reduce global warming over the next 50 years, with the potential to prevent millions of deaths worldwide from outdoor air pollution. Furthermore, some crop yields could be improved by decreasing agricultural damage. Most of the measures thus appear to have economic benefits well above the cost of their implementation. </jats:p>

<jats:title>Binary Revelation</jats:title> <jats:p> Binary star systems that contain a neutron star or a black hole are expected to emit gamma rays. These gamma-ray binaries are a rare class of objects, which are also expected to emit x-rays. Indeed, several such systems were initially detected through their x-ray emission. The <jats:bold>Fermi LAT Collaboration</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="189" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1213974">189</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="6065" page="175" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215895">Mirabel</jats:related-article> </jats:bold> ) reports the detection of a gamma-ray binary that was previously unknown as an x-ray source. Follow-up observations reveal that the system is also a source of x-rays and that the companion star is a class O star, a type that is very hot and very luminous. </jats:p>

<jats:title>Breaking Up the Indivisible</jats:title> <jats:p> The famous Millikan oil drop experiment demonstrated that electric charge is quantized and cannot be divided into parts smaller than that of an electron. Decades later, the fractional quantum Hall effect was discovered that could only be explained through the existence of quasi-particles of fractional charge. Now, <jats:bold> Isakov <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="193" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1212207">193</jats:related-article> ) numerically demonstrate the existence of an even more exotic object, a fractionalized quantum critical point (QCP), in the so-called Kagome lattice of bosons. Quantum Monte Carlo simulations were used to measure the critical exponents and revealed the fractionalization by comparison with a QCP of real bosons. </jats:p>

<jats:title>Structured Memories</jats:title> <jats:p> High-density magnetic memory is generally produced by using ferromagnetic materials. As the density increases and the memory elements become closer together, stray fields can result in cross-talk and a corruption of the stored information. Antiferromagetic structures, however, are expected to be relatively insensitive to magnetic fields and so should, in principle, allow the elements to be packed in even closer. <jats:bold> Loth <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="196" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214131">196</jats:related-article> ) carried out low-temperature experiments to construct antiferromagnetic structures atom by atom. Electrical switching of the magnetic states was observed, and data could be robustly stored on the structure for several hours, albeit at low temperature. </jats:p>

<jats:title>Dispersal in 3D</jats:title> <jats:p> The fabrication of composites containing small proportions of nanoparticles is limited by the ability to disperse the particles uniformly in all three dimensions. <jats:bold> Erb <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="199" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1210822">199</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="6065" page="177" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215841">Fratzl</jats:related-article> </jats:bold> ) describe a process for creating nanoparticle composites in which a magnetic field is used to align the nanoparticles. Surprisingly, the magnetic alignment of iron-oxide functionalized nanorods and discs was enabled using very small magnetic fields and low-volume fractions of magnetic nanoparticles, which allowed control of the orientation of the nanorods and discs three-dimensionally. </jats:p>

<jats:title>Criegee Sighting</jats:title> <jats:p> Standard mechanistic models for the reaction of ozone with unsaturated hydrocarbons implicate a transient carbonyl oxide compound, termed the “Criegee intermediate,” which has largely eluded detection. <jats:bold> Welz <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="204" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1213229">204</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="6065" page="178" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1217165">Marston</jats:related-article> </jats:bold> ) have now detected the compound by using mass spectrometry, following the low-pressure photolytic reaction of oxygen with diiodomethane, and measured its decay kinetics in the presence of nitric oxide, nitrogen dioxide, and sulfur dioxide. Reaction rates were higher than expected, suggesting that the intermediate may play a more prominent role in atmospheric chemistry than previously assumed. </jats:p>

<jats:title>That Sweet Sensation</jats:title> <jats:p> Photosynthesis in the leaf generates sucrose that must be transported via the phloem to other parts of the plant in order, for example, to be incorporated into harvestable produce. Studying <jats:italic>Arabidopsis</jats:italic> and rice, <jats:bold> Chen <jats:italic>et al.</jats:italic> </jats:bold> (p. 207, published online 8 December; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6065" page="173" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1216828">Braun</jats:related-article> </jats:bold> ) identified the SWEET family of sucrose efflux transporters that are responsible for carrying sucrose out of the leaf cells. When the transporters were disabled, sucrose accumulated in the leaves. Functioning properly, the SWEET transporters carry sucrose across the plasma membrane and other transporters move it further into the phloem. </jats:p>