Catálogo de publicaciones - revistas

<jats:p>A genetic study of microbes in an acid mine drainage site provide evolutionary rate estimates for wild microbe populations.</jats:p>

<jats:p>Numerical models show that protoplanetary nebulae are sites of chemical activity even in the cold outer disk.</jats:p>

<jats:p>Studying the phenotypic differences between genetically identical cells rather than their general features can reveal novel regulatory mechanisms for diverse cellular processes.</jats:p>

<jats:p>The discovery of calcification inside present-day cyanobacteria raises questions about their geologic record.</jats:p>

<jats:p>Incorporating unnatural amino acids into proteins presents challenges in expanding the genetic code.</jats:p>

<jats:p>“Appropriate Design for Global Health,” the IBI Prize–winning module, primes students to respond to global health challenges with novel technological solutions.</jats:p>

<jats:p> A monthly roundup of recent news and projects of <jats:italic>Science</jats:italic> 's publisher, the American Association for the Advancement of Science. </jats:p>

<jats:title>Getting Around the Block</jats:title> <jats:p> Diblock copolymers provide a rich variety of morphologies that depend on the length of the polymer blocks, the overall fraction of each block, and their chemical dissimilarity. New synthetic methods have made it possible to make copolymers with three or more components and in a range of chemical architectures. However, this growth in design choices can offer too many variables to work with, and rational design is important, especially when trying to transform small-scale products in engineered commodities. <jats:bold> Bates <jats:italic>et al.</jats:italic> </jats:bold> (p. 434) review the opportunities and complexities that exist when working in this expanded playground of block copolymers. </jats:p>

<jats:title>Synchronize Watches</jats:title> <jats:p> Time standards based on the energy-level transitions of atoms and ions provide the most accurate and precise methods of time keeping. Measurements made in one laboratory and in another must be done with clocks that have been synchronized and calibrated to ensure that the same measurement is being made. Such clocks, however, are not particularly mobile and are housed in national metrology labs. <jats:bold> Predehl <jats:italic>et al.</jats:italic> </jats:bold> (p. 441; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6080" page="421" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1220826">Warrington</jats:related-article> </jats:bold> ) linked two optical clocks separated by over 900 kilometers using optical fiber to show that the clocks can be synchronized, with the clocks showing a frequency stability better than 3.7 × 10 <jats:sup>−19</jats:sup> . Such long-distance synchronization should allow for tests of fundamental physics, such as general relativity and quantum electrodynamics. </jats:p>

<jats:title>Working the Angles on Chemical Bonding</jats:title> <jats:p> The forces exerted by chemical bonds depend not only on the distances between atoms but also upon the angles between them. <jats:bold>Welker and Giessibl</jats:bold> (p. 444; see the cover) probed the angular dependence of the CO molecule adsorbed on top of a copper atom on an atomically flat Cu(111) surface using both atomic force microscopy and scanning tunneling microscopy (STM). Probe tips with three different tip-atom-symmetry environments were used. All three tips delivered similar STM images, but force probes revealed the angular dependence of the CO bond to the surface and provided data for a model of the changes in bond energy. </jats:p>