Catálogo de publicaciones - revistas

<jats:p>Improved materials for storing heat could save energy in applications such as heating and cooling and could enhance generation from solar thermal plants.</jats:p>

<jats:p>Can the brain combine a previous memory into a current situation, creating the memory of an imaginary experience?</jats:p>

<jats:p>An unconventional molecular biologist used the electron microscope to take snapshots of active genes.</jats:p>

<jats:title>Lights, Sound, Images</jats:title> <jats:p> Optical microscopy can readily image thin samples such as cells, but thicker samples, such as tissue, are more difficult to image directly, because of the multiple scattering of light. <jats:bold>Wang and Hu</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1458" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1216210">1458</jats:related-article> ) review methods for imaging biological samples on length scales ranging from organelles to whole organs that rely on the photoacoustic effect—the excitation of ultrasonic pressure waves when light is absorbed by molecules in solution. The incident light can be focused and scanned across a sample in a microscopy mode to create ultrasound images, or the entire region of interest can be illuminated and the ultrasound waves analyzed with a computer algorithm in a tomography mode. Imaging studies can reveal changes in oxygen metabolism and gene expression and in image biomarkers and vasculature. </jats:p>

<jats:p>One to two percent of 14,000 people tested in 20 studies showed evidence of prior H5N1 infection.</jats:p>

<jats:title>Interacting Topological Insulator</jats:title> <jats:p> Topological insulators (TIs) hold great promise as a setting for exotic fundamental phenomena, as well as for more practical applications such as quantum computing. This new state of matter has been discovered in materials such as Bi <jats:sub>2</jats:sub> Se <jats:sub>3</jats:sub> , where electrons' spins are correlated with their orbital motion, but interactions between the electrons themselves are negligible. For a TI to fulfill its potential, a material with interacting electrons is desirable. <jats:bold> Zhang <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="1464" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1216184">1464</jats:related-article> ) used density functional calculations to predict that strong interactions in actinide compounds such as AmN may drive a transition into a TI state, with a large insulating gap favorable for device applications. </jats:p>

<jats:title>Hidden from Magnetic View</jats:title> <jats:p> An electromagnetic cloak is a device within which electromagnetic fields cannot penetrate, but, more importantly, the device itself does not disturb the electromagnetic fields surrounding it. An article placed in the cloak therefore vanishes from view, creating no shadow or reflection. Such devices have been demonstrated, but only for a particular band of frequencies. Confirming theoretical work that predicts such cloaking should be possible down to zero frequency, <jats:bold> Gömöry <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="1466" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1218316">1466</jats:related-article> ) designed a cloak for a dc magnetic field. With a composite design of ferromagnetic and superconducting material, together with a relatively simple structure, the device could potentially find immediate application. </jats:p>

<jats:title>Lignin to the Rescue?</jats:title> <jats:p> The increasing demand for rechargeable batteries is putting a strain on the availability of certain key raw materials. Lignin is the second most common biopolymer and typically makes up 25% of wood. Lignin derivatives are also readily available as by-products from the pulp and paper industry. <jats:bold>Milczarek and Inganäs</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1468" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215159">1468</jats:related-article> ) combined lignin derivatives, which are electronic insulators, with polypyrole, a conductive polymer, into an interpenetrating composite suitable for use as a cathode. </jats:p>

<jats:title>Tamer Triangulations</jats:title> <jats:p> Diazomethane is a broadly useful precursor to carbene (CH <jats:sub>2</jats:sub> ), which, in turn, reacts with olefins to form triangular carbon cycles known as cyclopropanes. These small rings are of fundamental interest for their strained bonds and turn up periodically in natural products, as well as in pharmaceutical and agrochemical research. Unfortunately, the flip side of diazomethane's facile reactivity is its dangerous tendency to explode—a hazard exacerbated by the need to isolate the compound after its preparation in highly basic water before it can be reacted with hydrophobic olefins. <jats:bold>Morandi and Carreira</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1471" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1218781">1471</jats:related-article> ) now show that an iron cyclopropanation catalyst can circumvent the need for the isolation step, inducing reaction of the hazardous compound in a biphasic aqueous/organic medium immediately after its generation. </jats:p>

<jats:title>Waste Not</jats:title> <jats:p> The organic matter in wastewater is a potentially vast and sustainable energy source; however, most wastewater treatment plants consume energy. <jats:bold> Cusick <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="1474" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1219330">1474</jats:related-article> , published online 1 March) combined a microbial fuel cell with a reverse-electrodialysis system to boost the voltage output and the power density over a simple microbial fuel cell. The use of ammonium bicarbonate as a fuel for reverse electrodialysis while microorganisms simultaneously turn organic matter into electricity not only allows for the capturing of waste heat, but could eventually produce enough energy to offset the energy used in conventional wastewater treatment systems. </jats:p>