Catálogo de publicaciones - revistas

<jats:title>Maximizing atomic magnetic memory</jats:title> <jats:p> A study of the magnetic response of cobalt atoms adsorbed on oxide surfaces may lead to much denser storage of data. In hard drives, data are stored as magnetic bits; the magnetic field pointing up or down corresponds to storing a zero or a one. The smallest bit possible would be a single atom, but the magnetism of a single atom —its spin—has to be stabilized by interactions with heavy elements or surfaces through an effect called spin-orbit coupling. Rau <jats:italic>et al.</jats:italic> (see the Perspective by Khajetoorians and Wiebe) built a model system in pursuit of single-atom bits—cobalt atoms adsorbed on magnesium oxide. At temperatures approaching absolute zero, the stabilization of the spin's magnetic direction reached the maximum that is theoretically possible. </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="6187" page="988" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1252841">988</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6187" page="976" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1254402">976</jats:related-article> </jats:p>

<jats:title>Intact NMDA receptor structure revealed</jats:title> <jats:p> For brains to develop and form memories, a signal must be transmitted from one neuron to the next. Glutamate is an important neurotransmitter that excites the receiving nerve cell by binding to an ion channel called an <jats:italic>N</jats:italic> -Methyl- <jats:sc>d</jats:sc> -Aspartate (NMDA) receptor. This activates the NMDA receptors, causing calcium ions to flood in, triggering signal transduction. Either under- or overactivation can result in a variety of neurological disorders and diseases. Karakas and Furukawa describe the crystal structure of an intact NMDA receptor composed of four separate subunits. </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="6187" page="992" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1251915">992</jats:related-article> </jats:p>

<jats:title>Help as hungry children helps young adults</jats:title><jats:p>Supporters of early childhood interventions follow the rule “better early than late,” but so far there's been limited evidence that the rule applies to disadvantaged children in developing countries. Gertler<jats:italic>et al.</jats:italic>looked at the earnings of young adults in Jamaica, 20 years after, as toddlers, they were given 2 years of help from community health workers. The earnings of the treatment group caught up to those of a comparison group of well-fed children, but the control group of undernourished children that did not receive the health worker visits has lagged behind.</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="6187" page="998" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1251178">998</jats:related-article></jats:p>

<jats:title>Pull, pull, pulling electrons along</jats:title> <jats:p> Organic photovoltaics operate by transferring charge from a light-absorbing donor material to a nearby acceptor. Falke <jats:italic>et al.</jats:italic> show that molecular vibrations smooth the way for this charge transfer to proceed. A combination of ultrafast spectroscopy and theoretical simulations revealed an oscillatory signal in a model donor/acceptor blend that implicates carbon-carbon bond stretching in concert with the electronic transition. This vibrational/electronic, or vibronic, process maintains a quantum-mechanical phase relationship that guides the charge more rapidly and directly than an incoherent migration from donor to acceptor. </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="6187" page="1001" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1249771">1001</jats:related-article> </jats:p>

<jats:title>Keeping semiconductors safe from harm</jats:title> <jats:p> Solar cells harvest the energy of sunlight to create electricity, but electricity is hard to store. Solar cells could also be used to make hydrogen from water, which can be stored as a fuel. Separating water into hydrogen and oxygen, however, presents challenges, especially if this is done directly by illuminating the anode that oxides water. Under the acidic or alkaline conditions needed for practical devices, semiconducting anode materials corrode during operation. Hu <jats:italic>et al.</jats:italic> now show that amorphous titanium dioxide coatings can protect semiconductors from alkaline corrosion while still allowing light through. </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="6187" page="1005" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1251428">1005</jats:related-article> </jats:p>

<jats:title>Blackjack water cluster detected</jats:title> <jats:p> Spectroscopy of protonated water clusters has played a pivotal role in elucidating the molecular arrangement of acid solutions. Whereas bulk liquids manifest broad spectral features, the cluster bands tend to be sharper. The 21-membered water cluster has for decades inspired particular interest on account of its stability and its place in the transition from two-dimensional to three-dimensional hydrogen-bonding network motifs, but the spectral signature of its bound proton has proved elusive. Fournier <jats:italic>et al.</jats:italic> have now detected this long-sought vibrational feature by applying an innovative ion cooling technique. </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="6187" page="1009" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1253788">1009</jats:related-article> </jats:p>

<jats:title>A close-up view of carbon-bromide bonds</jats:title> <jats:p> Polarizing filters are widely used in optical microscopy to highlight a range of material properties that cause optical path boundaries or birefringence in a material. Palmer <jats:italic>et al.</jats:italic> (see the Perspective by Lidin) developed an analog method for x-ray microscopy using linearly polarized x-ray beams and an area detector inside a synchrotron. The technique revealed the orientation of the C-Br bonds within crystalline materials. </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="6187" page="1013" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1253537">1013</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6187" page="969" related-article-type="in-this-issue" vol="344" xlink:href="10.1126/science.1254902">969</jats:related-article> </jats:p>