Catálogo de publicaciones - revistas

<jats:p>Controlling electron spins on semiconductor quantum dots with help from nuclear spins may speed up fundamental steps in quantum computing.</jats:p>

<jats:p>Scanning tunneling microscopy reveals indications of fractal electronic structure in a magnetic semiconductor.</jats:p>

<jats:p>Proteins existing as ensembles of conformations may be key to understanding signal transduction processes.</jats:p>

<jats:p>Ocean acidification may reduce the biological availability of iron, affecting the ocean's ability to absorb more carbon dioxide.</jats:p>

<jats:title>Development of Myeloid Immune Cells</jats:title> <jats:p> As leukocytes develop to maturity, they proceed through an array of phenotypically distinct intermediates. For T and B lymphocyte populations, the different developmental stages, anatomical locations, and cell signals required for progression are well established. However, until recently, much less has been known about how development proceeds in the myeloid lineage, which includes monocytes, macrophages, and dendritic cells. <jats:bold> Geissmann <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="656" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1178331">656</jats:related-article> ) review our current understanding of myeloid lineage development and describe the developmental pathways and cues that drive differentiation. </jats:p>

<jats:p>The maximum switching frequency of these devices exceeds that of silicon transistors with similar gate-electrode dimensions.</jats:p>

<jats:title>Pulsar Wind Nebula</jats:title> <jats:p> Pulsar wind nebulae are the result of the interaction between the wind of relativistic charged particles emitted by pulsars and their surrounding interstellar medium. Using the AGILE satellite, <jats:bold> Pellizzoni <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="663" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183844">663</jats:related-article> , published online 31 December) detected extended gamma-ray emission between 100 megaelectron volts and 3 gigaelectron volts from the 10,000-year-old Vela pulsar wind nebula. This detection sets constraints on the relativistic particle wind of pulsars, its energetic content, and its interactions with the surrounding medium. It also suggests that pulsar wind nebulae could form a subset of the yet unidentified galactic gamma-ray sources. </jats:p>

<jats:title>Metal-Insulator Transition</jats:title> <jats:p> At near-zero temperatures, some materials undergo a metal-insulator transition and their electronic properties change from conducting to insulating. In the dilute magnetic semiconductor Ga <jats:sub> 1− <jats:italic>x</jats:italic> </jats:sub> Mn <jats:sub> <jats:italic>x</jats:italic> </jats:sub> As, a promising spintronics material, the metal-insulator transition is driven by the substitution of Ga atoms with Mn. While disorder clearly plays a key role in this transition, the influence of electron-electron correlations has been far from clear. <jats:bold> Richardella <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="665" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183640">665</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="5966" page="652" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1186118">Fiete and de Lozanne</jats:related-article> </jats:bold> ) used scanning tunneling microscopy to study the electronic states of this system. The autocorrelation function of the local density of states exhibited a power law (rather than an exponential) decay at Fermi energy. Thus, electron-electron interactions are indeed crucial for understanding dilute magnetic semiconductors. </jats:p>

<jats:title>Splitting Quantum States</jats:title> <jats:p> The ability to manipulate the spin and charge states in quantum dots electrically make them attractive as the building blocks (qubits) for quantum information processing systems. <jats:bold> Petta <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="669" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183628">669</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="5966" page="650" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1185548">Burkard</jats:related-article> </jats:bold> ) now show that the avoided crossing of a spin-singlet state and spin-triplet state of a double quantum dot can operate as a state splitter. By controlling the rate at which an incoming state is swept across the crossing region, it can be separated into either the singlet or triplet states. The ability to manipulate the quantum states without needing high or local magnetic fields should prove useful in integrated quantum circuits. </jats:p>

<jats:title>Freezing Supercool Water</jats:title> <jats:p> Under equilibrium conditions, water will freeze at 0°C, but, under certain conditions, it can be kept in a supercooled liquid form below this temperature. <jats:bold> Ehre <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="672" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1178085">672</jats:related-article> ) present a careful and detailed study of the freezing of water drops on both positively and negatively charged pyroelectric surfaces using a combination of optical microscopy and x-ray diffraction: Supercooled water froze at different temperatures, depending on the charge of the substrate with the initial freezing occurring at the liquid-substrate interface on a positively charged substrate and at the air-water interface on a negatively charged substrate. Thus, freezing could be induced upon heating when the substrate charge also changed from negative to positive. </jats:p>