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<jats:p>The behavior of a type of complex fluid (exemplified by mayonnaise and concrete) can depend on the sample's flow history.</jats:p>

<jats:title>Cooling All Atoms</jats:title> <jats:p> Laser cooling can be used to chill atoms to ultralow temperatures. However, the characteristics of the atoms and of the lasers limit the technique to a select few elements of the periodic table. Techniques are thus being explored that can be applied more generally. <jats:bold>Raizen</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1403" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1171506">1403</jats:related-article> ) reviews recent work on the magnetic coilgun cooling technique—where a series of magnetic pulses are applied to a cloud of atoms or molecules and can cool them to millikelvin temperatures. The only requirement of the atoms is paramagnetism—a property of most of the elements in the periodic table. </jats:p>

<jats:p>Discovered in 1852 and used for polarizing light, the crystal structure of iodoquinine sulfate has been solved.</jats:p>

<jats:title>Stellar Hourglass Figure</jats:title> <jats:p> Star-forming clouds are thought to be supported against gravity by ordered interstellar magnetic fields, which are strong enough to slow gravitation collapse but too weak to prevent it. <jats:bold> Girart <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="1408" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1171807">1408</jats:related-article> ) measured polarized radio waves from dust particles around a forming massive star, which reveal an hourglass shape. The data imply that a magnetic field strength dominates over turbulence—the telltale signs of magnetically controlled star formation. These conditions mimic those found in low-mass star-forming regions, suggesting that the magnetic field plays an important role in star formation, irrespective of differences in mass. </jats:p>

<jats:title>From X-ray Binary to Pulsar</jats:title> <jats:p> Pulsars with millisecond rotational periods are thought to originate from neutron stars in low-mass x-ray binaries that had their spin frequencies increased by long-lasting mass transfer from their companion stars. Using data from a radio pulsar survey, <jats:bold> Archibald <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="1411" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1172740">1411</jats:related-article> , published online 21 May; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1396" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1175012">Kramer</jats:related-article> </jats:bold> ) found a neutron star in a low-mass X-ray binary that is in the process of turning into a radio millisecond pulsar. The system, which consists of a solar-like star and a 1.69-millisecond radio pulsar, has gone through a recent accretion phase, characteristic of low-mass X-ray binaries, but it shows no accretion disk anymore, confirming the evolutionary connection between millisecond radio pulsars and low-mass X-ray binaries. </jats:p>

<jats:title>Evolving Entanglement</jats:title> <jats:p> Quantum mechanical entanglement is a powerful but fragile resource for quantum information processing. It lends itself to increased computational power over classical computers. However, when quantum systems interact with their environment, which they must do if you want to follow what they are doing, then the entanglement can be lost. <jats:bold> Jiménez Farías <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="1414" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1171544">1414</jats:related-article> , published online 14 May) present an experimental and theoretical study on entangled photon pairs, showing that they can determine and understand how the entanglement evolves as the system interacts with its surroundings. </jats:p>

<jats:title>Colloidal Nanocrystal Compounds</jats:title> <jats:p> Colloidal nanocrystals have properties that fall between those of the individual atoms but also differ from bulk due to confinement effects. They can thus be thought of as analogs of atoms, and, like atoms, there is a desire to bond together neighboring particles, which will also affect their properties. During synthesis, organic ligands are used to prevent the colloidal nanocrystals from growing too large or agglomerating, but these ligands result in poor interparticle coupling and communication. <jats:bold> Kovalenko <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="1417" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1170524">1417</jats:related-article> ) show that chalcogenide complexes (compounds based on S, Se, or Te) can effectively link together neighboring particles. Upon gentle heating, the ligands can be converted from insulating to semiconducting without altering the chemistry of the nanocrystals. </jats:p>

<jats:title>Ferroelectric Patterning with High Fields</jats:title> <jats:p> Ferroelectric oxides have a net polarization that can switch direction upon application of a sufficiently high electric field. In principle, a ferroelectric thin film should be able to act as a polar switch—tunneling an electron through the film would effectively switch on or off depending on the direction of the polarization. In practice, the length scale needed for a sufficiently small tunneling barrier is nearly the same as the scale at which films no longer support ferroelectricity. <jats:bold> Maksymovych <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="1421" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1171200">1421</jats:related-article> ) now show that the tip of an atomic force microscope can be used to pattern polarization domains in a thin film of lead zirconate titanate in high electric fields similar to those for field emission tips. </jats:p>

<jats:title>Confining Carriers in Diamond</jats:title> <jats:p> Charge carriers can be confined in thin layers created by quantum wells. These multilayer structures alternate nanoscale layers of materials with slightly different band-gap energies, such as AlGaAs and GaAs, and create a confining potential. <jats:bold> Watanabe <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="1425" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1172419">1425</jats:related-article> ) demonstrate quantum confinement of electrons by diamond multilayers that vary only in isotopic composition; the carbon-12 and carbon-13 layers differ in band-gap energy by ∼17 millielectron volts. Cathodoluminescence experiments performed at 80 kelvin showed that in alternating layers (as thin as 30 nanometers or as thick as 350 nanometers), emission comes from charge carriers recombining in the carbon-12 layer, which has a lower band gap. Carriers from the carbon-13 layer appear to transfer with little loss into carbon-12 layers. </jats:p>

<jats:title>Spotting Charges</jats:title> <jats:p> Many nanoscale physical systems are sensitive to the position of isolated charges, such as single-electron transistors and molecular assemblies that separate charges with energy from photons. In order to probe the location of a charged atom, the most general methods would work on insulating surfaces. <jats:bold> Gross <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="1428" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1172273">1428</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1397" related-article-type="in-this-issue" vol="324" xlink:href="10.1126/science.1175869"> <jats:bold>Meyer and Glatzel</jats:bold> ) </jats:related-article> </jats:bold> show that a tuning-fork atomic force microscope (AFM) operating in a noncontact mode at cryogenic temperatures can resolve the charge state of gold and silver atoms absorbed on a sodium chloride film. Charged atoms set up image charges in the AFM tip, which creates an electrostatic force not present with a neutral atom. </jats:p>