Catálogo de publicaciones - revistas

<jats:p>The relaxation of a spin on a surface was imaged with a scanning tunneling microscope at 50-ns intervals.</jats:p>

<jats:p>Innervation is required to maintain epithelial progenitor cells that support salivary gland growth and development.</jats:p>

<jats:p>Brain cells are exquisitely sensitive to the pattern of inputs on their dendritic branches.</jats:p>

<jats:p>A South African Web site imparts basic immunology information to clinicians and other health-care workers.</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>Turing Model Explained</jats:title> <jats:p> The reaction-diffusion (Turing) model is a theoretical model used to explain self-regulated pattern formation in biology. Although many biologists have heard of this model, a better understanding of the concept would aid its application to many research projects and developmental principles. <jats:bold>Kondo and Miura</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1616" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1179047">1616</jats:related-article> ) now review the reaction-diffusion model. Despite the associated mathematics, the basic idea of the Turing model is relatively easy to understand and relates to morphogen gradients. In addition, user-friendly software makes it easy to understand how a whole variety of patterns can be produced by this simple mechanism. </jats:p>

<jats:p>Fossil evidence suggests that daisies and sunflowers may have originated in South America more than 47 million years ago.</jats:p>

<jats:title>Dust to Dust</jats:title> <jats:p> Recently, the so-called coreshine effect was identified in a nearby interstellar cloud. The coreshine effect refers to the scattering of mid-infrared light by micron-sized dust grains in the densest regions of molecular clouds, the places where stars and planets are known to form. Using data from the Spitzer telescope, <jats:bold> Pagani <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="1622" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1193211">1622</jats:related-article> ) now show that, rather than being limited to one single molecular cloud, the coreshine effect is common all over our galaxy, but is not universal and could be used to learn about the properties of star-forming cores and the dust therein. </jats:p>

<jats:title>Let Me See Your Supernova</jats:title> <jats:p> As the matter expelled from a supernova travels through and interacts with the interstellar medium, it creates a radiating structure called a supernova remnant. In 1987, astronomers detected a bright supernova in our galaxy, SN 1987A, the remains of which are now expanding into and interacting with a dense ring of gas and dust that surrounds the explosion site. <jats:bold> France <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="1624" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192134">1624</jats:related-article> , published online 2 September; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5999" page="1604" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1196301">Laming</jats:related-article> </jats:bold> ) obtained spectroscopic data of the ring surrounding SN 1987A and compared it with similar data acquired in 2004. Because SN 1987A is so close to us, the explosion was visible to the naked eye and the results provide a glimpse into the hydro dynamics and kinetics of fast astrophysical shocks in a young supernova remnant. </jats:p>

<jats:title>In a Spin</jats:title> <jats:p> The relaxation dynamics of electron spins in solid-state systems is of crucial importance for their usage in quantum computation and information storage. The interaction of the spin with its local environment results in lifetimes in the pico- to microsecond range. Thus, high temporal and spatial resolutions are needed to measure the relaxation time with atomic precision. <jats:bold> Loth <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="1628" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191688">1628</jats:related-article> , see the cover; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5999" page="1609" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1194918">Morgenstern</jats:related-article> </jats:bold> ) used a scanning tunneling microscope with a spin-polarized tip to monitor the electron spin relaxation times of individual atoms adsorbed on a surface. A spin was excited by a pump signal, and its state read out after a variable time delay with a weak probe pulse that produced a spin-sensitive tunneling current. This general technique may be applicable to other systems with fast dynamics. </jats:p>