Catálogo de publicaciones - revistas

<jats:p> The series of precisely spaced, sharp spectral lines that form an optical frequency comb is enabling unprecedented measurement capabilities and new applications in a wide range of topics that include precision spectroscopy, atomic clocks, ultracold gases, and molecular fingerprinting. A new optical frequency comb generation principle has emerged that uses parametric frequency conversion in high resonance quality factor ( <jats:italic>Q</jats:italic> ) microresonators. This approach provides access to high repetition rates in the range of 10 to 1000 gigahertz through compact, chip-scale integration, permitting an increased number of comb applications, such as in astronomy, microwave photonics, or telecommunications. We review this emerging area and discuss opportunities that it presents for novel technologies as well as for fundamental science. </jats:p>

<jats:p>Two types of bulk insulator are realized in the same family of compounds through chemical doping.</jats:p>

<jats:p>Bulk photoemission studies of iron pnictides suggest a role for orbital fluctuations in creating the superconducting state.</jats:p>

<jats:p>The crystallinity and resistivity of a compound semiconductor was changed with current pulses delivered by nanoelectrodes.</jats:p>

<jats:p>Efficient organic light-emitting transistors use carbon nanotubes as the source electrode.</jats:p>

<jats:title>Putting the F in Friedel-Crafts</jats:title> <jats:p> The Friedel-Crafts class of reactions, among the oldest and most broadly applied in organic chemistry, form carbon-carbon bonds between aromatic rings and a variety of non-aromatic substituents, such as alkyl groups. Generally, a metal complex is used to activate chlorinated or brominated precursors of these substituents, but by using silicon-based reagents to activate a fluorinated precursor, <jats:bold> Allemann <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="574" related-article-type="in-this-issue" vol="332" xlink:href="10.1126/science.1202432">574</jats:related-article> ) extend the reaction to coupling of two different aromatic sites, leading to efficient formation of elaborate polycyclic structures. The method relies on the unusual strength of silicon-fluorine bonds as a driving force. </jats:p>

<jats:p>Observations with the Venus Express Orbiter reveal complex polar atmospheric dynamics.</jats:p>

<jats:p>Deep-reaching eddies transport heat and material hundreds of kilometers from the northern East Pacific Rise.</jats:p>

<jats:p>Evolution of the perceptual abilities of mormyrid electric fishes increased signal variation and species diversification.</jats:p>

<jats:p>Cycling of active and quiescent states of the hair follicle integrates activator and inhibitor signals for patterning.</jats:p>