Catálogo de publicaciones - revistas

<jats:p>Catalysts make alcohols more reactive by taking away hydrogen to create carbonyl compounds and then returning the hydrogen to the final products.</jats:p>

<jats:p>Maternal and paternal influences on gene expression play a surprisingly large role in the epigenetic regulation of mammalian brain function.</jats:p>

<jats:p>Ultraviolet radiation has detrimental and beneficial effects in freshwater ecosystems.</jats:p>

<jats:p>Magnetic impurities in a topological insulator provide a route to control its electronic properties.</jats:p>

<jats:p>When do germ cells establish their separate, independent identity during animal development?</jats:p>

<jats:p>An enzyme that reduces nitrogen to ammonia can also reduce carbon monoxide to hydrocarbons.</jats:p>

<jats:title>Parental Influences</jats:title> <jats:p> Genomic imprinting results in the preferential expression of either the paternally or the maternally inherited allele of certain genes. Two papers by <jats:bold> Gregg <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="643" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1190830">643</jats:related-article> , published online 8 July; and p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="682" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1190831">682</jats:related-article> , published online 8 July; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5992" page="636" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1194692">Wilkinson</jats:related-article> ) use a genome-wide approach to characterize the repertoire of genes with parent-of-origin allelic effects in the mouse embryonic and adult brain. The studies uncovered over 1300 loci with maternal or paternal allelic bias. Comparison of the parent-of-origin allelic expression bias in the adult hypothalamus and cortex, and in the developing brain, revealed spatiotemporal, sex-specific, and isoform-specific regulation. Parent-of-origin effects thus represent a major and dynamic mode of epigenetic regulation of gene expression in the brain. </jats:p>

<jats:title>The Storage of Emotions</jats:title> <jats:p> The neural mechanisms involved in emotional learning are well understood. However, how and where emotional memories are stored is still largely unclear. <jats:bold>Sacco and Sacchetti</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="649" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1183165">649</jats:related-article> ) now show that Pavlovian fear memories are stored in a modality-specific way in the secondary, but not primary, sensory cortices. The site of storage depended on whether the conditioned stimulus was visual, auditory, or olfactory. Only “old,” not new, memories were stored in this way, and lesions of secondary cortices, while disrupting the old memories, did not prevent the acquisition of new memories. </jats:p>

<jats:title>Measuring Motion</jats:title> <jats:p> Within a solid, atoms vibrate about their mean position in a series of frequencies known as the normal modes, which relate to the thermal and mechanical transport properties of the material. <jats:bold> D. Kaya <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="329" xlink:href="10.1126/science.1187988">656</jats:related-article> ) used video microscopy to observe the motion of colloidal crystals made from microgel particles. The colloidal particles varied slightly in their properties, allowing the behavior of disordered materials to be probed. Long-wavelength plane-wave modes were observed, characteristic of perfect crystals, and a conventional elastic behavior, modified by short-wavelength features, was also observed, in spite of the disorder of the colloidal crystals. The analysis method will allow studies on the effects of different types of disorder on the structure of the normal modes and the elasticity in a range of material systems. </jats:p>

<jats:title>Opening a Surface Gap</jats:title> <jats:p> Many properties of topological insulators are a consequence of their so-called gapless surface state, in which electrons are protected from back-scattering, thanks to time-reversal symmetry. Breaking the time-reversal symmetry and opening a surface gap offers prospects for studying phenomena relevant to particle physics, such as axion electrodynamics. To achieve this, <jats:bold> Chen <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="659" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1189924">659</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5992" page="639" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1194123">Franz</jats:related-article> ) doped the three-dimensional topological insulator Bi <jats:sub>2</jats:sub> Se <jats:sub>3</jats:sub> with magnetic dopants and observed the opening of a surface gap. Simultaneous doping with charge dopants was used to shift the Fermi energy to the inside of the surface gap, thus achieving an insulating gapped Dirac state. Both the size of the gap and the position of the Fermi energy level were tunable by varying the nature and the density of the dopants. </jats:p>