Catálogo de publicaciones - revistas

<jats:title>Character Transplant</jats:title> <jats:p> When engineering bacteria, it can be advantageous to propagate the genomes in yeast. However, to be truly useful, one must be able to transplant the bacterial chromosome from yeast back into a recipient bacterial cell. But because yeast does not contain restriction-modification systems, such transplantation poses problems not encountered in transplantation from one bacterial cell to another. Bacterial genomes isolated after growth in yeast are likely to be susceptible to the restriction-modification system(s) of the recipient cell, as well as their own. <jats:bold> Lartigue <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="1693" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1173759">1693</jats:related-article> , published online 20 August) describe multiple steps, including in vitro DNA methylation, developed to overcome such barriers. A <jats:italic>Mycoplasma mycoides</jats:italic> large-colony genome was propagated in yeast as a centromeric plasmid, engineered via yeast genetic systems, and, after specific methylation, transplanted into <jats:italic>M. capricolum</jats:italic> to produce a bacterial cell with the genotype and phenotype of the altered <jats:italic>M. mycoides</jats:italic> large-colony genome. </jats:p>

<jats:title>Correspondence Communications</jats:title> <jats:p> Statistical physicists and social scientists have attempted to describe human activities, in terms of physical models, and look for universal principles. Correspondence patterns are thought to be driven primarily by the need to respond to other individuals with both e-mail and letter correspondence showing power-law distributions. Because there are different exponents for the two modes of correspondence, it has been suggested that human correspondence falls into one of two universality classes and that e-mail and letter correspondence are fundamentally different activities. Now <jats:bold> Malmgren <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="1696" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1174562">1696</jats:related-article> ) tested whether human correspondence patterns are instead driven by mechanisms such as circadian cycles, task repetition, and changing communication needs. Letter correspondence, like e-mail correspondence, was accurately modeled as a cascading nonhomogeneous Poisson process giving rise to non-Gaussian statistics, but not to power-law statistics. Instead, the correspondence patterns of each individual could be uniquely characterized by the parameters of the model; that is, the process was shown to be universal, but the parameters were not. Thus, an individual's affinity toward a particular life-style will affect communication patterns, which can be modeled as a complex system. </jats:p>

<jats:title>Butterfly Navigation</jats:title> <jats:p> Monarch butterflies migrate to Mexico from various parts of North America in the fall and navigate with the aid of Sun compass. This navigational mechanism, also employed by migratory birds, uses the circadian clock to compensate for the positional change of the Sun in the sky throughout the day. The mechanism behind time-compensated Sun compass orientation has remained obscure. <jats:bold> Merlin <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="1700" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1176221">1700</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="5948" page="1629" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1178935">Kyriacou</jats:related-article> </jats:bold> ) now provide comprehensive data showing that the mechanism resides in the antennae of the butterflies, rather than the brain, as previously thought. The “antennal clocks” found in the monarchs probably provide the primary timing mechanism for Sun compass orientation. These findings reveal a further function for the antennae—a function that may extend widely to other insects that use this orientation mechanism. </jats:p>

<jats:title>Rethinking Vaccine Distribution</jats:title> <jats:p> The distribution of vaccines is a complex issue lying at the intersection of public health, economics, and ethics and it cannot be decided in hindsight as an epidemic unfolds. Thus, mathematical modeling can be valuable for guiding policy, and <jats:bold>Medlock and Galvani</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1705" related-article-type="in-this-issue" vol="325" xlink:href="10.1126/science.1175570">1705</jats:related-article> , published online 20 August) present an analysis of how to distribute influenza vaccine among different age groups in a way that will minimize transmission. Scenarios were developed for different outcomes that tell us what happens, in terms of numbers of infections, mortality, and cost, when various cohorts are targeted for vaccination under different epidemic conditions, and compare 1918- and 1957-like epidemics. The scenarios could apply equally well to antiviral drug distribution. The conclusion is that the current recommendations for vaccine distribution from the U.S. Centers for Disease Control and Prevention may need to be revised to include age-related patterns of transmission to minimize the impact of epidemic influenza. </jats:p>

<jats:p>The show includes challenges to carbon capture and storage, human correspondence patterns, linking nutrition to violent behavior, and more.</jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>