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Institución detectada Período Navegá Descargá Solicitá
No detectada desde mar. 1997 / hasta dic. 2023 Science Journals

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Tipo de recurso:

revistas

ISSN impreso

0036-8075

ISSN electrónico

1095-9203

Editor responsable

American Association for the Advancement of Science (AAAS)

País de edición

Estados Unidos

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Sestrin as a Feedback Inhibitor of TOR That Prevents Age-Related Pathologies

Jun Hee Lee; Andrei V. Budanov; Eek Joong Park; Ryan Birse; Teddy E. Kim; Guy A. Perkins; Karen Ocorr; Mark H. Ellisman; Rolf Bodmer; Ethan Bier; Michael Karin

<jats:title>Sestrin and the Consequences of Aging</jats:title> <jats:p> The protein kinase TOR (target of rapamycin) plays key roles in the control of fundamental biological processes, including growth, metabolism, aging, and immune function. Sestrin proteins show increased abundance in response to stress and have been implicated in control of TOR activity. <jats:bold> Lee <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/cgi/content/full/327/5970/1223">1223</jats:ext-link> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5970" page="1210" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187497"> <jats:bold>Topisirovic and Sonenberg</jats:bold> </jats:related-article> </jats:bold> ) characterized <jats:italic>Drosophila</jats:italic> fruit flies lacking sestrins. Sestrins were implicated in a negative feedback loop in which the abundance of sestrins is controlled by TOR activity with sestrins concomitantly also inhibiting activity of TOR. Furthermore, flies lacking sestrins showed accumulation of fat, muscle degeneration, and heart abnormalities similar to those that plague aging humans with a sedentary life-style. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1223-1228

Symmetric Inertial Confinement Fusion Implosions at Ultra-High Laser Energies

S. H. Glenzer; B. J. MacGowan; P. Michel; N. B. Meezan; L. J. Suter; S. N. Dixit; J. L. Kline; G. A. Kyrala; D. K. Bradley; D. A. Callahan; E. L. Dewald; L. Divol; E. Dzenitis; M. J. Edwards; A. V. Hamza; C. A. Haynam; D. E. Hinkel; D. H. Kalantar; J. D. Kilkenny; O. L. Landen; J. D. Lindl; S. LePape; J. D. Moody; A. Nikroo; T. Parham; M. B. Schneider; R. P. J. Town; P. Wegner; K. Widmann; P. Whitman; B. K. F. Young; B. Van Wonterghem; L. J. Atherton; E. I. Moses

<jats:title>Ignition Set to Go</jats:title> <jats:p> One aim of the National Ignition Facility is to implode a capsule containing a deuterium-tritium fuel mix and initiate a fusion reaction. With 192 intense laser beams focused into a centimeter-scale cavity, a major challenge has been to create a symmetric implosion and the necessary temperatures within the cavity for ignition to be realized (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5970" page="1208" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187275">Norreys</jats:related-article> </jats:bold> ). <jats:bold> Glenzer <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="1228" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1185634">1228</jats:related-article> , published online 28 January) now show that these conditions can be met, paving the way for the next step of igniting a fuel-filled capsule. Furthermore, <jats:bold> Li <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="1231" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1185747">1231</jats:related-article> , published online 28 January) show how charged particles can be used to characterize and measure the conditions within the imploding capsule. The high energies and temperature realized can also be used to model astrophysical and other extreme energy processes in a laboratory settings. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1228-1231

Charged-Particle Probing of X-ray–Driven Inertial-Fusion Implosions

C. K. Li; F. H. Séguin; J. A. Frenje; M. Rosenberg; R. D. Petrasso; P. A. Amendt; J. A. Koch; O. L. Landen; H. S. Park; H. F. Robey; R. P. J. Town; A. Casner; F. Philippe; R. Betti; J. P. Knauer; D. D. Meyerhofer; C. A. Back; J. D. Kilkenny; A. Nikroo

<jats:title>Ignition Set to Go</jats:title> <jats:p> One aim of the National Ignition Facility is to implode a capsule containing a deuterium-tritium fuel mix and initiate a fusion reaction. With 192 intense laser beams focused into a centimeter-scale cavity, a major challenge has been to create a symmetric implosion and the necessary temperatures within the cavity for ignition to be realized (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5970" page="1208" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187275">Norreys</jats:related-article> </jats:bold> ). <jats:bold> Glenzer <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="1228" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1185634">1228</jats:related-article> , published online 28 January) now show that these conditions can be met, paving the way for the next step of igniting a fuel-filled capsule. Furthermore, <jats:bold> Li <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="1231" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1185747">1231</jats:related-article> , published online 28 January) show how charged particles can be used to characterize and measure the conditions within the imploding capsule. The high energies and temperature realized can also be used to model astrophysical and other extreme energy processes in a laboratory settings. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1231-1235

Deglacial Meltwater Pulse 1B and Younger Dryas Sea Levels Revisited with Boreholes at Tahiti

Edouard Bard; Bruno Hamelin; Doriane Delanghe-Sabatier

<jats:title>Episodic Rise</jats:title> <jats:p> Sea-level rise between the end of the Last Glacial Maximum and the beginning of the Holocene accelerated episodically, with the fastest rate occurring during meltwater pulse 1A (14,000 years ago) and perhaps during another interval called meltwater pulse 1B (11,300 years ago). However, existing records are not precise enough to confidently assess sea-level change during meltwater pulse 1B or the Younger Dryas cold event (12,900 to 11,600 years ago). <jats:bold> Bard <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="1235" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1180557">1235</jats:related-article> , published online 14 January) present data from three cores drilled in coral reefs in Tahiti that allow a better quantification of sea-level changes between 14,000 and 9000 years ago. No significant change in the rate of sea-level rise could be detected for the period previously identified as meltwater pulse 1B; reducing the likelihood that such an episode occurred. Furthermore, sea level rose more rapidly at the start of the Younger Dryas but slowed during the rest of the cold event. These findings have implications for our understanding of the dynamics of deglaciation. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1235-1237

Geodynamo, Solar Wind, and Magnetopause 3.4 to 3.45 Billion Years Ago

John A. Tarduno; Rory D. Cottrell; Michael K. Watkeys; Axel Hofmann; Pavel V. Doubrovine; Eric E. Mamajek; Dunji Liu; David G. Sibeck; Levi P. Neukirch; Yoichi Usui

<jats:title>Early Origin of Earth's Magnetic Field</jats:title> <jats:p> Earth's magnetic field protects us from stellar winds and radiation from the Sun. Understanding when, during the Earth's formation, the large-scale magnetic field was established is important because it impacts understanding of the young Earth's atmosphere and exosphere. By analyzing ancient silicate crystals, <jats:bold> Tarduno <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="1238" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183445">1238</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="5970" page="1206" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187051">Jardine</jats:related-article> </jats:bold> ) demonstrate that the Earth's magnetic field existed 3.4 to 3.45 billion years ago, pushing back the oldest record of geomagnetic field strength by 200 million years. This result combined with estimates of the conditions within the solar wind at that time implies that the size of the paleomagnetosphere was about half of that typical today, but with an auroral oval of about three times the area. The smaller magnetosphere and larger auroral oval would have promoted loss of volatiles and water from the early atmosphere. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1238-1240

Calibrating the Cryogenian

Francis A. Macdonald; Mark D. Schmitz; James L. Crowley; Charles F. Roots; David S. Jones; Adam C. Maloof; Justin V. Strauss; Phoebe A. Cohen; David T. Johnston; Daniel P. Schrag

<jats:title>Aging Snowball Earth</jats:title> <jats:p> Earth's glacial cycles have varied dramatically over time; at one point glaciers may have covered nearly the entire planet. Correlating various paleoclimate proxies such as fossil and isotope records from that time hinges on the ability to acquire precise age estimates of rocks deposited around the time of this so-called “Snowball Earth.” <jats:bold> Macdonald <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="1241" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183325">1241</jats:related-article> ) report new high-precision U-Pb dates of Neoproterozoic strata in the Yukon and Northwest Territories, Canada, to calibrate the timing of carbon isotope variation in rocks from other locations around the globe. Based on the estimated past positions of where these rocks were deposited, glaciers probably extended to equatorial latitudes. The overlap with the survival and, indeed, diversification of some eukaryotes in the fossil record suggests that life survived in localized ecological niches during this global glaciation. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1241-1243

The Role of Sulfuric Acid in Atmospheric Nucleation

Mikko Sipilä; Torsten Berndt; Tuukka Petäjä; David Brus; Joonas Vanhanen; Frank Stratmann; Johanna Patokoski; Roy L. Mauldin; Antti-Pekka Hyvärinen; Heikki Lihavainen; Markku Kulmala

<jats:title>Little Things Do Matter</jats:title> <jats:p> Gas-phase sulfuric acid is important during atmospheric particle formation, but the mechanisms by which it forms new particles are unclear. Laboratory studies of the binary nucleation of sulfuric acid with water produce particles at rates that are many orders of magnitude too small to explain the concentration of sulfuric acid particles found in the atmosphere. <jats:bold> Sipilä <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="1243" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1180315">1243</jats:related-article> ) now show that gas-phase sulfuric acid does, in fact, undergo nucleation in the presence of water at a rate fast enough to account for the observed abundance of sulfuric acid particles in the atmosphere. These particles, which contain 1 to 2 sulfuric acid molecules each, were not detectable previously, owing to their small size, with diameters as small as 1.5 nanometers. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1243-1246

Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf

Natalia Shakhova; Igor Semiletov; Anatoly Salyuk; Vladimir Yusupov; Denis Kosmach; Örjan Gustafsson

<jats:title>Bubble, Bubble, Warming and Trouble</jats:title> <jats:p> Vast quantities of methane are stored in ocean sediments, mostly in the form of clathrates, but methane is also trapped in submerged terrestrial permafrost that was flooded during the last deglaciation. There is thus concern that climate warming could warm ocean waters enough to release methane cryogenically trapped beneath the seabed, causing even more warming. <jats:bold> Shakova <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="1246" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1182221">1246</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="5970" page="1211" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187270">Heimann</jats:related-article> </jats:bold> ) report that more than 80% of the bottom water, and more than 50% of the surface water, over the East Siberian Arctic Shelf, is indeed supersaturated with methane that is being released from the sub-sea permafrost, and that the flux to the atmosphere now is as great as previous estimates of that from the entire world ocean. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1246-1250

Hippocampal Short- and Long-Term Plasticity Are Not Modulated by Astrocyte Ca 2+ Signaling

Cendra Agulhon; Todd A. Fiacco; Ken D. McCarthy

<jats:title>Reexamining Glial Function</jats:title> <jats:p> In the last 20 years glial cells have been elevated from being considered as passive elements during neuronal transmission. By eliciting astroglial calcium rises, so-called gliotransmitters such as glutamate, ATP, or <jats:sc>d</jats:sc> -serine can be released and the activity of neighboring neurons modulated. However, this emerging picture has been challenged. <jats:bold> Agulhon <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="1250" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1184821">1250</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="5970" journal-id="" page="1212" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1187420">Kirchhoff</jats:related-article> </jats:bold> ) reexamined these questions using two previously characterized mouse models. Calcium elevations induced selectively in astrocytes caused no change in multiple measures of synaptic activity. Furthermore, in mutant mice unable to elevate intracellular calcium, all synaptic measures were at wild-type levels. Astrocytic calcium signaling activity was thus not tied to the release of gliotransmitters and didn't affect synaptic transmission, short and long-term synaptic plasticity. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1250-1254

RTEL-1 Enforces Meiotic Crossover Interference and Homeostasis

Jillian L. Youds; David G. Mets; Michael J. McIlwraith; Julie S. Martin; Jordan D. Ward; Nigel J. ONeil; Ann M. Rose; Stephen C. West; Barbara J. Meyer; Simon J. Boulton

<jats:title>Managing Crossovers</jats:title> <jats:p> In all sexual eukaryotes a special type of cell division called meiosis produces gametes or spores. For chromosomes to segregate properly to the daughter cells during meiosis, DNA crossovers must occur between every pair of homologous chromosomes. The position and number of these crossovers, which help to hold the homologous chromosomes together, is carefully controlled, in part by the condensin I complex. <jats:bold> Youds <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="1254" related-article-type="in-this-issue" vol="327" xlink:href="10.1126/science.1183112">1254</jats:related-article> ) show that in the nematode, <jats:italic>Caenorhabditis elegans</jats:italic> , crossovers are regulated at a second level by the anti-recombinase RTEL-1 (regulator of telomere elongation helicase–1). RTEL-1 prevents crossovers occurring too close to each other, and ensures that only one occurs per pair of homologous chromosomes. </jats:p>

Palabras clave: Multidisciplinary.

Pp. 1254-1258