Catálogo de publicaciones - revistas

<jats:p>Very-low-mass stars (those less than 0.3 solar masses) host orbiting terrestrial planets more frequently than other types of stars. The compositions of those planets are largely unknown but are expected to relate to the protoplanetary disk in which they form. We used James Webb Space Telescope mid-infrared spectroscopy to investigate the chemical composition of the planet-forming disk around ISO-ChaI 147, a 0.11-solar-mass star. The inner disk has a carbon-rich chemistry; we identified emission from 13 carbon-bearing molecules, including ethane and benzene. The high column densities of hydrocarbons indicate that the observations probe deep into the disk. The high carbon-to-oxygen ratio indicates radial transport of material within the disk, which we predict would affect the bulk composition of any planets forming in the disk.</jats:p>

<jats:p> Axis formation in fish and amphibians typically begins with a prepattern of maternal gene products. Annual killifish embryogenesis, however, challenges prepatterning models as blastomeres disperse and then aggregate to form the germ layers and body axes. We show that <jats:italic>huluwa</jats:italic> , a prepatterning factor thought to break symmetry by stabilizing β-catenin, is truncated and inactive in <jats:italic>Nothobranchius furzeri</jats:italic> . Nuclear β-catenin is not selectively stabilized on one side of the blastula but accumulates in cells forming the aggregate. Blocking β-catenin activity or Nodal signaling disrupts aggregate formation and germ layer specification. Nodal signaling coordinates cell migration, establishing an early role for this signaling pathway. These results reveal a surprising departure from established mechanisms of axis formation: Huluwa-mediated prepatterning is dispensable, and β-catenin and Nodal regulate morphogenesis. </jats:p>

<jats:p> Brown adipose tissue (BAT) is a heater organ that expresses thermogenic uncoupling protein 1 (UCP1) to maintain high body temperatures during cold stress. BAT thermogenesis is considered an overarching mammalian trait, but its evolutionary origin is unknown. We show that adipose tissue of marsupials, which diverged from eutherian mammals <jats:bold>~</jats:bold> 150 million years ago, expresses a nonthermogenic UCP1 variant governed by a partial transcriptomic BAT signature similar to that found in eutherian beige adipose tissue. We found that the reconstructed UCP1 sequence of the common eutherian ancestor displayed typical thermogenic activity, whereas therian ancestor UCP1 is nonthermogenic. Thus, mammalian adipose tissue thermogenesis may have evolved in two distinct stages, with a prethermogenic stage in the common therian ancestor linking UCP1 expression to adipose tissue and thermal stress. We propose that in a second stage, UCP1 acquired its thermogenic function specifically in eutherians, such that the onset of mammalian BAT thermogenesis occurred only after the divergence from marsupials. </jats:p>

<jats:p> Chemical reactions, in which bonds break and form, are highly dynamic quantum processes. A fundamental question is whether coherence can be preserved in chemical reactions and then harnessed to generate entangled products. Here we investigated this question by studying the 2KRb <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>→</mml:mo> </mml:math> </jats:inline-formula> <jats:inline-formula> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mtext>K</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> </jats:inline-formula> + Rb <jats:sub>2</jats:sub> reaction at 500 nanokelvins, focusing on the nuclear spin degrees of freedom. We prepared the initial nuclear spins in KRb (potassium-rubidium) in an entangled state by lowering the magnetic field to where the spin-spin interaction dominates and characterized the preserved coherence in nuclear spin wave function after the reaction. We observed an interference pattern that is consistent with full coherence at the end of the reaction, suggesting that entanglement prepared within the reactants could be redistributed through the atom-exchange process. </jats:p>

<jats:p>The control of thermal radiation by shaping its spatial and spectral emission characteristics plays a key role in many areas of science and engineering. Conventional approaches to tailoring thermal emission using metamaterials are hampered both by the limited spatial resolution of the required subwavelength material structures and by the materials’ strong absorption in the infrared. In this work, we demonstrate an approach based on the concept of topology. By changing a single parameter of a multilayer coating, we were able to control the reflection topology of a surface, with the critical point of zero reflection being topologically protected. The boundaries between subcritical and supercritical spatial domains host topological interface states with near-unity thermal emissivity. These topological concepts enable unconventional manipulation of thermal light for applications in thermal management and thermal camouflage.</jats:p>