Catálogo de publicaciones - revistas

<jats:title>Imaging twisty magnets</jats:title> <jats:p> Twisting monolayers of graphene with respect to each other has led to a number of unusual correlated states. This approach has inspired researchers to try their hand at twisting two-dimensional (2D) magnets, but such experiments have proven a difficult challenge. Song <jats:italic>et al</jats:italic> . made structures out of layers of the 2D magnet chromium triiodide with a small twist angle (see the Perspective by Lado). Using nitrogen vacancy centers in diamond as a magnetometer, the authors imaged the magnetic domains in both twisted monolayer and twisted trilayer structures. For twisted trilayers, a periodic pattern of ferromagnetic and antiferromagnetic domains was revealed. —JS </jats:p>

<jats:title>Extinctions and grassland fire</jats:title> <jats:p> Grassland herbivores are known to play a role in limiting wildfires by consuming potentially flammable material. Karp <jats:italic>et al</jats:italic> . present evidence that that herbivore-fire interactions affected fire on a global scale in the past. They compared the severity of late Quaternary continent-level megaherbivore extinctions with changes in paleofire activity calculated from sedimentary charcoal data from grassy biomes. The extent of extinctions varied between continents, and this pattern was reflected in the changes in fire activity. Fire frequency increased most where the megaherbivore extinctions were greatest (South America) and least where few extinctions occurred (Africa). This loss of large-bodied grazers in the Quaternary drastically altered global fire regimes. —AMS </jats:p>

<jats:title>Shaping the Hamiltonian</jats:title> <jats:p> Ultracold atoms have proven to be a versatile setting for simulating more complicated quantum systems. However, the type of the simulated Hamiltonian usually cannot be changed once the system has been engineered, although the parameters can be tuned. Geier <jats:italic>et al</jats:italic> . used rubidium-87 atoms in two excited Rydberg states to create a system in which the type of the Hamiltonian could be modified by periodic driving. The researchers started with a system that was initially described by the so-called Heisenberg XX Hamiltonian. By using a periodic series of pulses, the Hamiltonian was transformed into a different target Hamiltonian, which was corroborated by monitoring the system’s dynamics. —JS </jats:p>

<jats:title>Ready to dice</jats:title> <jats:p> In the biogenesis of small RNAs, the Dicer family endonucleases act as a molecular ruler to cut the substrate RNA into defined lengths. Wang <jats:italic>et al</jats:italic> . report a structure of the dicing-competent state of plant DICER LIKE PROTEIN 3 (DCL3) in complex with a pre–small interfering RNA (pre-siRNA). Toward one end of the pre-siRNA, DCL3 uses a positively charged pocket and an aromatic cap to specifically recognize the 5′-phosphorylated adenosine of the guide strand and the 3′ overhang of the complementary strand, respectively. On the other end, the paired ribonuclease III domains of DCL3 cut both strands of the RNA, determining the precise length of the product small RNA. —DJ </jats:p>

<jats:title>Strategic fliers</jats:title> <jats:p> Forests are often crowded and complex, presenting numerous and varied challenges for species flying through them. Le Roy <jats:italic>et al</jats:italic> . looked at the Amazonian <jats:italic>Morpho</jats:italic> butterfly group and found differences in both morphological and behavioral perspectives across species that occupy the canopy relative the understory. Species that evolved to occupy the canopy have improved gliding abilities because of a combination of wing shape and flight behavior. The combination of these traits varied across species even within this single genus, which suggests that there was not one route that led to colonization of this part of the forest. —SNV </jats:p>

<jats:title>Immune memory after vaccination</jats:title> <jats:p> Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has proven highly effective at preventing severe COVID-19. However, the evolution of viral variants, and waning antibody levels over time, raise questions regarding the longevity of vaccine-induced immune protection. Goel <jats:italic>et al</jats:italic> . examined B and T lymphocyte responses in individuals who received SARS-CoV-2 messenger RNA vaccines. They performed a 6-month longitudinal study of individuals who never had SARS-CoV-2 infection compared with people who had recovered from SARS-CoV-2. Humoral and cellular immune memory was observed in vaccinated individuals, as were functional immune responses against the Alpha (B.1.1.7), Beta (B.1.351), and Delta (B.1.617.2) viral variants. Analysis of T cell activity suggested that robust cellular immune memory may prevent hospitalization by limiting the development of severe disease. —PNK </jats:p>

<jats:p> Marom and Rak claim, on the basis of a few mandibular features, that the Nesher Ramla (NR) <jats:italic>Homo</jats:italic> is a Neanderthal. Their comments lack substance and contribute little to the debate surrounding the evolution of Middle Pleistocene <jats:italic>Homo</jats:italic> . Limitations and preconceptions in their study prevented them from achieving resolution beyond a dichotomous interpretation of the NR as either a Neanderthal or a modern human. </jats:p>

<jats:p> Hershkovitz <jats:italic>et al</jats:italic> . (Reports, 25 June 2021, p. 1424) conclude that the Nesher Ramla (NR) fossils represent a distinctive <jats:italic>Homo</jats:italic> paleodeme that played a role as a source population for Neanderthals. However, the highly diagnostic features of the Neanderthal mandible—clearly displayed by the NR fossils—are largely overlooked. Our analyses indicate that the NR fossils represent simply a Neanderthal. </jats:p>

<jats:title>The nonconserved primitive streak</jats:title> <jats:p> In human development, a linear structure called the primitive streak appears 14 days after fertilization. This structure marks the transition of the embryo from having radial to bilateral symmetry. The primitive streak also gives anterior-posterior and dorsal-ventral spatial information to cells undergoing gastrulation and forming the various body cell types. In a Review, Sheng <jats:italic>et al</jats:italic> . present a phylogenetic and ontogenetic overview of the primitive streak. They discuss organismal, cellular, and molecular features of the primitive streak and how it functions in amniote gastrulation. The observation that this structure is not conserved and is not required for development in vitro has implications for embryonic stem cell–based models and considerations about human development research. —BAP </jats:p>