Catálogo de publicaciones - revistas

<jats:p>Prior to ~1 million years ago (Ma), variations in global ice volume were dominated by changes in obliquity; however, the role of precession remains unresolved. Using a record of North Atlantic ice rafting spanning the past 1.7 million years, we find that the onset of ice rafting within a given glacial cycle (reflecting ice sheet expansion) consistently occurred during times of decreasing obliquity whereas mass ice wasting (ablation) events were consistently tied to minima in precession. Furthermore, our results suggest that the ubiquitous association between precession-driven mass wasting events and glacial termination is a distinct feature of the mid to late Pleistocene. Before then (increasing), obliquity alone was sufficient to end a glacial cycle, before losing its dominant grip on deglaciation with the southward extension of Northern Hemisphere ice sheets since ~1 Ma.</jats:p>

<jats:p> <jats:italic>N</jats:italic> <jats:sup>6</jats:sup> -methyladenosine (m <jats:sup>6</jats:sup> A) is the most abundant internal modification on mammalian messenger RNA. It is installed by a writer complex and can be reversed by erasers such as the fat mass and obesity-associated protein FTO. Despite extensive research, the primary physiological substrates of FTO in mammalian tissues and development remain elusive. Here, we show that FTO mediates m <jats:sup>6</jats:sup> A demethylation of long-interspersed element-1 (LINE1) RNA in mouse embryonic stem cells (mESCs), regulating LINE1 RNA abundance and the local chromatin state, which in turn modulates the transcription of LINE1-containing genes. FTO-mediated LINE1 RNA m <jats:sup>6</jats:sup> A demethylation also plays regulatory roles in shaping chromatin state and gene expression during mouse oocyte and embryonic development. Our results suggest broad effects of LINE1 RNA m <jats:sup>6</jats:sup> A demethylation by FTO in mammals. </jats:p>

<jats:p> Two-dimensional materials with out-of-plane (OOP) ferroelectric and piezoelectric properties are highly desirable for the realization of ultrathin ferro- and piezoelectronic devices. We demonstrate unexpected OOP ferroelectricity and piezoelectricity in untwisted, commensurate, and epitaxial MoS <jats:sub>2</jats:sub> /WS <jats:sub>2</jats:sub> heterobilayers synthesized by scalable one-step chemical vapor deposition. We show <jats:italic>d</jats:italic> <jats:sub>33</jats:sub> piezoelectric constants of 1.95 to 2.09 picometers per volt that are larger than the natural OOP piezoelectric constant of monolayer In <jats:sub>2</jats:sub> Se <jats:sub>3</jats:sub> by a factor of ~6. We demonstrate the modulation of tunneling current by about three orders of magnitude in ferroelectric tunnel junction devices by changing the polarization state of MoS <jats:sub>2</jats:sub> /WS <jats:sub>2</jats:sub> heterobilayers. Our results are consistent with density functional theory, which shows that both symmetry breaking and interlayer sliding give rise to the unexpected properties without the need for invoking twist angles or moiré domains. </jats:p>

<jats:p> Organic hydrotrioxides (ROOOH) are known to be strong oxidants used in organic synthesis. Previously, it has been speculated that they are formed in the atmosphere through the gas-phase reaction of organic peroxy radicals (RO <jats:sub>2</jats:sub> ) with hydroxyl radicals (OH). Here, we report direct observation of ROOOH formation from several atmospherically relevant RO <jats:sub>2</jats:sub> radicals. Kinetic analysis confirmed rapid RO <jats:sub>2</jats:sub> + OH reactions forming ROOOH, with rate coefficients close to the collision limit. For the OH-initiated degradation of isoprene, global modeling predicts molar hydrotrioxide formation yields of up to 1%, which represents an annual ROOOH formation of about 10 million metric tons. The atmospheric lifetime of ROOOH is estimated to be minutes to hours. Hydrotrioxides represent a previously omitted substance class in the atmosphere, the impact of which needs to be examined. </jats:p>

<jats:p>The dynamic interactions between noble metal particles and reducible metal-oxide supports can depend on redox reactions with ambient gases. Transmission electron microscopy revealed that the strong metal-support interaction (SMSI)–induced encapsulation of platinum particles on titania observed under reducing conditions is lost once the system is exposed to a redox-reactive environment containing oxygen and hydrogen at a total pressure of ~1 bar. Destabilization of the metal–oxide interface and redox-mediated reconstructions of titania lead to particle dynamics and directed particle migration that depend on nanoparticle orientation. A static encapsulated SMSI state was reestablished when switching back to purely oxidizing conditions. This work highlights the difference between reactive and nonreactive states and demonstrates that manifestations of the metal-support interaction strongly depend on the chemical environment.</jats:p>

<jats:p>Rivers can abruptly shift pathways in rare events called avulsions, which cause devastating floods. The controls on avulsion locations are poorly understood as a result of sparse data on such features. We analyzed nearly 50 years of satellite imagery and documented 113 avulsions across the globe that indicate three distinct controls on avulsion location. Avulsions on fans coincide with valley-confinement change, whereas avulsions on deltas are primarily clustered within the backwater zone, indicating a control by spatial flow deceleration or acceleration during floods. However, 38% of avulsions on deltas occurred upstream of backwater effects. These events occurred in steep, sediment-rich rivers in tropical and desert environments. Our results indicate that avulsion location on deltas is set by the upstream extent of flood-driven erosion, which is typically limited to the backwater zone but can extend far upstream in steep, sediment-laden rivers. Our findings elucidate how avulsion hazards might respond to land use and climate change.</jats:p>

<jats:p> Emerging resistance to currently used antibiotics is a global public health crisis. Because most of the biosynthetic capacity within the bacterial kingdom has remained silent in previous antibiotic discovery efforts, uncharacterized biosynthetic gene clusters found in bacterial genome–sequencing studies remain an appealing source of antibiotics with distinctive modes of action. Here, we report the discovery of a naturally inspired lipopeptide antibiotic called cilagicin, which we chemically synthesized on the basis of a detailed bioinformatic analysis of the <jats:italic>cil</jats:italic> biosynthetic gene cluster. Cilagicin’s ability to sequester two distinct, indispensable undecaprenyl phosphates used in cell wall biosynthesis, together with the absence of detectable resistance in laboratory tests and among multidrug-resistant clinical isolates, makes it an appealing candidate for combating antibiotic-resistant pathogens. </jats:p>

<jats:p> T cell quiescence is essential for maintaining a broad repertoire against a large pool of diverse antigens from microbes and tumors, but the underlying molecular mechanisms remain largely unknown. We show here that CD8α is critical for the maintenance of CD8 <jats:sup>+</jats:sup> T cells in a physiologically quiescent state in peripheral lymphoid organs. Upon inducible deletion of CD8α, both naïve and memory CD8 <jats:sup>+</jats:sup> T cells spontaneously acquired activation phenotypes and subsequently died without exposure to specific antigens. PILRα was identified as a ligand for CD8α in both mice and humans, and disruption of this interaction was able to break CD8 <jats:sup>+</jats:sup> T cell quiescence. Thus, peripheral T cell pool size is actively maintained by the CD8α–PILRα interaction in the absence of antigen exposure. </jats:p>

<jats:p> Harmful cyanobacteria are a global environmental problem, yet we lack actionable understanding of toxigenic versus nontoxigenic strain ecology and toxin production. We performed a large-scale meta-analysis including 103 papers and used it to develop a mechanistic, agent-based model of <jats:italic>Microcystis</jats:italic> growth and microcystin production. Simulations for Lake Erie suggest that the observed toxigenic-to-nontoxigenic strain succession during the 2014 Toledo drinking water crisis was controlled by different cellular oxidative stress mitigation strategies (protection by microcystin versus degradation by enzymes) and the different susceptibility of those mechanisms to nitrogen limitation. This model, as well as a simpler empirical one, predicts that the planned phosphorus load reduction will lower biomass but make nitrogen and light more available, which will increase toxin production, favor toxigenic cells, and increase toxin concentrations. </jats:p>

<jats:p>Temporary postoperative cardiac pacing requires devices with percutaneous leads and external wired power and control systems. This hardware introduces risks for infection, limitations on patient mobility, and requirements for surgical extraction procedures. Bioresorbable pacemakers mitigate some of these disadvantages, but they demand pairing with external, wired systems and secondary mechanisms for control. We present a transient closed-loop system that combines a time-synchronized, wireless network of skin-integrated devices with an advanced bioresorbable pacemaker to control cardiac rhythms, track cardiopulmonary status, provide multihaptic feedback, and enable transient operation with minimal patient burden. The result provides a range of autonomous, rate-adaptive cardiac pacing capabilities, as demonstrated in rat, canine, and human heart studies. This work establishes an engineering framework for closed-loop temporary electrotherapy using wirelessly linked, body-integrated bioelectronic devices.</jats:p>