Diamond and 學網adamantane (Ad) share a?Td-symmetric carbon skeleton, but converting Ad to diamond has been challenging because it requires selective carbon-hydrogen (C–H) bond cleavage and monomer assembly into a diamond lattice. Our approach differs from the conventional high-temperature, high-pressure diamond syntheses. We electron-irradiated Ad submicrocrystals at 80 to 200 kilo–electron volts and 100 to 296 kelvin in vacuum for tens of seconds. This process yielded defect-free nanodiamonds (NDs) of cubic crystal structure, accompanied by hydrogen gas evolution. Time-resolved transmission electron microscopy revealed the initial formation of Ad oligomers transforming into spherical NDs. A sizable kinetic isotope effect indicates that C–H cleavage was rate-determining, and other hydrocarbons tested failed to form NDs.
Order-to-disorder transition due to entropy in layered and 2D carbides
In compositionally complex materials, there is controversy on the effect of enthalpy versus entropy on the structure and short-range ordering in so-called high-entropy materials. To help address this controversy, we synthesized and probed 40 M4AlC3?layered carbide phases containing two to nine metals and found that short-range ordering from enthalpy was present until the entropy increased enough to achieve complete disordering of the transition metals in their atomic planes. We transformed all of these layered carbide phases into two-dimensional (2D) sheets and showed the effects of the order versus disorder on their surface properties and electronic behavior. This study suggests the key effect that the competition between enthalpy and entropy has on short-range order in multicompositional materials.
医学Medicine
Estrogen-regulated renal progenitors determine pregnancy adaptation and preeclampsia
The global burden of kidney disease displays marked sexual dimorphism. Lineage tracing and single-cell RNA-sequencing revealed that starting from puberty, estrogen signaling in female mice supports self-renewal and differentiation of renal progenitors to increase filtration capacity, reducing sensitivity to glomerular injury compared with that of males. This phenomenon accelerated as female kidneys adapted to the workload of pregnancy. Deletion of estrogen receptor α in renal progenitors disrupted this adaptation, leading to preeclampsia, fetal growth restriction, and increased maternal risk of hypertension and chronic kidney disease. Offspring from affected mothers had fewer nephrons, resulting in early-life hypertension and greater susceptibility to kidney disease. These results highlight the fundamental role of kidney fitness and renal progenitors for pregnancy and preeclampsia and as a determinant of sexual dimorphism in kidney disease.
化学Chemsitry
Photochemical?H2?dissociation for nearly quantitative CO2?reduction to ethylene
Producing olefins by carbon dioxide (CO2) hydrogenation is a long-standing goal. The usual products are multicarbon mixtures because the critical step of heterolytic hydrogen (H2) dissociation at high temperatures complicates selectivity control. In this study, we report that irradiating gold–titanium dioxide at 365 nanometers induces heterolytic H2?dissociation at ambient temperature. This process likely relies on interfacial electric dipoles from photogenerated electrons and holes situated on the metallic gold nanoparticles and interfacial gold–oxygen–titanium scaffolds. The heterolytic H2?dissociation is further promoted by light-induced coating of gold nanoparticles with a titanium oxide layer. The resulting nucleophilic hydrogen species reduce CO2?to ethane in >99% yield under light irradiation in a flow apparatus. Furthermore, cascading with a subsequent photocatalytic ethane dehydrogenation generates ethylene in >99% yield over 1500 hours of irradiation.
Cell extrusion is essential for homeostatic self-renewal of the intestinal epithelium. Extrusion is thought to be triggered by crowding-induced compression of cells at the intestinal villus tip. In this study, we found instead that a local “tug-of-war” competition between contractile cells regulated extrusion in the intestinal epithelium. We combined quantitative live microscopy, optogenetic induction of tissue tension, genetic perturbation of myosin II activity, and local disruption of the basal cortex in mouse intestines and intestinal organoids. These approaches revealed that a dynamic actomyosin network generates tension throughout the intestinal villi, including the villus tip region. Mechanically weak cells unable to maintain this tension underwent extrusion. Thus, epithelial barrier integrity depends on intercellular mechanics.
地球科学Earth Science
Very-long-range dynamic triggering of mud volcano unrest and silent magnitude-6 fault slip
Seismic waves from large earthquakes are known to trigger slip on distant faults, but the underlying mechanisms remain unclear. Using interferometric synthetic aperture radar and local geodetic and seismic data, we show that the 1000-kilometer-distant, February 2023 Kahramanmara? earthquakes in southeastern Türkiye triggered deformation and/or eruption at 56 mud volcanoes and centimeter-scale aseismic slip on seven faults over tens of kilometers within the fluid-rich Kura Basin in the West Caspian region. This transient deformation event, with an equivalent moment magnitude of 6.1, was coupled with local inflation below major hydrocarbon fields. We postulate that seismic waves led to a change in pore pressure at depth, which in turn triggered aseismic slip along several crustal faults crossing the basin and its surroundings.
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