Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has ...been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.
An efficient aryl to vinyl 1,4‐palladium migration/Heck sequence was developed for the stereoselective synthesis of 1,3‐dienes. High stereoselectivity was observed not only for 1,3‐dienes bearing two ...similar aryl groups at terminal positions, but also for those with configurations shown to be unfavorable with previous methods.
1,4 all: An efficient aryl to vinyl 1,4‐palladium/Heck sequence has been developed for the stereoselective synthesis of 1,3‐dienes. High stereoselectivity was observed not only for 1,3‐dienes bearing two similar aryl groups at terminal positions, but also for those with configurations shown to be unfavorable with previous methods.
Time-reversed evolution has substantial implications in physics, including applications in refocusing of classical waves or spins and fundamental studies such as quantum information scrambling. In ...quantum metrology, nonlinear interferometry based on time-reversal protocols supports entanglement-enhanced measurements without requiring low-noise detection. Despite the broad interest in this topic, it remains challenging to reverse the quantum dynamics of an interacting many-body system, which is typically realized by an (effective) sign flip of the system’s Hamiltonian. Here we present an approach that is broadly applicable to cyclic systems for implementing nonlinear interferometry without invoking time reversal. As time-reversed dynamics drives a system back to its starting point, we propose to accomplish the same by forcing the system to travel along a ‘closed loop’ instead of explicitly tracing back its antecedent path. Utilizing the quasiperiodic spin mixing dynamics in a three-mode 87Rb atomic spinor condensate, we implement such a closed-loop nonlinear interferometer and achieve a metrological gain of 5.01−0.76+0.76 decibels over the classical limit for a total of 26,500 atoms. Our approach unlocks the potential of nonlinear interferometry by allowing the dynamics to penetrate into the deep nonlinear regime, which gives rise to highly entangled non-Gaussian states.Nonlinear interferometry based on time reversal enables entanglement-enhanced measurements without the need for low-noise detection. An alternative approach now exploits cyclic dynamics and shows performance beyond the standard quantum limit.
Local increase in blood flow during neural activity forms the basis for functional brain imaging, but its mechanism remains poorly defined. Here we show that cortical astrocytes in vivo possess a ...powerful mechanism for rapid vasodilation. We imaged the activity of astrocytes labeled with the calcium (Ca(2+))-sensitive indicator rhod-2 in somatosensory cortex of adult mice. Photolysis of caged Ca(2+) in astrocytic endfeet ensheathing the vessel wall was associated with an 18% increase in arterial cross-section area that corresponded to a 37% increase in blood flow. Vasodilation occurred with a latency of only 1-2 s, and both indomethacin and the cyclooxygenase-1 inhibitor SC-560 blocked the photolysis-induced hyperemia. These observations implicate astrocytes in the control of local microcirculation and suggest that one of their physiological roles is to mediate vasodilation in response to increased neural activity.
The growth factor progranulin (PGRN) has been implicated in embryonic development, tissue repair, tumorigenesis, and inflammation, but its receptors remain unidentified. We report that PGRN bound ...directly to tumor necrosis factor receptors (TNFRs) and disturbed the TNFα-TNFR interaction. PGRN-deficient mice were susceptible to collagen-induced arthritis, and administration of PGRN reversed inflammatory arthritis. Atsttrin, an engineered protein composed of three PGRN fragments, exhibited selective TNFR binding. PGRN and Atsttrin prevented inflammation in multiple arthritis mouse models and inhibited TNFα-activated intracellular signaling. Collectively, these findings demonstrate that PGRN is a ligand of TNFR, an antagonist of TNFα signaling, and plays a critical role in the pathogenesis of inflammatory arthritis in mice. They also suggest new potential therapeutic interventions for various TNFα-mediated pathologies and conditions, including rheumatoid arthritis.
The asymmetric rhodium‐catalyzed alkenylation of enones and imines with arylboronic acids has been developed. A highly controllable aryl to vinyl 1,4‐rhodium migration is the key step. Stereodefined ...vinyl moieties were installed in excellent enantioselectivies for most examined examples. DFT calculations reveal that the driving force of this rhodium migration is a kinetically favored process.
The asymmetric rhodium‐catalyzed alkenylation of enones and imines with arylboronic acids has been developed. A highly controllable aryl to vinyl 1,4‐rhodium migration is the key step. Stereodefined vinyl moieties were installed in excellent enantioselectivies for most examined examples. DFT calculations reveal that the driving force of this rhodium migration is a kinetically favored process.
The aryl to vinyl palladium 1,4-migration was realized for the first time. The generated alkenyl palladium species was trapped by diboron reagents under Miyaura borylation conditions, providing a new ...method to synthesize β,β-disubstituted vinylboronates. The excellent regioselectivity and broad substrate scope were observed for this novel transformation.
MicroRNA‐425‐5p (miR‐425‐5p) has been reported to be involved in the tumorigenesis of several tumors, but its function in breast cancer is still unknown. In this study, miR‐425‐5p was found ...significantly upregulated in breast cancer cells, and predicted a poor prognosis for breast cancer patients. Overexpression of miR‐425‐5p could significantly promote breast cancer cell growth. Further studies showed that overexpression of miR‐425‐5p upregulated the protein levels of Cyclin D1, Cyclin D3, CDK4, and CDK6. However, inhibiting miR‐425‐5p downregulated their expression and induced cell cycle arrest at G0/G1 phase. In mechanism, overexpression of miR‐425‐5p increased the phosphorylation of PI3K p85 and AKT, but inhibiting miR‐425‐5p displayed opposite effects. Moreover, miR‐425‐5p bound to the 3'UTR of PTEN mRNA, and downregulated the expression levels of PTEN in both mRNA and protein levels in breast cancer cells. Collectively, the results above demonstrated that miR‐425‐5p was involved in the tumorigenesis of breast cancer by inducing PI3K/AKT signaling and indicated that miR‐425‐5p could be as a potential target for breast cancer therapy in the future.
The interfacial behavior of a flexible polymer with activity, which is named active Brownian polymer (ABPO), is studied by Langevin dynamics simulations. On the dependence of the adsorption strength ...and activity characterized by the Péclet number (Pe), the polymer displays two typical states on the surface: adsorption and desorption states. We find that the diffusion behavior of ABPO that is parallel to the surface yields the “active Rouse model” and the activity causes the adsorption–desorption transition at a certain adsorption strength. Particular attention is given to how the desorption time, τdes, changes with the activity. At intermediate activity, τdes displays an exponential decay with the inverse of the effective temperature, T eff ∝1 + Pe 2/18, which is reminiscent of the mechanism of thermal activation. At higher activity, due to easily overcoming the attractive energy barrier, τdes ∝Pe –1 is found. At lower activity, a power-law dependence of τdes on the diffusion coefficient perpendicular to the surface (D ⊥) is observed (τdes ∼D ⊥ –1.28). Further, we observed a non-monotonic dependence of desorption time on the rotation diffusion coefficient D R of the monomer and found that τdes exists on a scaling relation with the chain length N, τdes ∼ N ϕ, and the scaling exponent ϕ decreases with the increase of activity. Our results highlight that the activity can be used to regulate the polymer adsorption and desorption behavior.
Actinomorphic flowers usually orient vertically (relative to the horizon) and possess symmetric nectar guides, while zygomorphic flowers often face horizontally and have asymmetric nectar guides, ...indicating that floral symmetry, floral orientation, and nectar guide patterning are correlated. The origin of floral zygomorphy is dependent on the dorsoventrally asymmetric expression of CYCLOIDEA (CYC)-like genes. However, how horizontal orientation and asymmetric nectar guides are achieved remains poorly understood. Here, we selected Chirita pumila (Gesneriaceae) as a model plant to explore the molecular bases for these traits. By analyzing gene expression patterns, protein-DNA and protein-protein interactions, and encoded protein functions, we identified multiple roles and functional divergence of 2 CYC-like genes, i.e. CpCYC1 and CpCYC2, in controlling floral symmetry, floral orientation, and nectar guide patterning. CpCYC1 positively regulates its own expression, whereas CpCYC2 does not regulate itself. In addition, CpCYC2 upregulates CpCYC1, while CpCYC1 downregulates CpCYC2. This asymmetric auto-regulation and cross-regulation mechanism might explain the high expression levels of only 1 of these genes. We show that CpCYC1 and CpCYC2 determine asymmetric nectar guide formation, likely by directly repressing the flavonoid synthesis-related gene CpF3'5'H. We further suggest that CYC-like genes play multiple conserved roles in Gesneriaceae. These findings shed light on the repeated origins of zygomorphic flowers in angiosperms.
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