Publications by authors named "Xichen Xu"

Mangroves protect coasts from extreme weather and erosion but can be destroyed by climate change and harvesting. However, there is no consistent formulation of protective capacity that integrates key factors such as area, width, height, and health. Here, we quantified and analyzed a process-based measure of mangrove coastal protection index (MCPI) incorporating cross-shore width, canopy height, and the normalized difference vegetation index (health index).

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Temperature-responsive materials with excellent reliability, sensitivity, and flame-retardant properties have always been an urgent need in the field of intelligent fire protection. In this discourse, we introduce a novel thermosensitive ionic hydrogel coating (gelatin/poly(acrylamide-co-acrylic acid)/CaCl/spindle-shaped aluminum hydroxide nanosheet/glycerol, HCA) synthesized via free radical polymerization. HCA not only demonstrates considerable mechanical properties with a fracture strain of up to 842.

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We aimed to estimate cardiac output (CO) from photoplethysmography (PPG) and the arterial pressure waveform (ART) using a deep learning approach, which is minimally invasive, does not require patient demographic information, and is operator-independent, eliminating the need to artificially extract a feature of the waveform by implementing a traditional formula. We aimed to present an alternative to measuring cardiac output with greater accuracy for a wider range of patients. Using a publicly available dataset, we selected 543 eligible patients and divided them into test and training sets after preprocessing.

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To measure stomatal traits automatically and nondestructively, a new method for detecting stomata and extracting stomatal traits was proposed. Two portable microscopes with different resolutions (TipScope with a 40× lens attached to a smartphone and ProScope HR2 with a 400× lens) are used to acquire images of living stomata in maize leaves. FPN model was used to detect stomata in the TipScope images and measure the stomata number and stomatal density.

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The formation of membraneless organelles in cells commonly occurs via liquid-liquid phase separation (LLPS) and is in many cases driven by multivalent interactions between intrinsically disordered proteins (IDPs). Investigating the nature of these interactions, and their effect on dynamics within the condensed phase, is therefore of critical importance but very challenging for either simulation or experiment. Here, we study these interactions and their dynamics by pairing a novel multiscale simulation strategy with microsecond all-atom MD simulations of a condensed, IDP-rich phase.

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The intrinsic electrophilic feature for the terminal nitrogen of α-diazo-β-ketoesters/ketones has been elucidated by the intermolecular nucleophilic addition of two molecules of a dimethylsulfonium ylide. This methodology allows for access to highly functionalized hydrazones with a broad scope and good functional group tolerance. The reaction operates under simple and mild conditions without using a catalyst.

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An enantioselective carbonyl-ene reaction of glyoxylate esters with 1,1-disubstituted alkenes catalyzed by chiral cationic dirhodium(II,III) carboxamidates is described. The paddlewheel dirhodium(II,III) carboxamidates having one open coordination site at each rhodium smoothly catalyze the carbonyl-ene reaction to afford homoallylic alcohol products in good isolated yields with high enantioselectivities.

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A survey of in situ, catalytically generated carbocations for coupling with enoldiazoacetate nucleophiles was performed. These couplings facilitate the rapid assembly of complex organodiazo compounds that provide a template for the synthesis of a variety of carbocyclic and heterocyclic ring systems.

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In a reaction that proceeds under mild conditions with remarkable functional group tolerance, structurally diverse 3-amino-2-cyclopentenones bearing a quaternary carbon at the 4-position have been synthesized through a formal [3+2]-cycloaddition reaction of silylated ketene imines (SKIs) and enoldiazoaceates by dirhodium catalysis.

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Convenient access to highly enantioenriched substituted quinolizidines has been achieved by chiral dirhodium(II) carboxylate-catalyzed dearomatizing formal [3 + 3]-cycloaddition of isoquinolinium/pyridinium methylides and enol diazoacetates. Coordination of Lewis basic methylides to dirhodium(II) prompts the rearrangement of the enol-carbene that is bound to dirhodium to produce a donor-acceptor cyclopropene. The donor-acceptor cyclopropene is in equilibrium with the dirhodium-bound enol-carbene and undergoes both enantioselective [3 + 3]-cycloaddition from the dirhodium-bound enol-carbene and diastereoselective [3 + 2]-cycloaddition by uncatalyzed reaction of the cyclopropene with isoquinolinium or pyridinium methylides.

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A highly diastereoselective formal [3+2+1]-cycloaddition reaction that produces multi-functionalized bicyclic pyrazolidinone derivatives is achieved in moderate to high yield by Rh2(4S-MPPIM)4-catalyzed reaction of azomethine imines with two molecules of a diazo ketone.

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Transition-metal catalysts direct 1,2-C→C, -O→C, and -N→C migrations from β-methylene-β-silyloxy-β-amido-α-diazoacetates with high selectivity. The key to achieving this unique display of differential selectivities relies on steric and stereoelectronic control by their catalytically generated metal carbenes.

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Association constants of the chiral dirhodium(II) carboxamidate Rh(2)(5S-MEPY)(4) with Lewis bases including acetonitrile and amides have been determined by UV-vis titration experiments. With chiral lactams and acyclic acetamides in their R- and S-configurations equilibrium constants with chiral dirhodium carboxamidates are measures of chiral differentiation, and equilibrium constant ratios as high as three have been determined. From equilibrium associations with acetamide, N-methylacetamide, and N,N-dimethylacetamide, as well as equilibrium constants for lactams and acyclic amides, higher values occur when both the amide carbonyl oxygen and N-H are bound to Rh(2)(5S-MEPY)(4).

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