Dilute alloying is an effective strategy to tune properties of solid catalysts but is rarely leveraged in complex reactions beyond small molecule conversion. In this work, dilute dopants are ...demonstrated to serve as activating centers to construct multiatom catalytic domains in metal nitride electrocatalysts for lithium–sulfur (Li–S) batteries, of which the sulfur cathode suffers from sluggish and complex conversion reactions. With titanium nitride (TiN) as a model system, the dilute cobalt alloying is shown to greatly improve the reaction kinetics while inducing negligible catalyst reconstruction. Compared to the pristine TiN, the dilute nitride alloy catalyst enables onefold increase in the high rate (2.0 C) capacities of Li–S batteries, as well as an impressively low cyclic decay rate of 0.17% at a sulfur loading of 4.0 mgS cm−2. This work opens up new opportunities toward the rational design of Li–S electrocatalysts by dilute alloying and also enlightens the understandings of complex domain‐catalyzed reactions in energy applications.
Dilute alloying implants “activating” centers in nitride alloy electrocatalysts to boost lithium–sulfur (Li–S) batteries. Dilute Co dopants activate the surrounding N and Ti atoms to construct multiatom active domains for efficient bidirectional catalysis of S redox reactions. The corresponding dilute nitride alloy improves the reaction kinetics and electrochemical performance of Li–S batteries.
Chiral 2,3‐allenols were constructed through copper(I)‐catalyzed asymmetric direct alkynylogous aldol reaction. With aromatic and heteroaromatic aldehydes, the alkynylogous aldol reaction with ...(R)‐DTBM‐SEGPHOS as the ligand proceeded smoothly to furnish the products in excellent regioselectivity with good to high diastereoselectivity and excellent enantioselectivity. In the cases of aliphatic aldehydes, esters of but‐2‐yn‐1‐ol as the substrates and (R,R)‐Ph‐BPE as the ligand were found to be crucial to get good to high regio‐ and diastereoselectivity. The produced chiral 2,3‐allenols are easily transformed into synthetically useful 2‐furanones through cyclization. Finally, the developed method was successfully applied in the rapid synthesis of two chiral intermediates toward the synthesis of two pharmaceutically active compounds that have been proposed for the treatment of neurological disorders.
Two by two: A copper(I)‐catalyzed asymmetric direct alkynylogous aldol reaction was developed that delivers chiral 2,3‐allenols with good to excellent regio‐, diastereo‐, and enantioselectivity. The produced chiral 2,3‐allenols are easily transformed into synthetically useful 2‐furanones through cyclization.
A protein‐sized (ca. 4.2×4.2×3.6 nm3) non‐biologically derived molecule {Nb288O768(OH)48(CO3)12} (Nb288) containing up to 288 niobium atoms has been obtained, which is by far the largest and the ...highest nuclearity polyoxoniobate (PONb). Particularly, in terms of metal nuclearity number, Nb288 is the second largest cluster so far reported in classic polyoxometalate chemistry (V, Mo, W, Nb, and Ta). Nb288 can be described as a giant windmill‐like cluster aggregate of six nanoscale high‐nuclearity PONb units {Nb47O128(OH)6(CO3)2} (Nb47) joined together by six additional Nb ions. Interestingly, the 47‐nuclearity Nb47 units generated in situ can be isolated and bridged by copper complexes to form an inorganic–organic hybrid three‐dimensional PONb framework, which exhibits effective catalytic activity for hydrolyzing nerve agent simulant of dimethyl methylphosphonate. The unique Nb47 cluster also provides a new type of topology to very limited family of Nb‐O clusters.
Friendly niobium giant: An unprecedentedly huge polyoxoniobate (PONb) with as many as 288 Nb centers has been made. This is by far the largest PONb and the second highest nuclearity polyoxometalate reported to date. It incorporates a unique 47‐nuclearity PONb building unit formed in situ, which can be stabilized by metal complexes to form an extended PONb framework with the capability of hydrolyzing dimethyl methylphosphonate.
Highly reactive metastable intermixed composites (MICs) have attracted much attention in the past decades. The MIC family of materials mainly includes traditional metal‐based nanothermites, novel ...core–shell‐structured, 3D ordered macroporous‐structured, and ternary nanocomposites. By applying special fabrication approaches, highly reactive MICs with uniformly dispersed reactants, “layer‐by‐layer” or “core–shell” structures, can be prepared. Thus, the combustion performance can be greatly improved, and the ignition characteristics and safety can be precisely controlled by using a certain preparation strategy. Here, the preparation and characterization of the MICs that have been developed during the past few decades are summarized. Traditional preparation methods for MICs generally include physical mixing, high‐energy ball milling, sol–gel synthesis, and vapor deposition, while the novel methods include self‐assembly, electrophoretic deposition, and electrospinning. Various preparation procedures and the ignition and combustion performance of different MIC reactive systems are compared and discussed. In particular, the advantages of novel structured MICs in terms of safety and combustion efficiency are clarified, based on which suggestions regarding the possible future research directions are proposed.
Highly reactive metastable intermixed composites (MICs) prepared by different strategies show various characteristics and properties. By applying special fabrication approaches, highly reactive MICs with uniformly dispersed reactants, assembled in either layer‐by‐layer or core–shell structure, can be prepared. Thus, the improved and desired performances can be achieved by using a certain preparation strategy.
Radical cascade cyclization of β,γ‐unsaturated hydrazones/oximes has recently emerged as an efficient and powerful protocol for the construction of diverse and valuable functionalized pyrazolines and ...isoxazolines. In this review, three catalytic ways of radical cascade cyclization of β,γ‐unsaturated hydrazones/oximes are summarized and classified; these are transition‐metal‐catalyzed systems, transition‐metal‐free systems, and photo‐/electrocatalytic systems, respectively. Through these methods, various functional groups are installed on the pyrazoline and isoxazoline skeletons to enrich the small organic molecule library.
Abstract
Kilonovae are generally believed to originate from the ejecta of binary neutron stars (NSs) or black hole–NS mergers. Free neutrons might be retained in the outermost layer of the ejecta to ...produce a precursor via
β
decay. During the propagation of kilonovae to observers, a small percentage of them might be gravitationally lensed by foreground objects. In this paper, three lens models, i.e., the point-mass model, the singular isothermal sphere (SIS) model, and the Chang–Refsdal model, were taken into consideration to explore the light curves and polarizations of gravitationally lensed kilonovae. We found that, if the time delay between two images exceeds the ejecta-heating timescale for the lens mass ∼10
10
M
⊙
in the SIS model, a tiny bump-like signal will be generated in the light curve, and the total luminosity will be magnified in all cases. The polarization of lensed kilonovae is significantly enhanced in most cases. Future detections of lensed kilonovae will impose constraints on the morphology of the ejecta and aid in the determination of the nature of compact object mergers and the search for strong gravitational lenses.
To develop and validate a radiomics nomogram for preoperative prediction of lymph node (LN) metastasis in patients with colorectal cancer (CRC).
The prediction model was developed in a primary cohort ...that consisted of 326 patients with clinicopathologically confirmed CRC, and data was gathered from January 2007 to April 2010. Radiomic features were extracted from portal venous-phase computed tomography (CT) of CRC. Lasso regression model was used for data dimension reduction, feature selection, and radiomics signature building. Multivariable logistic regression analysis was used to develop the predicting model, we incorporated the radiomics signature, CT-reported LN status, and independent clinicopathologic risk factors, and this was presented with a radiomics nomogram. The performance of the nomogram was assessed with respect to its calibration, discrimination, and clinical usefulness. Internal validation was assessed. An independent validation cohort contained 200 consecutive patients from May 2010 to December 2011.
The radiomics signature, which consisted of 24 selected features, was significantly associated with LN status (P < .001 for both primary and validation cohorts). Predictors contained in the individualized prediction nomogram included the radiomics signature, CT-reported LN status, and carcinoembryonic antigen level. Addition of histologic grade to the nomogram failed to show incremental prognostic value. The model showed good discrimination, with a C-index of 0.736 (C-index, 0.759 and 0.766 through internal validation), and good calibration. Application of the nomogram in the validation cohort still gave good discrimination (C-index, 0.778 95% CI, 0.769 to 0.787) and good calibration. Decision curve analysis demonstrated that the radiomics nomogram was clinically useful.
This study presents a radiomics nomogram that incorporates the radiomics signature, CT-reported LN status, and clinical risk factors, which can be conveniently used to facilitate the preoperative individualized prediction of LN metastasis in patients with CRC.
A
bstract
We investigate the gravitation waves produced from QCD and electroweak phase transitions in the early universe by using a 5-dimension holographic QCD model and a holographic technicolor ...model. The dynamical holographic QCD model is to describe the pure gluon system, where a first order confinement-deconfinement phase transition can happen at the critical temperature around 250 MeV. The minimal holographic technicolor model is introduced to model the strong dynamics of electroweak, it can give a first order electroweak phase transition at the critical temperature around 100-360 GeV. We find that for both GW signals produced from QCD and EW phase transitions, in the peak frequency region, the dominant contribution comes from the sound waves, while away from the peak frequency region the contribution from the bubble collision is dominant. The peak frequency of gravitation wave determined by the QCD phase transition is located around 10
−7
Hz which is within the detectability of FAST and SKA, and the peak frequency of gravitational wave predicted by EW phase transition is located at 0.002 – 0.007 Hz, which might be detectable by BBO, DECIGO, LISA and ELISA.
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