Platinum‐catalyzed formal 5+2 and 4+2 annulations of isoxazoles with heterosubstituted alkynes enabled the atom‐economical synthesis of valuable 1,3‐oxazepines and 2,5‐dihydropyridines, respectively. ...Importantly, this Pt catalysis not only led to unique reactivity dramatically divergent from that observed under Au catalysis, but also proceeded via unprecedented α‐imino platinum carbene intermediates.
Gold's deviant relative: Platinum‐catalyzed formal 5+2 and 4+2 annulations of isoxazoles and heterosubstituted alkynes provided valuable 1,3‐oxazepines and 2,5‐dihydropyridines (see scheme). This reactivity deviates dramatically from that observed under gold catalysis and involves the generation of an α‐imino platinum carbene. A computational study provided evidence for the proposed mechanism of this unusual tandem sequence.
Carbonyl ylides have proven to be powerful synthons for the efficient construction of various valuable O‐heterocycles, and the formation of carbonyl ylides by the reaction of metal carbenes with ...carbonyls has attracted increasing attention over the past decades. However, a catalyst‐controlled highly enantioselective reaction of carbonyl ylides from metal carbenes is extremely challenging. Herein, we report a novel copper‐catalyzed asymmetric formal 2+1 and 4+1 annulations of diynes with ketones via carbonyl ylides. Importantly, this protocol not only represents the first example of successful asymmetric epoxidation via carbonyl ylides, but also constitutes the first reaction of vinyl cations with carbonyl compounds. This method leads to the divergent, practical and atom‐economical synthesis of a range of chiral oxiranes and dihydrofurans in moderate to excellent yields with generally excellent enantioselectivities and diastereoselectivities via remote‐stereocontrol strategy.
A copper‐catalyzed asymmetric formal 2+1 and 4+1 annulation of diynes with ketones via carbonyl ylides is disclosed. This protocol enables the divergent, practical and atom‐economical synthesis of a range of chiral oxiranes and dihydrofurans in moderate to excellent yields with generally excellent enantioselectivities and diastereoselectivities.
A doubly heavy baryon can be regarded as composed of a heavy diquark and a light quark. In this picture, we study the masses of the doubly heavy diquarks in the Bethe-Salpeter (BS) formalism first, ...which are then used as one of the inputs in studying the masses of the doubly heavy baryons in the quark-diquark model. We establish the BS equations for both the heavy diquarks and the heavy baryons with and without taking the heavy quark limit, respectively. These equations are solved numerically with the kernel containing the scalar confinement and one-gluon-exchange terms. The mass of the doubly charmed baryon Ξcc(⁎) is obtained in both approaches, 3.60∼3.65GeV (Ξcc(⁎)) under the heavy quark limit, 3.53∼3.56GeV for Ξcc and 3.61∼3.63GeV for Ξcc⁎ without taking the heavy quark limit. The masses of Ξbc′, Ξbc(⁎), Ξbb(⁎), Ωcc(⁎), Ωbc′, Ωbc(⁎) and Ωbb(⁎) are also predicted in the same way. We find that the corrections to the results in the heavy quark limit are about −0.02GeV∼−0.11GeV for the masses of the doubly heavy baryons.
Abstract
Based on an exact formulation, we present a master equation approach to transport through Majorana zero modes (MZMs). Within the master equation treatment, the occupation dynamics of the ...regular fermion associated with the MZMs holds a quite different picture from the Bogoliubov–de Gennes (BdG)
S
-matrix scattering process, in which the ‘positive’ and ‘negative’ energy states are employed, while the master equation treatment does not involve them at all. Via careful analysis for the structure of the rates and the rate processes governed by the master equation, we reveal the intrinsic connection between both approaches. This connection enables us to better understand the confusing issue of teleportation when the Majorana coupling vanishes. We illustrate the behaviors of transient rates, occupation dynamics and currents. Through the bias voltage dependence, we also show the Markovian condition for the rates, which can extremely simplify the applications in practice. As future perspective, the master equation approach developed in this work can be applied to study important time-dependent phenomena such as photon-assisted tunneling through the MZMs and modulation effect of the Majorana coupling energy.
We report herein the first examples of chiral phosphoric acid‐catalyzed enantioselective Diels–Alder reactions between 2‐trifluoroacetamido‐1,3‐dienes 1 and α,β‐unsaturated carbonyl compounds 2. ...Polysubstituted 1‐acetamido cyclohexenes 3 were formed in high yields with excellent diastereo‐ and enantioselectivities. The reaction proceeds through a stepwise process as shown by deuterium labelling experiments. A catalytic enantioselective three‐component reaction of 1, 2 and ortho‐hydroxybenzhydryl alcohols 4 was subsequently developed furnishing the densely functionalized hexahydroxanthenes 5 in a highly stereoselective manner. This multicomponent reaction generates four chemical bonds with concurrent creation of five contiguous stereocenters.
CPA‐catalyzed annulation of 2‐trifluoroacetamido‐1,3‐dienes with α,β‐unsaturated carbonyl compounds affords highly functionalized 1‐trifluoroacetamido cyclohex‐1‐ene derivatives 3 in high yields with excellent diastereo‐ and enantioselectivities. An asymmetric three‐component reaction of 1, 2 and ortho‐hydroxybenzhydryl alcohols 4 provides the densely functionalized hexahydroxanthenes with concurrent creation of five contiguous stereocenters.
To identify the epidemiological characteristics and transmission patterns of pediatric patients with the 2019 novel coronavirus disease (COVID-19) in China.
Nationwide case series of 2135 pediatric ...patients with COVID-19 reported to the Chinese Center for Disease Control and Prevention from January 16, 2020, to February 8, 2020, were included. The epidemic curves were constructed by key dates of disease onset and case diagnosis. Onset-to-diagnosis curves were constructed by fitting a log-normal distribution to data on both onset and diagnosis dates.
There were 728 (34.1%) laboratory-confirmed cases and 1407 (65.9%) suspected cases. The median age of all patients was 7 years (interquartile range: 2-13 years), and 1208 case patients (56.6%) were boys. More than 90% of all patients had asymptomatic, mild, or moderate cases. The median time from illness onset to diagnoses was 2 days (range: 0-42 days). There was a rapid increase of disease at the early stage of the epidemic, and then there was a gradual and steady decrease. The disease rapidly spread from Hubei province to surrounding provinces over time. More children were infected in Hubei province than any other province.
Children of all ages appeared susceptible to COVID-19, and there was no significant sex difference. Although clinical manifestations of children's COVID-19 cases were generally less severe than those of adult patients, young children, particularly infants, were vulnerable to infection. The distribution of children's COVID-19 cases varied with time and space, and most of the cases were concentrated in Hubei province and surrounding areas. Furthermore, this study provides strong evidence of human-to-human transmission.
LRRK2 G2019S mutation is the most common genetic cause of Parkinson's disease (PD). Cellular pathology caused by this mutant is associated with mitochondrial dysfunction and augmented autophagy. ...However, the underlying mechanism is not known. In this study, we determined whether blocking excessive mitochondrial fission could reduce cellular damage and neurodegeneration induced by the G2019S mutation. In both LRRK2 G2019S-expressing cells and PD patient fibroblasts carrying this specific mutant, treatment with P110, a selective peptide inhibitor of fission dynamin-related protein 1 (Drp1) recently developed in our lab, reduced mitochondrial fragmentation and damage, and corrected excessive autophagy. LRRK2 G2019S directly bound to and phosphorylated Drp1 at Threonine595, whereas P110 treatment abolished this phosphorylation. A site-directed mutant, Drp1(T595A), corrected mitochondrial fragmentation, improved mitochondrial mass and suppressed excessive autophagy in both cells expressing LRRK2 G2019S and PD patient fibroblasts carrying the mutant. Further, in dopaminergic neurons derived from LRRK2 G2019S PD patient-induced pluripotent stem cells, we demonstrated that either P110 treatment or expression of Drp1(T595A) reduced mitochondrial impairment, lysosomal hyperactivity and neurite shortening. Together, we propose that inhibition of Drp1-mediated excessive mitochondrial fission might be a strategy for treatment of PD relevant to LRRK2 G2019S mutation.
The cobalt‐catalyzed alkoxylation of C(sp2)H bonds in aromatic and olefinic carboxamides has been developed. The reaction proceeded under mild conditions in the presence of Co(OAc)2⋅4H2O as the ...catalyst and tolerates a wide range of both alcohols and benzamide substrates, including even olefinic carboxamides. In addition, this reaction is the first example of the direct alkoxylation of alkenes through CH bond activation.
Alcohols in action: A wide range of alcohols and benzamide substrates functionalized with electron‐rich or electron‐poor substituents are tolerated in the title reaction. This practical reaction occurs under mild conditions.
► Introduce a spatiotemporal model of land use change. ► To manage the spatial distribution of land use, the model uses ant colony optimization and cellular automata to discover the local transition ...rules. ► To control the total amount of land use coverage, the model uses Markov process to predict the transition area matrix of land use.
This paper proposes a spatiotemporal model of land use change based on ant colony optimization (ACO), Markov chain and cellular automata (CA). These three methodologies have previously been used separately or in pairs to simulate land use change. In this paper, we apply them in combination, using ant colony optimization and cellular automata to manage the spatial distribution of land use, and applying Markov chain and cellular automata to manage the total amount of land use coverage. We first describe the principle and implementation of the model. Then a land use map of an experimental area (Changping, a district of Beijing) based on land use maps from 1988 and 1998 is simulated for 2008 using the model. By analyzing with real situation, accuracy of the simulation result manifests that the model is useful for land use change simulation. And compared with the other two models (CA–Markov model and ACO–CA model), the model is more appropriate in predicting both the quantity and spatial distribution of land use change in the study area. Therefore the model proposed by this paper is capable of simulating land use change.
For the past three decades, the coordination-driven self-assembly of three-dimensional structures has undergone rapid progress; however, parallel efforts to create large discrete two-dimensional ...architectures-as opposed to polymers-have met with limited success. The synthesis of metallo-supramolecular systems with well-defined shapes and sizes in the range of 10-100 nm remains challenging. Here we report the construction of a series of giant supramolecular hexagonal grids, with diameters on the order of 20 nm and molecular weights greater than 65 kDa, through a combination of intra- and intermolecular metal-mediated self-assembly steps. The hexagonal intermediates and the resulting self-assembled grid architectures were imaged at submolecular resolution by scanning tunnelling microscopy. Characterization (including by scanning tunnelling spectroscopy) enabled the unambiguous atomic-scale determination of fourteen hexagonal grid isomers.
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