The authors examine research involving organocatalytic asymmetric Morita-Baylis-Hillman/aza-Morita-Baylis-Hillman reactions. The Morita-Baylis-Hillman is a carbon-carbon reaction.
Fifty years have passed since the publication of the first regression tree algorithm. New techniques have added capabilities that far surpass those of the early methods. Modern classification trees ...can partition the data with linear splits on subsets of variables and fit nearest neighbor, kernel density, and other models in the partitions. Regression trees can fit almost every kind of traditional statistical model, including least-squares, quantite, logistic, Poisson, and proportional hazards models, as well as models for longitudinal and multiresponse data. Greater availability and affordability of software (much of which is free) have played a significant role in helping the techniques gain acceptance and popularity in the broader scientific community. This article surveys the developments and briefly reviews the key ideas behind some of the major algorithms.
Photoluminescence of metal-organic frameworks (MOFs) is sensitive to the structure and concentration of chemical species in the surroundings since MOFs combine the advantages of highly ordered porous ...structures, varied luminescence origins and diversified host-guest interactions. The diversity and combination flexibility of the organic and inorganic components together with the voids within MOFs offer ample possibilities for tuning their luminescence properties. On the basis of their intrinsic framework structures and biocompatible building blocks, MOFs have stimulated great interest in the area of biosensors. By elaborating on these points, this review will provide up-to-date developments in luminescent MOFs (LMOFs) with emphasis on synthetic approaches and their application in sensing biomolecules. The design outline of LMOFs including functionalization with fluorescent linkers and metal centers and incorporating fluorescent guest molecules within MOFs is presented, and the sensing properties of LMOFs for biomolecules such as DNA/RNA, enzymes/proteins, amino acids, glucose, ascorbic acid, and antibiotics are summarized.
This review focuses on the recent development of luminescent MOFs with synthetic approaches and their application in sensing biomolecules.
Tandem catalysis is a promising way to break the limitation of linear scaling relationship for enhancing efficiency, and the desired tandem catalysts for electrochemical CO2 reduction reaction ...(CO2RR) are urgent to be developed. Here, a tandem electrocatalyst created by combining Cu foil (CF) with a single‐site Cu(II) metal–organic framework (MOF), named as Cu–MOF–CF, to realize improved electrochemical CO2RR performance, is reported. The Cu–MOF–CF shows suppression of CH4, great increase in C2H4 selectivity (48.6%), and partial current density of C2H4 at −1.11 V versus reversible hydrogen electrode. The outstanding performance of Cu–MOF–CF for CO2RR results from the improved microenvironment of the Cu active sites that inhibits CH4 production, more CO intermediate produced by single‐site Cu–MOF in situ for CF, and the enlarged active surface area by porous Cu–MOF. This work provides a strategy to combine MOFs with copper‐based electrocatalysts to establish high‐efficiency electrocatalytic CO2RR.
A tandem electrocatalyst Cu–MOF–CF by combining Cu foil with Cu–MOF is developed to realize improved C2H4 product selectivity for CO2RR, which is attributed to the improved microenvironment of the Cu active sites that inhibits CH4 production, more CO intermediate produced by single‐site Cu–MOF for CF, and the enlarged active surface area by porous Cu–MOF.
Abstract
Artificial neural network is also referred to as neural network or connection model, it’s a model animal neural network, the mathematical model of distributed and information processing ...algorithm. Because of its good abstract classification, Has been used in all aspects of life. And in recent years, the traditional English teaching mode in colleges and universities has been gradually replaced by CAI new teaching methods, much progress has been made, Increasing resources to open schools and curricula, effectively promote the sharing of quality teaching resources, it promotes the improvement of students’ English listening, speaking, reading, writing and translation. But the general problems of English CAI teaching have gradually emerged, for example, curriculum design does not pay enough attention to individual differences, online teaching lacks interaction between teachers and students, lack of effective supervision and assessment of learning results. At present, the student-centered teaching concept based on the class-flipping classroom and the “online and offline” mixed teaching model is becoming popular, which has had a great impact on the traditional foreign language teaching model. Designing English intelligent computer-assisted teaching (intelligent computer-assisted teaching) can intelligently meet the individual needs of students according to the learning effect, realize the interaction between teachers and students through human-computer interaction, and facilitate the management and evaluation of the teaching process by managers. This is referred to as ICAI. It is an urgent problem in English teaching, especially in the teaching of college English public courses. This paper designs an English ICAI language curriculum system based on BP neural network algorithm and SSH architecture.
•LncRNA-SNHG12 is involved in the response to I/R-induced cerebral injury.•Knockdown of SNHG12 inhibits cell proliferation and induces cell apoptosis in vitro.•miR-199a inhibits cell proliferation ...and induces cell apoptosis of N2a cells under OGD/R condition.•SNHG12 upregulates SIRT1 by inhibiting miR-199a and then activating AMPK pathway.
Cerebral ischemia caused severe disability, and associated with a series of neurological events. Long non-coding RNA SNHG12 was found to be upregulated in mouse brain microvascular endothelial cells by cerebral ischemia. Moreover, it was reported that SNHG12 could directly interact with miR-199a and sirtuin 1 (SIRT1) as a direct target of miR-199a in other diseases. However, the function and mechanism of SNHG12 in cerebral ischemia and reperfusion (I/R) injury of neuronal cells remains unclear. The present study was thus designed to explore the potential effect of SNHG12 and to investigate the underlying mechanism in I/R neuronal cells. we found that
SNHG12 was upregulated in primary neuronal cells and N2a cells and peaked at 12 h and 24 h after OGD/R treatment, respectively. Meanwhile, MTT assay showed that knockdown SNHG12 inhibited cell proliferation under OGD/R condition. And flow cytometry analyses revealed more apoptosis rate was caused by SNHG12 knockdown. Mechanistically, SNHG12 interacted with miR-199a and decreased the expression of miR-199a. Overexpression miR-199a largely inhibited the cell proliferation and induced the cell apoptosis. Meanwhile, SNHG12 was proven to target miR-199a and then activated SIRT1 expression, which finally led to activation of AMPK signaling pathway.
In summary, we demonstrate SNHG12 targets miR-199a to upregulate SIRT1 expression, which attenuates cerebral ischemia/reperfusion injury through AMPK pathway activation. Our findings provide molecular mechanism by which SNHG12 attenuates cerebral I/R injury and facilitate development of therapeautical strategies for treating ischemia-induced stroke.
Catalytic asymmetric synthesis has received considerable attention over the past few decades, becoming a highly dynamic area of chemical research with significant contributions to the field of ...organic synthesis. In the development of new catalysts, the concept of multifunctional catalysis described by Shibasaki and co-workers, namely, the combination of more than one functional group within a single molecule to activate the transformation, has proved a powerful strategy in the design of efficient transition metal-containing catalysts. A variety of reactions have since been addressed with multifunctional organocatalysts. One example is the Morita−Baylis−Hillman (MBH) reaction, in which a carbon−carbon bond is created between the α-position of an activated double-bond compound and a carbon electrophile. The seminal report on this reaction in 1972 described the prototypical couplings of (i) ethyl acrylate with acetaldehyde and (ii) acrylonitrile with acetaldehyde; the reaction is promoted by the conjugate addition of a nucleophilic catalyst to the α,β-unsaturated aldehyde. Many variations of the MBH reaction have been reported, such as the aza-MBH reaction, in which an N-tosyl imine stands in for acetaldehyde. Recent innovations include the development of chiral molecules that catalyze the production of asymmetric products. In this Account, we describe the refinement of catalysts for the MBH and related reactions, highlighting a series of multifunctional chiral phosphines that we have developed and synthesized over the past decade. We also review similar catalysts developed by other groups. These multifunctional chiral phosphines, which contain Lewis basic and Brønsted acidic sites within one molecule, provide good-to-excellent reactivities and stereoselectivities in the asymmetric aza-MBH reaction, the MBH reaction, and other related reactions. We demonstrate that the reactivities and enantioselectivies of these multifunctional chiral phosphines can be adjusted by enhancing the reactive center’s nucleophilicity, which can be finely tuned by varying nearby hydrogen-bonding donors. Artificial catalysts now provide highly economic access to many desirable compounds, but the general adaptability and reactivity of these platforms remain problematic, particularly in comparison to nature’s catalysts, enzymes. The multifunctional organocatalysts described in this Account represent another positive step in the synthetic chemist’s efforts to profitably mimic nature’s catalytic platform, helping develop small-molecule catalysts with enzyme-like reactivities and selectivities.
Rational engineering active sites and vantage defects of catalysts are promising but grand challenging task to enhance photoreduction CO2 to high value‐added C2 products. In this study, we designed ...an N,S‐codoped Fe‐based MIL‐88B catalyst with well‐defined bipyramidal hexagonal prism morphology via a facile and effective process, which was synthesized by addition of appropriate 1,2‐benzisothiazolin‐3‐one (BIT) and acetic acid to the reaction solution. Under simulated solar irradiation, the designed catalyst exhibits high C2H4 evolution yield of 17.7 μmol g−1⋅h, which has been rarely achieved in photocatalytic CO2 reduction process. The synergistic effect of Fe‐N coordinated sites and reasonable defects in the N,S‐codoped photocatalyst can accelerate the migration of photogenerated carriers, resulting in high electron density, and this in turn helps to facilitate the formation and dimerization of C−C coupling intermediates for C2H4 effectively.
The integration of new active sites with beneficial defects in Fe‐MOF MIL‐88B catalysts gives enhanced photoreduction of CO2 to C2H4 under visible light. The modified structure promotes the migration and separation of the photoelectrons to produce the pivotal C−C coupling intermediate for the generation of C2H4, a result supported by in situ FT‐IR analysis.
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