The first example of highly enantioselective fluoroarylation of gem‐difluoroalkenes with aryl halides is presented by using a new chiral sulfinamide phosphine (Sadphos) type ligand TY‐Phos. ...N‐Me‐TY‐Phos can be easily synthesized on a gram scale from readily available starting materials in three steps. Salient features of this work including readily available starting materials, good yields, high enantioselectivities as well as broad substrate scope make this approach very practical and attractive. Notably, the asymmetric synthesis of an analogue of a biologically active molecule is also reported.
Highly enantioselective fluoroarylation of gem‐difluoroalkenes with aryl halides is presented by using a new chiral sulfinamide phosphine (Sadphos) type ligand (TY‐Phos). The salient features of this reaction include readily available starting materials, high yields and enantioselectivity, and broad substrate scope.
Abstract
This paper summarizes the development and application experience of computer aided design software for control system. Discusses how to arrange interaction with users with extensive ...experience. This includes question and answer dialog boxes using macro tools and different types of menu driven systems. A set of software packages for modeling, identification, analysis, simulation and design are described. The problems related to architecture, portability, and maintainability and extensible are discussed. Experience in developing and using software packages in teaching and industrial environments.
Heavy metal ions are highly toxic and widely spread as environmental pollutants. New strategies are being developed to simultaneously detect and remove these toxic ions. Herein, we take the intrinsic ...advantage of covalent organic frameworks (COFs) and develop fluorescent COFs for sensing applications. As a proof-of-concept, a thioether-functionalized COF material, COF-LZU8, was “bottom-up” integrated with multifunctionality for the selective detection and facile removal of mercury(II): the π-conjugated framework as the signal transducer, the evenly and densely distributed thioether groups as the Hg2+ receptor, the regular pores facilitating the real-time detection and mass transfer, together with the robust COF structure for recycle use. The excellent sensing performance of COF-LZU8 was achieved in terms of high sensitivity, excellent selectivity, easy visibility, and real-time response. Meanwhile, the efficient removal of Hg2+ from water and the recycling of COF-LZU8 offers the possibility for practical applications. In addition, X-ray photoelectron spectroscopy and solid-state NMR investigations verified the strong and selective interaction between Hg2+ and the thioether groups of COF-LZU8. This research not only demonstrates the utilization of fluorescent COFs for both sensing and removal of metal ions but also highlights the facile construction of functionalized COFs for environmental applications.
•The machinery prognostic program is divided into four technical processes.•The four technical processes are reviewed systematically in order.•Some typical public datasets for prognostics are ...summarized.•The health indicator construction and health stage division processes are reviewed.•This paper gives a comprehensive review through analyzing large amount of references.
Machinery prognostics is one of the major tasks in condition based maintenance (CBM), which aims to predict the remaining useful life (RUL) of machinery based on condition information. A machinery prognostic program generally consists of four technical processes, i.e., data acquisition, health indicator (HI) construction, health stage (HS) division, and RUL prediction. Over recent years, a significant amount of research work has been undertaken in each of the four processes. And much literature has made an excellent overview on the last process, i.e., RUL prediction. However, there has not been a systematic review that covers the four technical processes comprehensively. To fill this gap, this paper provides a review on machinery prognostics following its whole program, i.e., from data acquisition to RUL prediction. First, in data acquisition, several prognostic datasets widely used in academic literature are introduced systematically. Then, commonly used HI construction approaches and metrics are discussed. After that, the HS division process is summarized by introducing its major tasks and existing approaches. Afterwards, the advancements of RUL prediction are reviewed including the popular approaches and metrics. Finally, the paper provides discussions on current situation, upcoming challenges as well as possible future trends for researchers in this field.
Enantiomerically enriched indole-containing heterocycles play a vital role in bioscience, medicine, and chemistry. As one of the most attractive subtypes of indole alkaloids, highly substituted ...tetrahydro-γ-carbolines are the basic structural unit in many natural products and pharmaceuticals. However, the syntheses of tetrahydro-γ-carbolines with high functionalities from readily available reagents are significant challenging. In particular, the stereodivergent syntheses of tetrahydro-γ-carbolines containing multi-stereogenic centers remain quite difficult. Herein, we report an expedient and stereodivergent assembly of tetrahydro-γ-carbolines with remarkably high levels of stereoselective control in an efficient cascade process from aldimine esters and indolyl allylic carbonates via a synergistic Cu/Ir catalyst system. Control experiments-guided optimization of synergistic catalysts and mechanistic investigations reveal that a stereodivergent allylation reaction and a subsequent highly stereoselective iso-Pictet-Spengler cyclization are the key elements to success.
•A new core building block, i.e., recurrent convolutional layer, is built to learn the temporal dependencies from time-series sensor data, which enables the prognostics network to effectively ...memorize useful degradation information over time and thus enhances its representation ability.•A probabilistic RUL prediction result is obtained based on variational inference, which breaks the inherent limitation of convolutional neural networks and is beneficial to maintenance decision making.•A systematic prognostics framework named recurrent convolutional neural network is proposed for RUL prediction of machinery, and its effectiveness and superiority are verified by two case studies, i.e., RUL prediction of rolling element bearings and RUL prediction of milling cutters.
Deep learning is becoming more appealing in remaining useful life (RUL) prediction of machines, because it is able to automatically build the mapping relationship between the raw data and the corresponding RUL by representation learning. Among deep learning models, convolutional neural networks (CNNs) are gaining special attention because of its powerful ability in dealing with time-series signals, and have achieved promising results in current studies. These studies, however, suffer from the two limitations: (1) The temporal dependencies of different degradation states are not considered during network construction; and (2) The uncertainty of RUL prediction results cannot be obtained. To overcome the above-mentioned limitations, a new framework named recurrent convolutional neural network (RCNN) is proposed in this paper for RUL prediction of machinery. In RCNN, recurrent convolutional layers are first constructed to model the temporal dependencies of different degradation states. Then, variational inference is used to quantify the uncertainty of RCNN in RUL prediction. The proposed RCNN is evaluated using vibration data from accelerated degradation tests of rolling element bearings and sensor data from life testing of milling cutters, and compared with some state-of-the-art prognostics approaches. Experimental results demonstrate the effectiveness and superiority of RCNN in improving the accuracy and convergence of RUL prediction. More importantly, RCNN is able to provide a probabilistic RUL prediction result, which breaks the inherent limitation of CNNs and facilitates maintenance decision making.
The efficient construction of enantiomerically enriched molecules from simple starting materials via catalytic asymmetric synthesis strategies is a key challenge in synthetic chemistry. Metallated ...azomethine ylides are commonly-used synthons for the preparation of N-heterocycles and α-amino acids. Remarkably, to date, the utilization of azomethine ylides for the facile access to chiral amines has proven elusive. Here, we report that a synergistic Cu/Ir-catalytic system combined with careful tuning of the steric congestion can be used to convert aldimine esters to a variety of chiral homoallylic amines via a cascade allylation/2-aza-Cope rearrangement. The elucidation of the distinct effects of each stereogenic center of the allylation intermediates on the stereochemical outcome and chirality transfer in the rearrangement further guided the selection of catalysts combination.
This data presented in this article pertain to measured data obtained from earth pressure balance (EPB) shield tunelling of Guangzhou-Foshan intercity railway project. The measured data consists of ...geological characteristics and the main shield parameters in each lining ring during shield tunnelling. The distribution of raw data was displayed, and the geological characteristics via field record were compared to the prediction results of improved stacking method. The value of the database is consideration of the relationship between shield operational parameters and geological characteristics encountered in the shield tunnelling area, including formations with soft soil, majority of soft soil, and majority of hard rock. The raw data was standardized and processed to low dimensional data by principal component analysis, which can be better used in geological characteristics classification. The presented data are applied to identify the geological characteristics in the article titled “Prediction of geological characteristics from shield operational parameters by integrating grid search and K-fold cross validation into stacking classification algorithm”.
Impressive progress has been made in the copper‐catalyzed asymmetric propargylic substitution (APS) reaction, but its use in remote asymmetric yne‐allylic substitution remains a challenging topic. ...Herein, we report the first remote enantioselective copper‐catalyzed sulfonylation of yne‐allylic esters with sodium sulfinates. The reaction is assumed to occur via a copper‐vinylvinylidene species as the key reactive intermediate. The use of readily available starting materials, the mild reaction conditions, and the excellent regio‐, enantio‐ and stereoselectivity, as well as broad substrate scope (>70 examples), show the practicality and attractiveness of this method.
An enantioselective copper‐catalyzed reaction was developed for the sulfonylation of yne‐allylic esters with sodium sulfinates. Salient features of this practical method include readily available starting materials, mild reaction conditions, excellent regio‐, enantio‐ and diastereoselectivity, as well as broad substrate scope.
For screening the active phloroglucinols on influenza virus (H5N1) from
NaKai, a database was established including twenty-three phloroglucinols that had been isolated from
. Their inhibitory effect ...on the neuraminidase (NA) of influenza virus H5N1 was screened by molecular docking. As a result, three candidates were selected. The rhizomes of
were subjected to isolation and purification processes to obtain the inhibitor candidates. Thirteen phloroglucinols were obtained, including three selected candidates and two new phloroglucinols. The five phloroglucinols were investigated for their inhibitory activity on NA in vitro. The results showed that dryocrassin ABBA and filixic acid ABA exhibited inhibitory effects on NA with IC
as 18.59 ± 4.53 and 29.57 ± 2.48 μM, respectively, and the other three phloroglucinols showed moderate inhibitory activity. Moreover, the anti-influenza virus (H5N1) activity and cytotoxicity of dryocrassin ABBA and filixic acid ABA were tested on Madin-Darby canine kidney (MDCK) cells with the cell counting kit-8 (CCK8) method. The results confirmed that dryocrassin ABBA exhibited an inhibitory activity with low cytotoxicity (TC
> 400 μM) against influenza virus (H5N1) which will have to be investigated in further detail. In conclusion, phloroglucinols from
were shown to have anti-influenza virus activity, and especially dryocrassin ABBA, one of the phloroglucinols, may have the potential to control influenza virus (H5N1) infection.
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