Palladium‐catalyzed enantioselective dearomative arylalkynylation of N‐substituted indoles, through a Heck/Sonogashira sequence, was established using a new BINOL‐based phosphoramidite as the chiral ...ligand. A wide range of 2,3‐disubstituted indolines, bearing vicinal quaternary and tertiary stereocenters, were efficiently constructed in one step with excellent enantioselectivities (up to 97 % ee) and diastereoselectivities (>20:1).
Double the function: A highly enantioselective dearomative arylalkynylation of N‐substituted indoles with alkynes has been established by using palladium and a BINOL‐based phosphoramidite as the chiral ligand. A wide range of 2,3‐disubstituted indolines, bearing vicinal tertiary and quaternary stereocenters, were constructed in one step with excellent enantio‐ and diastereoselectivities.
Polymer dielectrics are highly desirable in capacitor applications due to their low cost, high breakdown strength, and unique self‐healing capability. However, existing polymer dielectrics suffer ...from either a low energy density or a high dielectric loss, thereby hindering the development of compact, efficient, and reliable power electronics. Here, a novel type of polymer dielectrics simultaneously exhibiting an extraordinarily high recoverable energy density of 35 J cm−3 and a low dielectric loss is reported. It is synthesized by grafting zwitterions onto the short side chains of a poly(4‐methyl‐1‐pentene) (PMP)‐based copolymer, which increases its dielectric constant from ≈2.2 to ≈5.2 and significantly enhances its breakdown strength from ≈700 MV m−1 to ≈1300 MV m−1 while maintaining its low dielectric loss of <0.002 and high charge–discharge efficiency of >90%. Based on a combination of the phase‐field method description of mesoscale structures, Maxwell equations, and theoretical analysis, it is demonstrated that the outstanding combination of high energy density and low dielectric loss of zwitterions‐grafted copolymers is attributed to the covalent‐bonding restricted ion polarization and the strong charge trapping by the zwitterions. This work represents a new strategy in polymer dielectrics for achieving simultaneous high energy density and low dielectric loss.
Zwitterion‐functionalized polymers are synthsized with a record‐high breakdown strength of 1300 MV m−1, energy density above 35 J cm−3, and charge–discharge efficiency of >90%, taking advantage of the covalent‐bonding‐restricted ion polarization and the charge trapping of the ion cluster phase.
This article introduces and explores, for the first time in any Western language, the gilded-silver xiangnang 香囊 (spherical incense burner) from Famen Temple, one of the largest xiangnang incense ...burners found in the Tang dynasty. The spherical incense burner evolved from censers for bedclothes known as beizhong xianglu 被中香爐 (literally “perfume burner to be placed among the covers of the bed, used as a warming device), which are chronicled as early as the Han dynasty in texts such as Xijing zaji 西京雜記 (Miscellaneous Records of the Western Capital). The silver spherical incense burner spread from China to the Islamic world and Venice, possibly influencing the development of the gyroscope for maritime navigation in Europe. This paper further examines the spherical incense burner’s relation to a device known as the Cardan Suspension (used to facilitate seafaring) and to the ritual of incense burning (imagined as a way to figuratively reach another world). It also discusses the spherical incense burner’s impact on similar objects from the Islamic world and Venice.
The rubric of the presence of Buddhist sculpture in the absence of an actual deity represents an admirable aspect of Buddhist art, especially sculpture, where the best works have drawn on this ...paradox in an astounding fashion. An important element in the realization of this religious archetype is the Buddhist statues’ sublime poses. This article demonstrates the Buddhist posture hierarchy, based on a case study of a Tang-Dynasty Chinese Buddhist Bronze collected by the Pulitzer Arts Foundation, the posture of which is identified as lalitāsana: one leg pendant and the other bent horizontally. This article shows how this pose engendered various other compositional situations and postures popular in East Asia icon design and, moreover, that this sculpture might form part of an assemblage, where the pose indicates the central Buddha figure, to which all of the other figures are formally and doctrinally posed following a hierarchy. This article argues that Buddhist figures of different religious ranks are characterized by their pose and degree of movement. This research proves that the myriad forms of Buddhist postures and hierarchy have been devised to illustrate mythologies and philosophical, doctrinal, or social concepts, and their representations, in turn, have engendered other myths and beliefs.
The discovery of the Northern Zhou (557–581AD) tomb of Shi Jun (494–579 CE) presents us with spectacular visual information about the Sogdians in medieval China, which was previously available to us ...only through written sources. The iconography-heavy sarcophagus in the tomb is an important vehicle for understanding the practices of religious (and everyday) life in the Sino-Sogdian community. The imagery on the Shi Jun sarcophagus reveals a mix of religious beliefs that existed among migrants in the premodern Eurasian world. Due to the absence of a dominant religion associated with Sino-Sogdian funerals, the iconography of the sarcophagus cannot be interpreted within an orthodox theological framework. Instead, it is possible that more syncretistic, indigenous, and regionally based folklore, tales, and hymns, in combination with a diversity of religious beliefs, might explain the sarcophagus’s enigmatic imagery, since the social order and religious order are often mutually reinforcing.
Carbonized bamboo‐derived carbon nanodots (CNDs) as efficient additives for application in perovskite solar cells (PSCs) are reported. These carboxylic acid‐ and hydroxyl‐rich CNDs interact with the ...perovskite through hydrogen bonds and, thereby, promote the carriers' lifetimes and realize high‐performance p–i–n PSCs having the structure indium tin oxide/NiOx/CH3NH3PbI3 (MAPbI3)/PC61BM/BCP/Ag. As a result of interactions between the CNDs and the perovskite, the presence of the nonvolatile CND additive increases the power conversion efficiency (PCE) of the PSC from 14.48% ± 0.39% to 16.47% ± 0.26%. Furthermore, adding urea, a Lewis base, increases the PCE to 20.2%—the result of a significant increase in the crystal size and a lower content of grain boundary defects and, therefore, longer carrier lifetimes. Cells containing these two additives (without encapsulation) exhibit excellent shelf‐life and air‐stability, maintaining their high PCEs after storage in air—at a temperature of 25 °C and a humidity of 40%—for over 500 h. This performance is among of the best ever reported for p–i–n PSC devices incorporating carbon‐based additives.
High‐performance air‐stable perovskite solar cells are obtained after embedding carbon nanodots and urea into the perovskite. The best device performance features a power conversion efficiency of 20.2%, with negligible hysteresis. The devices displays excellent air‐stability for over 500 h without any encapsulation under 40% humidity (25 °C).
Chemical compound space (CCS), the set of all theoretically conceivable combinations of chemical elements and (meta-)stable geometries that make up matter, is colossal. The first-principles based ...virtual sampling of this space, for example, in search of novel molecules or materials which exhibit desirable properties, is therefore prohibitive for all but the smallest subsets and simplest properties. We review studies aimed at tackling this challenge using modern machine learning techniques based on (i) synthetic data, typically generated using quantum mechanics based methods, and (ii) model architectures inspired by quantum mechanics. Such Quantum mechanics based Machine Learning (QML) approaches combine the numerical efficiency of statistical surrogate models with an ab initio view on matter. They rigorously reflect the underlying physics in order to reach universality and transferability across CCS. While state-of-the-art approximations to quantum problems impose severe computational bottlenecks, recent QML based developments indicate the possibility of substantial acceleration without sacrificing the predictive power of quantum mechanics.
In this letter, a low-profile four-port microstrip patch antenna (MPA) with wide isolation bandwidth and same polarization is proposed by using characteristic mode analysis. Firstly, the internal ...electric-field and modal significance (MS) of the shorted two-port MPA are theoretically studied. It shows that the null point of its internal electric-field can be reallocated to the unexcited feeding port by combining different modes. As such, the specific pins1, pins2, pins3 are loaded so as to gain three minimum poles for mutual coupling reduce. After that, the pins4 are further inserted to move these three minimum poles closely to each other, resulting in wideband isolation and broadside-beam. In addition, ring slots is etched to improve its input impedance. In final, our proposed four-port MPA is designed and tested. The results prove that its isolation bandwidth (| S 11 | of -10 dB and isolation of above 20 dB) is obviously extended to about 16.2%, while keeping the broadside pattern with same polarization. Additionally, the MPA remains low-profile (0.06λ0), single-layer, and single-radiator.
Approximately 30% of patients with Epstein-Barr virus (EBV)-positive advanced nasopharyngeal carcinoma (NPC) display chemoresistance to cisplatin-based regimens, but the underlying mechanisms are ...unclear. The Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1), a functional homologue of the tumor necrosis factor receptor family, contributes substantially to the oncogenic potential of EBV through the activation of multiple signaling pathways, and it is closely associated with a poorer prognosis for NPC. Recent studies show that EBV infection can induce the expression of many cellular miRNAs, including microRNA-21, a biomarker for chemoresistance. However, neither a link between LMP1 expression and miR-21 upregulation nor their cross talk in affecting chemoresistance to cisplatin have been reported. Here, we observed that stable LMP1-transformed NPC cells were less sensitive to cisplatin treatment based on their proliferation, colony formation, the IC50 value of cisplatin and the apoptosis index. Higher levels of miR-21 were found in EBV-carrying and LMP1-positive cell lines, suggesting that LMP1 may be linked to miR-21 upregulation. These data were confirmed by our results that exogenous LMP1 increased miR-21 in both transiently and stably LMP1-transfected cells, and the knock down of miR-21 substantially reversed the resistance of the NPC cells to cisplatin treatment. Moreover, the proapoptotic factors programmed cell death 4 (PDCD4) and Fas ligand (Fas-L), which were negatively regulated by miR-21, were found to play an important role in the program of LMP1-dependent cisplatin resistance. Finally, we demonstrated that LMP1 induced miR-21 expression primarily by modulating the PI3K/AKT/FOXO3a signaling pathway. Taken together, we revealed for the first time that viral LMP1 triggers the PI3K/Akt/FOXO3a pathway to induce human miR-21 expression, which subsequently decreases the expression of PDCD4 and Fas-L, and results in chemoresistance in NPC cells.
PDF
