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Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals have attracted increasing attention in electro-optic and nonlinear optical applications. In this paper, it was found that the domain configuration of PMN–PT single crystals was influenced by machining and electric process, such as cutting, grinding, polishing, and electrical field poling. The ordered herringbone/stripe domain pattern can be changed into an unexpected disordered domain state in tetragonal PMN–PT crystals which was observed in some crystal samples. Those chaotic structures can decrease transmittance and increase possibility of cracking during poling. However, the disordered domain pattern can be eliminated by a temperature cycling process. Crack-free single-domain crystals were successfully obtained by electric field poling, exhibiting complete optical extinction in an orthogonal polarized light microscope. The results suggest that the domain configuration of PMN–PT single crystals is sensitive to machining process and can be controlled by proper temperature and electric field. [ABSTRACT FROM AUTHOR]

The low uniformity in properties of relaxor ferroelectric crystals is a long‐standing issue in the ferroelectric community, which limits the available volume of the entire crystal boule. The aim of this study is to develop a relaxor ferroelectric crystal with improved property uniformity and excellent piezoelectricity. To this end, Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 is doped with Nd2O3 (Nd–PIN–PMN–PT) to improve the crystal performance. Along the crystal boule, the piezoelectric coefficient d33 varies from 2800 to 3500 pC N−1, and the dielectric constant ranges from 8400 to 9800, with variations of 25% and 16%, respectively. Such high property uniformity results in over 75% available volume of the crystal boule, compared to 30–50% for undoped crystals grown by Bridgman method. At the electric field of 1 kV cm−1, the converse piezoelectric response is up to 4780 pm V−1. In addition, its Curie temperature (TC) and coercive field (EC) are above 150 °C and 3 kV cm−1, respectively. Compared with Pb(Mg1/3Nb2/3)O3–PbTiO3 crystal (d33: 1500 pC N−1, TC: 135 °C, EC: 2.3 kV cm−1), the larger piezoelectricity, the higher TC and EC, and improved uniformity make Nd–PIN–PMN–PT crystals promising candidates for advanced piezoelectric applications. [ABSTRACT FROM AUTHOR]

The diastereo‐ and enantioselective construction of vicinal all‐carbon quaternary stereocenters is a formidable task. We here report a synergistic bimetallic catalysis via a chiral N,N′‐dioxide‐europium (Eu) complex and a phosphoramidite‐iridium (Ir) catalyst for the asymmetric allylation of oxindole derivatives by using challenging trisubstituted allylic esters. The allylated products bearing vicinal all‐carbon quaternary stereocenters were obtained with good diastereoselectivities (up to 20 : 1 dr) and excellent enantioselectivities (up to 99 % ee). Control experiments showed that the complementary diastereomers of the products were not accessible by the change of the stereochemistry of the chiral N,N′‐dioxide ligand. [ABSTRACT FROM AUTHOR]

The ubiquity of sulfur‐containing molecules in biologically active natural products and pharmaceuticals has long attracted synthetic chemists to develop efficient strategies towards their synthesis. The strategy of direct α‐C(sp3)−H modification of sulfides provides a streamlining access to complex sulfur‐containing molecules. Herein, we report a photoinduced chemo‐, site‐ and stereoselective α‐C(sp3)−H functionalization of sulfides using isatins as the photoredox reagent and coupling partner catalyzed by a chiral gallium(III)‐N,N′‐dioxide complex. The reaction proceeds through a verified single‐electron transfer (SET) mechanism with high efficiency, excellent functional group tolerance, as well as a broad substrate scope. Importantly, this cross‐coupling protocol is highly selective for the direct late‐stage functionalization of methionine‐related peptides, regardless of the inherent structural similarity and complexity of diverse residues. [ABSTRACT FROM AUTHOR]

Relaxor‐PbTiO3 crystals exhibit excellent piezoelectric properties (d33 > 2000 pC N−1 and k33 > 90%) and thus attractes widespread attention in the past two decades. However, the inevitable segregation of components during the crystal growth results in relatively low‐performance consistency of Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) crystals, which seriously affects their practical applications. In this work, Nd3+ as A‐site substitution is introduced to improve the uniformity of electromechanical performance of PMN‐PT crystal. The results show that the crystal exhibits a high piezoelectric coefficient of 3000 pC N−1 in rhombohedral phase with a variation of 36%. The electron probe X‐ray microanalyzer indicates that the opposite separation characteristics of Nd3+ and Ti4+ lead to improved uniformity of piezoelectric performance along the crystal boule. The giant piezoelectricity in Nd‐doped PMN‐PT is attributed to the enhanced local structural heterogeneity introduced by doping Nd. Furthermore, the Nd‐doped PMN‐PT crystal shows the rhombohedral‐tetragonal phase transition temperature in the range of 74–87 °C, which indicates that Nd‐doped PMN‐PT crystal can be a promising candidate for the design of advanced piezoelectric transducers. [ABSTRACT FROM AUTHOR]

An asymmetric allylic C−H functionalization has been developed by making use of transient chiral nucleophiles, as well as bimetallic synergistic catalysis with an achiral Pd0catalyst and a chiral N,N′‐dioxide‐CoIIcomplex. A variety of β‐ketoesters and N‐Boc oxindoles coupled with allylbenzenes and aliphatic terminal alkenes were well tolerated, furnishing the desired allylic alkylation products in high yields (up to 99 %) with excellent regioselectivities and enantioselectivities (up to 99 % ee). [ABSTRACT FROM AUTHOR]

Relaxor-PbTiO3 (PT-based) ferroelectric single crystals are important for many piezoelectric applications because of their outstanding performances. In order to expand their usage and avoid the failure during application, frequency dependence of coercive fields EC for [001]- and [011]-poled rhombohedral Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals was investigated from the frequency of 1 Hz to 300 kHz by using hysteresis loop measurement (frequency: from 1 Hz to 2 kHz) and a critical value method (frequency: from 5 to 300 kHz). The results showed that the coercive field EC, remnant polarization Pr, and saturation polarization Ps strongly depended on the crystal orientation and frequency. Compared with the [001]-poled crystals, the [011]-poled PIN-PMN-PT single crystals possessed higher EC, Pr, and Ps at the same testing frequencies. With increasing frequency from 1 Hz to 300 kHz, the coercive fields EC of the [001]- and [011]-poled PIN-PMN-PT single crystals increased from 4.0 and 4.8 kV/cm to 11.5 and 14.9 kV/cm, respectively. Moreover, the frequency dependence of the coercive fields was found to be consistent with the growth kinetics model, where the coercive fieldsEC were proportional to ƒβ. This work benefits to the design of piezoelectric devices based on PIN-PMN-PT single crystals operated at high frequencies and high driving fields. [ABSTRACT FROM AUTHOR]

To date, the complete sets of electromechanical-related coefficients of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals have been reported only at room temperature (RT). To meet the demands of practical applications, the full sets of elastic, piezoelectric, and dielectric constants of [001]-poled rhombohedral PIN-PMN-PT single crystals were measured as a function of temperature ranging from −10 °C to 70 °C by the resonance method. Variation trends of the material constants with temperature are discussed, and the corresponding mechanisms are analyzed. With increasing temperature, absolute values of the elastic compliance constants, the piezoelectric coefficients $d_{\mathrm {ij}}$ , and the dielectric permittivities $\varepsilon _{\mathrm {ij}}$ increase, but the piezoelectric voltage coefficients $g_{\mathrm {ij}}$ and the characteristic frequencies decrease. The electromechanical coupling factors $k_{\mathrm {ij}}$ are not sensitive to temperature, of which $k_{33}$ keeps 91% in the temperature range of −10 °C to 70 °C. Compared with other coefficients, the piezoelectric coefficients $d_{31}$ , $d_{33}$ , and $d_{15}$ , and the dielectric permittivities $\varepsilon _{11}^{T}$ , $\varepsilon _{33}^{T}$ , $\varepsilon _{11}^{S}$ , and $\varepsilon _{33}^{S}$ , show the largest enhancements with increasing temperature. For example, the piezoelectric coefficients $d_{31}$ and $d_{33}$ , and the dielectric permittivities $\varepsilon _{11}^{T}$ and $\varepsilon _{33}^{T}$ change from −560 pC/N, 1130 pC/N, 1050, and 3300 at −10 °C to −890 pC/N, 1700 pC/N, 2030, and 6140 at 70 °C, increasing by more than 50% from −10 °C to 70 °C. [ABSTRACT FROM AUTHOR]

Abstract: To explore new relaxor‐PbTiO3 systems for high‐power and high‐temperature electromechanical applications, a ternary ferroelectric ceramic system of Pb(Lu1/2Nb1/2)O3–Pb(In1/2Nb1/2)O3–PbTiO3 (PLN–PIN–PT) have been investigated. The phase structure, dielectric, piezoelectric, and ferroelectric properties of the as‐prepared PLN–PIN–PT ceramics near the morphotropic phase boundary (MPB) were characterized. A high rhombohedral‐tetragonal phase transition temperature TR‐T of 165°C and a high Curie temperature TC of 345°C, together with a good piezoelectric coefficient d33 of 420 pC/N, were obtained in 0.38PLN–0.20PIN–0.42PT ceramics. Furthermore, for (0.8−x)PLN–0.2PIN–xPT ceramics, the temperature‐dependent piezoelectric coefficients, coercive fields and electric‐field‐induced strains were further studied. At 175°C, their coercive fields were found to be above 9.5 kV/cm, which is higher than that of PMN–PT and soft P5H ceramics at room temperature, indicating PLN–PIN–PT ceramics to be one of the promising candidates in piezoelectric applications under high‐driven fields. The results presented here could benefit the development of relaxor‐PbTiO3 with enhanced phase transition temperatures and coercive fields. [ABSTRACT FROM AUTHOR]

Abstract: An atypical guanine exchange factor, Dock2 is specifically expressed in hematopoietic cells and regulates activation and migration of immune cells through activating Ras‐related C3 botulinum toxin substrate (Rac). Dock2 was shown to be critical in the development of various inflammatory diseases, including allergic diseases, HIV infection, and graft rejection in organ transplantation. DOCK2 mutation in infants was recently identified to be associated with T and B cell combined immunodeficiency. Furthermore, Dock2 is involved in host protection during enteric bacterial infection and is also associated with the proliferation of cancer cells. It was also shown that patients with digestive tract cancer had high frequency mutation of DOCK2. This review summarizes the latest research progresses on the role of Dock2 for the development of various inflammatory diseases and cancers, and discusses the potential application of Dock2 modulators for patient treatment. [ABSTRACT FROM AUTHOR]

A biomimetic total synthesis of racemic homodimericin A was achieved in seven steps, including two cascade reactions. Aqueous buffer solutions are found to help both the oxidative dimerization cascade and the intramolecular Diels-Alder cascade. This synthetic sequence validates key steps in the biogenetic proposal of homodimericin A. [ABSTRACT FROM AUTHOR]

The measurement of risk perception and risk attitudes, and their link to actual risk behaviors have been extensively discussed. However, the potential impact of perception of risk management instruments on the decision to use those instruments has rarely been addressed. This article hypothesizes that the degree of perception of insurance contracts and participation decisions could have substantial mutual influence depending on the development of the market. An empirical work is carried out based on a survey of data for paddy rice farmers in Hunan Province, China. It shows that the sampled farmers’ crop insurance perception was surprisingly low despite years of pilot programs and tens of billions of expenditure in government subsidies. The result of simultaneous equations model indicates that crop insurance perception and participation are simultaneously determined and mutually improving. Moreover, empirical evidence indicates that the impact of crop insurance participation on perception is slightly stronger than that of perception on participation, and thus provides weak evidence of a ‘learning-by-doing’ stage in China at present. Together with evidence of substantial local disparities in perception, implications for the Chinese government in further cultivating the crop and rural insurance market are discussed. [ABSTRACT FROM AUTHOR]

The availability of enantiomerically enriched 1,3-dienyl substituted quaternary stereocenters is highly valuable for the synthesis of complex natural compounds. Despite great advances in the area of construction of alkenyl-substituted types, a general, practical catalytic system that works for enantioselective formation of 1,3-diene derivatives still remains to be developed. Herein, we disclose the first asymmetric Claisen rearrangement of allenyl vinyl ethers to access optically active β-ketoesters, containing branched 1,3-butadienyl substituted stereocenters. A variety of substrates bearing a range of useful functional groups were well tolerated, thus affording the corresponding products with excellent enantioselectivities (up to 99% ee) and high yields (up to 91%). [ABSTRACT FROM AUTHOR]

Highly efficient kinetic resolution of 2 H-azirines by an asymmetric imine amidation was achieved in the presence of a chiral N, N′-dioxide/ScIII complex, thus providing a promising method to obtain the enantioenriched 2 H-azirine derivatives and protecting-group free aziridines at the same time. It is rare to find an example of N1 of an oxindole participating in a reaction over C3. Moreover, chiral 2 H-azirines were stereospecifically transformed into an unprotected aziridine and α-amino ketone. [ABSTRACT FROM AUTHOR]

The asymmetric propargyl Claisen rearrangement provides a convenient entry to chiral allene motifs. Herein, we describe the development of a kinetic resolution and asymmetric rearrangement of racemic propargyl vinyl ethers. This transformation afforded chiral allene products along with the enantiomerically enriched substrate in good yields with excellent diastereo- and enantioselectivity. The complete chirality transfer and facially selective rearrangement enabled the simultaneous construction of an axially chiral allenic unit and a quaternary carbon stereocenter. [ABSTRACT FROM AUTHOR]

Highly efficient catalytic asymmetric Claisen rearrangements of O-propargyl β-ketoesters and O-allyl β-ketoesters have been accomplished under mild reaction conditions. In the presence of the chiral N,N'-dioxide/NiII complex, a wide range of allenyl/allyl-substituted all-carbon quaternary β-ketoesters was obtained in generally good yield (up to 99%) and high diastereoselectivity (up to 99:1 d.r.) with excellent enantioselectivity (up to 99% ee). [ABSTRACT FROM AUTHOR]

A highly efficient N,N′-dioxide-scandium(III) complex catalytic system has been developed for the asymmetric vinylogous Michael reaction of α-angelica lactone and its derivatives to α,β-unsaturated γ-keto esters, affording the corresponding γ,γ-disubstituted butenolide products in moderate to good yields (up to 93%) with high dr (up to >19:1) and ee values (up to 97%) under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Abstract: Intrusion detection using sequential pattern mining is a research focusing on the field of information security. This paper first introduces several common sequential pattern mining algorithms, and then expounds its current development with comparisons about the merits and shortcomings with the current mainstream technologies, at the same time, presenting some further discussion upon the future direction of the sequential pattern mining algorithms based intrusion detection. [Copyright &y& Elsevier]

Abstract: The asymmetric domino three-component Knoevanagel-Diels–Alder addition (ATCDA) reaction, as an important methodology, has been utilized to construct complex product from ordinary starting materials. In this report, many typical organoamine catalysts were investigated to achieve highly efficient asymmetric three-component reaction of enones 2, aldehydes 3 and Meldrum’s acid 4. Various pharmacological multi-substituted spiro[5,5]undecane-1,5,9-triones promoted by 9-amino-9-deoxy-epi-quinine 1 g in one-pot, were obtained in moderate to good yields (up to 81%) with excellent diastereo-(>99:1 dr) and enantioselectivities (up to 97% ee). Meanwhile, based on the controlled experiments and analytical data, a reasonable mechanism of dual-activity for this reaction has been proposed. [Copyright &y& Elsevier]

An asymmetric inverse-electron-demand hetero-Diels–Alder reaction between o-quinone methides and azlactones to generate potentially pharmacological active dihydrocoumarins has been achieved efficiently by using a chiral N,N′-dioxide–Sc(iii) complex as the catalyst. The desired products were obtained in high yields with excellent enantioselectivities and diastereoselectivities (up to 94% yield, 96% ee and ＞19 : 1 dr) under mild reaction conditions. A concerted reaction pathway was confirmed by Operando IR and control experiments. [ABSTRACT FROM AUTHOR]

Review: 54 refs + subrefs. [ABSTRACT FROM AUTHOR]

The title reaction affords spirocyclopropane-oxindoles with contiguous tertiary and quaternary centers in high yields with excellent diastereo- and enantioselectivities through a stepwise biradical mechanism. [ABSTRACT FROM AUTHOR]

The kinetic resolution of racemic propargyl vinyl ethers (I) through an enantioselective Claisen rearrangement affords chiral allenes (II) and enantiopure ethers (S)-(I). [ABSTRACT FROM AUTHOR]

The novel hierarchical S-scheme heterojunction of MoS 2 /Zn 0.5 Cd 0.5 S was designed and fabricated, which possesses an improved photocatalytic hydrogen evolution performance of 33.8 mmol‧g−1‧h−1, about 16 times and 786 times more than single ZnCdS and MoS 2. The unique S-scheme hierarchical structure greatly promotes the utilization of the visible spectrum, shortens the distance of the carrier's movement, and improves the transfer and separation of photogenerated carriers. [Display omitted] • A novel hierarchical S-scheme heterojunction of 0D/3D Zn 0.5 Cd 0.5 S/MoS 2 is successfully synthesized by simple hydrothermal and coprecipitation. • The hierarchical structure greatly improves the utilization of visible light and shortens the transfer distance of carriers. • The S-scheme between Zn 0.5 Cd 0.5 S and MoS 2 significantly promotes the separation and transfer of photogenerated carriers. • The rate of H 2 -evolution over 10% MoS 2 / Zn 0.5 Cd 0.5 S reaches 33.8 mmol‧g−1‧h−1. Heterojunctions with specialized surface morphologic structures could remarkably promote the photocatalytic efficiency of catalysts on account of the suitable component contents. In this study, a novel 3D MoS 2 structure of hollow micro-flower is fabricated via the template method, on which 0D Zn 0.5 Cd 0.5 S (ZnCdS) nanoparticles are in-situ grown, forming a unique MoS 2 /Zn 0.5 Cd 0.5 S (M/ZCS) hierarchical structure. Using 10 vol% lactic acids as the sacrificial agent, the uppermost hydrogen evolution efficiency of 10% M/ZCS is 33.8 mmol‧g−1‧h−1, which is around 16 times and 786 times higher than that of single ZnCdS (2.1 mmol‧g−1‧h−1) and MoS 2 (0.043 mmol‧g−1‧h−1). Furthermore, the apparent improvement in photocatalytic performance is mainly ascribed to the construction of the M/ZCS hierarchical structure, which resultful inhibits the agglomeration of ZnCdS nanoparticles, increases the availability of visible light, and shortens the transfer distance of carriers. Meanwhile, the S-Scheme heterojunction formed between ZnCdS and MoS 2 significantly promotes the transfer and separation of photogenerated electrons and holes. This paper provides a novel strategy for the further synthesis of high-performance photocatalysts with hollow architecture and significant heterojunction for hydrogen evolution. [ABSTRACT FROM AUTHOR]

A diagram is presented which explains the enantioselective synthesis of dihydrocoumarin derivatives.

This is a highly efficient Ni(II)-catalyzed Claisen rearrangement of a variety of both propargyl and allyl vinyl ethers using a chiral N,N-dioxide as ligand. [ABSTRACT FROM AUTHOR]

The catalyst system efficiently promotes the asymmetric addition of enones to cyclic 1,3-diones to form chromenone derivatives like (III) and (VI) and the anticoagulant warfarin (VIII). [ABSTRACT FROM AUTHOR]