Effects of trace Ag on precipitation behavior and mechanical properties of extruded Mg−Gd−Y−Zr alloys

The effects of trace Ag element on the precipitation behaviors and mechanical properties of the Mg−7.5Gd−1.5Y−0.4Zr(wt.%)alloy by means of tensile test,X-ray diffractometry,scanning electron microscopy,electron backscattered diffractometry,and scanning transmission electron microscopy.There is an unusual texture(á0001ñ//extrusion direction)in the extruded Mg−Gd−Y−Zr alloys containing 0.5 wt.%Ag.During the aging periods at 225℃,the addition of the trace Ag does not form new precipitates,just accelerates aging kinetics,and refinesβ′precipitates,thereby increasing the number density of theβ′precipitates by Ag-clusters.Moreover,the Mg−Gd−Y−Zr alloy containing 0.5 wt.%Ag shows the most excellent synergy of strength and plasticity(408 MPa of ultimate tensile strength,265 MPa of yield strength,and 12.9%of elongation to failure)after peak-aging.

Chemical Constituents from the Whole Plant of Cuscuta reflexa

Two new 2H-pyran-2-one glucosides,cuscutarosides A(1)and B(2),and one new steroidal glucoside,7β-methoxy-β-sitosterol 3-O-β-glucopyranoside(3),together with 12 known compounds(4-15)were isolated from the whole plant of Cuscuta reflexa(Convolvulaceae)collected from Myanmar.The chemical structures of these new compounds were elucidated based on extensive spectroscopic analysis.The antiobesity activity of these isolates was evaluated using porcine pancreatic lipase(PPL),and the antiplatelet aggregation activity was screened using rabbit platelets induced by thrombin,platelet-activating factor(PAF),arachidonate(AA),or collagen.7β-Methoxy-β-sitosterol 3-O-β-glucopyranoside(3)showed weak PPL inhibitory activity.Cuscutaroside A(1),its acetylated derivative(1a),and scrophenoside B(8)showed weak inhibitory activity against rabbit platelet aggregation induced by collagen.Compound 1a also showed inhibitory activity against rabbit platelet aggregation induced by AA.

Chemical Constituents from Ethanoic Extracts of the Aerial Parts of Leea aequata L.,a Traditional Folk Medicine of Myanmar

We aimed at reporting the chemical constituents and antimicrobial activities of Leea aequata L.,a traditional folk medicine used in Myanmar for the treatment of wounds and skin diseases.A new neolignan,(7S,8R)-9′-O-acetylcedrusin(1),a new lactam,(3S,4S)-4-chloro-3-hydroxypiperidin-2-one(2),along with 21 known compounds,including fve lignans(3-7),four favonoid glycosides(8-11),and others(12-23),were isolated from the ethanoic extract of the aerial parts of L.aequata.The structures of the new compounds were determined by NMR,MS,and ECD spectra.For all the antimicrobial tests of the 23 compounds,only 3,4,5-trihydroxybenzoic acid ethyl ester(17)showed weak inhibitory activities against Escherichia coli and Salmonella enterica subsp.enterica.

Identification of Above-Threshold Ionization by Imaging Photoelectrons from Ammonia Molecules in an Intense Femtosecond Laser Field

The above-threshold ionization process of ammonia molecules induced by a femtosecond laser field at 800 nm is studied in the intensity range from 1.6×10^(13) to 5.7×10^(13)W/cm^(2).Channel switching under different laser intensities is observed and identified in the photoelectron kinetic energy spectra of ammonia.Based on the photoelectron kinetic energy distributions and the photoelectron angular distributions,the characteristic peaks observed are exclusively assigned to the multiphoton resonance through certain intermediate states,followed by multiphoton above-threshold ionization.

基于热活化敏化荧光机制的有机发光二极管材料与器件

热活化敏化荧光(TSF)被称作有机发光二极管(OLED)“第四代发光技术”,是以热活化延迟荧光材料作为敏化剂,高效发光的荧光材料作为掺杂染料,通过二者之间高效的Förster能量传递实现100%激子利用,突破了三线态高效上转换与单线态高效辐射跃迁之间的矛盾.本文围绕TSF-OLED器件的发光效率、寿命及光色等核心指标,针对激子的调控和利用这一关键科学问题,重点介绍了我们课题组近年来在TSF技术的机理研究、高效稳定敏化剂及窄光谱材料的设计开发以及高性能器件的构筑等方面的研究工作.最后讨论了TSF技术所存在的挑战和未来发展前景.

A double transition metal Ti_(2)NbC_(2)T_(x) MXene for enhanced lithium-ion storage

MXene,an emerging two-dimensional(2D)layered material,has received worldwide attention in various energy storage systems because of its excellent properties.Nevertheless,the low capacity of pristine MXene restricts its application in energy storage devices especially for the lithium-ion batteries(LIBs).To address the above issue,herein,a stable and highly conductive double transition metal MXene(Ti_(2)NbC_(2)T_(x)) is successfully fabricated,which provides enlarged interlayer spacing and excellent conductivity for fast ion diffusion and charge transfer.Taking the Ti_(2)NbC_(2)T_(x)s anode for LIBs,a superior specific capacity of 196.2 mAh·g-1and an excellent long-term cycling stability of~100%after 400cycles under 0.1 A·g^(-1) are achieved for LIBs.In particular,Ti_(2)NbC_(2)T_(x) delivers an impressive capacity retention of 81%over 4000 cycle under 1 A·g^(-1),outperforming the Ti_(3)C_(2)T_(x) and various previously reported MXene-based materials.Our results offer an attractive strategy for the future application of MXene-based materials.

Synthesis of axially chiral oxazoline–carbene coordinated palladium complexes with a N-phenyl framework

A family of tropos ligands bearing a N-heterocyclic carbene and a chiral oxazoline coordination group with a N-phenyl framework were easily prepared,and their coordination behavior with Pd（Ⅱ）acetate was performed,affording a series of axially chiral palladium complexes in good yields.

Synthesis and insecticidal activities of novel bridged-neonicotinoids

A series of novel bridged-neonicotinoid analogues were designed and synthesized, which were constructed by starting material 8 with cyclopentenone or cyclohexenone in the presence of catalyst aluminium chloride. All of the compounds were characterized and confirmed by^1H NMR,^（13）C NMR, HRMS and IR. The bioassay tests showed that compounds 5 and 6a showed higher bioactivities than imidacloprid against Aphis craccivora.