Mixed disorder in GaAs/AlxGa1−xAs superlattices and its effect on the range of wavelength infrared lasers

By introducing a mixed disorder on GaAs/Al_xGa_1−xAs superlattices, a wide range of infrared (15–248 μm) was achieved. The studied systems consist of two different structures randomly distributed along the growth direction, with the additional constraint that the structure with height barrier V₂ and thickness d_b2 appear only by doublet or triplet. The exact Airy – function formalism combined with a transfer matrix technique was used for evaluating the transmission probability and laser wavelength. The analysis of the proposed model shows that the far infrared wavelength is obtained when the aluminum mole fraction increase and mixed disorder is introduced by trimer.     

自旋多重度对钛三聚体原子结构的影响

基于密度泛函理论，获得了钛三聚体在不同自旋多重度下的原子结构，并计算了对应的振动频率.发现自旋多重度对钛三聚体的原子结构有重要的影响，特别是对键长和振动频率.考虑自旋多重度后，钛三聚体的基态结构为自旋七重态. 关键词： 钛三聚体 自旋多重度 原子结构     

Tunable Fano resonances and plasmonic hybridization of gold triangle–rod dimer nanostructure

A gold dimer structure consisting of a notched triangle nanoslice and a rectangle nanorod is proposed to produce distinct Fano resonance. Owing to the coupling between the dipole plasmon mode of the nanorod and the dipole or quadrupole plasmon mode of the nanoslice, the extinction spectrum with a deep Fano dip is formed and can be well fitted by the Fano interference model for different geometry parameters. In addition, Fano resonance of the gold dimer nanostructure also intensely depends on the polarization direction of incident light. Moreover, Fano resonance of the triangle–rod trimer is also analyzed by adding another nanorod into the former dimer and exhibits the splitting of plasmonic resonant peak in high order coupling modes. The plasmonic hybridizations in these nanostructures have been analyzed for revealing the physical origin of the Fano resonance.     

式根岛海绵宏基因组文库的抗菌吲哚三聚体

构建了式根岛海绵的宏基因组文库,对其进行双层琼脂抗菌活性功能筛选,得到1株抗菌活性克隆pDC111. 以抗菌活性为指导,对pDC111的化学成分进行分析和分离,得到化合物1,并通过1D NMR（¹H NMR和 ¹³C NMR）及2D NMR（¹H-¹H COSY,HMQC和HMBC）结合HR-TOFMS数据,确定其结构为吲哚三聚体. 抗菌活性实验结果表明,化合物1在10 μg/paper（id=6 mm）时,对蜡状芽孢杆菌的抑菌圈达到12 mm. 本文利用功能宏基因组方法,从蕴藏大量不可培养微生物的海绵中寻找到活性物,并具有通过分子生物学技术获得其功能基因的潜能.     

Linear trimerization of 1-ethynylcyclohexan-1-ol catalysed by nickel(II) complexes

The catalytic reaction of 1-ethynylcyclohexan-1-ol (EC) in the presence of bisphosphine nickel(II) complexes yields a linear trimer. The trimer could be isolated and characterized by means of MS, IR and NMR spectroscopies. The reaction mechanism is also discussed.     

Investigation of molecular association in mixtures of dimethylsulfoxide with trichloromethane by vibrational spectroscopy and <Emphasis Type="Italic">ab initio</Emphasis> calculations

Vibrational spectroscopy methods (IR absorption and Raman scattering) are employed to investigate molecular association in dimethylsulfoxide (DMSO)-trichloromethane (TCM) mixtures. A spectral manifestation of the interactions between DMSO and TCM molecules are revealed. The ground state geometry of the complexes of DMSO with TCM (dimers and trimers) are calculated by the ab initio MP2 method using the 6-31G** basis set.     

An ab initio study of intermolecular interactions of nitromethane dimer and nitromethane trimer

Different geometries of nitromethane dimer and nitromethane trimer have been fully optimized employing the density functional theory B3LYP method and the 6-31++G** basis set. Three-body interaction energy has been obtained with the ab initio supermolecular approach at the levels of MP2/6-31++G**//B3LYP/6-31++G** and MP2/aug-cc-pVDZ//B3LYP/6-31++G**. The internal rotation of methyl group induced by intermolecular interaction has been observed theoretically. For the optimized structures of nitromethane dimer, the strength of C--H...O--N H-bond ranges from -9.0 to -12.4 kJ mol(-1) at the MP2/aug-cc-pVDZ//B3LYP/6-31++G** level, and the B3LYP method underestimates the interaction strength compared with the MP2 method, while MP2/6-31++G**//B3LYP/6-31++G** calculated DeltaE(C) is within 2.5 kJ mol(-1) of the corresponding value at the MP4(SDTQ)/6-31G**//B3LYP/6-31++G** level. The analytic atom-atom intermolecular potential has been successfully regressed by using the MP2/6-31++G**//B3LYP/6-31++G** calculated interaction energies of nitromethane dimer. For the optimized structures of nitromethane trimer the three-body interaction energies occupy small percentage of corresponding total binding energies, but become important for the compressed nitromethane explosive. In addition, it has been discovered that the three-body interaction energy in the cyclic nitromethane trimer is more and more negative as intermolecular distances decrease from 2.2 to 1.7 A.     

Effect of terminal aryl rings of liquid crystal trimers on liquid crystalline properties

Liquid crystalline properties of five series of biphenyl derivatives connected with p-nitrophenyl, phenyl, 2-naphthyl, 9-phenathryl and bromo as the terminal groups via flexible spacers were studied. All the compounds exhibited nematic phase. The nematic–isotropic or isotropic–nematic transition properties resulted in an odd–even effect as the length of the spacers was varied, in which the even members exhibited higher values, for the compounds with p-nitrophenyl, phenyl, 2-naphthyl and 9-phenanthryl groups, while the transitional properties of the compounds substituted with bromo atom as the terminal group instead of the aryl groups did not show such odd–even effect. These results suggest that the aryl rings, such as p-nitrophenyl, phenyl, 2-naphthyl and 9-phenanthryl groups, play a role of mesogen while the terminal bromo atom does not. The effect of the terminal aryl rings on the liquid crystalline properties will be reported.     

Room temperature liquid crystal of symmetric gallic trimer containing cyanuric core: synthesis and mesomorphism

Three novel gallic monomer 7, dimer 10 and trimer 12 with conjugated cyanuric core were designed and synthesised by Schiff-base condensation mode in yields of 80–90%. Their structures were characterised by fourier transform infrared spectroscopy, ¹H NMR (nuclear magnetic resonance), electrospray ionization mass spectrometry and elemental analyses. Their mesomorphic behaviours were investigated by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. The gallic monomer 7 has no mesomorphic property, but the dimer 10 and trimer 12 possess good mesomorphic properties. The trimer 12 with high symmetry exhibited the typical hexagonal columnar liquid crystal at room temperature. The temperature range of mesophase is as wide as 149°C (14–163°C). The results suggested that the more gallic units and symmetric structures are favourable for excellent mesomorphic properties.     

点击化学合成盘-棒-盘状液晶三聚体

本文设计并合成了一系列盘-棒-盘状液晶三聚体.此类三聚体由两个相同的苯并菲盘状介晶基元和一个联苯棒状介晶基元通过CuI-NEt3体系催化端基炔和端基叠氮化合物的点击反应连接形成.该三聚体结构通过核磁、红外和高分辨质谱表征;介晶性通过偏光显微镜(POM)、差示扫描量热法(DSC)和X射线衍射(XRD)进行了研究.结果显示:此类液晶三聚体均为室温液晶,呈现四方柱状相(Colr).连接3个介晶基元的柔性间隔基的长度对化合物的相转变温度具有明显影响.