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1.
Neville Boden Richard J. Bushby Kevin Donovan Quanying Liu Zhibao Lu Theo Kreouzis 《Liquid crystals》2013,40(12):1739-1748
A synthesis has been developed for 2,3,7,8,12,13-hexakis[2-(2-methoxyethoxy)ethoxy]-tricycloquinazoline (TCQ6EO2M) in which the ethylenoxy side chains are introduced before elaboration of the heterocylic core. This discogen gives a hexagonal columnar phase (Colh) between 77 and 233°C. n-Doping using potassium metal is facilitated firstly by the electron poor/π-deficient nature of the core and secondly by the polyethylenoxy side chains which complex the potassium K+ counter-ions. The conductivity of the Colh phase of TCQ6EO2M doped with 10 mol % potassium (σ ∥ = 1.1 x 10-3 S m-1) is substantially higher than that previously reported for 2,3,7,8,12,13-hexa(hexylthio)tricycloquinazoline doped with 6 mol % potassium (σ ∥ = 2.9 x 10-5 S m-1). Photoconductivity studies of TCQ6EO2M using a time of flight sample configuration show transient photocurrents for both holes and electrons. From these an upper limit on the mobility for the electrons is estimated as ~10-4 cm2 V-1 s-1 at 150°C which is of the same magnitude as that for hole mobilities in other columnar discotic liquid crystals. 相似文献
2.
The palladium-catalyzed cyclization–allylation reaction of ortho-azido propynylbenzenes 1 and allyl methyl carbonate 2d gives the corresponding allylated quinolines in moderate to good yields. The reaction of 1-azido-2-(2-propynyl)benzene 1a proceeds smoothly with 10 mol % Pd(PPh3)4 and 5 equiv K3PO4 or NaOAc in DMF at 100 °C to afford 3,4-diallylquinoline 3a in 69% yield in the case of R2 = H and 3-allylquinoline 4 in 67% yield in the case of R2 ≠ H. 相似文献
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4.
The probability distributions of sand particles' lift-off and incident velocities in a wind-blown sand flux play very important
roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles
located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry (PDA) in
a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also
the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal
components can be obtained by the equal distance histogram method. It is found, according to the results of the χ2-test for these probability distributions, that the probability density functions (pdf's) of the sand particles' lift-off
and incident velocities as well as their vertical components are described by the Gamma density function with different peak
values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal
and the Gamma density functions. These pdf's depend on not only the sand particle diameter but also the wind speed.
The project supported by the National Natural Science Foundation of China (10532040) and the Hundred Talents Project, the
Knowledge Innovation Project of Chinese Academy of Sciences (KZCX2-304). The English text was polished by Keren Wang. 相似文献
5.
高精密度无损伤检测黄金首饰技术 总被引:4,自引:0,他引:4
本文提出了一种高精密度无损伤检测黄金首饰技术。通过测定黄金首饰在测量液中的浮力后计算密度再查表而得。其特征是测量液为表面张力和粘度均较小的有机溶剂或其溶液,而且在测定浮力的同时同步测定该测量液的密度或温度。本技术简便可靠,标准偏差S=±0.0035,T检法t90=0.15。精密度±0.01%,速率12样/小时,既快又准,易于普及推广。 相似文献
6.
Zhibao Huo 《Tetrahedron letters》2008,49(38):5531-5533
Reaction of 2-alkynylbenzaldoximes 1 with 5 equiv of iodine in EtOH at room temperature gives the corresponding iodoisoquinoline N-oxides 2 in good to excellent yields. The cyclization proceeds very smoothly and quickly without any additives such as bases under very mild reaction conditions. 相似文献
7.
The homogeneous (unseeded) precipitation of nesquehonite (MgCO3·3H2O) was studied over the temperature range of 10‐40 °C. Precipitation was triggered by the supersaturation created by mixing MgCl2 solution (0.5‐1.5 M) with Na2CO3 solution in the same concentration range. The Meissner's method was adopted in the calculation of supersaturations during the MgCl2‐Na2CO3 reaction to monitor the precipitation. Solids were identified using X‐ray diffraction (XRD) analysis and scanning electron microscope (SEM) images. In the temperature range of 10‐40 °C, MgCO3·3H2O with needle‐like or gel‐like morphology was precipitated. It was seen that the length, width and surface smoothness of the particles changed with reaction temperature and supersaturation. The supersaturation (S) was in the range of 1.09‐58.68 during titration of Na2CO3 solution. The dimension of the crystals increased with longer addition time (or lower initial concentration of reactant) at the same temperature. Slower addition via titration of 2 h followed by 2 h of equilibration at 40 °C proved successful in producing well developed needle‐like MgCO3·3H2O crystals of 30‐50 μm long and 3‐6 μm wide. MgCO3·3H2O obtained were calcined to produce highly pure magnesium oxide (MgO) at 800 °C. The morphology of MgO was similar to that of their corresponding precursors. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
A sufficient and then a necessary condition are given for a function to be an extreme point of the unit ball of the Banach space of continuous functions, under the supremum norm, from a compact Hausdorff topological space into a Banach space equipped with its weak topology . Strongly extreme points of the unit ball of are characterized as the norm-one functions that are uniformly strongly extreme point valued on a dense subset of . It is shown that a variety of stronger types of extreme points (e.g. denting points) never exist in the unit ball of . Lastly, some naturally arising and previously known extreme points of the unit ball of are shown to actually be strongly exposed points.
9.
核磁共振法测定苯乙烯和甲基丙烯酸正丁酯竞聚率的研究 总被引:6,自引:0,他引:6
以苯乙烯(St)-甲基丙烯酸正丁酯(BMA)共聚体系为研究对象,在共聚单体组成敏感点附近做重复实验,进行了40、60、80、100,120、140℃下的共聚合,用NMR方法测定共聚物的组成,用Mayo-Lewis微分组成方程的误差变量法计算竞聚率,同时给出竞聚率的95%可信椭圆区间.并根据竟聚率对温度的依赖关系得到一组合理的竞聚率值. 相似文献
10.
高强高模单丝纤维模量测定的修正 总被引:3,自引:1,他引:3
当测定具有高强度和高模量单丝纤维的力学性能时,应力传感系统将受到很大的拉力,并产生相应的形变。微小的形变与被测高模量样品的形变相比,已达到不可忽略的程度。本文提出模量修正的原理和求算方法,在测定高强高模单丝纤维的模量时,可对仪器的应力传感系统给出相应的模量修正系数,从而得到真实的弹性模量值。本修正方法能作为单丝力学性能测试标准的补充。 相似文献