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881.
Ferroelectric liquid crystals can be optimized for speed, but such materials tend to have small switching angles and consequently low contrast in the smectic A(*) phase. We describe a method whereby such a low-contrast but fast-switching effect can be enhanced, in theory giving the same contrast as a material with a switching angle of 22.5 degrees . This method therefore promises liquid-crystal modulators of high contrast and with speeds of the order of hundreds of nanoseconds. The theoretical basis of this method and initial results that support this analysis are presented. 相似文献
882.
The complex, [Zn(L)(NCO)]Cl · 3H2O (1) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane), has been synthesized and structurally characterized. 1 crystallizes in the monoclinic system, space group P21/n with a = 10.530(3), b = 9.315(2), c = 27.188(3) Å, = 92.58(1)°, V = 2664.1(9)Å3, and Z = 4. The zinc atom is in a distorted squarepyramidal environment with the four nitrogen atoms of the macrocycle and one nitrogen atom of the isocyanate ligand. 相似文献
883.
R. Droopad K. T. Shiralagi R. A. Puechner K. Y. Choi G. N. Maracas 《Journal of Crystal Growth》1992,120(1-4):200-205
Low temperature growth of GaAs by gas source molecular beam epitaxy (GSMBE) is investigated. Reflection high energy electron diffraction is used to monitor the low temperature buffer (LTB) growth and anneal conditions. Growth at low temperatures with dimeric arsenic is more sensitive to the V/III flux ratios and substrate temperatures than with As4 used in solid source MBE. Temperature dependent conductivity and deep level transient spectroscopy measurements are presented to observe trap outdiffusion from the LTB into subsequently grown FET channels. Low temperature photoluminescence spectra show degradation of quantum well properties when LTBs are grown with increasing V/III flux ratios. 相似文献
884.
Ki-Young Choi 《Journal of chemical crystallography》2000,30(5):335-338
The complex [Co(L)]Cl2·10H2O (1) (L = 2,13,-bis(2-pyridylmethyl)-3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,01.18,07.12]docosane) has been synthesized and structurally characterized. Compound 1 crystallizes in the triclinic system, space group P-1 with a = 9.731(2) Å, b = 9.789(2) Å, c = 11.998(1) Å, = 66.66(1)°, = 76.95(1)°, = 87.99(2)°, V = 1020.4(3) Å3, and Z = 1. The crystal structure of 1 shows that the complex is centrosymmetric and the cobalt(II) ion has a slightly distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendent arms at the axial positions. Cyclic voltammetry for 1 undergoes reversible one-electron oxidation to the Co(III) and irreversible one-electron reduction to the Co(I). 相似文献
885.
A novel compound catena-(-CrO4-O,O)[Ni(L1)Ni(L2)] 3H2O (1) (L1 = 3,5,10,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane and L2 = 2,5,9,12-tetramethyl-1,4,8,11-tetraazacyclotetradecane) has been synthesized for the first time and structurally characterized. 1 crystallizes in the triclinic space group P with a = 9.623(1), b = 10.084(1), c = 12.723 (3) Å, = 66.74(2), = 75.20(1), = 72.02(1)°, V = 1066.2(3) Å3, and Z = 2. The coordination environment around the Ni(II) ions is an axially elongated octahedron with the secondary amines of the isomeric ligands and two oxygen atoms of [CrO4]2–. 相似文献
886.
Choi MG Ryu de H Jeon HL Cha S Cho J Joo HH Hong KS Lee C Ahn S Chang SK 《Organic letters》2008,10(17):3717-3720
The chemodosimetric behavior of dichlorofluorescein derivatives toward Hg(2+) ions was investigated. Simple chemodosimetric systems showed selective and efficient signaling behaviors toward micromolar concentrations of Hg(2+) ions over other common interfering metal ions in an aqueous environment. The signaling mechanism is selective mercuration of the 4',5'-position of the xanthene moiety, which results in efficient chromogenic and fluorogenic signaling of Hg(2+) ions in aqueous environment. 相似文献
887.
Liu X Abd El-Aty AM Choi JH Khay S Mamun MI Jeon HR Lee SH Chang BJ Lee CH Shin HC Shim JH 《Journal of separation science》2008,31(22):3847-3856
The current study was undertaken to validate the performance for the determination of both TBA and beta-trenbolone (beta-TB) residues in porcine muscle at concentrations required to monitor compliance with the maximum residue limit (MRL). The method involves a one phase liquid-liquid extraction, cleanup with low-temperature fat precipitation, separation of the respective compounds by HPLC on a Capcell pak C(18) column, use of a methanol-water isocratic system as an eluent, and measurement by UV absorbance detection at 340 nm. Both compounds were confirmed using LC-MS/MS with electrospray interface (ESI) and a triple quadrupole (QqQ) analyzer. The method was found to be precise and accurate, with a linearity range of 1-10 microg/kg (r(2) >0.973). The intra- and interday precision showed good reproducibility with RSDs < or =13.25%. The LODs were 0.12 and 0.22 microg/kg, and the LOQs were 0.37 and 0.66 microg/kg, for TBA and beta-TB, respectively. The applicability of the method was demonstrated by analyzing real samples collected from major cities in the Republic of Korea. No residues of the selected compounds were detected in any of the samples. The advantages of our method are that it is: selective, sensitive, requires a short time for analysis (13 min), and performs simple sample extraction and clean-up procedure with low-temperature fat precipitation as compared to the previously published methods. 相似文献
888.
We introduce property (quasi ‐α), which implies property (A) defined by Lindenstrauss [10] and whose dual property is property (quasi‐β) [2]. We consider relations between this property and other sufficient conditions for property (A), and study the denseness of norm attaining mappings under the conditions of these properties. In particular, if each of the Banach spaces Xk , 1 ≤ k ≤ n – 1, has property (quasi‐α) and Xn has property (A), then the projective tensor product X1 ··· Xn has property (A). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
889.
Choi Yun Sung; Garcia Domingo; Maestre Manuel; Martin Miguel 《Quarterly Journal of Mathematics》2008,59(4):455-474
We study the relation between the polynomial numerical indicesof a complex vector-valued function space and the ones of itsrange space. It is proved that the spaces C(K, X) and L(µ,X) have the same polynomial numerical index as the complex Banachspace X for every compact Hausdorff space K and every -finitemeasure µ, which does not hold any more in the real case.We give an example of a complex Banach space X such that, forevery k 2, the polynomial numerical index of order k of X isthe greatest possible, namely 1, while the one of X** is theleast possible, namely kk/(1–k). We also give new examplesof Banach spaces with the polynomial Daugavet property, namelyL(µ, X) when µ is atomless, and Cw(K, X), Cw*(K,X*) when K is perfect. 相似文献
890.
Choi JC Kohno K Masuda D Yasuda H Sakakura T 《Chemical communications (Cambridge, England)》2008,(6):777-779
Iron triflate, in situ-formed from FeCl3 and triflic acid, or FeCl3 and silver triflate efficiently catalyse the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters; the reaction is applicable to the synthesis of unstable esters, such as acrylates. 相似文献