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11.
12.
The substoichiometric precipitation of fluoride with lanthanum was studied by using18F and140La tracers and it was found that fluoride could be precipitated substoichiometrically with lanthanum and the reaction ratio
between fluoride and lanthanum was 3∶1. The pH range at which fluoride can be separated substoichiometrically with lanthanum
is between 2 and 8. Barium and indium interfere in the precipitation of fluoride, sodium, copper and manganese, however, not.
Fluorosilicate can also be precipitated substoichiometrically by using lanthanum as a precipitant and the reaction ratio between
fluorosilicate and lanthanum was 1∶2. This separation was applied for the determination of oxygen in silicon crystals. The
concentration of oxygen measured in some silicon crystals was between 5 and 27 ppm and in good agreement with those by non-destructive
method and infrared spectrophotometry. 相似文献
13.
A new ternary ruthenium oxide Na(2)RuO(4) was prepared and shown to crystallize with a new structure type. Single crystal X-ray diffraction measurements reveal that Na(2)RuO(4) consists of RuO(4) chains made up of RuO(5) trigonal bipyramids by sharing axial corners. Na(2)RuO(4) is a magnetic semiconductor with a variable range hopping behavior, and its molar magnetic susceptibility chi(mol) has a broad maximum at approximately 74 K. The derivative d(chi(mol).T)/dT exhibits a peak at 37.7 K which has been confirmed by heat capacity measurement to be due to long-range antiferromagnetic ordering. 相似文献
14.
Tsutsumi T Amakura Y Nakamura M Brown DJ Clark GC Sasaki K Toyoda M Maitani T 《The Analyst》2003,128(5):486-492
The chemical-activated luciferase expression (CALUX) assay is a reporter gene assay that detects dioxin-like compounds based on their ability to activate the aryl hydrocarbon receptor (AhR) and thus expression of the reporter gene. In this paper, the CALUX assay was examined for its application in the screening of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) in retail fish. The sample extracts were cleaned up on a sulfuric acid-silica gel column followed by an activated carbon column, and the AhR activity of the separated PCDD/F and dioxin-like PCB fractions was determined using the assay. The quantitative limit for 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) was 0.98 pg ml(-1) (0.19 pg assay(-1) in the standard curve, corresponding to 0.16 pg g(-1) of CALUX-based toxic equivalency (2,3,7,8-TCDD equivalents) in the tested sample. Recovery tests in which dioxins were added to fish samples resulted in acceptable recoveries (77-117%). The CALUX assay performed well in the analysis of dioxins in fish samples and a comparative study revealed a strong correlation between the CALUX assay and high-resolution gas chromatography-high-resolution mass spectrometry analysis for the determination of PCDD/Fs (r = 0.89) and dioxin-like PCBs (r = 0.91) in retail fish (n = 22). These data revealed that the CALUX assay would be a useful screening method for PCDD/Fs and dioxin-like PCBs in retail fish. 相似文献
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17.
Asymmetric cross-coupling of dinaphtho[2,1-b:1',2'-d]thiophene with ArMgBr (Ar = Ph, 4-MeC6H4, 4-MeOC6H4) proceeded with high enantioselectivity in THF at 20 degrees C in the presence of 3 mol % of a nickel catalyst generated from Ni(cod)2 and a chiral oxazoline-phosphine ligand to give high yields of axially chiral 2-mercapto-2'-aryl-1,1'-binaphthyls, whose enantiomeric excesses are over 93%. The mercapto group in the chiral binaphthyl was converted into iodo, boryl, and phosphino groups without racemization. 相似文献
18.
Shigeyuki Mayama Toshikazu Tani Tamio Ueno Kazumasa Hirabayashi Tadakazu Nakashima Hiroshi Fukami Yukio Mizuno Hiroshi Irie 《Tetrahedron letters》1981,22(22):2103-2106
The major phytoalexin from oat leaves has been identified as 2-[2-(4-hydroxyphenyDethenyl] -6-hydroxy-4H-3,1-benzoxazin-4-one (). 相似文献
19.
[reaction: see text] A rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to fumaric and maleic compounds has been developed. While phosphorus-based chiral ligands fail to induce high stereoselectivity, chiral norbornadiene ligands have proved to be uniquely effective to achieve high enantioselectivity in these 1,4-addition reactions. 相似文献
20.
Hayashi T Ueyama K Tokunaga N Yoshida K 《Journal of the American Chemical Society》2003,125(38):11508-11509
As a new type of chiral ligand, a C2-symmetric norbornadiene derivative (1R,4R)-2,5-dibenzylbicyclo[2.2.1]hepta-2,5-diene (1) was prepared and used for the rhodium-catalyzed asymmetric addition of organoboron and -tin reagents to alpha,beta-unsaturated ketones, which gave high yields of the 1,4-addition products with up to 99% enantioselectivity. 相似文献