The half-life of41Ca has been redetermined to be (1.01 ±0.10)×105 yr from the specific activity of a sample of enriched calcium material and its41Ca concentration. The activity was measured with a Si(Li) detector via the 3.3-keV X rays emitted in the electron capture decay of41Ca to41K. The41Ca concentration was measured by mass spectrometry. Since our result agrees well with the two most recent half-life measurements of Mabuchi et al. (1974), (1.13±0.12)×105 yr, and Klein et al. (1990), (1.03±0.07)×105 yr, we recommend the weighted mean of these three measurements, t1/2=(1.04±0.05)×105 yr, as the most accurate value of the half-life of41Ca.Dedicated to Prof. Dr. P. Kienle on the occasion of his 60th birthday 相似文献
One new compound 3,7,11,15,19-pentamethyl-9α,10α,11α,17α,18α-pentahydroxy-n-tetracosan-1-oxy-p-hydroxycaffeoate (oryzaterpenyl
caffeoate) (1), together with three known fatty acids linoleic acid, stearic acid and myristic acid were isolated and identified from the
rice grain of Oryza sativa. The structure of the new compound was elucidated by 1D and 2D NMR spectroscopic techniques (1H-1HCOSY, 1H-13C HETCOR) aided by EI-MS, and IR spectra.
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Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 535–537, November–December, 2005. 相似文献
Mathematical equations governing the ratio of210Bi/210Pb and210Po/210Pb activities are used to explain the ingrowth of210Bi and210Po in environmental samples during post collection. Procedures are described for radiochemical separation of210Pb,210Bi, and210Po in a state of radioactive disequilibrium and quantification by alpha- and beta-counting. Also, the special case is considered where210Bi is in equilibrium with210Pb, but both are in disequilibrium with210Po. In this case, the activities of both210Pb and210Po are computed by measuring210Po activity twice, using alpha-counting. 相似文献
In this study, the Co-based catalyst was prepared by cobalt immobilization on the surface of functionalized silica-coated magnetic NPs (Fe3O4@SiO2-CT-Co) as a magnetically core–shell nanocatalyst and characterized by FT-IR, TGA, XRD, VSM, SEM, TEM, EDX, EDX mapping, and ICP techniques and appraised in the Suzuki–Miyaura cross-coupling reaction under mild reaction conditions. The results displayed the superparamagnetic behavior of the Fe3O4 NPs core encapsulated by SiO2 shell, and the size of the particles was estimated about 30 nm. Compared with the previously reported catalysts, the engineered Fe3O4@SiO2-CT-Co catalyst provided perfect catalytic performance for the Suzuki–Miyaura cross-coupling reaction in water as a green solvent and it was much cheaper in the comparison with the traditional Pd-based catalysts. Importantly, the durability of magnetic nanocatalyst was studied and observed that it is stable under the reaction conditions and could be easily reused for at least six successive cycles without any significant decrease in its catalytic activity.
The imidazole nucleosides, 4(5)-bromo-5(4)-nitro-1-β-D-ribofuranosylimidazoles, have been prepared via glycosylation of the trimethylsilylated aglycone, 4(5)-bromo-5(4)-nitroimidazole, with tetra-O-acetyl-β-D-ribo-furanose followed by removal of the acetyl protecting groups. The 5-bromo-4-nitro-1-β-D-ribofuranosylimidazole nucleoside was acetonated to produce 5-bromo-4-nitro-1-(2,3-O-isopropylidene-β-D-ribofuranosyl)-imidazole which was cyclized to provide the corresponding anhydronucleoside 5,5′-anhydro-4-nitro-5-oxo-1-(2,3-O-isopropylidene-β-D-ribofuranosyl)imidazole. Sodium hydrosulfide treatment of 5-bromo-4-nitroimidazole nucleoside provided 5-mercapto-4-nitro-1-β-D-ribofuranosylimidazole 5-sodium salt which was alkylated with E-1,5-diiodopent-1-ene to yield 5-(E-1-iodo-1-penten-5-yl)thio-4-nitro-1-β-D-ribofuranosylimidazole. The corresponding iodine-125-labeled compound was prepared similarly using radiolabeled diiodopentene. The 5-bromo-4-nitroimidazole, 5-mercapto-4-nitroimidazole, and 5-iodopentenylthio-4-nitroimidazole nucleosides were cytotoxic to Molt-3 cells in vitro at concentrations higher than 10 μg/mL. The radiolabeled 5-iodopentenylthio-4-nitroimidazole nucleoside showed 2-fold higher uptake in a rapidly growing tumor as compared to uptake in a relatively slower growing tumor in mice. 相似文献
High-precision measurements ofKAuger electron andK x-ray intensities have been made for several transuranium elements and these have been used to determineK-shell fluorescence yields (ωK). The electron spectra were measured with a cooled Si(Li) spectrometer and the photon spectra were taken with Ge(Li) diodes. Very thin mass-separated samples of nuclides, which decay predominantly by electron capture, were used in the present experiments. From our present measurements the following values ofK- shell fluorescence yield have been obtained: Np, 97.2±0.3%; Pu, 97.2±0.4%; Cm, 97.1 ±0.6%; Bk, 97.1±0.4%; Cf, 97.3±0.4%; and Es, 97.2±0.5%. These numbers indicate that theK-fluorescence yield for elements in theZ=93 toZ=99 region remains constant within the experimental error. The weighted average of these numbers is 97.19% with external error of 0.03% and internal error of 0.17%. This value is in excellent agreement with known theoretical calculations. 相似文献
A simple versatile method for the conversion of 1 -aroyl-2-(substituted benzylidene)-hydrazines to 1-aryl-phthalazines using polyphosphate ester (PPE) is described. 相似文献
Liquid chromatography coupled to a silver electrode based flow-through amperometric detector (LC-EC-Ag) was developed for the determination of aminothiols in white wines. The C18 reversed phase LC system operated in the isocratic mode at 0.7 mL min−1 and used an acidic mobile phase composed of formic acid, EDTA, sodium nitrate, sodium hydroxide, and methanol 1% (v/v) at pH 4.5. The working electrode operated at 0.08 V vs Ag/AgCl, 3 M KCl and its manual cleaning was realized once a month by smoothing on a polishing cloth. The analyzed aminothiols were resolved and eluted within 4 min, and all standard curves were linear in the range 2 × 10−7–2 × 10−5 M. The analyzed wine samples needed no preparation other than dilution with the mobile phase. The concentration of cysteine (CYS), homocysteine (HCYS), glutathione (GSH) and N-acetylcysteine (NAC) in bottled white wines, determined by the method of standard addition, was found to be in the low μM range (0.2–2 mg L−1) depending on the wine type and its age. 相似文献