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1.
S. S. Rattan A. V. R. Reddy V. S. Mallapurkar R. J. Singh Satya Prakash 《Journal of Radioanalytical and Nuclear Chemistry》1981,67(1):95-99
A simple method is reported in this paper to estimate229Th in the presence of228Th. The total activity of229Th and228Th was determined by following the alpha activity growth (using a liquid scintillation counter and proportional counter) of
purified thorium samples. The activity ratio of229Th/228Th was determined by alpha spectrometry. From the initial total activity and ratio, disintegration rates of229Th and228Th were calculated. The values obtained for the activities have a precision better than ±2%. 相似文献
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C. Agarwal A. Goswami P. C. Kalsi S. Singh A. Mhatre A. Ramaswami 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(2):445-451
Cumulative yields of 27 fission products have been determined in 229Th(n,f) by recoil catcher technique followed by gamma-ray spectrometry. Absolute fission yields were arrived at from the fission
rate measured by track etch counting method. Mass yields were obtained from the cumulative yields using the charge distribution
parameters reported in the literature. The values agree well with the reported values obtained both by physical and radiochemical
methods. The resulting asymmetric mass distribution shows strong fluctuation in the yields in the light and heavy wings with
a periodicity of five mass units. 相似文献
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Myllykylä E. Lavonen T. Koivula L. Ollila K. Siitari-Kauppi M. 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(1):225-235
Journal of Radioanalytical and Nuclear Chemistry - The sparingly soluble ThO2 dissolution behaviour was studied under conditions that are expected to prevail in bedrock after the closure of the... 相似文献
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Structural and chemical properties of the building block of silica nanowires, (SiO(2))(6), are investigated with the theory of atoms and molecules (QTAIM). Twenty-five conformers have been analyzed, ten of which have not been reported before. We extend the silica (SiO(2))(6) topology phase space using QTAIM; the Poincaré-Hopf topological sum rules are applied and used to identify the spanning set of topologies, and this includes finding eight new distinct topologies that satisfy the Poincaré-Hopf relation. A simple phase diagram of the solutions of the Poincaré-Hopf relation is created with the aid of a new classification scheme to determine the boundary between topological stability and instability. Sum rules are then found to be applicable to any set of isomers. We determine that O-O bonding interactions exist for the silica (SiO(2))(6) conformers in regions where the energy surface is flattest. In addition, we identify unstable local minima in the topology of the charge density in order to further compare conformer instabilities. We quantify the dimensionality of a molecule using the Poincaré-Hopf relation instead of Euclidean geometry. This quantum topological definition of geometry shows that the four most energetically stable (SiO(2))(6) conformers are quantified as two-dimensional within the new quantum topology. 相似文献
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Cavalli JF Tomi F Bernardini AF Casanova J 《Magnetic resonance in chemistry : MRC》2004,42(8):709-711
4-Epi-cis-dihydroagarofuran was isolated from the bark oil of Cedrelopsis grevei and its structure was elucidated by 1D and 2D-NMR spectroscopy. 相似文献
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Wei Liu Wen Fang Dong Xiang Wei Liao Bao He Guan Zhan Zhu Liu 《Journal of heterocyclic chemistry》2011,48(2):414-418
A new approach that tried to obviate the use of bromine protection groups was studied to synthesize (?)‐renieramycin G from L ‐tyrosine. It was found that the first intermolecular Pictet–Spengler reaction proceeded successfully to give the correct tetrahydroisoquinoline precursor 6 . However, the second intramolecular Pictet–Spengler cyclization step failed to give the desired product, and an isomer of the skeleton of the renieramycins was obtained via 12 steps starting from L ‐tyrosine. J. Heterocyclic Chem., (2011). 相似文献
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Attempted synthesis of 1,8-dicyclooctatetraenylnaphthalene (1) by the palladium(0)-catalyzed coupling of 1,8-dibromonaphthalene with cyclooctatetraenyltrimethylstannane afforded a single unsymmetrical isomer of 1 in 88% yield. Two-dimensional NMR methods and spectral synthesis were employed to assign the structure of the isomer (2). AM1 geometry-optimized structures of 2 and its isomers showed that the unexpected unsymmetrical structure of 2 results from the minimization of repulsive inter-ring H-H interactions. Compound 2 is postulated to arise via tandem [2 + 2] cycloaddition and 6 pi --> 4 pi + 2 sigma electrocyclization reactions of 1. 相似文献
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[reaction: see text] Irradiation of 5,12-didecyloxytetracene (1) leads to photodimers P(1) (planosymmetric) and P(2) (centrosymmetric). P(1) is characterized by naphthalene excimer fluorescence, whereas P(2) emits naphthalene monomer fluorescence. 相似文献
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Conclusions From the racemes ofC. xanthifolia Fresen. have been isolated a sesquiterpene lactone C16H20O4, the structural (+)-isomer of (–)-coronopilin, which has not been studied previously; structure I has been proposed for it.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 5, pp. 375–377, 1969 相似文献
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Photocycloadditlon of (+)-isoplperltenone and cyclobutene-1-carboxylic acid gives an adduct which upon reduction with NaCNBH3 followed by thermolysis yields an isomer of isoaristolactone in an overall yield of 26%. 相似文献
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用浅显的方法具体实例化地介绍了求解同分异构体计数问题的图论及群论的数学抽象表示和数学原理,以及从生成函数及树型结构计数的概念到结构异构和立体异构两类同分异构体计数问题的求解。最后通过数学软件Maple16的简单编程,给出了具体实现的方法。 相似文献
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A method is described for the determination of228Th,230Th, and232Th in environmental samples from uranium mining and milling operations. The analytical procedure is based on the direct determination
of228Th in the sample by high resolution γ-spectrometry followed by extraction and purification of the thorium fraction using high
molecular weight amines and an anion-exchange technique, respectively, prior to α-spectrometry to determine isotopic ratios.
The lowest level of detection for each thorium isotope is 0.01 pCi/g for solid samples and 20 pCi/l for aqueous samples. Replicate
analyses of a typical mine waste stream gave a standard deviation of ±3% for228Th. Standard deviations of the230Th and232Th increased to ±11% apparently due to traces of210Po interfering in the α-spectrometry. 相似文献
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The rotational spectrum of protonated carbonyl sulfide, HSCO(+), has now been detected in the centimeter-wave band in a molecular beam by Fourier transform microwave spectroscopy. Rotational and centrifugal distortion constants have been determined from transitions in the K(a)=0 ladder of the normal isotopic species, and DSCO(+) and H(34)SCO(+). HSCO(+) is systematically more abundant by a factor of three than HOCS(+), the isomer obtained by attaching the H(+) to the other end of the molecule, which ab initio calculations long predicted to be higher in energy by 4-5 kcalmol. Because HSCO(+) is comparable in polarity to HOCS(+) and is apparently more stable and because OCS is widely distributed in astronomical sources, HSCO(+) is a good candidate for detection with radio telescopes. 相似文献
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trans, trans-2,4-hexadiene is quantitatively converted into cis-3-hexene by photoinduced hydrogenation catalyzed by chromium carbonyl complexes in presence of acetone which allows both acceleration and selectivity. 相似文献