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排序方式: 共有135条查询结果,搜索用时 609 毫秒
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S. Perries A. Astier L. Ducroux R. Duffait Y. Le Coz M. Meyer N. Redon F. Azaiez S. Bouneau C. Bourgeois R. Collatz I. Deloncle B. J. P. Gall F. Hannachi I. Hibbert A. Korichi A. Lopez-Martens R. Lucas V. Méot N. Poffé M. G. Porquet C. Schück H. Sergolle J. F. Sharpey-Schafer R. Wadsworth A. N. Wilson 《Zeitschrift für Physik A Hadrons and Nuclei》1996,354(1):1-2
The francium isotopes200–202Fr were produced in the reaction35Cl+170Yb using bombarding energies of 4.9–5.3 MeV/nucleon. Fusion products were separated in-flight from the primary beam using
a gas-filled recoil separator. An alpha line with the alpha particle energy and half-life of (7468±9) keV and (19
−6
+13
) ms, respectively, was assigned to200Fr. Previously reported decay properties of201,202Fr were confirmed.
Communicated by V. Metag 相似文献
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A method is described for the determination of ten trace metals (V, Cr, Fe, Co, Ni, Cu, Zn, Mo, Cd, Pb) in aqueous samples by simultaneous solvent extraction followed by flame atomic absorption spectrometry. 2,6-DimethyI-4-heptanone is preferred to 4-methyl-2-pentanone as the solvent, and ammonium pyrrolidinedithiocarbamate to sodium diethyl-dithiocarbamate as the extractant except when relatively large amounts of iron are present. Calibration graphs are linear, usually over the range 0–50 μg l-1. The effects of interfering substances, in particular iron, are shown, and the need for calibration by standard additions is demonstrated. The general need for preoxidation of samples is discussed. 相似文献
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Xinhao Yang Naresh Kumar Hua Chi D. Brynn Hibbert Peter W. Alexander 《Electroanalysis》1997,9(7):549-553
Three double-armed diazacrown ethers with two thiophene side groups, 7,16-dithenyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTDC), 7,16-dithenoyl-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTODC), and 7,16-di-(2-thiopheneacetyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (DTAODC), have been synthesized and used as novel neutral lead(II) ionophores in ion selective electrode applications. The relationship between the molecular structure of these ionophores and electrochemical properties (linear range, response time, selectivity) of the membrane electrode is discussed. The optimum conditions for the preparation of the electrodes are described. The optimized dithenoyldiazacrown had a detection limit of pPb = 5.7, and Nernstian range with slope 29.2 mV decade−1 from pPb = 5.0 to 2.7. Mercury and silver ions are the major interferences. These electrodes are applied to potentiometric titrations of lead(II) ions and show promise for the determination of lead ions in water samples. 相似文献
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A multi-sensor cell containing a new photo-cured calcium ion selective electrode sensor is reported. Four membranes containing different components are prepared to determine the one with optimum selectivity and sensitivity. This is shown to consist of the N,N,N',N'-tetracyclohexyl-3-oxapentanediamide ligand (ETH 129) as the ionophore, 2-nitrophenyl octyl ether as the plasticiser and tetradodecyl ammonium tetrakis(4-chlorophenyl) borate as the lipophilic additive. The photo-curing process is applied after coating a thin membrane on a silver wire as substrate transducer to produce the calcium sensor. The curing process is demonstrated to be faster (1 min) than previous methods and does not require a nitrogen atmosphere for reproducible production of membrane response characteristics. Four sensors constructed with the identical optimum membrane are shown to function reproducibly in a multi-sensor flow-through cell using the steady-state mode of flow measurement, and an average calibration slope of 28.5+/-0.4 mV change per activity decade is observed over a log-linear concentration range between 0.01 and 10 mM. The sensor is also shown to respond to changes in pH. Hence, in the flow injection potentiometric mode, a constant carrier buffer composition of pH 8.3 is required for accurate potentiometric calcium determinations. The sensor is used to determine calcium in water samples by flow injection potentiometry. The accuracy of the electrode determination relative to atomic absorption spectroscopy was in the range 5-9% for three different water samples. 相似文献
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The x-ray diffraction intensities of Bragg reflections have been measured at room temperature for thulium selenide, samarium sulphide, samarium selenide and samarium telluride. On the basis of a common amplitude approximation, the Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. The values of the Debye temperatures and mean amplitudes of vibration are 176±16°K, 0·185 ± 0·017 Å (TmSe), 155 ± 7°K, 0·244 ± 0·012 Å (SmS), 153 ± 14°K, 0·221 ± 0·020 Å (SmSe) and 151 ± 20°K, 0·204 ± 0·027 Å (SmTe). 相似文献
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Yang W Jaramillo D Gooding JJ Hibbert DB Zhang R Willett GD Fisher KJ 《Chemical communications (Cambridge, England)》2001,(19):1982-1983
An electrochemical metal ion sensor has been developed with a detection limit of less than 0.2 ppt by the covalent attachment of the tripeptide Gly-Gly-His as a recognition element to a 3-mercaptopropionic acid modified gold electrode. 相似文献