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21.
E. Ph. Horwitz M. L. Dietz R. Chiarizia 《Journal of Radioanalytical and Nuclear Chemistry》1992,161(2):575-583
A simple method for the separation and preconcentration of radiostrontium from acidic nuclear waste solutions for subsequent determination is described. The method involves passage of the waste solution, acidified to at least 2M with nitric acid, through an extraction chromatographic column consisting of a 1M solution of bis-4,4(5)[(t-butyl)cyclohexano]-18-crown-6 in 1-octanol sorbed on an inert polymeric substrate, which preferentially retains strontium. The strontium may then be stripped from the column with a small volume of either dilute (0.05M) nitric acid or water. Actinides present are removed quantitatively prior to strontium separation by passage of the sample through an actinide-specific extraction chromatographic column.Work performed under the auspices of the Office of Basic Energy Sciences, Division of Chemical Sciences, U. S. Department of Energy, under contract number W-31-109-ENG-38. 相似文献
22.
Ph. Choquard B. Piller R. Rentsch P. Vieillefosse 《Journal of statistical physics》1989,55(5-6):1185-1262
We report analytical and numerical studies of surface correlations in finite, homogeneously polarizable, classical Coulomb systems placed in an insulating or conducting environment. Their purpose is to understand the phenomenological, shape-dependent laws of electrostatics, from the point of view of statistical mechanics; we focus on the knowledge of the dielectric susceptibility of the system, a quantity proportional to the equilibrium fluctuation of the system's instantaneous polarization per unit volume. This goal has been achieved for a system in a conducting state. The picture is that the shape-dependent part of the susceptibilities results from the action of unbounded observables (the second moments of the instantaneous polarization of the system) on long-range surface correlations and that the relations of electrostatics are verified by means of shape-dependent thermodynamic limits. This picture is supported (i) by exact solutions and asymptotic analysis of the Debye-Hückel approximation of multicomponent plasmas in disks and spheres with insulating and conducting environment and also in ellipses in a vacuum, and (ii) by computer simulations of a one-component plasma in a disk with different environments, notably a conducting environment with permeable and impermeable wall. These observations have revealed for the first time the reason why the susceptibility of a conducting disk in a conductor with impermeable walls diverges linearly with the radius of the disk: this is due to the occurrence of long-range radial correlations in the conductor. These findings are quantitatively interpreted in terms of a novel canonical Debye-Huckel approximation as contrasted to the ordinary grand canonical version. Lastly a fresh look at the problem of the surface correlations of a conductor in a vacuum, which places the observer close to the surface of the conductor but in the vacuum, is presented and applied to the disk, the ellipse, the cylinder, the sphere, and the wedge. 相似文献
23.
24.
Bréchignac C Cahuzac P Kebaili N Lando A Masson A Schmidt M 《The Journal of chemical physics》2004,121(19):9617-9622
The synthesis of silver rich molybdate clusters is achieved by laser induced chemical reaction of coadsorbed MoO(3) and O(2) molecules on free silver clusters. The reactants MoO(3) and/or O(2) molecules condensed at low temperature (77 K-175 K) on free silver clusters. Then, the silver clusters together with their adsorbed molecules are flashed either ionized with a discharge or ionized and heated by a laser. Then they are cooled down by evaporation. The synthesized chemical compounds are analyzed by a high-resolution time-of-flight mass spectrometer. If only one type of reactant is adsorbed on the cluster, only one oxide molecule is stabilized on the metallic core after the heating and cooling cycle. On the contrary, the coadsorption of the two types of molecules MoO(3) and O(2) on Ag(n) (+), at 77 K, leads to complex aggregates that transform, after laser heating, into a molybdate rich metal clusters. These synthesized species cool down by evaporating silver atoms showing evidence of a binary oxide that is more stable than the metallic core. Moreover we demonstrate that for small size molybdate clusters, a stoichiometric composition may differ from the bulk one. 相似文献
25.
S. F. Biagi M. Bourquin R. M. Brown H. J. Burckhart P. Extermann M. Gailloud C. N. P. Gee W. M. Gibson P. Jacot-Guillarmod J. Perrier K. J. Ragan Ph. Rosselet P. Schirato H. W. Siebert V. J. Smith K. P. Streit J. J. Thresher A. T. Wood C. Yanagisawa 《Zeitschrift fur Physik C Particles and Fields》1987,34(2):175-185
In an experiment at the CERN-SPS charged hyperon beam, we have investigated the inclusive \(\Lambda \bar K^0 \) and \(\Sigma ^0 \bar K^0 \) final states formed in Ξ? Be interactions. In the \(\Lambda \bar K^0 \) channel, we observe a signal at 1826 MeV/c2 which can be identified with the known Ξ(1820) resonance. We determine its mass and width to be:M=1826±4 MeV/c2, Г=12±14 MeV/c2. A moment analysis is consistent with a spin of 3/2 and indicates a negative parity for this spin assignment. Also in the \(\Lambda \bar K^0 \) channel, we observe a 3.6σ signal with the following parameters:M=1963±5 MeV/c2, Г=25±15 MeV/c2. This state, which we call Ξ(1960), is not observed in the \(\Sigma ^0 \bar K^0 \) channel, leading to an upper limit on the ratio of partial widths \(\Sigma \bar K/\Lambda \bar K\) of 2.3 (90% confidence level). A moment analysis of the \(\Lambda \bar K^0 \) final state indicates a spin of 5/2 or greater in the natural spin-parity series 5/2+, 7/2?, etc. 相似文献
26.
Photocatalytic Systems. XLIV. On the Intervalence Charge Transfer Behaviour of Ion Pairs of Octacyanomolybdate [Mo(CN)8]4? ions are forming coloured ion pairs with FeIII, CuII, UVIO2, and VIVO, the long-wavelength absorption band of which could be assigned to an intervalence charge-transfer transition. From the solvent dependence of the IT band, interionic distances could be estimated. 相似文献
27.
Kinetics of oil saponification by lead salts in ancient preparations of pharmaceutical lead plasters and painting lead mediums 总被引:1,自引:0,他引:1
M. Cotte E. Checroun J. Susini P. Dumas P. Tchoreloff M. Besnard Ph. Walter 《Talanta》2006,70(5):1136
Lead soaps can be found in archaeological cosmetics as well as in oil paintings, as product of interactions of lead salts with oil. In this context, a better understanding of the formation of lead soaps allows a follow-up of the historical evolution of preparation recipes and provides new insights into conservation conditions. First, ancient recipes of both pharmaceutical lead plasters and painting lead mediums, mixtures of oil and lead salts, were reconstructed. The ester saponification by lead salts is determined by the preparation parameters which were quantified by FT-IR spectrometry. In particular, ATR/FT-IR spectrometer was calibrated by the standard addition method to quantitatively follow the kinetics of this reaction. The influence of different parameters such as temperature, presence of water and choice of lead salts was assessed: the saponification is clearly accelerated by water and heating. This analysis provides chemical explanations to the historical evolution of cosmetic and painting preparation recipes. 相似文献
28.
Hemmerlé J Roucoules V Fleith G Nardin M Ball V Lavalle P Marie P Voegel JC Schaaf P 《Langmuir : the ACS journal of surfaces and colloids》2005,21(23):10328-10331
Mechanically responsive surfaces that allow to switch reversibly from a hydrophobic to a hydrophilic substrate are reported. The surfaces are constituted of polyelectrolyte multilayers deposited on modified charged silicone sheets. n bilayers of poly(allylamine)-Nafion (PAH-Naf) and m bilayers of poly(allylamine)-poly(acrylic acid) (PAH-PAA) composed the multilayers. A (PAH-Naf)(n) film possesses a water contact angle of around 105 degrees, whereas the contact angle of a (PAH-Naf)(4)-(PAH-PAA)(m) multilayer is around 50 degrees. When such a film with m < 5 and terminated by PAA is stretched out, its water contact angle increases up to around 100 degrees. Successive elongation/retraction cycles allow the water contact angle to alternate reversibly between 100 and 57 degrees indicating the reversible mechanical responsive nature of the film. 相似文献
29.
J. P. Durand F. Dawans Ph. Teyssie 《Journal of polymer science. Part A, Polymer chemistry》1970,8(4):979-990
In the course of investigations of polymerization of diolefins by transition metal derivatives, we have synthesized various monometallic nickel coordination catalysts. The complexes were prepared by reacting 2,6,10-dodecatriene-1,12-diyl nickel with protonic acids; they were shown to initiate the stereospecific polymerization of 1,3-butadiene. The study of these catalysts showed the strong influence of the nature of the counteranion used on the stereospecificity and the polymerization rate. Moreover, by adding various ligands, we were able to modify the behavior of the catalytic systems and to prepare either pure cis-1,4 or pure trans-1,4 or cis–trans equibinary polybutadienes, starting from the same complex and keeping a high 1,4 specificity. Some of these modifications were shown to be reversible. 相似文献
30.
Ph. Albert 《Journal of Radioanalytical and Nuclear Chemistry》1980,55(2):453-462
In this article the research topics dealt with at Research Group for Applications of Nuclear Reactions to Chemical Analysis
(GARNAC) are described. Particular emphasis is laid on the main contribution of the GARNAC to the development and the evolution
of charged particle activation analysis, evolving with the analytical studies performed and with the scientific and technical
progress realized in material and semiconductors science.
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