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J. I. Skorovarov L. I. Ruzin A. V. Lomonosov G. K. Tselitschev 《Journal of Radioanalytical and Nuclear Chemistry》1998,229(1-2):111-A117
Phosphorites of sedimentary origin utilized in manufacturing of fertilizer contain uranium, thorium and products of their
radioactive decay, as well as health-endangering compounds of cadmium, arsenic and fluorides. Some of them may transit into
the phosphoric acid, when breaking down the phosphorites with sulphuric, acid, and then into the fertilizer. The purpose of
the phosphoric acid cleaning is its decontamination from uranium and thorium as well as the removal of toxic cadmium. The
above task can be achieved by solvent extraction. The paper presents the results of the extraction of uranium and cadmium
from phosphoric acid using polyalkyl phosphasene and trioctyl amine, respectively. The extraction kinetics, equilibrium distribution
of uranium and cadmium within the phases, the effect of extractant concentrations and temperature of the process is also discussed.
The technological schemes for cleaning phosphoric acid from uranium and cadmium are given. 相似文献
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Garcia Ruano JL Alemparte C Martin Castro AM Adams H Rodriguez Ramos JH 《The Journal of organic chemistry》2000,65(23):7938-7943
The behavior of (Z)-3-p-tolylsulfinylacrylonitrile (1) as a chiral dienophile has been evaluated from its reactions with furan and acyclic dienes. Electrostatic interactions of the cyano group with the sulfinyl one restrict the conformational mobility around the C-S bond, thus controlling the pi-facial selectivity, which is almost complete in all cases, the approach of the diene from the less-hindered face of the dienophile (that bearing the lone electron pair) in the predominant rotamer being the favored one. The regioselectivity is also completely controlled by the cyano group. Additionally, the reactivity of compound 1 as well as its endo-selectivity are both higher than those observed for the corresponding (Z)-3-sulfinylacrylates, thus proving the potential of sulfinylnitriles as chiral dienophiles. 相似文献
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EI Rodriguez Martinez CI Barriga-Paulino MI Zapata CC Chinchilla AM López-Jiménez CM Gómez 《BMC neuroscience》2012,13(1):104-23
ABSTRACT: BACKGROUND: The peri-adolescent period is a crucial developmental moment of transition from childhood to emergent adulthood. The present report analyses the differences in Power Spectrum (PS) of the Electroencephalogram (EEG) between late childhood (24 children between 8 and 13 years old) and young adulthood (24 young adults between 18 and 23 years old). RESULTS: The narrow band analysis of the Electroencephalogram was computed in the frequency range of 0--20 Hz. The analysis of mean and variance suggested that six frequency ranges presented a different rate of maturation at these ages, namely: low delta, delta-theta, low alpha, high alpha, low beta and high beta. For most of these bands the maturation seems to occur later in anterior sites than posterior sites. Correlational analysis showed a lower pattern of correlation between different frequencies in children than in young adults, suggesting a certain asynchrony in the maturation of different rhythms. The topographical analysis revealed similar topographies of the different rhythms in children and young adults. Principal Component Analysis (PCA) demonstrated the same internal structure for the Electroencephalogram of both age groups. Principal Component Analysis allowed to separate four subcomponents in the alpha range. All these subcomponents peaked at a lower frequency in children than in young adults. CONCLUSIONS: The present approaches complement and solve some of the incertitudes when the classical brain broad rhythm analysis is applied. Children have a higher absolute power than young adults for frequency ranges between 0-20 Hz, the correlation of Power Spectrum (PS) with age and the variance age comparison showed that there are six ranges of frequencies that can distinguish the level of EEG maturation in children and adults. The establishment of maturational order of different frequencies and its possible maturational interdependence would require a complete series including all the different ages. 相似文献
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A. A. Prishchenko M. V. Livantsov I. F. Lutsenko M. V. Lomonosov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Dialkylaminomethylation of trimethylsilyl esters of trivalent phosphorus acids using bis(dialkylamino)methanes was carried out for the first time. This reaction is a convenient method for preparation of quaternary coordinated phosphorus compounds, including dialkylaminomethyl and functional groups. Thus trimethylsilylphosphites and -phosphonites of various structures react with bis(dialklamino)-methanes according to Arbuzov reaction in the presence of zinc chloride as a catalyst, when heated to 120°C, resulting in formation of phosphonates and phosphinates (I) 相似文献
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The kinetics of the oxidative coupling of methane (OCM) in the presence of La/MgO and NaWMn/SiO2 catalysts in a flow reactor at low reactant conversions was studied. It was found that, in spite of different compositions and properties of the test catalysts, the formation of ethane from methane and ethylene from ethane can be described within the framework of the Mars-van Krevelen redox model in both cases. The rate laws of side reactions, which lead to the formation of carbon oxides, are different from the rate laws of the target reactions of the conversion of methane into ethane and ethane into ethylene. The kinetic parameters required for the numerical simulation of the OCM process were determined for either of the catalysts. 相似文献
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Measurement of the critical fracture strength of single-crystal silicon was carried out by contact-free laser-based excitation and detection of nonlinear surface acoustic wave (SAW) pulses. The three crystallographic geometries Si(112)111[over ], Si(112)1[over ]1[over ]1, and Si(110)11[over ]1 were examined. A comparison of the optically detected SAW transients and numerically calculated stress-strain fields allowed an estimate of the intrinsic mechanical strength without using an artificial precrack. Depending on the geometry, the critical strength varied between 5 and 7 GPa. 相似文献