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The applicability of the traditional kinetic power equation to describe the thermal destruction of solids, and in particular polymers, is discussed. It is shown that in the majority of cases the use of such an equation is reasonable, even though the true mechanism of the process under study is either obscure or so complex that it cannot be analytically described in detail. In such cases the effective rather than the true kinetic parameters are obtained and provide certain useful information on the process.

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Abstract  

Procedures for determining traces of calcium, titanium, vanadium, chromium, iron, copper, niobium, molybdenum and tungsten in tantalum are described utilizing 11 MeV proton activation. The instrumental method of analysis with the use of a Ge(Li) detector and the radiochemical separation of the corresponding fractions are described. The formula for the calculation of the concentration of traces with the use of thick target yields is given. Experimental data on the thick target yields of radioisotopes44Sc,52Mn,56Co,65Zn,93mMo,96Tc are presented. Based on the experimental data, the detection limits are estimated at 1–10 ppb for the above mentioned metal traces in tantalum. The successful solution of the task of the simultaneous determination of nine elements in tantalum confirms the wide applicability of proton activation analysis.

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Abstract  

A solubility of nitrogen in natural basalts and synthesized albite at 1250 °C and 3 kbar was studied by -activation method based on the reaction14N(,n)13N with radiochemical separation of nitrogen by high-temperature extraction at 1800 °C. Detection limit of 0.2 g in the samples of 15–20 mg weight is obtained. The investigation originated from the study of processes of accumulation and redistribution of nitrogen in rock-forming alumosilicate melt of the Earth mantle. The dependence of nitrogen solubility on the oxygen volatility and pressure were obtained (within 1–3 kbar in the presence of IW buffer [iron(Fe)-wustite(FeO)]) and NNO (Ni–NiO), and essential effect of the composition of the initial matrix was found. Special attention was given to standards, background, interference reactions, reliability and accuracy of the results.

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Abstract  

A selective liquid scintillation method is suggested for plutonium determination by alpha-spectrometry in the presence of uranium. The analytical process consists of extracting plutonium from nitric acid solutions using BPHA, TOA and MTOA nitrate as extractants into toluene scintillator. Effect of various extractants and nitric acid concentration on the extraction of Pu(IV) and U(VI) together with scintillations quenching were investigated. A simple and fast two-stage selective scintillation method is also suggested for Pu determination in the irradiated uranioum samples.

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Abstract  

The possibility of detecting trace amounts of neptunium atoms and molecular compounds by laser resonance ionization spectroscopy has been investigated in acetylene-air and acetylene-nitrous oxide flames. Experimentally evaluated atomization coefficients of neptunium in the process of thermal dissociation in flames (10–4% for C2H2-air and 10–2% for C2H2–N2O) do not allow to use atomic ionization signal for determination of neptunium microamounts in solutions. High yield multiphoton ionization of NpO molecule has been realized in fuel rich C2H2–N2O flame. This pehnomenon has been used for determination of trace quantities of Np in solution. The detection limit was 2·10–9 g/ml.

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Abstract  

The distribution of lanthanides and actinides in a two-phase liquid system obtained by mixing an aqueous solution of poly(ethylene glycol) and ammonium sulfate has been studied as a function of pH. Conditions are reported which provide the heterogeneity of the system suggested. It is shown that thorium and plutonium can be separated from transplutonium elements and lanthanides. Conditions have been chosen for quantitative group extraction of actinides and lanthanides.

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Journal of Thermal Analysis and Calorimetry
Authors:
Yu. A. Gaponov
,
B. I. Kidyarov
,
N. A. Kirdyashkina
,
N. Z. Lyakhov
, and
V. B. Okhotnikov

The kinetics of isothermal dehydration of two crystal hydrates with equivalent water molecule sublattices (LiCOOH.H2O and LiSO4.H2O) was investigated in vacuum with a quartz crystal microbalance, and the dynamics of structural reorganization of the substances was studied by the synchrotron radiation method. Differences were found both in the nucleation stage and in the stage of reaction interface advance. The results indicate that the kinetic behaviour of isothermal decomposition of solids is determined by the structural reorganization of a metastable intermediate.

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Abstract  

Oxygen and fluorine have been simultaneously determined by 14-MeV INAA in samples containing boron. Both boron and fluorine can cause serious interferences in the determination of oxygen. The fluorine and boron interference corrections for oxygen determination have been determined to be 0.43±0.01 and 0.0832±0.0017 apparent g oxygen per g of fluorine and boron, respectively, for our system. Boron can be determined in the same sample by a second irradiation. Mutual interferences have been evaluated and the procedure has been applied to NIST SRM and several other compounds.

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Phenolic contents and antioxidant capacities from different solvent extracts (petroleum ether, ethyl acetate, methanol, butanol and water) of Aster scaber leaf were investigated. Antioxidant activity was evaluated by three different methods, namely DPPH radical scavenging activity, reducing power assay and phosphomolybdenum activity. A total of twenty-three polyphenolic compounds were identified and quantified from A. scaber leaf extracts, including hydroxybenzoic acids, hydroxycinnamic acids, flavonols and other groups of phenolic compounds. Ultra high performance liquid chromatography (UHPLC) analysis of the leaf extract revealed that myricetin (4850.45 μg/g) was the most dominant flavonols, compared to quercetin and kaempferol. Caffeic acid was the dominant phenolic compound in A. scaber leaf extracts, it constituted about 104.20 μg/g, followed by gentisic acid (84.50 μg/g), gallic acid (61.05 μg/g) and homogentisic acid (55.65 μg/g). The total phenolic and flavonoid content was the highest in ethyl acetate extract (322.43 and 6.51 mg/g). The decreasing order of antioxidant activity among the A. scaber leaf extracts assayed through all the three methods was found to be ethyl acetate > butanol > methanol > petroleum ether > water extract.

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Saccharomyces cerevisiae MERIT.ferm was used as mono- and mixed-cultures with Williopsis saturnus var. mrakii NCYC500 in mango wine fermentation. A ratio of 1:1000 (Saccharomyces:Williopsis) was chosen for mixed-culture fermentation to enable longer persistence of the latter. The monoculture of S. cerevisiae and mixed-culture was able to ferment to dryness with 7.0% and 7.7% ethanol, respectively. The monoculture of W. mrakii produced 1.45% ethanol. The mango wines fermented by S. cerevisiae alone and the mixed-culture were more yeasty and winey, which reflected their higher amounts of fusel alcohols, ethyl esters and medium-chain fatty acids. The mango wine fermented by W. mrakii alone was much less alcoholic, but fruitier, sweeter, which corresponded to its higher levels of acetate esters.

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