Authors:T. Shakhtshneider, E. Ivanov, and V. Boldyrev
The thermal solid-state isomerizations of Copy2Cl2 (py=pyridine), Nien2(NO2)2 and Nien2(NCS)2 (en=ethylenediamine) were studied by thermal analysis, thermomicroscopy, X-ray diffraction and IR-spectroscopy. It was shown that the reactions proceed by nuclear formation and growth. The kinetic-morphological peculiarities of the processes suggest that the process-determining stage is a phase stage, i. e. structural transformation. The topography and kinetics of processes are therefore determined by the crystal structures of the initial material and the reaction product, and by the contact conditions at the interface. The stress relaxation processes affect the morphology of the products and the kinetics of the transformation.
The uniform weighted approximation errors of Baskakov-type operators are characterized for weights of the form for γ0,γ∞∊[−1,0]. Direct and strong converse theorems are proved in terms of the weighted K-functional.
Authors:I. Ivanov, V. Sedov, V. Shatkov, and E. Shashukov
Diffusion coefficients of22Na,90Sr and134Cs in some aluminoborosilicate and silicophosphate glasses and ceramics have been determined by the integral residual radioactivity
method. The temperature dependence of22Na diffusion coefficients has also been found.
Authors:I. Ivanov, V. Sedov, A. Gulin, V. Shatkov, and E. Shashukov
Diffusion coefficients of radionuclides237Np,239Pu and241Am in simulated alumina phosphate and alumina borosilicate glasses at temperatures lower than their transformation temperature were determined. Actinides are known to be the least mobile elements. In particular, the diffusion coefficients of actinides in alumina phosphate glasses at 673 K are about 10–18 m2·s–1, and in alumina borosilicate at 773 K about 10–19 m2·s–1. It is shown that crystallization of glasses leads to increasing237Np diffusion mobility. It is also shown that a rather small quantity of water absorbed by a crystallized alumina phosphate glass in tensifies low-temperature migration of237Np.
Authors:B. Constantinescu, D. Galeriu, E. Ivanov, G. Pascovici, and D. Ploştinaru
Results of post-Chernobyl measurement on some foodstuff samples /eggs, meat, fruit, honey, medicinal herbs/ from South-Eastern Roumania are presented. Gamma-ray spectrometry was used; the radioactive concentration values are given in nCi.kg–1
wet weight. A strong decrease in concentrations for eggs from 6–7 May /3.0–7.4 nCi for131I, 0.25–0.40 nCi for134Cs, 0.40–0.85 nCi for137Cs per one egg, mainly in the yolk/ to 19–25 May /0.3–1.0 nCi for131I, 0.15–0.25 nCi for134Cs, 0.25–0.40 nCi for137Cs/ was observed. The mean values for lamb meat /joint muscle/ were 500 nCi.kg–1 for131I, 12 nCi.kg–1 for134Cs, 22 nCi.kg–1 for137Cs /18–25 May/. Relatively reduced values were found for fruits, e.g. compared to dairy products1. In May–June 1986, the food consumption in Roumania was strictly limited and controlled by competent authorities.
Authors:B. Constantinescu, E. Ivanov, G. Pascovici, and D. Plştinaru
We present results on the determination of phosphorus, sulfur, fluorine and chlorine in various matrices and some consideration about the possbility of using fast neutrons in elemental analysis based on the variable energy U-120 Cyclotron of the Institute of Atomic Physics (IAP).
Authors:B. Constantinescu, D. Galeriu, E. Ivanov, G. Pascovici, and D. Plostinaru
Various samples from the south-east region of Roumania/greens, fodder, cheese/were analyzed for131I,134Cs and137Cs concentrations in May and July 1986 by -ray spectrometry. The concentrations are reported in nCi. kg–1 wet weight. For greens, a considerable decrease was observed for131I/to 3.0–7.0 nCi. kg–1/,134Cs/to 0.5–2.0 nCi.kg–1/ and137Cs /to 1.0–4.0 nCi. kg–1/ from the first half /5–15 May/ till the end of May 1986. For cheese, maximum values were measured between 5 and 15 May /sheep cottage cheese: 500–800 nCi.kg–1 for131I, 25–50 nCi. kg–1 for134Cs, 40–80 nCi. kg–1 for137Cs/; at the beginning of July a considerable decrease /to 5–10 nCi. kg–1 for131I, 1.2–2.0 nCi.kg–1 for134Cs, 2.2–3.0 nCi. kg–1 for137Cs/ was observed. In autumn 1986 a small increase up to 2.0–3.0 nCi. kg–1 for134Cs and 3.4–5.0 nCi. kg–1 for137Cs /in November/ was reported. The population's internal possible contamination was strongly limited by the authorities' severe control of the food-stuff.
Authors:B. Constantinescu, E. Ivanov, D. Plostinaru, A. Popa-Nemoiu, and G. Pascovici
The reaction14N(p, n)14O(71 s) is used, with a proton beam of 14 MeV energy and 100 nA intensity. The14O activity is detected by means of its characteristic 2.312 MeV gamma-ray (9.4%), with a NaI(T1) detector. The intensity ratio of gamma-rays to that of the incident particles for the sample, related to a similar ratio in adequate standards determines the nitrogen content in the sample. The measurement is completely automated. If we protect the embryo region during irradiation, the future germination of the analyzed seeds will be normal. Good correlation has been obtained between the results of the present method and those of the chemical Kjeldahl method.
Authors:S. Dragoev, D. Balev, G. Ivanov, B. Nikolova-Damyanova, T. Grozdeva, E. Filizov, and K. Vassilev
Lipid oxidation is one of the main factors responsible for the quality loss in refrigerated and frozen stored fish products. The aim of the study was to evaluate the effect of superficial treatment of Atlantic salmon (Salmo salar) with dihydroquercetin (DHQ) solutions on the hydrolytic and oxidative changes in fish lipids during refrigerated storage. It was found that treatment with DHQ solution (1.0 g l−1) reduced approximately twice the free fatty acids content of chilled stored salmon. After 11 days of storage at 1 °С, the contents of hydroperoxides (HPO) and 2-thiobarbituric acid reactive substances (TBARS) of these samples decreased with 45.00 and 0.91 mg MDA/kg, respectively. The share of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) in control and experimental samples did not differ significantly (P>0.05). Results obtained show that the superficial treatment of salmon with DHQ solution (1.0 g l−1) delayed the hydrolytic and oxidative changes in fish lipids significantly, thus preserving the salmon freshness up to 11 days of storage at 1 °С.
Authors:N. Shilo, E. Ippolitov, V. Ivanenko, B. Kustov, V. Zheleznov, G. Aristov, A. Shtan, I. Ivanov, V. Kovalenko, and N. Kondrat’ev
A facility using a californium neutron source and a method for the neutron activation analysis of gold were developed. The
sensitivity of the determination is 0.1 g/t. The sources of random and systematic errors have been studied. It has been concluded
that in prospection and evaluation of gold ore deposits, the traditional test tube analysis for gold may be replaced with
the developed method.