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排序方式: 共有59条查询结果,搜索用时 15 毫秒
21.
Stankov Sv. Rusanov V. Angelov V. Haussühl S. Trautwein A. X. 《Hyperfine Interactions》2002,141(1-4):223-229
Hyperfine Interactions - Angle-dependent Mössbauer investigation on single crystals of barium nitroprosside (BNP) using a-, b- and c-crystal cuts has been performed. The EFG tensor has been... 相似文献
22.
N. R. Stankov 《Journal of Radioanalytical and Nuclear Chemistry》1996,205(2):175-179
Mercury isotopes are now broadly applied in various fields of science and technology. They are used in medicine, nuclear physics investigations, RF standards, nuclear gyroscopes, mercury analysing devices etc. One of the most promising applications is the use of weakly enriched (up to 3%) isotope196Hg in fluorescent lamps for enhancing their light efficiency. Besides, the application of201Hg and202Hg as the target material for the production at low-energy cyclotrons of one of the most consumed201Tl isotope in medicine seems to be perspective. Various methods were proposed and examined for the separation of mercury isotopes. There are: electromagnetic, photochemical, centrifugal, laser, photoionizing method etc. But only two of them were effective for the mercury isotope separation: electromagnetic and photochemical ones. This paper presents a review of the experimental results on separation of various mercury isotopes by different methods. 相似文献
23.
I. G. Koprinkov K. V. Stamenov K. A. Stankov 《Applied physics. B, Lasers and optics》1984,33(4):235-238
An intensive generation of radiation from a discharge-pumped atomic-fluorine gas laser is reported. A peak power exceeding 330 kW and a total energy of more than 2 mJ is obtained for a number of lines in the red, using a NF3He (1100) gas mixture at total pressure of 500 Torr. The circuitry optimization is described and the conditions for effective operation of the atomic-fluorine laser are discussed. The temporal and the spectral characteristics of the laser emission are also presented. 相似文献
24.
Violeta D. Mitić Marija D. Ilić Vesna P. Stankov Jovanović Aleksandra S. Djordjevic Marija S. Marković Gordana S. Stojanović 《Natural product research》2020,34(18):2698-2701
AbstractThe chemical composition of the essential oil and the volatiles obtained by static headspace (HS) of Inula oculus-christi L. is presented. The GC-MS analysis of the hydrodistilled oil resulted in the identification of 90 components, representing 92.7% of the oil. The most abundant compounds were: caryophyllene oxide (9.8%), trans-longipinocarveol (9.2%), eucalyptol (7.3%) and intermedeol (6.2%). The major constituent of I. oculus-christi L. HS volatiles was eucalyptol (87.4%). The antioxidant activity was evaluated by four different methods: 2,2-diphenyl-1-picryl-hydrazylhydrate free radical assay (DPPH), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) method, total reducing power (TRP), ferric reducing antioxidant power (FRAP), and cupric reducing antioxidant capacity (CUPRAC). Total phenolic content in (TPC) examined oil was 177.95?µg GAE/mg oil. Radical scavenging potential of the oil was promising RSC-DPPH was 57.4% and RSC-ABTS was 82.7%. 相似文献
25.
Jelena S. Nikolić Violeta D. Mitić Vesna P. Stankov Jovanović Marija V. Dimitrijević Marija D. Ilić Strahinja R. Simonović 《Analytical letters》2018,51(7):1087-1107
Polycyclic aromatic hydrocarbons (PAHs) represent priority contaminants, and the development of fast, reliable and accurate methods for their determination is of essential importance. The soil is a part of the environment which easily accumulates PAHs, making them available for transport to the air and water over long time periods and by plants through the food chain to humans. The aim of present study was to introduce a novel sorbent to the quick, easy, cheap, effective, rugged, and safe technique for soil sample preparation for the determination of 16 European Union priority PAHs by gas chromatography–mass spectrometry. Two solvent systems, 2:1 (v/v) hexane:acetone and ethyl acetate, were investigated in combination with five clean-up sorbents [Primary secondary amine (PSA), C18, florisil, clinoptilolite, and diatomaceous earth] in this study. The highest overall recovery of the method was achieved by the combination of hexane:acetone with clinoptilolite (recoveries of 70–110%) with limits of detection in the range of 0.60–1.53?µg?kg?1. The analysis of 20 soil samples from Ni?, Serbia resulted in the identification of 11 samples with concentration greater than the values prescribed by law. The ratios of phenanthrene/anthracene and fluoranthene/pyrene were used to elucidate the origin of the PAHs as pyrolytic. 相似文献
26.
27.
Gordana Stojanović Ivana Zrnzević Ivana Zlatanović Miroslava Stanković Vesna Stankov Jovanović Violeta Mitić 《Natural product research》2020,34(4):549-552
AbstractThe aim of this study was to determine, for the first time, the chemical composition of Peltigera horizontalis thallus and apothecia extracts (ether, ethyl acetate, dichloromethane and acetone) by HPLC-UV and GC-MS, and evaluate activity of genotoxic, anticholinesterase, antioxidant and antibacterial potential of acetone extracts. Major constituents of thallus extracts were gyrophoric acid, and methyl gyrophorate while dominant component of apothecia extracts was tenuiorin. The predominant volatile compounds in extracts were methyl orsellinate, dodecyl acrylate, orcinol and orcinol monomethyl ether. The thallus acetone extract at concentration of 2.0 µg mL?1 gave the greatest decrease in the micronuclei frequency (22.4%) of all tested extracts. Apothecia extract showed stronger antioxidant activity as compared to thallus extract. Tested extracts at concentration of 10?mg mL?1 exhibited inhibitory effect (16.5% for thallus and 12.8% for apothecia) on pooled human serum cholinesterase. P. horizontalis acetone extracts had no activity against the tested five bacteria strains. 相似文献
28.
Jelena S. Nikolic Vesna P. Stankov Jovanovic Marija V. Dimitrijevic Dragan J. Cvetkovic Ljiljana P. Stanojevic Ljubisa B. Nikolic 《International journal of environmental analytical chemistry》2017,97(2):112-123
Dichloromethane soil samples extracts were prepared using Soxhlet extraction technique, and after clean-up step, gas chromatography-mass spectrometry analysis of 16 priority polycyclic aromatic hydrocarbons (PAHs) was carried out. A comparison of dispersive solid-phase extraction (dSPE) and column chromatography (cC), as clean-up techniques, was evaluated. Six different sorbents (silica, diatomaceous earth, primary–secondary amine, C18, clinoptilolite and florisil) were tested as dispersive clean-up sorbents versus activated silica and alumina for cC. Best results for three concentration levels among dSPE were obtained using diatomaceous earth, with recovery values in the range of 75–112% for 13 of 16 analysed compounds, while cC recoveries were in the range of 75–111% for all analysed PAHs. Analysis of 12 soil samples from urban area of Ni? (Serbia) singled out acenaphthene as the most abundant compound. 相似文献
29.
Stankov S Röhlsberger R Slezak T Sladecek M Sepiol B Vogl G Chumakov AI Rüffer R Spiridis N Łazewski J Parliński K Korecki J 《Physical review letters》2007,99(18):185501
The confinement of materials in low-dimensional structures has significant impact on propagating excitations like phonons. Using the isotope-specific 57Fe nuclear resonant vibrational spectroscopy we were able to determine elastic and thermodynamic properties of ultrathin Fe films on W(110). With decreasing thickness one observes a significant increase of the mean atomic displacement that goes along with an enhancement of vibrational modes at low energies as compared to the bulk. The analysis reveals that these deviations result from atomic vibrations of the single atomic layers at the two boundaries of the film, while the atoms inside the films vibrate almost bulklike. 相似文献
30.
Dragan Stankov 《Monatshefte für Mathematik》2010,159(1-2):115-131
We investigate the class of ± 1 polynomials evaluated at a real number q> 1 defined as: $$A(q)=\{\epsilon_0+\epsilon_1q+\cdots+\epsilon_k q^k : \epsilon_i\in\{-1,1\}\}$$ and usually called spectrum. Λ(q) is defined by analogy where the coefficients are extended to ± 1,0. In this paper an algorithm for finding the spectrum of a real algebraic integer q without a conjugate of modulus 1 is given. The algorithm can check and terminate if A(q) or Λ(q) is not discrete. Using this criterion a part of a conjecture of Borwein and Hare is proved: if 1 < q < 2 and A(q) is discrete, then all real conjugates of q are of modulus less than q. For an infinite sequence r 2m Zaimi has proved that A(r 2m ) is discrete, and here it is proved that Λ(r 2m ) is not discrete. For given ${q\in (1,2)}$ , an algorithm counting a sequence of ± 1 polynomials P n (x) such that, solutions α n > q of equations ${P_n(x)=\frac{1}{x-1}}$ satisfy α n → q, is presented. 相似文献