排序方式: 共有29条查询结果,搜索用时 21 毫秒
21.
Sergey Markov Vitali Nagirnyi Andrey Vasil’ev Vladimir Makhov Raul Laasner Sebastian Vielhauer Marco Kirm Rimantas Grigonis Valdas Sirutkaitis 《Central European Journal of Physics》2012,10(4):1002-1008
The analytical expressions for the three-dimensional spatial distribution of excitons and luminescence decay kinetics of wide band-gap crystals were derived taking into account the saturation effect for absorption near the centre of the incident laser beam with Gaussian transversal profile. The model is verified for the excitonic emission of CdWO4 crystals under excitation by ultra-short laser pulses in the region of weak excitonic absorption. 相似文献
22.
Eugenijus Norkus Giedrė Grincienė Tapani Vuorinen Rimantas Vaitkus 《Journal of inclusion phenomena and macrocyclic chemistry》2004,48(3-4):147-150
Polarographic investigations of Cu(II) complexation in aqueous alkaline solutions containing an excess of β-cyclodextrin (β-CD) show that the complex formation begins at pH > 11, the concentration of free (uncomplexed) Cu(II) ions being in the range from ca. 10-12 to ca. 10-19 M, depending on β-CD concentration and pH. The formation of copper(II) 1:1 hydroxy-complex with β-cyclodextrin anion (CD2-) was observed at pH 11–14. The logarithm of the stability constant of CuCD(OH)2- 2 complex is 19.7 ± 0.2 (20 °C, ionic strength 1.0), the values of the molar extinction coefficient and of the diffusion coefficient of this complex are 50 M-1 cm-1 (λmax = 660 nm) and 1.0 × 10-6 cm2 s-1, respectively. 相似文献
23.
In the paper, we present some general theorems on large deviations of random vectors with cumulants satisfying the generalized Statulevi?ius condition. The results obtained are applicable in derivation of limit theorems in the scheme of series, including the case where the dimension of the considered random vectors is growing indefinitely. 相似文献
24.
Maris Lauberts Galina Telysheva Petras Rimantas Venskutonis Liga Lauberte Tatiana Dizhbite Rita Kazernavičiūte Audrius Pukalskas 《Chemical Papers》2017,71(5):1007-1012
Diarylheptanoid-rich extracts (DAHEs) isolated from grey and black alder bark with pressurized ethyl acetate were tested in mayonnaise as a dietary antioxidant using the Oxipres method. DAHE contains >700 mg g?1 of oregonin possessing quite similar structure to the well-known dietary antioxidant curcumin, which is widely used as a bioactive constituent of food supplements. Strong radical scavenging capacity of oregonin was clearly demonstrated by the online HPLC–DPPH? scavenging assay. The antioxidative effect of DAHEs in mayonnaise was dose dependent; however, even the lowest concentration (0.5 mg g?1) of DAHE additive increased the induction period of oxidation more than two times. Consequently, DAHE may be considered as a promising natural antioxidant for commercial applications. 相似文献
25.
The paper is devoted to the supremum-type multivariate goodness-of-fit tests based on the empirical characteristic function. Particular attention is devoted to the composite hypothesis of normality and Gaussian distribution mixture model. An analytical way to approximate the null asymptotic distributions of the considered test statistics is discussed applying the theory of large excursions of differentiable Gaussian random fields. The produced comparative Monte Carlo power study shows that the considered tests are powerful competitors to the existing classical criteria, clearly dominating in verification of the goodness-of-fit hypotheses against the specific types of alternatives. 相似文献
26.
Giedre Nenartaviciene Ramunas Skaudzius Rimantas Raudonis Aivaras Kareiva 《Central European Journal of Chemistry》2009,7(3):362-368
The aqueous sol-gel synthesis technique for the preparation of (Pb,Sr)Sr2(Y,Ca)Cu2O7±x (Pb-1212) and (Pb2,Cu)Sr2(Y,Ca)Cu2O8±x (Pb-3212) superconductors using two different complexing agents, namely 1,2-ethanediol and tartaric acid was studied. The
phase transformations, composition and micro-structural features in the polycrystalline samples were studied by powder X-ray
diffraction analysis (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). XRD analysis of the ceramic
samples obtained by calcination of Pb-Sr-Y-Ca-Cu-O acetate-glycolate precursor gels in air, for 10 hours at 800°C and at 825°C,
showed the presence of homogeneous Pb-1212 and Pb-3212 crystallites as major phases. The XRD patterns of the ceramics obtained
from Pb-Sr-Y-Ca-Cu-O acetate-tartrate precursor gels, however, showed multiphasic character. The critical temperature of superconductivity
(TC (onset)) observed by resistivity measurements were found to be 91 K and 75 K for Pb-1212 and Pb-3212 samples, respectively.
相似文献
27.
Dalia Jonynaite Darius Jasaitis Rimantas Raudonis Algirdas Selskis Remigijus Juskenas Jurate Senvaitiene Aivaras Kareiva 《Central European Journal of Chemistry》2012,10(5):1574-1583
In the present work, the formation of cobalt aluminium spinel (CoAl2O4) as well as novel cobalt neodymium-aluminates with nominal compositions of CoAl1.75Nd0.25O4, CoAl1.5Nd0.5O4 and CoAlNdO4 by an aqueous sol-gel process and the sinterability of the products are investigated. The metal ions, generated by dissolving
starting materials of metals in the diluted acetic acid were complexed by 1,2-ethanediol to obtain the precursors for the
mixed metal ceramics. The phase purity of the synthesized compounds was characterized by powder X-ray diffraction analysis
and infrared spectroscopy. The microstructural evolution and morphological features of the products were studied by scanning
electron microscopy and atomic force microscopy, which together with the optical characterization of these new compounds showed
that the sol-gel-derived materials could be successfully used as effective cobalt-based ceramic pigments.
相似文献
28.
The paper deals with a mathematical model which describes how the collection of key phrases (and key words) evolves as a field of science develops. The experimental material is based on statistical observations on the sets of key phrases which have been assigned to papers in representative major journals in the field in question. Asymptotic properties of the model are considered, as well as estimators for the parameters of the model with particular emphasis on estimators that can indicate at what stage a collection of key phrases can be assumed as complete for the field in question at a given moment in time. 相似文献
29.