Results 1 - 10 of 667
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[en] Derivative constant-energy synchronous luminescence spectrometry (DCESLS) was evaluated using four-component mixtures of fluorene, carbazole, anthracene and perylene. The results show the effectiveness of DCESLS for the identification and determination of polynuclear aromatic hydrocarbons. (author). 27 refs.; 3 figs.; 2 tabs
[en] Extensive observations of the Stokes and anti-Stokes fluorescence spectra of 1,12-benzoperylene in n-heptane solution from -90 to +90degreeC are reported and analyzed. Corresponding absorption spectra over the same temperature range are used in the assignment of the vibronic states and transitions. The normal fluorescence spectrum has five bands, corresponding to the S01→S00, S10, S20, S30, S40 transitions (S/sup V//sub E/ refers to a singlet electronic state S/sub E/ in a vibrational level V), which are the origins of symmetric nu-bar5 vibrational progressions. Three bands beyond the S01→S00 transitions are identified as S11, S21, S31→S00 hot fluorescence and one band as S02→S00 fluorescene, and these are the origins of similar nu-bar5 progressions. It is proposed that the S01→S/sup m/0(mnot-equal0), S/sup n/1→S00 (nnot-equal0), and S01→S00 transitions are induced by vibronic coupling to allowed S/sup m/2→S/sup m/0, S02→S00, and S12→S00 transitions, respectively. The S02→S00 fluorescence is partly directly excited and partly thermally excited from S01. Separation of these two components leads to an evaluation of the S02 lifetime (21 +- 4 ps) and the S02→S/sup n/1 internal conversion rate
[en] Full text:Yttrium-90 (90Y)-microspheres administered via the hepatic artery has been used for the treatment of unresectable primary or metastatic cancer in the liver.Y-90 is a pure betta-emitter and emits betta-particles to decay to stable Zr-89 having peak energy of 2.28 MeV and an average energy of about 0.94 MeV.The dosimetery of low-energy betta-sources is inherently complicated due to the sharp dose gradients and the limited range in tissue of the betta-particles. The distribution of elements within the microspheres can be effective in the dosimetery. So in this study we focused on the distribution of elements into the microspheres.The quantitative analysis of the microstructure of microspheres is able, by the use of SEM mapping as shown in Figure 1. In this figure, the topographical analysis of microspheres cross sections is given. Figure 1 shows EDS maps of Azar sphere (yttrium aluminum silicate) microspheres. The EDS map indicated the distribution of the Y, Si, O, and Al elements into the microspheres at cross section.SEM/EDS line scan techniques was employed for determination of the elemental redistribution across the cross section microspheres for silicon, yttrium, aluminum and oxygen element.In figure 2, a line scan with SEM-EDX is shown along the cross section of Azar sphere sample. The results of the scan showing the variations of concentrations of Si, Y, O and Al are shown in figure 2.
[en] This thesis describes the conformational analysis of some polynucleotides in aqueous solution. A new graphical method is presented as an aid in the pseudorotational analysis of the sugar rings in DNA by means of sums of proton-proton coupling constants. (Auth.)
[en] The two-photon ionization and excitation spectra of fluoranthene in liquid n-pentane have been measured and together with laser power versus signal intensity measurements have been utilized to elucidate the multiphoton ionization mechanism for this and other molecules in liquids
[en] Full text: Complexons and organic compounds are widely used in NPP operating: for decontamination and rinses of heat-and-power equipment. Later these compounds go to the waste waters, make the process of their treatment more complicated and as a result negatively influence on environment. According to initial investigation polynuclear hydroxocomplexes of polyvalent cations (Fe, Cr, Co) may be used as effective catalysts in electrochemical destruction of waste water organic compounds. The aim of the work is to investigate the complexion destruction by hydrogen peroxide, to develop the method for obtaining homogeneous catalyst and to choose the conditions for catalytic oxidizing process of complexing and organic compounds. The efficiency and significance of the results consist in improvement of ecological situation due to waste water purification and toxic substances involving environmental prevention.