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71.
V. Dondur R. Dimitrijevi? Lj. Damjanovi? S. Macura 《Journal of Physics and Chemistry of Solids》2008,69(11):2827-2832
The Li+- and Na+-doped hexacelsians (HC) synthesized from Ba-LTA synthetic zeolite as precursors were used for preparation of monoclinic celsians (MC). The doped pure MC and mixture HC/MC species were obtained by thermally induced polymorphous transformation at 1200 °C. Synthesized-doped MC have been characterized by X-ray powder diffraction and spectroscopic (infrared, Raman and 29Si magic angle spinning nuclear magnetic resonance) methods. The obtained results suggest that in all investigated samples Na+ or Li+ dopants were incorporated in MC crystal structures during thermal transformation of a zeolite. It has been shown that HC→MC transformation depends on molar fractions of alkali cations. These findings combined with used temperature/time conditions could help in optimization of MC synthesis route. 相似文献
72.
Đ. Petrović A. Đukić K. Kumrić B. Babić M. Momčilović N. Ivanović Lj. Matović 《Journal of Radioanalytical and Nuclear Chemistry》2014,302(1):217-224
Ordered mesoporous carbon (OMC) was used as an adsorbent for the removal of pertechnetate (TcO4 ?) anion. The maximum uptake (93 %) of TcO4 ? was obtained after 60 min of contact. The adsorption of TcO4 ? is almost pH-independent in very wide pH region (from 4.0 to 10.0). Maximum K d of 6.6 × 103 cm3 g?1 was found at pH 2.0. TcO4 ? interacts with carboxylic functional groups present at the surface of the OMC by displacing the OH? ions with TcO4 ? via ion exchange mechanism. 相似文献
73.
74.
A. Vertačnik D. Barišić Lj Musani E. Prohić M. Juračić 《Journal of Radioanalytical and Nuclear Chemistry》1997,218(1):45-52
Concentrations of Ag, Ba, Cd, Ce, Cs, Co, Cr, Eu, Fe, Rb, Sc, Sr, Th, and Zn exchangeable fractions were determined in alluvial sediments at waste disposal site area in the vicinity of water-well field. Samples have been leached with 0.5M NH4Cl at a sample/solution ratio of 120 during 24 hours without shaking. INAA of dry NH4Cl residues show that the concentrations of exchangeable elements determined in the most of the sediments below the wastes have natural levels. Ag, Ba and Sr are readily exchangeable; Rb, Cs and Zn have lower exchangeability, while Cd, Ce, Th, Sc, Eu, Cr, Fe and Co are rather immobile. Extremely high total and exchangeable silver concentration was found at 6.5–6.8 meters below waste in the aerated layer occasionally under the water table. Exchangeable concentrations in deeper water-bearing sediment layers are not elevated. Due to this, one can presume that the upper sediment layers act as chemical filter generally preventing the infiltration from overlying wastes into water-bearing layers. 相似文献
75.
S. P. Sovilj V. M. Vasié D. Lj. Stojié 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(5):709-712
The influence of cationic surfactant hexadecyltrimethylammonium bromide (CTAB) on the kinetics of the spontaneous reduction
of the analytically important compound, sodium hexanitrocobaltate(III), was studied. The spontaneous reduction was monitored
spectrophotometrically at pH 2 and 5 and at concentrations of CTAB from 1 × 10−5 to 5 × 10−4 M. The mechanism of this process was described using two consecutive first-order reactions. A decrease in the rate constant
for reduction at pH 5 in solutions containing CTAB in concentrations of 5.6 × 10−5 M (critical micelle concentration) compared with its rate in an aqueous solution was observed. These effects could be explained
by electrostatic and hydrophobic/hydrophilic interactions between the micellar pseudophase and the hexanitrocobaltate(III)
ion.
The article is published in the original. 相似文献
76.
Ivona R. Radović Mirjana Lj. KijevčaninEmila M. Djordjević Bojan D. DjordjevićSlobodan P. Šerbanović 《Fluid Phase Equilibria》2008
The densities of binary mixtures of (1-propanol, or 1-butanol, or 2-butanol, or 1-pentanol + chlorobenzene) have been measured at temperatures 288.15, 293.15, 298.15, 303.15, 308.15 and 313.15 K and atmospheric pressure while for the system (2-methyl-2-propanol + chlorobenzene) measurements were performed at the same pressure and temperatures 303.15, 308.15, 313.15, 318.15 and 323.15 K. All measurements were performed by means of an Anton Paar DMA 5000 digital vibrating-tube densimeter. Excess molar volumes VE were determined and fitted by the Redlich–Kister equation. It was observed that in all cases, VE increase with rising of temperature. The values of limiting excess partial molar volumes have been calculated, as well. The obtained results have been analysed in terms of specific molecular interactions present in these mixtures taking into consideration effect of the chain length of alcohols, degree of branching in the chain, relative position of the alkyl and OH group in an alcohol and the effect of temperature on them. In addition, the correlation of VE binary data was performed with the Peng–Robinson–Stryjek–Vera cubic equation of state (PRSV CEOS) coupled with the van der Waals (vdW1) and CEOS/GE mixing rule introduced by Twu, Coon, Bluck and Tilton (TCBT). Also, the possibility of cross prediction between VE and VLE by means of the NRTL parameters of GE model available in literature and those incorporated in the TCBT model was tested. 相似文献
77.
D. Djur?i? Lj.D.R. Ko?inac M.R. ?i?ovi? 《Journal of Mathematical Analysis and Applications》2007,327(2):1297-1306
We investigate the class R∞,s of rapidly varying sequences from different points of view. It is shown: (1) a sequence (cn)n∈N of positive real numbers is rapidly varying if and only if the corresponding function x→c[x], x?1, is rapidly varying; (2) the class R∞,s satisfies some selection properties, as well as game-theoretical and Ramsey-theoretical conditions. 相似文献
78.
Mira S.Bjelakovi LjubinkaB. Lorenc VladimirD. Pavlovi MihailoLj. Mihailovi Bernard Tinant Jean-Paul Declercq Jaroslav Kalvoda 《Helvetica chimica acta》1999,82(5):707-721
Oxidations of 14α-hydroxy-5α-cholestan-3β-yl acetate ( 5 ) with lead tetraacetate under thermal or photolytic conditions or in the presence of iodine proceed mainly by fragmentation of the C(13)−C(14) bond to give as the primary products the 13,18-didehydro-13,14-seco derivative 6 and the (E )-Δ12-13,14-seco ketone 11 , respectively. Further transformations of these compounds under conditions of their formation afforded, in addition, the acetoxy derivatives 7 – 9 (from 6 ), and the D-homo-C-nor compound 12 and (12R,13R)-epoxide 13 (from 11 ). Unexpectedly, the photolytic lead-tetraacetate oxidation of 5 resulted partly (to ca. 20%) in a reversible fragmentation involving scission and recombination of the C(8)−C(14) bond followed by formation of the 14β,22-ether 10 . Possible mechanisms for the observed transformations are discussed. 相似文献
79.
N. Pejić J. Maksimović D. Ribič Lj. Kolar-Anić 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(9):1490-1495
Dynamic behavior of hydrogen peroxide decomposition catalyzed by iodate and hydrogen ions (the Bray-Liebhafsky reaction),
in a continuous stirred tank reactor is investigated. The experimental results are obtained at one operational point in concentration
phase space by varying mixed inflow concentrations of the sulfuric acid. The experimental evidences for the onset and termination
of oscillatory behavior via the saddle node infinite period bifurcation as well as some kind of the Andronov-Hopf bifurcation are presented. In addition,
the possibility of excitability of a stable steady state by thiamine was observed.
The article is published in the original. 相似文献
80.
Lj.B. ?iri? 《Topology and its Applications》2009,156(17):2838-2844
In this paper, a concept of monotone generalized contraction in partially ordered probabilistic metric spaces is introduced and some fixed and common fixed point theorems are proved. Presented theorems extend the results in partially ordered metric spaces of Nieto and Rodriguez-Lopez [Contractive mapping theorems in partially ordered sets and applications to ordinary differential equations, Order 22 (2005) 223-239; Existence and uniqueness of fixed point in partially ordered sets and applications to ordinary differential equations, Acta Math. Sin. (Engl. Ser.) 23 (2007) 2205-2212], Ran and Reurings [A fixed point theorem in partially ordered sets and some applications to matrix equations, Proc. Amer. Math. Soc. 132 (2004) 1435-1443] to a more general class of contractive type mappings in partially ordered probabilistic metric spaces and include several recent developments. 相似文献