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91.
Summary: Three pyridine strong base anion exchangers as beads were obtained by quaternization reactions of a 4-vinylpyridine : 8% divinylbenzene copolymer of gel type. These resins possess methyl / ethyl / butyl radicals as substituents on N+ atoms and have exchange capacities of 4.80 mEq/g and 2.10 mEq/mL. For pyridine strong base anion exchangers, the behaviours in the retention processes of Cr(VI) as oxyanions and Ga(III) as [GaCl4]− complex anion were evaluated with the bath method. All the resins exhibited retention properties, but the retained amounts of the metal cations are different as a function of the alkyl length as substituent on N+ atoms and the complex anion nature. Thus, Cr(VI) oxyanions are best retained by the resin with CH3 as substituent on N+ atoms while [GaCl4]− complex anion by the resin with C4H9 as substituent on N+ atoms. By aminolysis reaction of an ethylacrylate : acrylonitrile : divinylbenzene copolymer as beads of macroporous type with NH2OH · HCl in the presence of C2H5OH a new chelating ion exchanger was performed which contains both amidoxime and hydroxamic acid functional groups. This ion exchanger has the retention property for different metal cations but its retention capacities values are strongly dependent of the nature of metal cation and the counterion as well as pH of the solution. Thus, in the static conditions Zn(II) cation with NOequation/tex2gif-stack-1.gif anion as counterion is retained with the best result at pH = 5. As an example, for the aqueous metal cation solution of 10−2 M concentration for Zn(NO3)2 the resin possess at equilibrium a retention capacity of 6.70 mmol Zn/g dry resin and for Cu(II) from Cu(NO3)2 solution of same concentration, the retention capacity is 0.22 mmol Cu/g dry resin and Fe(III) from Fe(NO3)3 solution is not retained. 相似文献
92.
Block parallel iterative methods for the solution of mildly nonlinear systems of equations of the form are studied. Two-stage methods, where the solution of each block is approximated by an inner iteration, are treated. Both
synchronous and asynchronous versions are analyzed, and both pointwise and blockwise convergence theorems provided. The case
where there are overlapping blocks is also considered. The analysis of the asynchronous method when applied to linear systems
includes cases not treated before in the literature.
Received June 5, 1997 / Revised version received December 29, 1997 相似文献
93.
Piergiulio Corsini Violeta Leoreanu 《Rendiconti del Circolo Matematico di Palermo》2002,51(3):527-536
Let μ
X
be the rough membership function. One compares μ
A
with μA∪B and μA∪B, by the associated hyperoperations. One finds a condition such that a functionμ ε [0, 1]
H
may be a rough membership function. 相似文献
94.
Vukadin M. Leovac Violeta S. Jevtovi Goran A. Bogdanovi 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(10):m514-m516
The title complex, [Cu(NO3)(C10H14N4O2S)(H2O)](NO3), is the first metal complex with a Schiff base derived from isothiosemicarbazide and pyridoxal (pyridoxal is 3‐hydroxy‐5‐hydroxymethyl‐2‐methylpyridine‐4‐carboxaldehyde). The CuII environment is a square pyramid, the equatorial plane of which is formed by the tridentate ONN‐coordinated isothiosemicarbazone and one water molecule, while the nitrate ligand is in the apical position. The existence of numerous strong intermolecular hydrogen bonds, and weak C—H?O and C—H?π interactions, leads to a three‐dimensional supramolecular structure. 相似文献
95.
96.
97.
The dependence of diffraction efficiency behaviour on absorption during recording is investigated, assuming that on reconstruction the grating is purely a phase one. This behaviour is described using the multiwave coupled-wave approach. The cases of both sinusoidal and non-sinusoidal recording are investigated, taking into account the photo-induced change in the refractive index depending on the energy. 相似文献
98.
Koleva BB Kolev T 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):786-793
The linear-dichroic infrared (IR-LD) spectroscopy of oriented solid samples as suspension in nematic liquid crystal have been carried out for experimental IR-band assignment and structural information of 2-{5,5-dimethyl-3-[2-(2,4,6-trimethoxyphenyl)vinyl]cyclohex-2-enylidene} malononitrile polymorphs. The last data have been compared with known crystallographic ones, thus determining the validity of IR-LD spectral conclusions as well as its possibility to determination of Davydov's splitting effect and separation of pairs of maxima corresponding to non-equivalent molecules included in the unit cell of given compound. The experimental structural and spectroscopic data in our case are supported with theoretical DFT ones, obtaining both the electronic structure and vibrational frequencies in gas phase. 相似文献
99.
Koleva BB Stoyanov S Kolev T Petkov I Spiteller M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(3):847-853
Structural and spectroscopic elucidation of merocyanine dye, 2,5-[1-metyl-4-[2-(4-hydroxyphenyl)ethenyl)]piridinium]-hexane tetraphenylborate, is performed in gas and condense phase by means of solution and solid-state conventional and linear-polarized IR-spectroscopy of oriented colloids in nematic liquid crystal suspension, UV-vis and fluorescence methods, HPLC MS/MS tandem and ESI mass spectrometry, (1)H, (13)C and (1)H-(1)H COSY NMR, TGV and DSC methods. Quantum chemical DFT calculations are performed for structural optimization and spectroscopic properties prediction. 相似文献
100.
In the present work, the Coats-Redfern method was used to determine the kinetic parameters and the possible reaction mechanism
of the thermal degradation of ultra-high molecular mass polyethene and its composites with fiber monocrystals in static air
at three different heating rates − 6, 10 and 16 K min−1. The analysis of the results obtained showed that the thermal degradation process of pure ultra-high molecular mass polyethene
corresponded to a diffusion controlled reaction (three-dimentional diffusion, mechanism D3), while its composites with fiber monocrystals degraded by two concurrent mechanisms (diffusion one D3 and A1,F1 mechanism). The fiber monocrystals used increased the thermal stability of the composite materials obtained. The values of
the activation energy, frequency factor, the changes of entropy, enthalpy and Gibbs energy for the active complex of the composites
were calculated. 相似文献