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81.
We present sets of real 3- symbols which correspond to explicitly given irreducible matrix representations for the two double group hierarchies T* C
3
*
and T* C
2
*
. They fit into the formalism exposed in a previous paper [1] on the general theory of 3- symbols and coupling coefficients and illustrate much of the discussion in a subsequent one [2] treating the particular properties of the double groups. 相似文献
82.
Experimental results on the electrophoretic velocity and mobility of Ca-montmorillonite in 2-propanol are reported. The variation of the electrophoretic velocity with the externally applied electric field and the particle size range, at constant volume fraction and temperature, is considered. Given the difficulties for determining the types and concentrations of ions present in these liquid media, two methods are discussed for the estimation of the double layer thickness and hence the product, necessary for the determination of the zeta potential () of the interface. Although both methods of calculation yield different values of, the results for the zeta potential are very similar in the regions of and characteristic of our systems. The application to the experimental data of three theoretical relations between electrophoretic mobility and zeta potential is also discussed. 相似文献
83.
Shinsaku Fujita 《Journal of mathematical chemistry》2007,42(2):215-263
The concepts of double coset representations and sphericities of double cosets are proposed to characterize stereoisomerism, where double cosets are classified into three types, i.e., homospheric double cosets, enantiospheric double cosets, or hemispheric double cosets. They determine modes of substitutions (i.e., chirality fittingness), where homospheric double cosets permit
achiral ligands only; enantiospheric ones permit achiral ligands or enantiomeric pairs; and hemispheric ones permit achiral
and chiral ligands. The sphericities of double cosets are linked to the sphericities of cycles which are ascribed to right
coset representations. Thus, each cycle is assigned to the corresponding sphericity index (a
d
, c
d
, or b
d
) so as to construct a cycle indices with chirality fittingness (CI-CFs). The resulting CI-CFs are proved to be identical
with CI-CFs introduced in Fujita’s proligand method (S. Fujita, Theor. Chem. Acc. 113 (2005) 73–79 and 80–86). The versatility
of the CI-CFs in combinatorial enumeration of stereoisomers is demonstrated by using methane derivatives as examples, where
the numbers of achiral plus chiral stereoisomers, those of achiral stereoisomers, and those of chiral stereoisomers are calculated
separately by means of respective generating functions. 相似文献
84.
C. Yaicle F. Fauth R. Retoux M. Hervieu A. Maignan 《Journal of solid state chemistry》2005,178(5):1652-1660
Combining low-temperature electron (ED) and synchrotron powder diffraction (SPD) techniques, we have precisely determined the phase-separated crystal structure of Pr0.5Ca0.5Mn0.97Ga0.03O3. We demonstrate that the phase separation is associated with the onset of charge/orbital ordering at ∼230 K and that two ordered phases coexist at low temperature. In order to account for the significant anisotropic linewidth broadening observed in the SPD patterns, we had to include a specific strain model in the refinements. One of the phases, the most severely strained, is suggested to result from an imperfect charge ordering. 相似文献
85.
3-Mercaptopropionic acid monolayer protected gold nanoclusters (MPA-MPCs) were synthesized and characterized by transmission electorn microscopy,UV-Vis spectroscopy,X-ray photoelectron spectroscopy and Fourler transform infrared spectroscopy.The exact value of quantized double-layer capacitance of MPCs in aqueous media was obtained by differential pulse voltammograms. 相似文献
86.
Yi‐Jun Huang Guo‐Rong Qi Yu‐Hua Wang 《Journal of polymer science. Part A, Polymer chemistry》2002,40(8):1142-1150
A double metal‐cyanide catalyst based on Zn3[Co(CN)6]2 was prepared. This catalyst is very effective for the ring‐opening polymerization of propylene oxide. Polyether polyols of moderate molecular weight having low unsaturation (<0.015 meq/g) can be prepared under mild conditions. The molecular weight of polymer is entirely controlled by a reacted monomer‐to‐initiator ratio. The polymers prepared with stepwise addition of monomer exhibit a narrower molecular weight distribution as compared with those prepared with one‐step addition of monomer. Various compounds containing active hydrogen, except basic compounds and low‐carbon carboxylic acid, may be used as initiators. The reaction rate increases with increasing catalyst amount and decreases with rising initiator concentration. Polymerization involves a rapid exchange reaction between the active species and the dormant species. It was also proven that, to a certain extent, the chain termination of this catalytic system is reversible or temporary. 13C NMR analysis showed that the polymer has a random distribution of the configurational sequences and head‐to‐tail regiosequence. It is assumed that the polymerization proceeds via a cationic coordination mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1142–1150, 2002 相似文献
87.
Bruce R. McGarvey 《Coordination chemistry reviews》1998,170(1):75-92
Using a newly proposed approach involving an internally consistent set of equations, the ligand field parameters Δ/ξ, V/ξ and k are obtained from literature values of the g matrix for strong field d5 systems of various conformations in which |Δ/ξ|≤10. Qualitative analysis of the observed results is done using the Angular Overlap Model, AOM. 相似文献
88.
Prilezhaeva I. N. Solov'ev N. P. Khramushin N. I. 《Russian Journal of Electrochemistry》2004,40(11):1223-1226
Transformation of impedance spectra into relaxation time spectra (RTS) is used for determining contributions of individual processes of the oxygen electroreduction reaction (OER) to the polarization resistance of the electrochemical cell. The transformation technique involves the solution of the convolution equation found with the aid of a modified Van Cittert iteration algorithm checked on model impedance spectra. The technique, when used to analyze impedance spectra of electrochemical cells air|Pt|YSZ|YSZ + Pt|air, shows that the conversion of a globular structure of the YSZ + Pt cermet layer to a columnar one is accompanied by a change of peak amplitudes in RTS. The revealed RTS dynamics when heated to 750°C is compared with peculiarities of individual processes in OER. 相似文献
89.
N-Bromosuccinimide-dibenzoyl peroxide/azobisisobutyronitrile is used to carry out several types of Z- to E-alkene isomerizations. The NBS-bromination conditions are sufficient for both allylic bromination and alkene isomerization. When the allylic hydrogens are not available in substrates, only the isomerization of the alkene takes place. The present conditions for isomerization of carbon-carbon double bonds are mild and efficient. 相似文献
90.
On the Reaction of Macrocycles with Lanthanoids. I. The Crystal Structure of [Li(thf)][(C22H22N4)2Ce] · THF In THF CeBr3 forms with [(TMTAA)Li2] the paramagnetic doubledecker complex [Li(thf)][(TMTAA)2Ce]. The complex crystallizes with 1 Mol THF per formula unit. The structure was characterized by X-ray single crystal structure analysis (space group C2 (No. 5), z = 6, a = 1741.8(2) pm, b = 1622.1(2) pm, c = 2540.4(3) pm, β = 104.72(1)°). The sandwich-like arrangement of the heterocyclic ligands leads to a quadratic-prismatic coordination of the Ce3+ ion. One macrocyclic ligand is additionally coordinated by a [Li(thf)]+ fragment. The coordination of the Li ion is square pyramidal. 相似文献