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1.
Starting with a partition of a rectangular box into subboxes, it is shown how to construct a natural tetrahedral (type-4) partition and associated trivariate C 1 quintic polynomial spline spaces with a variety of useful properties, including stable local bases and full approximation power. It is also shown how the spaces can be used to solve certain Hermite and Lagrange interpolation problems. 相似文献
2.
Mikhailov Oleg V. Kazymova Marina A. Shumilova Tatyana A. Solovieva Svetlana S. 《Transition Metal Chemistry》2003,28(6):665-667
The complexing processes in the triple copper(II)–thiocarbohydrazide–propanone system taking place in a copper(II) hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous-alkaline solutions (pH12), containing thiocarbohydrazide and propanone, have been studied. Template synthesis leading to a macrocyclic coordination compound with the tetradentate N,N,S,S-donor ligand, (4,4,6-trimethyl-2,3,7,8-tetraazanonen-6-dithiohydrazide-1,9), occurs under these specific conditions when thiocarbohydrazide and propanone are the ligand synthons. 相似文献
3.
Katritzky AR Nair SK Khokhlova T Akhmedov NG 《The Journal of organic chemistry》2003,68(14):5724-5727
Enynes 5a-g were prepared in moderate to good yields from 1-(triphenylphosphoranylideneaminoalkyl)benzotriazoles. Ring-closing metathesis of 5a-f afforded functionalized dienes 6a-f, respectively, which were used in a Diels-Alder cycloaddition reaction in the synthesis of the corresponding hexahydroisoquinoline derivatives 7a-f. 相似文献
4.
We consider the fixed point property (FPP) in an ordered set of width two (every antichain contains at most two elements). The necessary condition of the FPP and a number of equivalent conditions to the FPP in such sets is established. The product theorem is proved, as well. 相似文献
5.
6.
Oleg V. Mikhailov Marina A. Kazymova Tatyana A. Shumilova Galina A. Chmutova Svetlana E. Solovieva 《Transition Metal Chemistry》2005,30(3):299-304
The complexing process proceeding in the NiII–thiocarbohydrazide (H2N–H–NC(=S)–NH–NH2)–propanone triple system in EtOH solution and nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix has been studied. It has been found that in the first case, template synthesis leading, as a minimum, to formation of three coordination compounds of NiII with (N,N,S,S)-donor tetradentate ligands having NiL1, NiL2 and NiL3compositions where L1 is 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-di(thiohydrazide)-1,9, L2 is 4,6,6,12-tetrametyl-1,9-dithio-2,3,7,8,10,11-hexaazatridekadien-3,11-hydrazide-1 and L3 is 2,8,10,10,16-pentamethyl-5,13-dithio-3,4,6,7,11,12,14,15-octaazaheptadekatrien-2,7,15 is observed, whereas in the gelatin-immobilized matrix, a complexing process in the system considered does not occur. 相似文献
7.
Huang W Todaro L Yap GP Beer R Francesconi LC Polenova T 《Journal of the American Chemical Society》2004,126(37):11564-11573
Vanadium environments in Keggin oxopolytungstates were characterized by (51)V solid-state MAS NMR spectroscopy. (C(4)H(9))(4)N(+)-, K(+)-, Cs(+)-, as well as mixed Na(+)/Cs(+)- salts of the mono-, di-, and trivanadium substituted oxotungstates, [VW(11)O(40)](4-), [V(2)W(10)O(40)](5-), and [V(3)W(9)O(40)](6-), have been prepared as microcrystalline and crystalline solids. Solid-state NMR spectra report on the local environment of the vanadium site in these Keggin ions via their anisotropic quadrupolar and chemical-shielding interactions. These (51)V fine structure constants in the solid state are determined by the number of vanadium atoms present in the oxoanion core. Surprisingly, the quadrupolar anisotropy tensors do not depend to any significant extent on the nature of the countercations. On the other hand, the chemical-shielding anisotropy tensors, as well as the isotropic chemical shifts, display large variations as a function of the cationic environment. This information can be used as a probe of the local cationic environment in the vanadium-substituted Keggin solids. 相似文献
8.
Imidazol-2-ylidenes, a family of N-heterocyclic carbenes (NHC), are efficient catalysts in the transesterification involving numerous esters and alcohols. Low catalyst loadings of aryl- or alkyl-substituted NHC catalysts mediate the acylation of alcohols with enol acetates in short reaction times at room temperature. Commercially available and more difficult to cleave methyl esters react with primary alcohols in the presence of alkyl-substituted NHC to efficiently form the corresponding esters. While primary alcohols are selectively acylated over secondary alcohols with use of enol esters as acylating agents, methyl and ethyl esters can be employed as protective agents for secondary alcohols in the presence of the more active alkyl-substituted NHC catalysts. The NHC-catalyzed transesterification protocol was simplified by generating the imidazol-2-ylidene catalysts in situ. 相似文献
9.
Dekhtyaryuk ES Zakharchenko TG Petryna YS Krasnopolskaya TS 《Chaos (Woodbury, N.Y.)》1994,4(4):637-650
Steady-state chaotic vibrations of a shallow shell as a system with a nonsymmetrical restoring force and one equilibrium state are considered. Mode interaction and its effect on a chaotic behavior of the shell is studied. The terms "natural" and "imposed" chaos are introduced for the response of resonant and nonresonant modes. It is shown that such a qualitative difference is important for better understanding of chaos in systems with distributed parameters, and may be very useful for numerical investigations. Some qualitative comparisons with previous papers on chaos in distributed mechanical systems are also made. (c) 1994 American Institute of Physics. 相似文献
10.
Marulanda D Tasayco ML Cataldi M Arriaran V Polenova T 《The journal of physical chemistry. B》2005,109(38):18135-18145
De novo site-specific 13C and 15N backbone and sidechain resonance assignments are presented for uniformly enriched E. coli thioredoxin, established using two-dimensional homo- and heteronuclear solid-state magic angle spinning NMR correlation spectroscopy. Backbone dihedral angles and secondary structure were derived from the statistical analysis of the secondary chemical shifts, and are in good agreement with solution values for the intact full-length thioredoxin, with the exception of a small number of residues located at the termini of the individual secondary structure elements. A large number of cross-peaks observed in the DARR spectra with long mixing times correspond to the pairs of carbon atoms separated by 4-6 angstroms, suggesting that DARR could be efficiently employed for observation of medium- and long-range correlations. The 108 amino acid residue E. coli thioredoxin is the largest uniformly enriched protein assigned to this degree of completeness by solid-state NMR spectroscopy to date. It is anticipated that with a combination of two-dimensional correlation experiments and high magnetic fields, resonance assignments and secondary structure can be generally derived for other noncrystalline proteins. 相似文献