The quantum permutation group of the set corresponds to the Hopf algebra . This is an algebra constructed with generators and relations, known to be isomorphic to for , and to be infinite dimensional for . In this paper we find an explicit representation of the algebra , related to Clifford algebras. For the representation is faithful in the discrete quantum group sense.
By performing ab initio electronic structure calculations, we observed a new high-pressure phase transition within the Pmcn structure of CaCO3. This transition is characterized by the change of the carbon's sp hybridization state and is driven by the intrinsic property of the carbon atom to form tetrahedral covalent bonds at high pressure. The formation of sp(3) hybridized bonds explains the stability of MgCO3 and CaCO3 at Earth's lower mantle pressure conditions and may serve as a criterion for searching new possible high-pressure phases of carbon bearing minerals. 相似文献
Four new coordination polymer frameworks, namely [(NiL(1))(3)(BTB)(2)]·6H(2)O, [(NiL(2))(3)(BTB)(2)]·6H(2)O, [(NiL(3))(3)(BTB)(2)]·6H(2)O and [(NiL(2))(3)(BTC)(2)]·10.25H(2)O (L(1) = 1,4,8,11-tetraazacyclotetradecane, L(2) = 3-methyl-1,3,5,8,12-pentaazacyclotetradecane, L(3) = 3,10-dimethyl-1,3,5,8,10,12-hexaazacyclotetradecane, BTC(3-) = benzene-1,3,5-tricarboxylate, BTB(3-) = 4,4',4'-benzene-1,3,5-triyl-tribenzoate) were prepared in water-N,N-dimethylformamide solutions. The molecular and crystal structures of these compounds are compared to the related coordination polymers formed by nickel(II) macrocyclic cations to examine the effect of carboxylate linker size on the framework architecture. Luminescent properties of the complexes based on the BTB(3-) bridging ligand are also discussed. 相似文献
The pore size distribution of porous media can be determined in a completely non-invasive manner using a new nuclear magnetic resonance (NMR) technique which monitors the magnetization decay due to diffusion in internal fields (DDIF). However, using of the DDIF technique is restricted to the low-phase encoding limit when only the relaxation mode and the first-order diffusion mode are excited. In the present work the fulfillment of such a limit is verified for a progressive increase of the magnetic impurity content of the porous media. If the higher order diffusion modes are excited they lead both to a stronger attenuation of the echo signal and to the appearance of ripples in the DDIF spectra which cannot be related to a pore size distribution. The samples used in this study are porous ceramics prepared using the replication technique and the magnetic impurity is iron (III) oxide which is introduced in an increasing concentration inside the porous matrix. All NMR experiments were done on water filling such porous ceramics using a low-field instrument operating at a proton resonance frequency of 20 MHz. The average pore dimension obtained with the DDIF technique in the weak encoding limit indicates a satisfactory agreement with that observed in optical microscopy images. 相似文献
We consider a nonlinear elliptic equation driven by a nonhomogeneous differential operator and with a (p?1)-superlinear Carathéodory reaction. Our formulation incorporates as a special case equations monitored by the p-Laplacian. Using variational methods coupled with truncation techniques and comparison principles, we show that the problem has at least five nontrivial smooth solutions. 相似文献
The regioselective cyclocondensation of aminoethyl-1,2,4-triazoles and glyoxal provides pentacyclic heterocycles in which two 7,8-dihydro-5H-6λ2-[1,2,4]triazolo[1,5-c]pyrimidine systems are connected through CH(OH) bridges generating a central piperazine-2,5-diol ring. The structure of the new compounds was elucidated based on 1H, 13C and 15N NMR spectroscopic methods. The molecular structure of the parent compound generated from aminoethyl-1,2,4-triazole was established by single crystal X-ray diffraction. 相似文献
This paper recalls the attention to an interesting compound having aromatic azomethine structure, namely: (E)-N-(biphenyl-4-ylmethylene)-4-butylaniline (PB4A). The molecular structure of PB4A was determined by X-ray single-crystal diffraction analysis. Besides the enantiotropic smectic B and nematic phases, this compound exhibits a monotropic crystal E phase. By polarising optical microscopy and differential scanning calorimetry, we confirmed the existence of these phases. FTIR measurements in attenuated total reflection configuration have been performed to investigate the evolution of significant absorption bands during phase transitions. 相似文献