The nature of the magnetic interactions in the chain compound Rb2FeF5 has been investigated using neutron diffraction and magnetic measurements under high applied fields. Rb2FeF5 orders antiferromagnetically at TN = 8.0 ± 0.5 K; the magnetic structure is of the AZ + GX mode and the moment of the Fe3+ ion extrapoled to 0K is 3.5 ± 0.2 μB, this low value being due to zero-point spin reduction. Within a chain the Fe3+ ions are antiferromagnetically coupled with an exchange constant of J/k = ?8.8 K. A spin-flop behavior has been observed and interpreted on the basis of the molecular field theory. The critical field was found to be HC = 65 kOe at 1.7 K. 相似文献
The extension of the Jahn-Teller distortion of the SnH4+ structure is estimated from ab initio SCF CI calculations using pseudopotential atomic approximation with and without relativistic correction. These calculations show the lowest minima of SnH4+ to have C2v symmetry and are very close to the C3v minima. The calculated photoelectron spectrum of SnH4 is in good agreement with the experimental values. 相似文献
The stoichiometric lanthanum disulfide LaS2 presents a reversible phase transition at about 750°C. The α low-temperature form is monoclinic with the LaSe2 type. All the crystals are twinned with the same twin law (100). The cell parameters are a = 8.18, b = 8.13, c = 4.03Å, γ = 90°, space group . The β high-temperature form has the orthorhombic structure previously described with the parameters a = 8.13, b = 16.34, c = 4.14 Å; space group Pnma. The two structures are compared. 相似文献
The use of decatungstate in combination with silanes to generate silyl radicals under green fluorescence bulb irradiation as well as sunlight exposure is described. The mechanisms are investigated by ESR and laser flash photolysis experiments. The high potential of this reaction is evidenced here when using a decatungstate/silane/diphenyl iodonium salt combination as an initiating system for the ring opening photopolymerization of epoxides.
DUV interferometric lithography and diblock copolymer self‐organization have successfully been combined to provide a simple and highly collective nanopatterning technique enabling the organization of nanoparticles over several orders of magnitude, from nanometre to millimetre. The nanostructural changes at the surface of the polymer film after thermal annealing have been monitored by AFM and the process parameters optimized for obtaining a long‐range organization of the lamellar domains. In particular, the impact of the annealing conditions and geometric parameters of the substrate patterns have been investigated. The nanopatterns resulting from the lamellar demixion of (PS‐b‐MMA) were used for a controlled deposition of nanoparticles. The affinity of the hydrophobic particles for the PS block was demonstrated, opening new doors towards the preparation of high‐density arrays of nanoparticles with potential applications in data storage.
New polyesters incorporating a variable quantity of imidazolium rings along the backbone are synthesized by Huisgen 1,3‐dipolar cycloaddition (“click” reaction). Subsequently, the imidazolium‐grafted copolymers reveal an efficient dispersing ability toward the carbon nanotubes (CNTs) through supramolecular interactions in organic media. Interestingly, these compounds offer a simple and reliable strategy to control the quantity of dispersed CNTs as a function of imidazolium content. This approach is particularly suitable for the elaboration of biosourced and biodegradable materials based on poly(butylene succinate) with high‐performance properties. 相似文献
Silica‐supported titanium(IV) chloride is readily reduced by Mashima and co‐workers' reagent (1‐methyl‐3,6‐bis(trimethylsilyl)‐1,4‐cyclohexadiene) to afford materials active in ethylene polymerisation without need of aluminum alkyl cocatalyst. 相似文献
From the defining exchange relations of the
elliptic quantum algebra, we construct subalgebras which can be characterized as q-deformed WN algebras. The consistency conditions relating the parameters p, q, N and the central charge c are shown to be related to the singularity structure of the functional coefficients defining the exchange relations of specific
vertex operators representations of
available when N = 2.
Communicated by Petr Kulish
Submitted: January 13, 2006; Accepted: March 6, 2006
Dedicated to our friend Daniel Arnaudon 相似文献
The continuous Hull of a repetitive tiling T in ℝd with the Finite Pattern Condition (FPC) inherits a minimal ℝd-lamination structure with flat leaves and a transversal which is a Cantor set. This class of tiling includes the Penrose & the Amman Benkker ones in 2D, as well as the icosahedral tilings in 3D. We show that the continuous Hull, with its canonical ℝd-action, can be seen as the projective limit of a suitable sequence of branched, oriented and flat compact d-manifolds. As a consequence, the longitudinal cohomology and the K-theory of the corresponding C*-algebra are obtained as direct limits of cohomology and K-theory of ordinary manifolds. Moreover, the space of invariant finite positive measures can be identified with a cone in
the dth homology group canonically associated with the orientation of ℝd. At last, the gap labeling theorem holds: given an invariant ergodic probability measure μ on the Hull the corresponding Integrated Density of States (IDS) of any selfadjoint operators affiliated to takes on values on spectral gaps in the ℤ-module generated by the occurrence probabilities of finite patches in the tiling.
Accepted in Revised Form: 7 May 2005 相似文献