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1.
Charlotte Doussier Philippe Léone Alain Meerschaut 《Journal of solid state chemistry》2007,180(8):2323-2334
The new oxy-chloro-sulfide (Mn1−xPbx)Pb10+ySb12−yS26−yCl4+yO (x ∈ [0.2-0.3]; y ∈ [0.3-1.6]) was synthesized by dry way at 500-600 °C. A single crystal ∼Mn0.7Pb11.0Sb11.3S25.3Cl4.7O indicates a monoclinic symmetry, space group C2/m, with a = 37.480(8), b = 4.1178(8), c = 18.167(4) Å, β = 106.37(3)°, V = 2690.2(9) Å3, Z = 2. Its crystal structure was determined by X-ray single crystal diffraction, with a final R = 5.11%. Modular analysis of the crystal structure reveals a “waffle” architecture, where complex rods with lozenge section delimitate an internal channel filled by a single chain of (Mn0.7Pb0.3)Cl6 octahedra connected by opposite edges. Minimal inter-chain distances are close to 18 Å. The rod wall, two-atom thick, presents, in alternation with S atoms, Pb or (Pb,Sb) cations with prismatic coordination in the internal atom layer, while the external atom layer is constituted exclusively by Sb cations with dissymmetric square pyramidal coordination. A (Pb,Sb)2S2 fragment connects two successive rods along (2 0 1) to form a waffle-type palissadic layer. The unique O position, half filled, presents the same environment than the isolated O positions in the oxy-sulfide Pb14Sb30S54O5, or oxy-chloro-sulfides Pb18Sb20S46Cl2O and (Cu,Ag)2Pb21Sb23S55ClO. This compound belongs to a pseudo-homologous series of chalcogenides with waffle structure, ordered according to the size of their lozenge shape channel. Such a complex senary compound of the oxy-chloro-sulfide type illustrates the structural competition between three cations, on one hand, and, on the other hand, three anions. This compound is of special interest regarding the 1D distribution of magnetic Mn2+ atoms at the ∼2 nm scale. 相似文献
2.
Surface-wave gas discharges sustained under the conditions of a diffusion controlled regime are studied on the basis of the fluid plasma model. The self-consistent behaviour of the plasma density and of the field intensity along the discharge length is obtained. It is shown that the nonlinearity in the particle balance equation due to stepwise ionisation determines the plasma density in terms of the field intensity and ensures self-consistent behaviour of the wave ? discharge characteristics in a diffusion controlled regime. 相似文献
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51V quadrupolar central transition NMR spectra of buffered (pH 7.6-8.0) solutions of bovine apo-transferrin (Tf) and bovine prostatic acid phosphatase (Pp) treated with vanadate show normal features (chemical shifts between -515 and -542 ppm) corresponding to the complexation of VO2+ to the Tf binding site and the Pp active centre, respectively. Addition of H2O2 leads to the temporary formation of complexed VO(O2)+ (delta approximately -595). Vanadate-dependent bromoperoxidase from the alga Ascophyllum nodosum exhibits an unusually high shielding both for the native (delta = -931) and the peroxo form (delta = -1135) of the enzyme. A resonance at -471 ppm is traced back to an inactive form with oxovanadium(V) in a trigonal-bipyramidal array. 相似文献
7.
Charlotte Froese Fischer 《International journal of quantum chemistry》1975,9(2):273-285
Results are reported for multiconfiguration Hartree–Fock studies of correlation in the lithium ground state, which maintain orthogonality of orbitals within a configuration. It is shown that when the 1s- and 2s-orbitals are fixed at their Hartree–Fock value, configurations for which Brillouin's theorem holds may be important, particularly for atomic properties other than energy. The Fermi contact term is considered as an example. 相似文献
8.
L. Grosse und W. Klaus 《Fresenius' Journal of Analytical Chemistry》1972,259(3):195-203
Zusammenfassung Es werden allgemeine und qualitative Merkmale von Natrium-Carboxymethylcellulose, Methylcellulose und Hydroxyäthylcellulose sowie gravimetrische und titrimetrische Bestimmungsmöglichkeiten der wasserlöslichen Celluloseäther insbesondere im Zusammenhang mit dem Substitutionsgrad beschrieben.Verfahren zur Ermittlung der Viscosität von Lösungen, des Polymerisationsgrades und des Gelteilchengehaltes werden besprochen. Abschließend werden charakteristische Beispiele für das analytische Vorgehen bei Substanzgemischen gegeben, die nur einen geringen Anteil Celluloseäther enthalten.
Erweiterte und umgearbeitete Fassung eines Vortrages, gehalten am 28. 6. 1971 in Baden-Baden.
Frau Dr. G. Bartelmus, Analyt. Laboratorium der Fa. Kalle AG, sprechen wir an dieser Stelle unseren herzlichen Dank für wertvolle Beratung aus. 相似文献
Analysis of water-soluble cellulose ethers
General and qualitative characteristics of sodium carboxymethylcellulose, methylcellulose and hydroxyethylcellulose are presented and gravimetric and titrimetric methods for the determination of water-soluble cellulose ethers are described, especially with regard to the degree of substitution. Procedures for the measurement of the viscosity of solutions, of the degree of polymerisation and of the content of gel particles are discussed. Characteristic examples are presented for the treatment of mixtures containing only a small percentage of cellulose ethers.
Erweiterte und umgearbeitete Fassung eines Vortrages, gehalten am 28. 6. 1971 in Baden-Baden.
Frau Dr. G. Bartelmus, Analyt. Laboratorium der Fa. Kalle AG, sprechen wir an dieser Stelle unseren herzlichen Dank für wertvolle Beratung aus. 相似文献
9.
Trifluoromethanesulfonic (triflic) acid is an excellent catalyst for inducing overall 5-endo cyclisation of homoallylic sulfonamides [e.g. 4] to give pyrrolidines [e.g. 5]. In competitive experiments, pyrrolidines or homopiperidines are formed in preference to piperidines, even when the latter would be obtained by trapping a tertiary carbocation. Cationic cascades terminated by a sulfonamide group are viable for the efficient formation of polycyclic systems. 相似文献
10.
Metz AW Ireland JR Zheng JG Lobo RP Yang Y Ni J Stern CL Dravid VP Bontemps N Kannewurf CR Poeppelmeier KR Marks TJ 《Journal of the American Chemical Society》2004,126(27):8477-8492
A series of low-melting, thermally stable cadmium metal-organic chemical vapor deposition (MOCVD) precursors have been synthesized, structurally and spectroscopically characterized, and implemented in growth of highly conductive and transparent CdO thin films. One member of the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N-diethyl-N',N'-dimethyl-ethylenediamine)cadmium(II), Cd(hfa)(2)()(N,N-DE-N',N'-DMEDA), represents a particularly significant improvement over previously available Cd precursors, owing to the low melting point and robust thermal stability. High-quality CdO films were grown by MOCVD on glass and single-crystal MgO(100) between 300 and 412 degrees C. Film growth parameters and substrate surface have large effects on microstructure and electron carrier transport properties. Enhanced mobilities observed for highly biaxially textured films grown on MgO(100) vs glass are attributed, on the basis of DC charge transport and microstructure analysis, to a reduction in neutral impurity scattering and/or to a more densely packed grain microstructure. Although single-grained films grown on MgO(100) exhibit greater mobilities than analogues with discrete approximately 100 nm grains and similar texture, this effect is attributed, on the basis of charge transport and Hall effect measurements as well as optical reflectivity analysis, to differences in carrier concentration rather than to reduced grain boundary scattering. Unprecedented conductivities and mobilities as high as 11,000 S/cm and 307 cm(2)/V.s, respectively, are obtained for epitaxial single-grained films (X-ray diffraction parameters: fwhm(omega) = 0.30 degrees, fwhm(phi) = 0.27 degrees ) grown in situ on MgO(100) at a relatively low temperature (400 degrees C). 相似文献