排序方式: 共有21条查询结果,搜索用时 15 毫秒
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Julie Cornette Thrse Merle‐Mjean Andreï Mirgorodsky Maggy Colas Mikhaël Smirnov Olivier Masson Philippe Thomas 《Journal of Raman spectroscopy : JRS》2011,42(4):758-764
Vibrational spectra of rhombohedral TeO3 (r‐TeO3) are analyzed along with those of ReO3‐like proto‐phase (c‐TeO3) and α‐TeO2 (paratellurite), emphasizing their lattice dynamic and crystal chemistry aspects. It is shown that (1) r‐TeO3 can be regarded as resulting from the condensation of a particular R‐point soft phonon of c‐TeO3; (2) the Raman spectra of r‐TeO3 and α‐TeO2 are indicative of the two fundamentally different (from the crystal chemistry point of view) types of crystalline oxides, namely, framework‐type and island‐type, respectively. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Hologne M Bertani P Azaïs T Bonhomme C Hirschinger J 《Solid state nuclear magnetic resonance》2005,28(1):50-56
The results of two techniques of dipolar recoupling, REDOR and CPMAS, are compared in the case of a coupled multiple-spin system. A fundamentally different behavior is observed for these two techniques. In REDOR, the terms associated with each interaction S-I(k) commute with each other and no truncation takes place so that each addition of spin I(k) causes a splitting with its dipolar frequency. In CPMAS, the flip-flop terms of the dipolar Hamiltonian do not commute with the dominant term from the strongly coupled spin pair so that the weak coupling terms from the neighboring spin I(k) are effectively truncated by the dominant pair interaction. Spin dynamics calculations are in agreement with the experimental data in a cubane shaped cluster. 相似文献
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Hologne M Faelber K Diehl A Reif B 《Journal of the American Chemical Society》2005,127(32):11208-11209
We show in this communication that dynamic information for uniformly 2H,13C,15N isotopically enriched, crystalline proteins can be obtained by MAS solid-state NMR spectroscopy. The experiments make use of the deuterium quadrupolar tensor, which is the dominant interaction mechanism. Dynamic properties are accessed by measurement of the size of the quadrupolar coupling constant, Cq, and the value of the asymmetry parameter, eta, via evolution of the deuterium chemical shift, as well as by measurement of deuterium T1 relaxation times. Three-dimensional experiments are performed in order to obtain site-specific resolution. Due to proton dilution, no proton decoupling is required in the carbon evolution periods at MAS rotation frequencies of 10 kHz. 相似文献
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Maggy?Manguian Maud?SaveEmail author Christophe?Chassenieux Bernadette?Charleux 《Colloid and polymer science》2005,284(2):142-150
Well-defined, positively charged, amphiphilic copolymers containing long alkyl side chains were used as stabilizers in the miniemulsion polymerization of styrene. The copolymers were prepared by controlled free-radical copolymerization of styrene and vinyl benzyl chloride using either the reversible addition-fragmentation chain transfer method or TEMPO-mediated polymerization. The benzyl chloride moities were modified by two different long alkyl chain tertiary amines (N,N-dimethyldodecyl amine and N,N-dimethylhexadecyl amine) to yield the amphiphilic copolymers with vinylbenzyl dimethyl alkyl ammonium chloride units. Owing to their high structural quality, only a small amount of these copolymers was required to stabilize the latex particles (0.5–2 wt% vs styrene). Moreover, in the absence of any hydrophobic agent, the amphiphilic comblike copolymer preserved the colloidal stability of both the initial liquid miniemulsion and the final latex. Ill-defined, analogous copolymers were synthesized by conventional free-radical polymerization and in comparison, exhibited poor stabilization properties. 相似文献
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Maggy Tomova 《Topology and its Applications》2009,156(4):783-794
Wu has shown that if a link or a knot L in S3 in thin position has thin spheres, then the thin sphere of lowest width is an essential meridional surface in the link complement. In this paper we show that if we further assume that L⊂S3 is prime, then the thin sphere of lowest width also does not have any vertical cut-disks. We also prove the result for a specific kind of tangles in S2×[−1,1]. 相似文献
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Lengke MF Fleet ME Southam G 《Langmuir : the ACS journal of surfaces and colloids》2006,22(17):7318-7323
Interaction of cyanobacteria (Plectonema boryanum UTEX 485) with aqueous platinum(IV)-chloride (PtCl(4) degrees ) has been investigated at 25-100 degrees C for up to 28 days, and 180 degrees C for 1 day. The addition of PtCl(4) degrees to the cyanobacteria culture initially promoted the precipitation of Pt(II)-organic material as amorphous spherical nanoparticles (< or =0.3 microm) in solutions and dispersed nanoparticles within bacterial cells. The spherical Pt(II)-organic nanoparticles were connected into long beadlike chains by a continuous coating of organic material derived from the cyanobacterial cells, and aged to nanoparticles of crystalline platinum metal with increase in temperature and reaction time. The stepwise reduction for the formation of platinum nanoparticles in the presence of cyanobacteria was deduced to be Pt(IV) [PtCl(4) degrees ] --> Pt(II) [Pt(II)-organics] --> Pt(0). Spherical platinum-bearing nanoparticles were not present in abiotic PtCl(4) degrees experiments conducted under similar conditions and duration. 相似文献
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Lengke MF Fleet ME Southam G 《Langmuir : the ACS journal of surfaces and colloids》2006,22(6):2780-2787
Plectonema boryanum UTEX 485, a filamentous cyanobacterium, has been reacted with aqueous Au(S(2)O(3))(2)(3)(-) and AuCl(4)(-) solutions ( approximately 400-550 mg/L Au) at 25-100 degrees C for up to 1 month and at 200 degrees C for 1 day. The interaction of cyanobacteria with aqueous Au(S(2)O(3))(2)(3)(-) promoted the precipitation of cubic (100) gold nanoparticles (<10-25 nm) at membrane vesicles and admixed with gold sulfide within cells and encrusted on the cyanobacteria, whereas reaction with AuCl(4)(-) resulted in the precipitation of octahedral (111) gold platelets ( approximately 1-10 microm) in solutions and nanoparticles of gold (<10 nm) within bacterial cells. Functional groups imaged by negative ion TOF-SIMS on (111) faces of the octahedral platelets were predominantly Cl and CN, with smaller amounts of C(2)H and CNO. 相似文献
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We present in this paper 2H,13C MAS correlation experiments that are performed on a uniformly 2H,13C,15N labeled sample of Nac-Val, and on the uniformly 2H,15N labeled dipeptide Nac-Val-Leu-OH. The experiments involve the measurement of 2H T1 relaxation times at two different magnetic fields, as well as the measurement of the 2H tensor parameters by evolution of the 2H chemical shift. The data are interpreted quantitatively to differentiate between different side chain motional models. 相似文献