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11.
The electron paramagnetic resonance spectrum of a single crystal of ZnAl2O4 (spinel structure) doped with manganese displays a fine structure characteristic of a purely cubic crystal field. Contrary to MgAl2O4: Mn2+, where the degree of inversion is sizable, ZnAl2O4 therefore is a normal spinel. 相似文献
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Cortese J Soulié-Ziakovic C Cloitre M Tencé-Girault S Leibler L 《Journal of the American Chemical Society》2011,133(49):19672-19675
In supramolecular polymers, directional interactions control the constituting units connectivity, but dispersion forces may conspire to make complex organizations. Here we report on the long-range order and order-disorder transition (ODT) of main-chain supramolecular polymers based on poly(propylene oxide) (PPO) spacers functionalized on both ends with thymine. Below the ODT temperature (T(ODT)), these compounds are semicrystalline with a lamellar structure, showing nanophase separation between crystallized thymine planes and amorphous PPO layers. Above T(ODT), they are amorphous and homogeneous even though their X-ray scattering spectrum reveals a peak. This peak is due to correlation hole effect resulting from contrast between end-functional groups and spacer. Macroscopically, the transition is accompanied by dramatic flow and mechanical properties changes. 相似文献
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Comparative Analysis of Conjugated Alkynyl Chromophore–Triazacyclononane Ligands for Sensitized Emission of Europium and Terbium
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Marine Soulié Frédéric Latzko Emmanuel Bourrier Dr. Virginie Placide Dr. Stephen J. Butler Dr. Robert Pal Dr. James W. Walton Dr. Patrice L. Baldeck Dr. Boris Le Guennic Dr. Chantal Andraud Dr. Jurriaan M. Zwier Dr. Laurent Lamarque Prof. David Parker Dr. Olivier Maury 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(28):8636-8646
A series of europium and terbium complexes based on a functionalized triazacyclononane carboxylate or phosphinate macrocyclic ligand is described. The influence of the anionic group, that is, carboxylate, methylphosphinate, or phenylphosphinate, on the photophysical properties was studied and rationalized on the basis of DFT calculated structures. The nature, number, and position of electron‐donating or electron‐withdrawing aryl substituents were varied systematically within the same phenylethynyl scaffold in order to optimize the brightness of the corresponding europium complexes and investigate their two‐photon absorption properties. Finally, the europium complexes were examined in cell‐imaging applications, and selected terbium complexes were studied as potential oxygen sensors. 相似文献
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Soulié F El Youssoufi MS Cherblanc F Saix C 《The European physical journal. E, Soft matter》2006,21(4):349-357
We investigate the macroscopic mechanical behaviour of wet polydisperse granular media. Capillary bonding between two grains
of unequal diameters is described by a realistic force law implemented in a molecular-dynamics algorithm together with a protocol
for the distribution of water in the bulk. Axial-compression tests are simulated for granular samples at different levels
of water content, and compared to experiments performed in similar conditions. We find good agreement between numerical and
experimental data in terms of the rupture strength as a function of water content. Our results show the importance of the
distribution of water for the mechanical behaviour. 相似文献
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L. De Carlan D. Franck P. Beaujard P. Burger B. Cahan O. Maillard C. Mazur P. Pihet R. Soulié 《Journal of Radioanalytical and Nuclear Chemistry》1997,226(1-2):205-210
Although much progress was made by using high purity gemanium detectors for direct measurement of239Pu in man, the improvement of lung spectroscopy sensitivity remains a challenge. Previous work showed that passivated implanted planar silicon detectors could provide an alternative by combining high-energy resolution at room temperature and planar geometry with large detection arrays. This paper reports on the status of this research based on the characterisation of 3×3 cm2 and 6×3 cm2 strip silicon detectors. Furthemore, the possibility to apply such detectors towards other monitoring problems for accidental situations such as the direct measurement of small contaminated surfaces was investigated. 相似文献
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Lifted cover inequalities are well-known cutting planes for 0–1 linear programs. We show how one of the earliest lifting procedures, due to Balas, can be significantly improved. The resulting procedure has some unusual properties. For example, (i) it can yield facet-defining inequalities even if the given cover is not minimal, (ii) it can yield facet-defining inequalities that cannot be obtained by standard lifting procedures, and (iii) the associated superadditive lifting function is integer-valued almost everywhere. 相似文献
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Cortese J Soulié-Ziakovic C Tencé-Girault S Leibler L 《Journal of the American Chemical Society》2012,134(8):3671-3674
We show here that complementary interactions can suppress mesoscopic order and thus lead to a counterintuitive change in material properties. We present results for telechelic supramolecular polymers based on poly(propylene oxide) (PPO), thymine (Thy), and diaminotriazine (DAT). The self-complementary systems based on Thy exhibit lamellar order and 2D crystallization of Thy in the bulk. We show that the microphase segregation is inhibited by addition of DAT: the strong complementary Thy-DAT interaction inhibits crystallization of thymine in microdomains and lamellar structuration. As a result, the supramolecular polymer with only weakly self-complementary stickers is a solid, whereas the supramolecular polymer with strongly complementary stickers is a liquid. 相似文献
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A powerful approach for the selection of 2-aminopurine substitution sites to investigate RNA folding
Soulière MF Haller A Rieder R Micura R 《Journal of the American Chemical Society》2011,133(40):16161-16167
A precise tertiary structure must be adopted to allow the function of many RNAs in cells. Accordingly, increasing resources have been devoted to the elucidation of RNA structures and the folding of RNAs. 2-Aminopurine (2AP), a fluorescent nucleobase analogue, can be substituted in strategic positions of DNA or RNA molecules to act as site-specific probe to monitor folding and folding dynamics of nucleic acids. Recent studies further demonstrated the potential of 2AP modifications in the assessment of folding kinetics during ligand-induced secondary and tertiary RNA structure rearrangements. However, an efficient way to unambiguously identify reliable positions for 2AP sensors is as yet unavailable and would represent a major asset, especially in the absence of crystallographic or NMR structural data for a target molecule. We report evidence of a novel and direct correlation between the 2'-OH flexibility of nucleotides, observed by selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE) probing and the fluorescence response following nucleotide substitutions by 2AP. This correlation leads to a straightforward method, using SHAPE probing with benzoyl cyanide, to select appropriate nucleotide sites for 2AP substitution. This clear correlation is presented for three model RNAs of biological significance: the SAM-II, adenine (addA), and preQ(1) class II (preQ(1)cII) riboswitches. 相似文献