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151.
We describe a class of groups with the property that the finite ones among them are precisely the complex reflection groups of rank 2. This situation is reminiscent of Coxeter groups, among which the finite ones are precisely the real reflection groups. We also study braid relations between complex reflections and indicate connections to an axiomatic study of root systems and to the Shephard–Todd “collineation groups.” 相似文献
152.
Chandra M Dowgiallo AM Knappenberger KL 《Journal of the American Chemical Society》2012,134(10):4477-4480
We report the first observation of a magnetic dipolar contribution to the nonlinear optical (NLO) response of colloidal metal nanostructures. Second-order NLO responses from several individual solid gold nanosphere (SGN) dimers, which we prepared by a bottom-up approach, were examined using polarization-resolved second harmonic generation (SHG) spectroscopy at the single-particle level. Unambiguous circular dichroism in the SH signal was observed for most of the dimeric colloids, indicating that the plasmon field located within the interparticle gap was chiral. Detailed analysis of the polarization line shapes of the SH intensities obtained by continuous polarization variation suggested that the effect resulted from strong magnetic-dipole contributions to the nanostructure's optical properties. 相似文献
153.
A review of recent developments in the speciation and location of arsenic and selenium in rice grain
Carey AM Lombi E Donner E de Jonge MD Punshon T Jackson BP Guerinot ML Price AH Meharg AA 《Analytical and bioanalytical chemistry》2012,402(10):3275-3286
Rice is a staple food yet is a significant dietary source of inorganic arsenic, a class 1, nonthreshold carcinogen. Establishing
the location and speciation of arsenic within the edible rice grain is essential for understanding the risk and for developing
effective strategies to reduce grain arsenic concentrations. Conversely, selenium is an essential micronutrient and up to
1 billion people worldwide are selenium-deficient. Several studies have suggested that selenium supplementation can reduce
the risk of some cancers, generating substantial interest in biofortifying rice. Knowledge of selenium location and speciation
is important, because the anti-cancer effects of selenium depend on its speciation. Germanic acid is an arsenite/silicic acid
analogue, and location of germanium may help elucidate the mechanisms of arsenite transport into grain. This review summarises
recent discoveries in the location and speciation of arsenic, germanium, and selenium in rice grain using state-of-the-art
mass spectrometry and synchrotron techniques, and illustrates both the importance of high-sensitivity and high-resolution
techniques and the advantages of combining techniques in an integrated quantitative and spatial approach. 相似文献
154.
Jean-Pierre Majoral Cédric-Olivier Turrin Régis Laurent Anne-Marie Caminade 《Macromolecular Symposia》2005,229(1):1-7
Summary: The influence of the size (the generation) of phosphorus dendrimers on their properties is discussed in three main fields of applications: catalysis, new materials, and biology. Typical examples are given to illustrate these three fields: Knoevenagel condensation for catalysis, elaboration of highly sensitive DNA chips for materials, transfection experiments, and anti-prion activity for biology. 相似文献
155.
A general synthesis of various polyazaphosphorus macrocycles involving [1 + 1], [2 + 2], or [3 + 3] cyclocondensations is reviewed, as well as the attempted synthesis of cryptands. Selective reduction (imino functions) methylation (PS groups), silylation (PO groups) are reported. Preparations of some macrocycle complexes are described. 相似文献
156.
Victor Furer Alexandr Vandyukov Jean-Pierre Majoral Anne-Marie Caminade Valery Kovalenko 《Molecules (Basel, Switzerland)》2022,27(23)
The structure of phosphorus-containing dendrimers has been studied by IR spectroscopy and optical polarization microscopy. The repeating units of dendrimer molecules are mesogens. This property arises from the conjugation of the aromatic ring and the hydrazone group. An analysis of the IR spectra showed that, with an increase in the generation number, the width of the stretching vibration bands ν(PN) and ν(PO) increases. Difficulties in packing molecules of higher generations cause conformational diversity. The shape of the dendrimer molecules was determined by analyzing the increments of dipole moments. Additionally, the modeling of the stacking of repeating links was performed. The spherical model of molecules does not satisfy the experimental dipole moments of the dendrimers. The flat disk model is more suitable for explaining step changes in dipole moments. The liquid-crystalline ordering of dendrimers under the action of applied pressure was found. With simultaneous heating and uniaxial compression, optical anisotropy appears in dendrimers. It is associated with the formation of liquid-crystalline order. However, a thermodynamically stable liquid-crystalline phase is not formed in this case. Dendrimers most likely have disk-shaped molecules. 相似文献
157.
Larisa Karpenko-Jereb Edyta Rynkowska Wojciech Kujawski Sarah Lunghammer Joanna Kujawa Stéphane Marais Kateryna Fatyeyeva Corinne Chappey Anne-Marie Kelterer 《Ionics》2016,22(3):357-367
The work is devoted to a computational study of three types of cationic polymeric membranes in Li+-ionic form, in water and methanol environments, at various solvation levels. The studied membranes Nafion, IonClad, and M3 possess the perfluorinated backbone; however, various side chains were terminated with the functional groups of distinctly different ionic strength. The paper discusses the structural features of the membrane-solvent clusters as well as an influence of the side chain nature on the dissociation of the functional groups and the binding energy of the solvent molecules. Additionally, the paper compares the obtained results for Li+-Nafion membrane in water with the results published earlier for H+ and Na+ forms. 相似文献
158.
The flat, triangular 3,4,5-tris-(p-n-dodecyloxybenzyloxy) benzoyloxy group (DOBOB) grafted onto a variety of rod, disc or cone-shaped molecules is shown to yield mesomorphic materials. 相似文献
159.
160.