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61.
Ruimin Qiao Timothy Chin Stephen J. Harris Shishen Yan Wanli Yang 《Current Applied Physics》2013,13(3):544-548
We performed a systematic study of soft X-ray absorption spectroscopy in various manganese oxides and fluorides. Both Mn L-edges and ligand (O and F) K-edges are presented and compared with each other. Despite the distinct crystal structure and covalent/ionic nature in different systems, the Mn-L spectra fingerprint the Mn valence and spin states through spectral lineshape and energy position consistently and evidently. The clear O- and F-K pre-edge features in our high resolution spectra enable a quantitative definition of the molecular orbital diagram with different Mn valence. In addition, while the binding energy difference of the O-1s core electrons leads to a small shift of the O-K leading edges between trivalent and quadrivalent manganese oxides, a significant edge shift, with an order of magnitude larger in energy, was found between divalent and trivalent compounds, which is attributed to the spin exchange stabilization of half-filled 3d system. This shift is much enhanced in the ionic fluoride system. This work provides the spectroscopic foundation for further studies of complicated Mn compounds. 相似文献
62.
<正>Two new terpenes,wilfornine H(1) and triptobenzene Q(2) were isolated from Tripterygium wilfordii,as well as 11 terpenes. Their structures were elucidated by spectroscopic methods.Compounds 5,9-13 showed significant immunosuppressive activities. 相似文献
63.
Cornelius von Morze Douglas A.C. Kelley Timothy M. Shepherd Suchandrima Banerjee Duan Xu Christopher P. Hess 《Magnetic resonance imaging》2010
Ventral and rostral regions of the brain are of emerging importance for the MRI characterization of early dementia, traumatic brain injury and epilepsy. Unfortunately, standard single-shot echo planar diffusion-weighted imaging of these regions at high fields is contaminated by severe imaging artifacts in the vicinity of air–tissue interfaces. To mitigate these artifacts and improve visualization of the temporal and frontal lobes at 7 T, we applied a reduced field-of-view strategy, enabled by outer volume suppression (OVS) with novel quadratic phase radiofrequency (RF) pulses, combined with partial Fourier and parallel imaging methods. The new acquisition greatly reduced the level of artifacts in six human subjects (including four patients with early symptoms of dementia). 相似文献
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65.
In order to investigate how the self-assembly of organic matrix influences crystallisation and growth of inorganic minerals, we selected collagen as the matrix and conducted three experiments of crystallisation of CaCO3 in different reaction systems: H2O system, as-assembled collagen fibrils system and self-assembling of collagen system. It is found that (i) the self-assembly process of organic matrix had a remarkable effect on the morphology of inorganic minerals: CaCO3 crystals formed in the as-assembled collagen fibrils system were global clusters and those formed in the self-assembling of collagen system appeared as interlaced networks and (ii) the organic matrix decided the polymorph of crystals: CaCO3 crystals were calcite in the H2O system and appeared vaterite in the collagen system. From this study, we can conclude that the self-assembly of collagen fibrils greatly affect the crystallisation and growth of CaCO3. Such results are significant in understanding the mechanism of biomineralisation in calcified tissues in general, and useful in the synthesis of biominerals. (a)?CaCO3 formed in the as-assembled collagen fibrils system. (b)?CaCO3 formed in the self-assembling of collagen monomer system.The TEM images of samples obtained in the as-assembled collagen fibrils and self-assembling of collagen monomer system, were observed, respectively. The result shows that crystals CaCO3 formed in the as-assembled collagen fibrils system were global clusters; crystals CaCO3 formed in the self-assembling of collagen monomer system appeared interlaced networks. 相似文献
66.
Yan Yang Liu-Ting Yan Xu-Jian Luo Rong-Huan Qin Wen-Gui Duan 《Supramolecular chemistry》2013,25(11):810-818
Three novel coordination polymers, [Co(NH2-Aip)(H2Bibim)] n (1), [Co(NH2-Aip)(HBibimop)] n √ nH2O (2) and [Mn(NH2-Aip) √ H2O] n √ 2nH2O (3) with NH2-Aip and similar benzimidazole derivative ligands (NH2-Aip = 5-aminoisophthalic acid, H2Bibim = 2,2′-bibenzimidazole and HBibimop = 1,3-bis(benzimidazol-2-yl)-2-oxapropane), have been synthesised under hydrothermal conditions and structurally characterised by single-crystal X-ray diffraction analysis, elemental analysis and IR spectroscopy. 5-Aminoisophthalic acid ligand adopts μ2-, μ3- and μ4-bridge coordination fashion and benzimidazole derivatives exist as terminal- and bridge-mode in complexes 1–3. The intricate hydrogen bonds and π–π stacking interactions in supramolecular framework are discussed. Using the combination of ultraviolet–visible absorption titration and fluorescence spectra, the experimental results show that complexes 1 and 2 bind to DNA in an intercalative mode and their DNA-binding constants (K b ) are also found. 相似文献
67.
Fu-Jun Duan Jin-Chang Ding Hong-Juan Deng Ding-Ben Chen Jiu-Xi Chen Miao-Chang Liu Hua-Yue Wu 《中国化学快报》2013,24(9):793-796
An efficient and facile method for the synthesis of N-substituted pyrroles in moderate to good yields by the Paal–Knorr reaction of γ-diketones with amines in the presence of β-cyclodextrin in aqueous media has been developed.Moreover,this process tolerated diamines(e.g.,para-,meta- or orthophenylenediamine)to construct bis-pyrrole or mono-pyrrole derivates.β-Cyclodextrin can be recovered easily after the reactions and reused without evident loss in activity. 相似文献
68.
The azido sugar,GalNAz,was successfully used for imaging and perturbing protein glycosylation in triple-negative breast cancer cell line,MDA-MB-231.After the incorporation of GalNAz in the triple-negative breast cancer cell line,the tumorigenicity of these cells was decreased.Results from gene analysis and drug treatment suggest that the tumorigenicity decrease may be attributed to the reduction of cancer stem cell population.Possible mechanisms of GalNAz induced cancer stem cells(CSCs) proportion change are discussed. 相似文献
69.
70.
Triazolo‐fused 2′,3′‐cyclic nucleoside analogs were synthesized by an intramolecular 1,3‐dipolar cycloaddition of nucleoside‐derived azido alkynes in a regio‐ and stereospecific manner. The uracil base in these target compounds was successfully transformed to the corresponding cytosine. The synthesized compounds were examined in a MAGI assay for their anti‐HIV activities, and in a H9 T lymphocytes assay for their cell toxicities. 相似文献