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51.
The first general method for direct displacement of sulfur from chiral carbon centers has been developed. Chiral mercaptans are readily converted to the corresponding thiaphosphonium salts by treatment with t-butyl hypochlorite and hexamethylphosphorous triamide. Metathesis with ammonium hexafluorophosphate provides stable, isolable, crystalline salts which undergo clean nucleophilic diplacement with a variety of heteroatom and carbon based nucleophiles, affording products in which the stereochemistry has been inverted. 相似文献
52.
Souhir Boujday Dr. Juliette Blanchard Dr. Richard Villanneau Dr. Jean‐Marc Krafft Christophe Geantet Prof. Catherine Louis Dr. Michèle Breysse Dr. Anna Proust Prof. 《Chemphyschem》2007,8(18):2636-2642
We use polyoxometalates as precursors for the preparation of heterogeneous catalysts. In the starting molecular precursor [{Ru(C6Me6)}2Mo5O18{Ru(C6Me6)(H2O)}], three ruthenium arene fragments are supported on a formally lacunary Lindqvist‐type polyoxomolybdate. This species was introduced by incipient wetness impregnation into the porosity of a SBA‐15‐type mesoporous silica. The evolution of the system under reducing atmosphere is followed by several methods, such as temperature‐programmed reduction (TPR), Raman, and X‐ray absorption spectroscopy (XAS). The results indicate that the polyoxometalate structure is retained after grafting on silica and allows the stabilization of Ru0 nanoparticles after reduction. The resulting system exhibits interesting catalytic activity in benzene hydrogenation. 相似文献
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54.
Céline Chizallet Guylène Costentin Jean-Marc Krafft Hélène Lauron-Pernot Michel Che 《Chemphyschem》2006,7(4):904-911
Photoluminescence decay studies of emitting species on MgO nanocubes at room temperature provide evidence of three surface species characterized by an excitation and emission wavelength couple {lambda(exc);lambda(em)}. Species A corresponds to {lambda(exc)=240 nm; lambda(em)=380 nm}, whereas the couple {lambda(exc)=280 nm; lambda(em)=470 nm} is assigned to two species: B and B', the former is involved in energy transfer from excited state A* and the latter in direct emission from excited state B'*. A simple model for energy transfer from species A* to B is proposed. The numerical resolution of equations corresponding to this model is in good agreement with experimental data. This method quantifies the kinetics of intrinsic emission and energy transfer processes. Lifetime values indicate that phosphorescence is taking place, and species A, B and B' are identified as edge O(2-) (4 C), corner O(2-) (3 C) and kink O(2-) (3 C) oxide ions respectively. 相似文献
55.
56.
Maximilian Krafft 《Mathematische Annalen》1927,97(1):430-453
Ohne Zusammenfassung 相似文献
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Ohne Zusammenfassung 相似文献
59.
Sobottka SB Geiger KD Salzer R Schackert G Krafft C 《Analytical and bioanalytical chemistry》2009,393(1):187-195
Infrared spectroscopic imaging is a promising intraoperative tool which enables rapid, on-site diagnosis of brain tumors during
neurosurgery. A classification model was recently developed using infrared spectroscopic images from thin tissue sections
to grade malignant gliomas, the most frequent class of primary brain tumor. In this study the model was applied to 54 specimens
from six patients with inhomogeneous gliomas composed of regions with different tumor density and morphology. The resection
was controlled using neuronavigation which transfers the findings obtained by preoperative magnetic resonance imaging (MRI)
into the operating field. For comparison, all specimens were independently evaluated by histopathology after hematoxylin and
eosin staining. The infrared-derived grading agreed with histopathology and MRI findings for almost all specimens. With regard
to histopathological assessment, sensitivities of 100% (22/22) and 93.1% (27/29) and specificities of 96.9% (31/32) and 88.0%
(22/25) were achieved, depending on whether the classification was based on the predominant or maximal tumor grade, respectively,
in the specimen. Altogether, in 98% (53/54) of all specimens the decision to continue or not continue tumor resection could
have been made according to the infrared spectroscopic classification. This retrospective study clearly demonstrates that
infrared spectroscopic imaging may help to define tumor margins intraoperatively and to detect high-grade tumor residues for
achieving more radical tumor resection.
MRT-guided tumor resection (left) is combined with infrared spectroscopy-based tissue classification (middle, right). With regard to histopathological assessment, sensitivities of 100% and 93.1% and specificities of 96.9% and 88.0% were
achieved for 54 specimens. (TIF 47.1 KB) 相似文献
60.
ER Badman GE Patterson JM Wells RE Santini RG Cooks 《Journal of mass spectrometry : JMS》1999,34(8):889-894
Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd. 相似文献