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Marta Legawiec-Jarzyna Anna rbowata Wojciech Juszczyk 《Reaction Kinetics and Catalysis Letters》2006,87(2):291-296
Summary Vezetéknév 相似文献
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《Comptes Rendus Chimie》2007,10(7):666-676
The ligand (i-Pr)2PCH2(oxazoline) (1a), of the P,N-donor type, was reacted with [PdMeCl(COD)] to yield the square planar methylpalladium(II) complex [PdClMe(P,N)] (P,N = 1a) (2a), from which the complex [PdMe(P,N)OTf] (OTf = OSO2CF3) (3a) was obtained by AgOTf-promoted chloride abstraction. The alkyl complexes (P,N = 1a) (5a, R = H; 7a, R = C(O)OMe) have been isolated from the initial CO/ethylene or CO/methyl acrylate insertion steps into the Pd–Me bond of 3a, respectively, and spectroscopically characterized. Complexes 2a, 3a and 7a have been fully characterized by single crystal X-ray diffraction. Complex 7a is still a rare example of a structurally characterized CO/methyl acrylate stepwise insertion product. These complexes are relevant to the alternating copolymerization of olefins and carbon monoxide catalyzed by palladium complexes. In addition, the centrosymmetric dinuclear complex trans-[Pd(μ-Cl){(i-Pr)2PCH2(oxazoline)}]2(OTf)2 (6) has been obtained and characterized by X-ray diffraction; it appears to be the first dinuclear complex of the type [Pd(μ-Cl)(P,N)]2 to be characterized by X-ray crystallography.
Résumé
Le ligand (i-Pr)2PCH2(oxazoline) (1a), de type donneur P,N, réagit avec [PdClMe(COD)] pour former le complexe plan carré méthylpalladium(II) [PdClMe(P,N)] (P,N = 1a) (2a), à partir duquel le complexe [PdMe(P,N)OTf] (OTf = OSO2CF3) (3a) a été obtenu par abstraction de chlorure à l'aide de AgOTf. Les complexes alkyles (P,N = 1a) (5a, R = H; 7a, R = C(O)OMe), ont été isolés lors des premières étapes d'insertion de CO/éthylène ou de CO/acrylate de méthyle, respectivement, dans la liaison Pd–Me de 3a, et caractérisés par méthodes spectroscopiques. Les complexes 2a, 3a et 7a ont été complètement caractérisés par diffraction des rayons X sur monocristal. Le complexe 7a est un exemple encore rare de produit d'insertion par étapes de CO/acrylate de méthyle qui ait été caractérisé structuralement. Ces complexes sont pertinents pour la copolymérisation alternée d'oléfines et de monoxyde de carbone catalysée par les complexes du palladium. En outre, le complexe dinucléaire centrosymétrique trans-[Pd(μ-Cl){(i-Pr)2PCH2(oxazoline)}]2(OTf)2 (6) a été obtenu et caractérisé par diffraction des rayons X; il s'agit du premier complexe dinucléaire de type [Pd(μ-Cl)(P,N)]2 à être caractérisé par diffraction des rayons X. 相似文献10.
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Bootstrapping can be used for the estimation of parameter variances, and it is straightforward to be implemented but computationally demanding compared with other methods for parameter error estimation. It is not bound to any restrictions such as the distribution of measurement errors. And because of the possible asymmetry of the probability densities of the parameters, the parameter estimation errors acquired by bootstrapping are likely to be more accurate. In this work the feasibility of a bootstrap‐based method for optimal experimental design was evaluated for the Peleg model. The optimal design was performed, based on the Cramér‐Rao lower bound as a benchmark. Afterwards, the optimal design was calculated based on the bootstrap method. It is demonstrated that a bootstrap‐based optimal design of experiments will give comparable results with the Cramér‐Rao lower bound optimal designs, however with slightly different measurement points in time. If the parameter errors obtained from both optimal experimental designs are compared, they deviate for the 2 methods on average by 1.5%. Bootstrapping can be used for problems, which cannot be solved using Cramér‐Rao lower bound because of necessary but invalid assumptions. However, the benefits of the bootstrap method come at the cost of a significant increase in computational effort. Under similar conditions, the computation time for a bootstrap‐based optimal design was 25 minutes compared with 5 seconds when using the Cramér‐Rao lower bound method. As computers get faster and faster over time, the increase in computational demand will probably become less relevant in the future. 相似文献
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《Comptes Rendus de l''Academie des Sciences Series IIB Mechanics Physics Astronomy》2000,3(2):139-146
New chiral enantiomerically pure ferrocenyl chromophores for non-linear optics (NLO) have been synthesized and their crystal structures were determined by X-ray analysis. The correlation between crystal packing and bulk NLO efficiency was studied exemplifying again the difficulty to preview crystal packing from the molecular structure. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASferrocene / chiral non-racemic / non-linear optics / X-ray structure/ crystal packing 相似文献
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《Physics and Chemistry of Liquids》2012,50(2):99-104
Abstract On a étudié le pouvoir thermoélectrique du sélénium en fonction de la température pour des échantillons de puretés diverses et dopés ayantn subi divers cyles thermiques. II varie beaucoup, passant d'un signe à l'autre; le dopage à l'iode tend à donner une conductibilité de type p. Thermoelectric power of selenium vs temperature has been studies for samples of variable purity or doped having undergone various thermal treatments. Large variations appear, with either sign; doping with iodine favours p-type conduction. 相似文献
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Y. C. Wong D. W. M. Sin Y. C. Yip L. Valiente A. Toervenyi J. Wang G. Labarraque P. Gupta D. Soni Surmadi E. Hwang C. Yafa O. Cankur E. Uysal G. Turk R. Huertas 《Accreditation and quality assurance》2009,14(3):151-158
A Comité Consultatif pour la Quantité de Matière (CCQM) inter-laboratory comparison program, CCQM-P97, for the analysis of
cadmium and lead in Herba Demodii Styracifolii was organized by the Hong Kong Government Laboratory. The objective of the program was to establish comparability of trace
metals analysis in herbal matrices amongst the participating national metrology institutes. The arithmetic mean values of
the 13 participants were 0.3186 mg kg−1 (RSD = 11.3%) and 1.650 mg kg−1 (RSD = 11.0%) for cadmium and lead, respectively. The participants using double-isotope dilution mass spectrometry technique
for their quantification were found to provide similar mean values to those of non-isotope dilution mass spectrometry users.
The observation indicated that trace metal analysis in herbal matrices was not method-dependent, but the use of the highest
metrological IDMS approach gave a better precision than other routine calibration methods. 相似文献
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《Comptes Rendus Chimie》2005,8(2):229-234
Influence of the synthesis medium on the saponite crystallisation: formation mechanism in acidic and basic media. The present work is relative to the hydrothermal synthesis of saponite, a clay mineral having the following chemical formula per half unit cell : MxMg3 (Si4–xAlx)O10(OH,F)2, 0.2 < x < 1.20, where M is an hydrated exchangeable cation and x is the layer charge. Syntheses were performed in fluorine medium in the pH range 1 to 12. Two mechanisms can be proposed: in acidic medium, tetrahedral polysilicic acid incorporate Al3+ cations and, in basic medium, silica polycondensation occurs around a [Mg(OH)2] brucite-like layer. To cite this article: M. Jaber, J. Miéhé-Brendlé, C. R. Chimie 8 (2005). 相似文献
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《Comptes Rendus de l''Academie des Sciences Series IIB Mechanics Physics Astronomy》2000,3(4):289-293
The synthesis of oligolignols grafted on polymer (LFP) was engaged in order to further study the properties and the biodegradation mechanisms of the different lignin sub-units in conditions more similar to those involved in the natural polymer. Simplified lignin models were grafted by an imine or amino link to a 1 % amino ethyl polystyrene resin without any protection of the hydroxyl functions. Infrared was used to characterize the supported models. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASsupported lignine / synthesis / lignin models 相似文献
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Silmarilly Bahfenne Ray L. Frost 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(2):637-639
Raman spectroscopy has been sued to study the antimony containing mineral roméite Ca2Sb2O6(OH,F,O) from three different origins. Roméite is a calcium antimonate mineral of the pyrochlore group. An intense Raman band at ~518 cm?1 for roméite is assigned to the SbO ν1 symmetric stretching mode and the band at 466 cm?1 to the SbO ν3 antisymmetric stretching mode. The Raman band at 303 cm?1 is attributed to the OSbO bending mode. Some variation in band positions is observed and is attributed to the variation in composition between the three mineral samples. 相似文献
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Mathematical modeling via the fast Padé transform (FPT) is applied according to experimental NMR data encoded from (a) normal,
non-infiltrated breast tissue, (b) benign pathology (fibroadenoma) and (c) malignant breast tissue. At a partial signal length
N
P
= 1500, the FPT provided exact reconstruction of all the input spectral parameters for the time signals corresponding to
the normal, benign as well as to the malignant lesions. The converged parametric results remained stable at longer signal
lengths. The Padé absorption spectra yielded unequivocal resolution of all the extracted physical metabolites, even of those
that were nearly completely overlapping (phosphocholine and phosphoethanolamine at 3.22 ppm). The capacity of the FPT to resolve
and precisely quantify the physical resonances as encountered in normal versus benign versus malignant breast is demonstrated.
In particular, the FPT unambiguously delineated and quantified diagnostically important metabolites such as lactate, as well
as choline, phosphocholine and glycerophosphocholine that are very closely overlapping and may represent MR-retrievable molecular
markers of breast cancer. This was achieved by the FPT without any fitting or numerical integration of peak areas. We conclude
that these advantages of the FPT could be of definite benefit for breast cancer diagnostics via NMR and that this line of
investigation should continue with encoded data from benign and malignant breast tissue, in vitro and in vivo. We anticipate
that Padé-optimized MRS will reduce the false positive rates of MR-based modalities and further improve their sensitivity.
Once this is achieved, and given that MR entails no ionizing radiation, new possibilities for screening/early detection open
up, especially for risk groups, e.g. Padé-optimized MRS could be used with greater surveillance frequency among younger women
with high breast cancer risk. 相似文献
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《Comptes Rendus de l''Academie des Sciences Series IIB Mechanics Physics Astronomy》2000,3(5):335-340
Relationship between the morphology of precursors and the microstructure of sintered WO3 ceramics. The aim of this study is to perfect an elaboration process of ceramic WO3, to control the main parameters, to understand the nature and the role of the precursors and to establish a relationship between the morphology of the powder and the microstructure of the final ceramic. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SASpowder / granulometric / microstructure / precursors / sintering / ceramics 相似文献