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11.
Alan D. Potoff Bertrand L. Chamberland Lewis Katz 《Journal of solid state chemistry》1973,8(3):234-237
A single crystal study of hydrothermally prepared eight-layer BaMnO3 has been carried out which confirms the (Zhdanov notation) 121121 layer stacking scheme for the BaO3 layers. The MnO6 octahedra share faces in strings of four, and these strings are connected to each other by corner sharing. The compound has an hexagonal unit cell of dimensions a = 5.667 ± 0.003 and c = 18.738 ± 0.009 Å, probable space group . Its structure has been determined from 352 independent reflections, of which 242 were considered observed, collected manually by a counter technique and refined to a conventional R value of 0.079. 相似文献
12.
The synthesis of 2,8-dimethyl 3,9-dichloro 6-sila[5.5] spiro undecatetra 2.4,8,10-ene is described. The thermal decomposition of the adduct formed by the reaction of this product with methyl acetylene dicarboxylate is studied. From the characterization of the copyrolysis products, two possible mechanisms are proposed which imply the formation of digonal silicon such as 2-silaallene and 2-silaketene. 相似文献
13.
The chemical behaviour of sila-2 butadienes, formed as transient intermediates either by thermolysis or by photolysis of various 1-vinylsilacyclobutanes, was studied with respect to hydroxylated compounds of different pKa values Two mechanisms can explain the nature of the products obtained on the co-thermolysis of the cyclic compounds with phenol, one with 1-silacyclobut-1-ene intermediate and the other involving an allylic silicenium cation. In both hypothetical mechanisms, the 2-silabutadienes behave as a conjugated system since they lead either to (2+2) cycloaddition or to (1,2)- and (1,4)-electrophilic addition. This evidence for a conjugation phenomenon through a silicon atom is supported by the calculation of the delocalisation energies of butadiene and 2-silabutadiene. 相似文献
14.
P. Marage M. Aderholz P. Allport N. Armenise J. P. Baton M. Berggren D. Bertrand V. Brisson F. W. Bullock W. Burkot M. Calicchio E. F. Clayton T. Coghen A. M. Cooper-Sarkar O. Erriquez P. J. Fitch G. Gerbier J. Guy F. Hamisi P. O. Hulth G. T. Jones P. Kasper H. Klein R. P. Middleton D. B. Miller M. M. Mobayyen D. R. O. Morrison S. Natali M. Neveu S. W. O'Neale M. A. Parker P. Petiau J. Sacton R. A. Sansum E. Simopoulou C. Vallée K. Varvell A. Vayaki W. Venus H. Wachsmuth J. Wells W. Wittek BEBC WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1986,31(2):191-197
The cross section for coherent production of a single π? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10?40 cm2/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ 2 dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV. 相似文献
15.
Pradier CM Rubio C Poleunis C Bertrand P Marcus P Compère C 《The journal of physical chemistry. B》2005,109(19):9540-9549
Adhesion of bacterial strains on solid substrates is likely related to the properties of the outer shell of the micro-organisms. Aiming at a better understanding and control of the biofilm formation in seawater, the surface chemical composition of three marine bacterial strains was investigated by combining Fourier transform IR spectroscopy, X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary-ion mass spectrometry (ToF-SIMS). The D41 strain surface showed evidence of proteins, as deduced from the NH2 and NCO XPS and ToF-SIMS fingerprints; this strain was found to adhere to stainless steel, glass, or Teflon surfaces in a much higher quantity (2 orders of magnitude) than the two other ones, DA and D01. The latter are either enriched in COOH or sulfates, and this makes them more hydrophilic and less adherent to all substrates. Correlations with physicochemical properties and adhesion seem to demonstrate the role of the external layer composition, in particular the role of proteins more than that of hydrophobicity, on their adhesion abilities. 相似文献
16.
The reaction of a stable aminoarylcarbene with 2-chloroacrylonitrile is reported. The resulting 1/1 adduct has been spectroscopically and structurally characterized. The initial Michael addition is not followed by cyclopropane formation but by a dearomatizing cyclization affording an original bicyclic structure. 相似文献
17.
A straightforward preparation of various sulfoforms of the trisaccharide 4-methoxyphenyl O-(sodium beta-d-glucopyranosyluronate)-(1-->3)-( beta-d-galactopyranosyl)-(1-->3)-beta-d-galactopyranoside (1), namely its 6a- and 4a-monosulfate, 6b- and 4b-monosulfate and 6a,6b-disulfate derivatives, is reported for the first time. These compounds, which are partial structures of the linkage region of proteoglycans, will serve as probes for the study of the biosynthesis and sorting of these macromolecules. A key trisaccharide derivative, in which the two similar d-Gal units were differentiated at C-4,6 with 4,6-benzylidene and 4,6-di-tert-butylsilylene acetals, respectively, was used as a common intermediate. Both acetal groups showed excellent orthogonality, and allowed the preparation of all target compounds in high yield. Noteworthy is the possibility to prepare the 6a- and 6b-monosulfated and the 6a,6b-disulfated species through a one-pot regioselective procedure starting from a tetrol precursor. 相似文献
18.
A large‐scale synthetic route to a variety of phosphaformamidines and phosphaformamidinates, a type of derivative that was not accessible by the methods previously known for preparing phosphaamidines and phosphaamidinates, is reported. Thermally stable ethyl N‐arylformimidates 1 (ArN?CH(OEt), Ar=2,4,6‐(Me)3Ph or 2,6‐(iPr)2Ph) readily reacted with lithium dialkyl‐ and diarylphosphanides to afford the corresponding N‐aryl phosphaformamidines in 80 and 60 % yield, respectively, whereas with lithium (aryl)(silyl)phosphanide, the N‐aryl‐N‐silylphosphaformamidine (60 % yield) was obtained. Addition of primary lithium arylphosphanides to 1 followed by addition of a stoichiometric amount of nBuLi gave rise to the respective phosphaformamidinates (70–88 % yield). Methanolysis of the products afforded the N‐aryl‐N‐hydrogenophosphaformamidines (90–95 % yield). The solid‐state structure of one of the phosphaformamidinates is also presented. 相似文献
19.
Y Kroviarski S Cochet C Vadon A Truskolaski P Boivin O Bertrand 《Journal of chromatography. A》1988,449(2):403-412
A method is presented for screening immobilized dyes applicable to the purification of enzymes from haemolysate (haemolysate can be considered as a nearly pure solution of haemoglobin containing only marginal amounts of enzymes). Haemolysate is loaded on immobilized dye mini-columns until haemoglobin and the studied enzymes are found in the column eluate at the same concentrations as those present in the haemolysate. Such a frontal mode of screening allows those dyes to be selected which, displaying a higher affinity for the enzyme of interest than for haemoglobin, can be used to displace the unwanted protein (haemoglobin) from the column by the enzyme of interest (present at a much lower concentration). 相似文献
20.
Jean-Charles Lancelot Bertrand Letois Sylvain Rault Max Robba Maria Rogosca 《Journal of heterocyclic chemistry》1994,31(2):501-504
Cyclization of 3-(1-pyrrolyl)thiophene-2-carboxamide derivatives of methyl 3-(1-pyrrolyl)-2-thiophenecarboxylate afforded imminium salts and resulted in the formation of thieno[2,3-b]pyrrolizine derivatives. 相似文献