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131.
Raymundo Cruz-Almanza Francisco Prez-Flores Leonardo Brea Eva Tapia Reyna Ojeda Aidee Fuentes 《Journal of heterocyclic chemistry》1995,32(1):219-222
Mexican Bentonitic earth (Tonsil) catalyzed the Claisen rearrangement of aryl 1,1-dimethylpropargyl ethers under mild conditions to provide 2,2-dimethyl-2H-1-benzopyrans. The synthesis of encecalin 2f and desmethoxyencecalin 2i , two biologically active products among other natural products ( 2b, 2e ) was performed by this procedure. 相似文献
132.
The application of a Fourier spectrometer to the study of the electronic structure in the far infrared of some intermediate valence or heavy fermion materials or of highT
c
superconductors showed that FT-reflectivity is a powerful tool of investigation at very low energies. A very careful control of the experimental conditions and of the reference measurements is necessary to eliminate spurious reflectivities.The results show optical transitions at very low energy and permit to evaluate the electronic structures and the effective mass of the carriers in the vicinity of the Fermi level. 相似文献
133.
134.
Pyrazole elimination and vinyl bromide were found as products in the Flash Vacuum Pyrolysis of (β-Bromo ethyl)-pyrazole. To obtain kinetic parameters (Ea) we carried out competitive reactions using (β-chloro ethyl)-pyrazole as an internal standard. A thermochemical study to calculate Δ(ΔH ) for this reaction was carried out. 相似文献
135.
Manzoni L Arosio D Belvisi L Bracci A Colombo M Invernizzi D Scolastico C 《The Journal of organic chemistry》2005,70(10):4124-4132
[reaction: see text] An efficient and operationally simple method for the synthesis of functionalized azaoxobicyclo[X.3.0]alkane amino acids has been devised. The key step is an intramolecular nitrone cycloaddition on 5-allyl- or 5-homoallylproline that was found to be completely regio- and stereoselective. 相似文献
136.
Andresa JS Reis RM Gonzalez EP Santos LS Eberlin MN de Paula Nascente PA Tanimoto ST Machado SA Rodrigues-Filho UP 《Journal of colloid and interface science》2005,286(1):303-309
The present paper describes the one-pot procedure for the formation of self-assembled thin films of two silanes on the model oxidized silicon wafer, SiO2/Si. SiO2/Si is a model system for other surfaces, such as glass, quartz, aerosol, and silica gel. MALDI-TOF MS with and without a matrix, XPS, and AFM have confirmed the formation of self-assembled thin films of both 3-imidazolylpropyltrimethoxysilane (3-IPTS) and 4-(N-propyltriethoxysilane-imino)pyridine (4-PTSIP) on the SiO2/Si surface after 30 min. Longer adsorption times lead to the deposition of nonreacted 3-IPTS precursors and the formation of agglomerates on the 3-IPTS monolayer. The formation of 4-PTSIP self-assembled layers on SiO2/Si is also demonstrated. The present results for the flat SiO2/Si surface can lead to a better understanding of the formation of a stationary phase for affinity chromatography as well as transition-metal-supported catalysts on silica and their relationship with surface roughness and ordering. The 3-IPTS and 4-PTSIP modified SiO2/Si wafers can also be envisaged as possible built-on-silicon thin-layer chromatography (TLC) extraction devices for metal determination or N-heterocycle analytes, such as histidine and histamine, with "on-spot" MALDI-TOF MS detection. 相似文献
137.
A Refinement of the Hofer-Zehnder Theorem on the Existence of Closed Characteristics Near a Hypersurface 总被引:1,自引:0,他引:1
The HoferZehnder theorem states that almost every hypersurfacein a thickening of a hypersurface S in a symplectic manifold(M, ) carries a closed characteristic, provided that S boundsa compact submanifold and (M, ) has finite capacity. It is shownthat it is enough to assume that the thickening of S has finitecapacity. 2000 Mathematics Subject Classification 70H12 (primary),34C25 (secondary). 相似文献
138.
Leonardo Castellani 《Letters in Mathematical Physics》1994,30(3):233-239
We obtain the inhomogeneousq-groups IGL
q
(n) via a projection from GL
q
(n + 1). The bicovariant differential calculus of IGL
q
(n) is constructed, and the corresponding quantum Lie algebra is given explicitly. 相似文献
139.
Leonardo Modesto 《International Journal of Theoretical Physics》2006,45(12):2235-2246
We extend the ideas introduced in the previous work to a more general space-time. In particular we consider the Kantowski-Sachs space time with space section with topology . In this way we want to study a general space time that we think to be the space time inside the horizon of a black hole. In this case the phase space is four dimensional and we simply apply the quantization procedure suggested by loop quantum gravity and based on an alternative to the Schroedinger representation introduced by H. Halvorson. Through this quantization procedure we show that the inverse of the volume density and the Schwarzschild curvature invariant are upper bounded and so the space time is singularity free. Also in this case we can extend dynamically the space time beyond the classical singularity.
PACS number: 04.60.Pp, 04.70.Dy 相似文献
140.
Tenorio-Lopez FA Valle Mondragon LD Olvera GZ Torres Narvaez JC Pastelin G 《Natural product research》2006,20(13):1176-1182
Viscum album L. aqueous extract, on the Langendorff isolated and perfused heart model, decreases coronary vascular resistance, when compared to control group (36.00 +/- 2.00 vs. 15.80 +/- 1.96 dyn s cm-5). Our data support the fact that this mechanism involves NOS-2 and NOS-3 overexpression (4.65 and 7.89 times over control, respectively), which is correlated with increases in NO (6.24 +/- 2.49 vs. 147.95 +/- 2.79 pmol) and cGMP production (43.94 +/- 2.00 vs. 74.81 +/- 1.96 pmol mg-1 of tissue), compared to control values. Such an effect is antagonized by gadolinium(III) chloride, L-NAME and ODQ. Therefore, coronary vasodilator effect elicited by V. album L. aqueous extract is mediated by the NO/sGC pathway. 相似文献