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We construct the first examples of minimal Kähler surfaces in R6 which are irreducible and neither holomorphic nor complex ruled. 相似文献
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Marcos A. P. Martins Alex F. C. Flores Rogrio A. Freitag Nilo Zanatta 《Journal of heterocyclic chemistry》1996,33(4):1223-1226
The investigation of the effect of the cyclopentane ring on the regiochemistry of the reactions of 2-acetylcyclopentanones 1a-d and β-methoxyvinyl trifluoromethyl ketone derivative 2a with hydroxylamine hydrochloride is reported. The reactions give regiospecifically the 4,5-trimethylene-4,5-dihydroisoxazoles 3a-d in good yields. 相似文献
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Marcos Duarte Maia 《General Relativity and Gravitation》1978,9(5):381-385
Some proposed models for a quantum field theory in general relativity are briefly analyzed. Their main difficulties are a consequence of the initial choice of the group of symmetries of the (quantum) field equations. The necessity of selecting space-time isometries in a general covariant theory and the unphysical character of the Poincaré translations in a tangent plane theory are discussed. Starting from some basic requirements, a model is proposed in which the groups of symmetries are derived from the proper homogeneous groups of isometries of the minimal isometric local embedding spaces of space-times.This essay received an honorable mention (1977) from the Gravity Research Foundation-Ed. 相似文献
208.
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
209.
Díez D Sanchez JM Rodilla JM Rocha PM Mendes RS Paulino C Marcos IS Basabe P Urones JG 《Molecules (Basel, Switzerland)》2005,10(8):1005-1009
Incubation of sclareol with Rhizopus stolonifer affords in high yield a mixture of triols with 18-hydroxy-sclareol as the main component. 相似文献
210.
Three non-equilibrium equations have been derived describing the evolution of the matrix elements, which are highly off-diagonal on the internal energy of the singlet density operator, ?(1), of a quantum dilute gas of molecules with internal levels. The first equation has been obtained by assuming the requirement of sufficient spacing of the spectral transition lines, the second one being its extension for weakly inhomogeneous gases and the third one the equation generalized for spectral transition lines of arbitrary spacing. They have been obtained inside the framework of the subdynamics theory of the Brussels Group where the Π̌-subdynamics have been explicitly constructed.Their linearized version is presented permitting to obtain closed equations for the ?(1)-operator, which can be shown useful in the correlation functions, being interesting in spectroscopic measurements. A discussion concerning the above aspects has been included as well. 相似文献