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131.
132.
Bolognesi P Coreno M Avaldi L Storchi L Tarantelli F 《The Journal of chemical physics》2006,125(5):054306
The N 1s Auger spectra for the two nonequivalent N atoms in N2O have been measured via Auger electron-photoelectron coincidence spectroscopy. The site-selected Auger spectra are compared with the normal Auger spectrum and with accurate theoretical calculations accounting for the effects of the dynamics of the nuclei on the energy and linewidth of the Auger bands. Such effects are found to be crucial factors in determining the different band shapes in the site-selected spectra. 相似文献
133.
Given a connected open set
and a function w ∈LN/p(Ω) if 1 < p < N and w ∈Lr (Ω) for some r ∈(1, ∞) if p ≧ N, with
we prove that the positive principal eigenvalue of the problem
is unique and simple. This improves previous works all of which assumed w in a smaller space than LN/p (Ω) to ensure that Harnack’s inequality holds. Our proof does not rely on Harnack’s inequality, which may fail in our case.
Received: 18 March 2005; revised: 7 April 2005 相似文献
134.
Adriana Garroni Marcello Ponsiglione Francesca Prinari 《Calculus of Variations and Partial Differential Equations》2006,27(4):397-420
In this paper we consider positively 1-homogeneous supremal functionals of the type . We prove that the relaxation $\bar{F}$ is a difference quotient, that is
where is a geodesic distance associated to F. Moreover we prove that the closure of the class of 1-homogeneous supremal functionals with respect to Γ-convergence is given exactly by the class of difference quotients associated to geodesic distances. This class strictly contains supremal functionals, as the class of geodesic distances strictly contains intrinsic distances.
Mathematics Subject Classification (2000) 47J20, 58B20, 49J45 相似文献
135.
A method for the synthesis of β3-amino acids starting from α-amino acids is described. This conversion can be effected by an eight-step procedure which involves the transformation of the carboxylic group into an alkyne followed by a selenium-mediated conversion of the carbon-carbon triple bond to a Se-phenyl selenocarboxylate intermediate. The reactive Se-phenyl selenocarboxylate intermediates can be trapped with water, alcohols or the amine of an amino acid derivative to give β3-amino acids, β3-amino esters or mixed peptides, respectively. The whole transformations of the carboxylic group into an alkyne and of the alkyne group into β3-amino acids may not require purification of the intermediate products but a work-up and isolation procedure of crude materials. 相似文献
136.
Silica-based columns are largely used in RNA purification, allowing fast extractions and good yields of high quality nucleic acid, but their major limitation is the high cost. The reuse of such columns, although desirable, is not recommended because of residual amounts of material from the previous sample trapped in the column matrix, which might be released during further purification. Thus, recycling does need previous complete removal of any detectable RNA trace, but to date no protocol which allows decontamination and reuse is available.We report a very rapid decontamination procedure, based on treatment with warm alkaline solution containing Triton X-100, which ensures no RNA carry-over, and allows the recycling of columns without impairment of their efficiency in high-quality RNA purification even after several regeneration rounds. 相似文献
137.
Giovanna Loredana La Torre Marcello SaittaAngela Giorgia Potortì Giuseppa Di BellaGiacomo Dugo 《Journal of chromatography. A》2010,1217(32):5215-5224
In the present study we report on the optimization and validation of a sensitive high performance liquid chromatography atmospheric pressure chemical ionization mass spectrometry (HPLC–APCI–MS) method for the determination of 8 bioactive amines (histamine, tyramine, tryptamine, 2-phenylethylamine, cadaverine, putrescine, spermidine and spermine) in donkey milk samples. The method involves donkey milk pre-treatment to remove proteins and pre-column dansylation of the amines. HPLC in reversed phase mode has been used for bioactive amines separation and the operating condition of the APCI–MS system proved to be powerful and very efficient for peak assignment. The separation was accomplished in a short time with an excellent resolution for all the amine peaks. Quantification was carried out by monitoring the characteristic [M+H]+ ion of each amine derivative. The method sensitivity, linearity and repeatability were assayed with satisfactory results. The detection limits of the analysed amines ranged from 0.5 μg L−1 to 15 μg L−1; the highest LOD was for spermine. Also remarkably good recovery values were obtained; at the lowest spiking level (1 μg L−1) the percent mean recoveries ranged from 77.7 to 109.7. Furthermore, as the investigations relate to a complex matrix as donkey milk, suitable studies on matrix effect were performed. Finally, the developed and validated method was applied to analyse 13 donkey milk samples. Among the identified bioactive amines, putrescine, spermine and spermidine proved to be the main amines in donkey milk. Their concentration levels in the present study were lower than the values determined in mature human, cow and sow milk. 相似文献
138.
An efficient protocol, based on advanced statistical diagnostics and robust fitting techniques applied to the least‐squares processing of kinetic data of chemical reactions, is presented and discussed. The procedure, which is aimed at obtaining highly accurate estimation of the fitting parameters, consists of the identification of the outliers that remarkably impair the fitting by means of the so‐called “leverage analysis” and some related diagnostics. This approach allows the elimination of the actually aberrant observations from the data set and/or their robust weighting to inhibit the negative effects induced on the data fitting, with consequent reduction of the bias introduced into the parameter estimates. It has been found that the proposed procedure, applied to experimental kinetic data, does yield to a significant improvement in the regression results. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 587–607, 2010 相似文献
139.
Marcello Tiecco Silvia Sternativo Francesca Del Verme Claudio Santi Luana Bagnoli Andrea Temperini 《Tetrahedron》2008,64(15):3337-3342
The first example of the enantioselective ring opening of meso-epoxides by (phenylseleno)silanes using salen(Cr)complexes as catalyst is described. This desymmetrization reaction constitutes a simple and convenient approach to synthetically versatile optically active β-hydroxy selenides. 相似文献
140.
Aramini A Cesta MC Coniglio S Bijani C Colagioia S D'Elia V Allegretti M 《The Journal of organic chemistry》2003,68(20):7911-7914
The unusual reactivity of 1-phenyl-1-ethanesulfonic acid in thionyl chloride was investigated. Mechanistic considerations led us to set up a new and efficient synthesis of E-arylethenesulfonamides starting from 1-hydroxy-1-arylalkanes. The easy availability of the starting materials and the straightforward, one-pot procedure make this process an attractive method for the preparation of these compounds currently largely employed in chemical and pharmaceutical fields. 相似文献