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171.
Muonium and hydrogen exchange in collinear I + MuI, I + HI, H + MuH and H + H2 reactions are studied by semiclassical techniques within the hyperspherical formalism. Bound states in IMuI, as an example of bond formation on repulsive surfaces, are also considered. 相似文献
172.
Aldo Conca 《manuscripta mathematica》1996,90(1):287-300
The aim of this note is to determine the Hilbert-Kunz functions of rings defined by monomial ideals and of rings defined by
a single binomial equationX
a−Xb with gcd(X
a, Xb)=1. 相似文献
173.
Aldo Andreani Lucedio Greci Giorgio Tosi Paolo Sgarabotto Franco Ugozzoli 《Journal of heterocyclic chemistry》1988,25(1):29-32
The study of the molecular geometry of 1-methyl-1,2,3,4-tetrahydropyrimido[1,2-a]indole-10-carboxaldehyde as determined by X-ray analysis and the electrochemical properties of that compound are reported. These are compared with those of a number of indole-3-carboxaldehyde, differently substituted at 1 and 2 position. This was done in order to understand the unsuccessful attempts to convert the title compound into the corresponding acid. The result indicate that this anomalous behaviour may be attributed to easy oxidizability of the pyrimido ring nitrogen. 相似文献
174.
175.
Inspired by a decomposition of the lattice Laplacian operator into massive terms (coming from the use of the block renormalization group transformation for bosonic systems), we establish a telescopic decomposition of the Dirac operator into massive terms, with a property named orthogonality between scales. Making a change of Grassmann variables and writing the initial fields in terms of the eigenfunctions of the operators related to this decomposition, we propose a multiscale structure for the generating function of interacting fermions. Due to the orthogonality property we obtain simple formulas, establishing a trivial link between the correlation functions and the effective potential theories. In particular, for the infrared analysis of some asymptotically free models, the two point correlation function is written as a dominant term (decaying at large distances as the free propagator) plus a correction with faster decay, and the study of both terms is straightforward once the effective potential theory is controlled. 相似文献
176.
Aldo Lagana' Aldo Marino Giovanna Fago 《Fresenius' Journal of Analytical Chemistry》1994,348(4):320-323
Summary A rapid, reliable and sensitive procedure is reported for the detection of residues of total diethylstilboestrol (DES) (free and conjugated) in bovine muscle samples. Prior to analysis, the DES in the sample was enzymatically deconjugated. Subsequently the sample was subjected to a clean-up procedure using a two-trap system composed of a first cartridge of non-specific adsorbing material (C 18) and of a second cartridge containing a sulphonic acid type silica-based anion exchanger. The determination was performed by HPLC with electrochemical detection. Analytical variables such as efficiency of hydrolysis, enzyme purification, hydrodynamic voltammetric studies and variation in the DES trans/cis ratio were investigated. Mean recovery of total DES was 87.3%. The precision of the procedure was 7.2% for DES levels of 0.5 ng/g and 2.1% for levels of 5 ng/g. 相似文献
177.
The coordinated ethylene molecule in the dicationic complex [(PNP)Pt(CH2=CH2)](BF4)2 (PNP = 2,6-bis(diphenylphosphinomethyl)pyridine) undergoes nucleophilic attack by free internal alkenes, giving the isolable complexes [(PNP)Pt(CH2=CHCH(Me)CMeRR'](BF4)2 (R, R' = H, Me) and providing a new effective pathway for a chemo- and regio-selective catalytic hydrovinylation reaction. 相似文献
178.
Anna Maria Gioacchini Aldo Roda Guido Carlo Galletti Paola Bocchini Anna Chiara Manetta Mario Baraldini 《Journal of chromatography. A》1996,730(1-2):31-37
The present work describes the development of an HPLC-electrospray mass spectrometric method for the analysis of phenolic acids and aldehydes. These compounds are important for the quality of foods and feeds, such as dietary fiber supplements, wine and lignicellulose by-products. Good separation was obtained with a phenyl column (3 μm particle size, 150 mm×3.9 mm I.D.), using McOH-H2O (30:70, v/v) as the mobile phase with 0.01% CH,COOH and 0.2 mM tetraethyl ammonium iodide as the ion pairing agent, at a flow-rate of 0.3 ml/min. This system permits post column splitting of the eluate for analysis by electrospray mass spectrometry with a flow-rate of 11 μl/min. This new method is extremely sensitive and less than 6 pg/inj of the studied phenols can be identified and quantified. This method was applied to standard compounds as well as to components of high-fiber dietary supplements (primarily wheat bran), cornmeal, and oat bran. 相似文献
179.
α-bromo Michael acceptors undergo ipso-substitution by phenol or benzenethiol in the K2CO3-acetone system, the reaction originating the (Z) isomers, via a stereospecific AdSNE process. 相似文献
180.
The molecular structure of p-dichlorobenzene in the vapour phase has been studied by electron diffraction. Least-squares refinement of a model with D2h symmetry has led to the accurate determination of the small deviations of the benzene ring from D6h symmetry caused by the chlorine substituents. The most appreciable effect is an increase from 120° to 121.6 ± 0.2° of the internal angle at the ipso carbon, associated with a shortening of the distance between the two ipso atoms. A less pronounced effect is a shortening of the C-C bonds that originate from the ipso carbons as compared to the central C-C bonds (rg = 139.0 ± 0.3 pm vs. 139.5 ± 0.4 pm). Other bond distances are rg (C-Cl) - 173.0 ± 0.4 pm and rg (C-H) = 109.4 ± 1.0 pm. The observed ring distortions are in agreement with those obtained by low-temperature X-ray crystallography on three different crystal phases of p-dichlorobenzene. They are also consistent with those obtained for chloro-benzene by gas-phase electron diffraction and by NMR spectroscopy in a nematic solvent. The rs structure of chlorobenzene obtained in a recent study by micro-wave spectroscopy is shown to need revision, as far as the ipso region of the ring is concerned. 相似文献