Phytoconstituents from the galls of Pistacia integerrima Stewart

Phytochemical investigation of the galls of Pistacia integerrima Stewart (Pistaceaceae) yielded three new phytoconstituents characterized as n-decan-3′-ol-yl-n-eicosanoate, n-octadecan-9,11-diol-7-one and 3-oxo-9β-lanost-1,20(22)-dien-26-oic acid along with the known compound β-sitosterol. The structures of these phytoconstituents have been elucidated on the basis of spectral data analysis and chemical reactions.     

Transient elastography in anisotropic medium: application to the measurement of slow and fast shear wave speeds in muscles

From the measurement of a low frequency (50-150 Hz) shear wave speed, transient elastography evaluates the Young's modulus in isotropic soft tissues. In this paper, it is shown that a rod source can generate a low frequency polarized shear strain waves. Consequently this technique allows to study anisotropic medium such as muscle. The evidence of the polarization of low frequency shear strain waves is supported by both numeric simulations and experiments. The numeric simulations are based on theoretical Green's functions in isotropic and anisotropic media (hexagonal system). The experiments in vitro led on beef muscle proves the pertinent of this simple anisotropic pattern. Results in vivo on man biceps shows the existence of slow and fast shear waves as predicted by theory.     

Extremal vectors and invariant subspaces

For a bounded linear operator on Hilbert space we define a sequence of so-called minimal vectors in connection with invariant subspaces and show that this presents a new approach to invariant subspaces. In particular, we show that for any compact operator some weak limit of the sequence of minimal vectors is noncyclic for all operators commuting with and that for any normal operator , the norm limit of the sequence of minimal vectors is noncyclic for all operators commuting with . Thus, we give a new and more constructive proof of existence of invariant subspaces. The sequence of minimal vectors does not seem to converge in norm for an arbitrary bounded linear operator. We will prove that if belongs to a certain class of operators, then the sequence of such vectors converges in norm, and that if belongs to a subclass of , then the norm limit is cyclic.

     

Cyclisation of optically active dihydromyrcenes (2,6-dimethyl-2,7-octadiene): A stereospecific ring contraction

The isomeric (+) and (?)-dihydromyrcene cyclise in organic acids through a stereospecific ring contraction process to give the esters of α-(S)-(+)-1-(α-hydroxyethyl)-3,3-dimethylcyclohexane and α(R)-(?)-1-(α-hydroxyethyl)-3,3-dimethylcyclohexane respectively. Small amounts of enantiomeric cis- and trans-tetrahydroeucarvyl esters are also formed. The absolute configuration of the chiral carbinol centres has been determined using Horeau's method. Also, the synthesis of both optical isomers of 3,3-dimethylcyclohexanol has been achieved for the first time.     

Etude theorique des proprietes thermodynamiques du radical CN et de ses dimeres

Using the ab initio LCAO—SCF—MO method and the 6–31G extended basis set, the CN radical and its possible dimers (NCCN, CNNC or CNCN) have been studied in terms of nuclear equilibrium geometries, normal modes of vibration, IR spectrum and thermodynamic properties. The results show that quantum chemical calculations enable these parameters to be obtained with adequate accuracy. Working properly, one can build a local potential energy surface on which to perform a harmonic vibrational analysis. Hence all the required information to apply the principles of statistical thermodynamical analysis is available.     

New Rh(I) and Rh(III) bisimidazol-2-ylidene complexes: synthesis,reactivity, and molecular structures

New chelate bis-heterocyclic-carbene complexes of Rh(I) and Rh(III) have been obtained and fully characterized. The molecular structures of the new species have been determined. The synthesis of the compounds starts from the bisimidazolium precursors, which are deprotonated with NEt(3) under mild reaction conditions, leading to coordination to the Rh complex. The Rh(III) compounds are generated from Rh(I) and [Rh(II)](2) species, although there is no apparent oxidizing agent in the reaction media.     

Molecular complexation of free base meso-tetraarylporphyrins with antimony(III) chloride in free solvent media

The reaction of meso-tetraarylporphyrins (H₂t(Xp)p) with SbCl₃ under free solvent conditions affords green complexes with a 1:1 H₂t(X)pp:SbCl₃ ratio. These complexes have dimeric structures with a (μ-Cl)₂bridge. UV–VIS, ¹H NMR and ¹³C NMR spectra data show that the porphyrin core of [(H₂t(Xp)p)₂Sb₂Cl₆], similar to 1:2 (donor:acceptor) molecular complexes of meso-tetraarylporphyrins and porphyrin diacid, is distorted, thus two nitrogen atoms of pyrrolenine in a side of the porphyrin plane act as electron donors to an antimony atom of SbCl₃. Molecular complexation of meso-tetraarylporphyrins with SbCl₃ produces a large downfield shift for the NH signal, although there is no hydrogen bonding present.     

Evaluation of the bond energy terms for the various types of boron-nitrogen bonds

Summary We have determined a series of bond energy terms in compounds containing dative, single, double and/or triple boron-nitrogen bonds. We describe various interesting applications based on these bond energy terms namely the determination of enthalpies of atomization and stabilization energies. More particularly, the conventional ring strain energies of three- and four-membered small ring containing boron and nitrogen atoms could be determined and the aromaticity of borazine, reexamined.Dedicated to Professor Alberte Pullman     

TEMPO-catalyzed aerobic oxidation of alcohols to aldehydes and ketones in ionic liquid [bmim][PF6

[reaction: see text]. A simple and mild TEMPO-CuCl catalyzed aerobic oxidation of primary and secondary alcohols to the corresponding aldehydes and ketones in ionic liquid [bmim][PF6] with no trace of overoxidation to carboxylic acids has been developed. The product can be isolated by a simple extraction with organic solvent, and the ionic liquid can be recycled or reused.     

Theoretical Approach to the Deformation-induced Luminescence in Metals

The present paper reports the mechanoluminescence (ML) produced during fracture of metals. The mechanism of ML in metals is based on the generation of holes during the decay of mobile dislocations on the surface and subsequent electron-hole radiative recombination. The following equation is derived for the transient ML intensity of the fracto-induced ML in metals . The above equation shows that I should be maximum for a particular value of time t. For β 〉 α, . This equation shows that I should decrease exponentially with time. For the fracto-induced ML in metals, t_M and I_m may be expressed by the following equations . The spectroscopy of ML in metals is also discussed. A good correlation is found between the theoretical and experimentals results.