X-ray determination of the mean amplitudes of vibration and debye temperatures of some rare earth monochalcogenides

The x-ray diffraction intensities of Bragg reflections have been measured at room temperature for thulium selenide, samarium sulphide, samarium selenide and samarium telluride. On the basis of a common amplitude approximation, the Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. The values of the Debye temperatures and mean amplitudes of vibration are 176±16°K, 0·185 ± 0·017 Å (TmSe), 155 ± 7°K, 0·244 ± 0·012 Å (SmS), 153 ± 14°K, 0·221 ± 0·020 Å (SmSe) and 151 ± 20°K, 0·204 ± 0·027 Å (SmTe).     

Synthesis of exo- and endocyclic enamino derivatives of 2-(3-arylprop-2-enoyl)cyclohexane-1,3-diones

Condensation of 2-acetylcyclohexane-1,3-diones with aromatic aldehydes in the presence of piperidine, pyrrolidine, hexamethyleneimine, or morpholine gave the corresponding 2-(3-arylprop-2-enoyl)cyclohexane-1,3-diones as the major products and 2-[3-aryl-1-cycloalkylaminoprop-2-en-1-ylidene]cyclohexane-1,3-diones as minor ones. Endocyclic enamino derivatives were synthesized in two steps through enol methyl ethers which reacted with amines. Endocyclic enamino derivatives of 2-(3-arylprop-2-enoyl)cyclohexane-1,3-diones containing an aryl group on the nitrogen atom readily underwent cyclization to 1,2,3,4,5,6,7,8-octahydroquinoline-4,5-dione derivatives.     

Analysis of coefficient identification problems associated to the inverse Euler-Bernoulli beam theory

A rigorous investigation of the identification of a heterogeneousflexural rigidity coefficient in the Euler-Bernoulli steady-statebeam theory in the presence of a prescribed load is presented.Mathematically, this study is an extension to higher-order differentialequations of the coefficient identification problem analysedby Marcellini (1982) for the one-dimensional Poisson equation.In addition, various types of boundary conditions are discussed.Conditions for the well-posedness of these inverse problemsare established and, furthermore, numerical results obtainedusing a regularization algorithm are presented.     

A critical investigation of the effects of the radio frequency potential on the trapping of externally injected ions in ion trap mass spectrometry

The sensitivity of all ion trap mass spectrometry (ITMS) methods is dependent on the trapping efficiency of the instrument. For ITMS instruments utilizing external ion sources, such as laser desorption, trapping efficiency is known to depend on the phase and amplitude of the radio frequency (RF) potential applied to the ring electrode at the time of ion introduction. It is remarkable that, in a considerable body of literature, no consensus exists regarding the effects of these parameters on the efficacy of trapping externally generated ions. In this paper, a summary of the literature is presented in order to highlight significant discrepancies. New laser desorption ion trap mass spectrometry (LD-ITMS) data are also presented, from which conclusions are drawn in our effort to clarify some of the confusion. Copyright 1999 John Wiley & Sons, Ltd.     

Synthesis and antiphospholipase activity of 3,5-disubstituted thiotetronic acid derivatives

The condensation of 3-acetyltetrahydrothiophene-2,4-dione with aromatic aldehydes in the presence of piperidine as a catalyst gave a series of 5-arylmethylidene-3-acetyltetrahydrothiophene-2,4-diones. The reaction with excess aldehyde (2.5 equiv) led to the formation of bis-condensation products, 5-arylmethylidene-3-(3-aryl-1-oxoprop-2-enyl)tetrahydrothiophene-2,4-diones. Analogous 3,5-disubstituted tetrahydrothiophene-2,4-dione derivatives with different aryl groups in the ring and the side chain were synthesized by two-step condensation with the use of differently substituted aromatic aldehydes. Catalytic hydrogenation of both mono-and bis-adducts resulted in the reduction of the side-chain double C=C bond, while ionic hydrogenation with triethylsilane in trifluoroacetic acid in the presence of lithium perchlorate involved both the double C=C bond and carbonyl group in the side chain. The isolated products showed an appreciable effect on the activity of two secretory phospholipases A₂ from various sources.