Yunnandaphninines F and G,New C30 Alkaloids from Daphniphyllum yunnanense

Eight C₃₀ Daphniphyllum alkaloids, including two new ones, yunnandaphninines F and G ( 1 and 2 , resp.), were isolated from the leaves and stems of Daphniphyllum yunnanense. Their structures were elucidated on the basis of the spectroscopic data.     

Inclusive sum rules for isotopic spin

Inclusive sum rules for non-abelian symmetry generators and in particular for isospin are studied. A compact formalism is introduced which allows to exaract in a simple way all the consequences of invaraince properties.     

The role of hydration water in isothermal step annealing of neutron irradiated sodium nitroprusside

A kinetic study of isothermal step annealing of neutron-irradiated sodium nitroprusside has been performed. The influence of water and -irradiation on the behaviour of the compound is analyzed and compared with previous results obtained with the analogous compound Na₂/Fe/CN/₅NO/.2H₂O. It is possible to characterize two different fundamental processes that, in spite of occurring at two different temperatures, present the same activation energy than the hydrated system.     

Formamidines and triazenes as precursors for the preparation of rhenium imido-complexes

Summary The rhenium(V) imido-complexes [Re(NR)Cl₃(PPh₃)₂] have been obtained by heating the rhenium(V) derivative [ReOCl₃(PPh₃)₂] with RNHCHNR R = Ph (1a), p-MeC₆H₄ (1b), p-ClC₆H₄ (1c) andp-FC₆H₄ (1d) in THF under reflux. [Re(NR)Cl₃(PPh₃)₂] (R =p-MeQ₆H₄) has also been obtained by heating the rhenium(III)-triazenido complex [ReCl₂(RN N NR)(PPh₃)₂] in CCl₄ under reflux.     

Configurational equilibria and 13C NMR spectra of tetracyclic saturated hydrocarbons

The stereoisomeric equilibrium composition over Pd/C at high temperature of a series of tetracyclic saturated hydrocarbons having general formula C₁₈H₃₀ was determined by gas chromatography and compared with that calculated on the basis of conformational analysis. Several stereoisomers were isolated. Their ¹³C NMR spectra agree very well with those calculated according to standard procedures. This method of structural determination was applied to perhydronaphthacene, perhydrobenzo(a)anthracene, 2- and 5-methylper-hydrobenzo (d,e)anthracene and 2,7-dimethylperhydropyrene.     

Determination of N-acetylcysteine in human plasma by gas chromatography-mass spectrometry

An automatic mass spectrometric method for the quantitation of N-acetylcysteine (NAC) in human plasma has been developed. NAC was extracted from plasma with ethyl acetate and derivatized in two steps with 2-propanol and pentafluoropropionic anhydride. The volatile derivative obtained was ideal for gas chromatographic-mass spectrometric analysis. Data obtained by analysing the plasma of healthy volunteers to whom 600 mg of NAC had been orally given are reported.     

The low-energy isoscalar dipole resonance in spherical nuclei

It is shown that localization of the low-energy isoscalar 1^? strength observed in a recent Groningen experiment may be caused by incompressible flow vibrations with considerable contribution of a solenoidal component. Calculations performed here without free parameters predict the energy of the isoscalar low-energy dipole resonance of the order of 40A ^?1/3,Me V. This estimate agrees well with data obtained on ⁹⁰Zrand ²⁰⁸Pb.     

Determination of ethyl formate in magnesium chloride used as Ziegler-Natta catalyst support by Fourier transform infrared attenuated total reflectance spectrometry

FT-IR Spectroscopy with total attenuated reflectance (ATR) was used for the quantitative determination of ethyl formate coordinated in inorganic matrices such as magnesium chloride. The spectra were recorded directly on solutions obtained by dissolving the inorganic Ziegler-Natta supports in water. The method proposed is sensitive and rapid and appears to be very reliable when compared with other methods, such as solvent extraction followed by gaschromatographic or thermogravimetric analysis.     

The “radiance law” in radiation transfer processes

The conservation law of radiance as a suitable tool for investigation of radiation transfer processes between two systems is treated. Original proofs of this law are given and its deep thermodynamical foundation is pointed out. Finally, applications to general problems of power coupling and particularly to the radiation transfer from incoherent sources (LED) into multimode optical fibres are carried out.