Itinerant electron metamagnetism and magnetocaloric effect in Dy(Co,Si)2

Itinerant electron metamagnetism in Dy(Co_1-xSi_x)₂ compounds was studied in the light of a recent theoretical model based on magnetovolume effect and spin fluctuations. The nature of the magnetic transition in these compounds was analyzed within the framework of this model. The magnetocaloric effect in these compounds has been calculated and correlated with the strength of itinerant electron metamagnetism. The domain wall pinning effect was found to be dominant at low temperatures.     

Biosynthesis of (+)-,(-)- and (±)-tetrahydropalmatines

Specific incorporation of didehydroreticuline and reticuline into (±)- (+)-, and (-)-tetrahydropalmatines in Cocculus laurifolius and of (R)- and (S)-reticulines into (R)- and (S)-tetrahydropalmatines respectively has been demonstrated. Feeding of[l-³H, 4'-methoxy-¹⁴C]reticuline suggested that reticuline was not converted in the plants into didehydroreticuline and racemisation of optically active forms of tetrahydropalmatine did not take place via dehydrotetrahydropalmatine     

Note on the boundary layer on a rotating

Ohne Zusammenfassung

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Miscellaneous

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Divers

     

Novel electron transfer mechanism in lithium alanate reduction of benzylic halides

Occurrence of a new electron transfer mechanism in the LiAlH₄ reduction of 9-chloromethylanthrancene, diphenylchloromethane and 9-bromofluorene is demonstrated. Alanate anion serves as a source of electrons and hydrogen atoms.     

Über die Verformung der Röntgenabsorptionskanten in Metallen und Legierungen durch Gitterleerstellen

In order to account for the distortion in the shape of x-ray absorption edges in some metals and alloys, a mechanism involving lattice vacancies is proposed. It is shown that an atom near a lattice vacancy will be under the influence of an electrical field resulting from the asymmetric surroundings. The magnitude of this field is found to be large enough to produce a Stark-splitting in the exciton orbit of the absorbing atom. The distortion appearing as a kink on the slope of the absorption curve is shown to be a consequence of this splitting.     

Forbidden transition LIINII in the spectrum of gadolinium-64

Using a 40 cm curved mica crystal spectrograph of the transmission type, the L spectrum of gadolinium has been investigated. The forbidden transition L_IIN_II at λ = 1618.9 X.U. has been reported for the first time.     

Fourier-transform infrared spectroscopic studies of dithia tetraphenylporphine

We present here infrared absorption spectra of dithia tetraphenylporphine and its cation in the 450–1600 and 2900–3400 cm⁻¹ regions. Most of the allowed IR bands are observed in pairs due to overallD _2h point group symmetry of the molecule. The observed bands have been assigned to the porphyrin skeleton and phenyl ring modes. Some weak bands, which are forbidden underD _2h , also appear in the spectra due to the distortion of the molecule from planarity-caused by the out-of-plane positioned N and S atoms. Increased intensity of some phenyl ring bands compared to free-base tetraphenylporphine is explained on the basis of rotation of phenyl rings towards the mean molecular plane. Contrary to the point group symmetry of cation of dithia tetraphenylporphine, certain bands are observed to be degenerate due to identical bonding arrangements in pyrrole rings of the cation     

X-ray energy levels: Deviations between experimental and theoretical values

Energy values ofK, L _II andL _III levels calculated by the relativistic self consistent field method have been used to compute the energies ofKα _{1, 2} lines. These values deviate considerably from the experimental values due to Bearden and Burr. The deviations are discussed and given an empirical fit.     

Biosynthesis of tetrahydropalmatine and palmatine

The incorporation of (±)-norlaudanosoline, norprotosinomenine, nororientaline, norlaudanidine, reticuline and laudanosine into tetrahydropalmatine and palmatine has been studied, and specific utilization of reticuline demonstrated. Feeding of (±)-[N-methyl-¹⁴C] reticuline showed that C atom 8 of tetrahydropalmatine and palmatine are formed by oxidative cyclisation of the N-Me group of reticuline. Parallel experiments with (R)-; and (S)-, reticulines demonstrated specific incorporation of (R)- isomer into these bases. Feeding experiments also revealed that the plants can convert tetrahydropalmatine into palmatine with high efficiency.