The lattice vibrations of CeD2.12

The complete phonon dispersion relation including both optic and acoustic modes has been measured along the major symmetry axes of a single crystal of CeD_2.12 at 295 K by coherent neutron scattering. The results show the inadequacy of simple models previously used for the analysis of neutron incoherent scattering studies of rare earth dihydrides. The interstitial mode of vibration due to the excess deuterium (above CeD₂ in octahedral sites has also been observed.     

Polycyclic biphenylenes : Part V. The pmr spectra of annelated biphenylenes

The proton magnetic resonance spectra of a number of annelated biphenylenes are given. The influences of ring currents and bond-localisation effects are demonstrated.     

The application of molecular modelling to the interpretation of inverse gas chromatography data

The use of molecular modelling in the interpretation of inverse gas chromatography data is discussed. Crystal faces can be visualised and likely cleavage planes calculated using the surface attachment energies. Assuming that the preferred cleavage plane is the crystal face with the smallest attachment energy then the predominant crystal faces of a crystalline particle can be predicted. Surface adsorption can be modelled using Van der Waals and electrostatic interactions to evaluate the interaction energies between individual atoms of the probe molecule and atoms of the test molecule orientated as in the surface. Using examples of pharmaceutical materials, modelling has been shown to be successful in the understanding of changes in the surface energetics.     

Photoénolisation-IX: Stéréospecificitéet régiospécificitéde la réaction de diels-alder avec les photodiénols issus de la méthyl-2 et de la diméthyl-2,

2-Methyl- and 2,4-dimethylbenzophenone were irradiated with the unsymetrical dienophiles methyl acrylate, acrylonitrile, methyl methacrylate and methyl propiolate. The dienols additions proceed regiospecifically yielding in each instance a single hydroxylic compound having the car?ylate or the carbonitrile group in vicinal position. Syntheses of 1,2,3,4-tetrahydro- and 1,4-dihydronaphthols with various substituents were thus achieved. 3,4-Dihydronaphthalenes and naphthalenes were also obtained by dehydration. 2,4-dimethylbenzophenone was irradiated with acetylenedicarbonitrile yielding the dehydrated addition product 6-methyl 1-phenylnaphthalene-2,3-dicarbonitrile.     

Interlaboratory comparison of methods for the determination of incurred tilmicosin residues in bovine liver

The objective of this study was to compare 2 methods for the determination of tilmicosin residues in bovine liver samples. Three laboratories participated in the comparison of the 2 methods. The first method was described in a New Animal Drug Application (NADA 140-929), and the second was a modification of that method in which hexane was substituted for carbon tetrachloride in one cleanup step. Each of the 3 laboratories analyzed subsamples of 10 bovine livers containing incurred tilmicosin. Residues ranged from 2.3 to 81 ppm tilmicosin in the 10 liver samples with an 11.8% relative standard deviation obtained by using both methods. In addition, fortified-control liver tissue samples were analyzed concurrently with tissues containing incurred residues by using the modified method in one of the laboratories. The fortification levels ranged from 0.3 to 112 ppm, with recoveries ranging from 76 to 92%. The results from the 3 laboratories were comparable, indicating that the modified method was not only as effective as the original NADA method, but also more desirable because of the change to a less hazardous solvent.     

The α-arylation of derivatives of malonic acid with aryllead triacetates. New syntheses of ibuprofen and phenobarbital.

Derivatives of Meldrum's acid and the sodium salts of substituted malonic esters undergo rapid arylation in high yield when treated with aryllead triacetates. These reactions have been applied to the synthesis of ibuprofen, an analgesic, and in a closely related reaction 5-ethylbarbituric acid has been reacted with phenyllead triacetate to give phenobarbital.     

Determination of 30 elements in coal and fly ash by thermal and epithermal neutron-activation analysis

Thirty elements are determined in coal and fly ash by instrumental neutron-activation analysis using both thermal and epithermal irradiation. Gamma-ray spectra were recorded 7 and 20 days after the irradiations. The procedure is applicable to the routine analysis of coals and fly ash. Epithermal irradiation was found preferable for the determination of Ni, Zn, As, Se, Br, Rb, Sr, Mo, Sb, Cs, Ba, Sm, Tb, Hf, Ta, W, Th and U, whereas thermal irradiation was best for Sc, Cr, Fe, Co, La, Ce, Nd, Eu, Yb and Lu. Results for SRM 1632 (coal) and SRM 1633 (fly ash) agree with those of other investigators.