Application of an electromagnetic analysis for coal characterization is attempted. By time domain reflectometry (TDR), dispersion spectra in the DC 5 GHz range of a wide variety of coals are obtained for room temperature. Static permittivity and relaxation frequency of the different samples are compared with parameters obtained by chemical analysis. Comparison reveals the usefulness of the electromagnetic characterization for the establishment of coal rank, and shows how an analysis of the dielectric characteristic parameters can provide approximate ideas about moisture, elemental carbon, hydrogen, and sulphur contents. PACS Nos.: 39.30+w, 82.53Kp, 77.22Gm
Structure cristalline et mol6culaire du cycladi~ne (di6neoestrolThe structure determination of dienestrol: C1802H18 (Pbca, Z=4) was performed by direct methods. Although the unit-cell dimensions (a=18.969, b= 14.296, c=5-380 A) look like those of the previously described orthorhombic form of diethylstilboestrol (DES), the molecular conformation is strongly perturbed and here the central dienic chain is nearly perpendicular (85.9 °) to the phenyl planes. The hydrogen bonds which explain the crystalline cohesion are even weaker than for DES (3.063 A) but really exist as is proved by the value of the corresponding O-H...O angle (167°).
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