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Ohne Zusammenfassung     

Characterizing tileorders

We define a tileorder to be a double order generated by a dissection of a rectangle into subrectangles. These structures are of interest both geometrically and as the order structures underlying double categories. We here give three different characterizations of those double orders which are tileorders.     

Fonction Dielectrique Complete D'un Cristal Moleculaire: Polarisabilite Moleculaire et Absorption Infrarouge

In the special case of a molecular crystal, it has been shown that the background of the infrared absorption spectra is not only a function of the dielectric constant at high frequency: the pertinent formulation introduces the entity (ε) _fc in which the contribution of all the optical modes have been taken into account. An analytical expression for (ε) _fc is suggested and make possible the determination of the oscillators strengths with a good accuracy. Calculations have been performed for polycrystalline samples of H.M.T and H.M.T.D. This new parameter has no effect upon the damping constants and slightly affects the static dielectric constant. On the other hand, its influence is clearly established for the infrared reflexion spectra.

The relation between microscopic molecular polarizability α(ω) and macroscopic dielectric function ε(ω) has been given. From the analytical expression of ε(ω), both real and imaginary parts of α(ω) have been expressed in terms of frequency. All the characteristic points of them have been calculated for spectral ranges corresponding to molecular crystal infrared absorption. Application to the F₂ vi-brational modes of solid H.M.T has been given. In other respects the contribution of the nuclei to the static molecular polarizability has been estimated with a good accuracy.     

Lien experimental entre la viscosité et la longueur de correlation ζ∥ dans les smectiques hexatiques B et F

Abstract

Nous présentons les premières mesures de viscosité en cisaillement parallèle aux couches dans la phase B hexatique du 65OBC (n-hexyl-4′-n-pentyloxybi-phenyle-4-carboxylate) et dans la phase F du 90.4 (4-n-nonyloxybenzilidene-4′-n-butylaniline). Le comportement pseudoplastique observé dans ces deux phases est analysé en termes de couplage entre l'écoulement et les dislocations. Leur viscosité intrinsèque est déduite des mesures à hautes fréquences. Nous montrons qu'elle est proportionnelle à la longueur de cohérence ζ∥ mesurée antérieurement dans les couches par diffraction des rayons X.     

Sur un nouveau Complexe entre l'oxyfluorure d'antimoine et l'oxalate. Structure cristalline de (NH4)4H2(C2O4)3(SbOF) 2 · H2O

On a New Complex of Antimony Oxide Fluoride and Oxalate. Crystal Structure of (NH₄)₄H₂(C₂O₄)₃(SbOF) ₂ · H₂O The crystal structure of (NH₄)₄H₂(C₂O₄)₃(SbOF) ₂ · H₂O has been fixed by X-ray diffraction on single crystal (R = 0.025 for 2124 planes). The antimony atom is complexed by the oxalate anions which are bidendate chelates. Antimony coordination is seven (five oxygen atoms, one fluorine atom, and the lone pair E). Antimony environment is a pentagonal bipyramid, one of the axial positions is occupied by the lone pair, the other one by the fluorine atom.     

Synthèse de N-Alkyl-arylamines par Thermolyse ou Photolyse d'Alkyl-3-diaryl-1,3-triazènes

Synthesis of N-Alkyl-arylamines by Thermolysis or Photolysis of 3-Alkyl-1,3-bis(p-chlorophenyl)triazenes The thermolysis of 3-alkyl-1,3-bis(p-chlorophenyl)triazenes in benzene or methanol leads to the formation of N-alkyl-p-chloroanilines ( 2 ) in 19–50% yield, N-alkyl-bis(p-chlorophenyl)amines ( 3 ) in 7.5–15.5% yield and 4,4′-dichlorobiphenyle ( 4 ) in 1–7% yield; besides with benzene as the substrate, 4-chlorobiphenyle ( 5 ) (12–20% yield) was also formed. The photolysis in methanol gives only the N-alkyl-p-chloroanilines ( 2 ) in 32–40% yield. In these two cases the results are consistent with a radical pair formation in a solvent cage, recombination (thermolysis) and/or diffusion (thermolysis and photolysis) with intermolecular abstraction of hydrogen. A free radical chain mechanism is involved in the photolytic process and the quantum yield is high.