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The angular dependence of neutron scattering by n‐C16H34 and n‐C36H74 in a medium having the approximate composition CD2 has been calculated from the positions of the actual scattering loci, the hydrogen atoms, on the basis of the rotational isomeric model for n‐alkane chains. The theoretical calculations satisfactorily represent the experimental results of Dettenmaier for n‐C36H74 and n‐C16H34 both in the melt and in solution over the scattering range 0

Depolarized Rayleigh scattering (DRS) of benzene, toluene, cumene, and t-butylbenzene, 2,4-diphenylpentane (DPP) 2,4,6-triphenylheptane (TPH), and atactic polystyrenes (PS) with average degrees of polymerization of 21, 38 and 96 have been measured in carbon tetrachloride at λ= 632.8 nm and T= 25°C. The optical anisotropies γ2 deduced from the DRS of benzene and toluene are consistent with results obtained by LeFevre and co-workers from the electric and magnetic birefringence. The anisotropy attributable to the phenyl group is altered markedly by methyl substitution in passing from benzene to toluene. Further substitution on the methyl group has only a minor effect. Optical anisotropies of PS and its oligomers DPP and TPH are calculated from the polarizability tensor for cumene, chosen as the closest analogue of the repeating unit of PS. Values of 〈γ2〉 computed on this basis by averaging over the conformations of meso and racemic DPP, of the mixture of isomers comprising TPH, and of atactic PS are in good agreement with the results of the DRS measurements. 〈γ2〉 for PS calculated as a function of stereochemical constitution decreases from 97 A6 to 30 A6 in passing from syndiotactic to isotactic chains.

Operationsindikationen fur primarye and metastatische Tumoren der Wirbelsaule bestehen zur Diagnosesicherung, bei spinaler and radicularer Kompression Bowie drohender oder manifester Instabilitat. Behandlungsziele sind die Tumorresektion and -reduction, die Dekompression und Wiederherstellung der Stabilitat. Bei benignen Tumoren gelingt die Heilung, neurologische Komplikationen werden verhindert. Bei malignen Systemerkrankungen erreicht die Tumorexcision in Kombination mit Chemo- and/oder Strahlentherapie beeindruckende Remissionen. Bei metastatischem Befall erbringt die Palliation trotz unveranderter kurzer Uberlebenszeit eine Verbesserung der Lebensqualitat and der Pflegesituation.

Seine Grosse und sein langer Gefassstiel empfehlen den M. latissimus dorsi als Spendermuskel bei ausgedehnten Weichteildefekten mit schlechter Vascularisation des Empfangergebietes. Der Muskel kann als alleiniger Muskellappen mit einem Spalthauttransplantat oder als myocutaner Lappen mit defektangepassten Hautinseln transferiert werden. Anhand unserer Erfahrungen mit 83 freien Muskelverpflanzungen stellen wir Vorgehen und Ergebnisse bei Patienten mit traumatischem Weichteilverlust, Verbrennungen, chronischen Infekten und Tumoren vor. Abhangig vom verwandten Gefassstiel werden verschiedene Moglichkeiten der Lappengestaltung gezeigt.

Bei den jahrlich ca. 40 Motorradrennen, die in Deutschland fur uber 3000 Lizenzfahrer veranstaltet werden, sturzen jeweils 10% der Fahrer. Die Verletzungsschwerpunkte liegen im Schultergurtel-, Handgelenks- und Unterschenkel-Fusbereich. Normale Strasenmotorradfahrer verunfallen statistisch haufiger. Eine vergleichende Analyse zeigt fur die Verletzungen der unteren Extremitat einen hoheren Anteil an komplizierten und offenen Frakturen. Das gunstigere Abschneiden der Rennfahrer erklart sich aus einer wesentlich besseren Unfallprevention.

The optical anisotropies γ2 and molar Kerr constants mK of C6H5X, p-CH3—C6H4—X and p-(CH3)2CH—C6H4—X where X = Cl or Br, and of atactic poly(p-chlorostyrene) have been determined from depolarized Rayleigh scattering and electric birefringence measurements in CCl4 solutions at 25°C using λ= 633 nm radiation; γ2 for poly(p-bromostyrene) was determined in a mixture of CCl4 and CBr4. The anisotropic part of the polarizability tensors for C6H5Cl and C6H5Br are well defined by γ2 and the molar Cotton–Mouton constant mC, values of which are available from the work of LeFevre and co-workers for these two compounds. Owing to the orientation of the dipole moment along one of the principal axes of , this tensor cannot be evaluated unambiguously from mK and γ2 for the other compounds. The anisotropy attributable to the arylene group about the axis joining the substituents appears to be little affected by substitution, however. Asymmetry of the arylene group perpendicular thereto depends appreciably on substitution; bond and group polarizabilities are not additive. The anisotropies of the polymers are formulated as the sums of tensors for the corresponding p-halogenocumenes. Averages 〈γ2〉 and 〈mK〉 over all conformations of the polymer chains are calculated as functions of the fraction wm of meso dyads. Values of 〈γ2〉 decrease about three-fold from syndiotactic (wm= 0) to isotactic (wm= 1). 〈mK〉 is extraordinarily sensitive to stereochemical composition; it decreases from a large positive value for wm= 0 to a large negative value for wm= 1. These results are interpreted in terms of structure and preferred conformations. Experimental measurements on atactic polymers support the calculations.

Mean-square optical anisotropies, γ2, of cyanocyclohexane, bicyclohexyl, and the trans-4-cyano-trans-4′-n-alkylbicyclohexyls, NC—C6H10—C6H10—CmH2m+1, with m= 2, 5 and 7, have been determined from depolarized Rayleigh light-scattering measurements conducted on dilute solutions in carbon tetrachloride. The results are treated on the basis of additive contributions of group anisotropies: ΓCC=ΔαCC– 2ΔαCH and ΓCCN=ΔαCCN–ΔαCH, where the Δα denote the anisotropies of the polarizabilities of the indicated bonds. Diverse conformations of the bicyclohexyl system are taken into account. The value Γ′CC= 0.68 A3 required for bonds comprising this group appreciably exceeds the value of ΓCC= 0.53 A for the n-alkanes and presumably for the alkyl chains. Similarly, ΓCCN= 3.3 A3 is required for the cyano group attached to bicyclohexyl, compared with 2.15 A3 for the same group in acyclic nitriles and in cyanocyclohexane. These differences appear to be due to inductive effects that are known to impair a simple additive scheme. Contributions of members of the alkyl chain beyond the first to the tensor â representing the anisotropy of the polarizability virtually vanish when averaged over the configuration of the chain. Hence, properties such as the electric birefringence should be independent of the length of the alkyl chain under conditions that allow the latter to be in a random configuration. The quadratic tensor invariant, γ2=Tr(ââ), should increase gradually with chain length. The relatively large alternating effects in the values of γ2 for odd and even values of m are explained by the persistence of correlations in the directions of successive bonds of the alkyl chain. The effect of a departure of the principal axis of the polarizability tensor from the major geometric axis of the molecule is illustrated and its relevance to the anisotropic dispersion forces operative in liquid crystals is pointed out. The orientation-dependent energy attributable to the anisotropy of the polarizability is much smaller than would be required by the observed nematic–isotropic transition temperatures. This suggests that the large dipole moment of the molecules may be responsible for the nematic stability of the cyanobicyclohexyls.

The unperturbed dimensions of the polyphosphate chain are interpreted using the rotational isomeric state theory of linear macromolecules. Rotation about one bond of the chain, while all its neighbours are trans, appears to be subject to little hindrance by either electrostatic or steric interactions. Simultaneous large rotations about pairs of adjoining bonds, irrespective of their relative signs, are impeded by both types of interactions. The unperturbed dimensions of the polyphosphate chain find satisfactory explanation on this basis.

Stereochemical equilibration of 2,4,6-trichloro-n-heptane (TCH) in dimethyl sulphoxide at 70°C in the presence of LiCl yields a mixture containing 11.1 ± 0.2 % of the isotactic isomer and 42.7 ± 0.2 % of the syndiotactic isomer. These results, in conjunction with the ratio 0.362/0.638 for the meso and racemic 2,4-dichloro-n-pentanes (DCP) at equilibrium at 70°C are interpreted according to the theory of stereochemical equilibrium.The statistical weight parameters thus evaluated are used for theoretical calculation of the proportions of various conformers in the three diastereoisomers of TCH. These calculations are compared with estimates of Doskocilova and coworkers from n.m.r. coupling constants. It is confirmed that the less-favoured conformations contribute appreciably to the conformer populations in the isomers of TCH, owing to the small size of the chlorine substituent. Stereochemical equilibria and conformer populations calculated for poly(vinyl chloride)(PVC) from the same parameters show significant departures from those of the oligomers. The calculated average length of sequences of the preferred conformation (tgtg, etc.) for isotactic PVC is much smaller than for an isotactic vinyl polymer having a larger substituent.

This investigation represents an attempt to understand why noncrystalline rubber‐like polymers suddenly lose their flexibility and become brittle when cooled to a particular temperature, and conversely why an amorphous plastic such as polystyrene when heated to a particular temperature suddenly becomes either flexible and rubbery or fluid.

When di(isobutylamino)phenylboron is pyrolysed, isobutylamine is eliminated and the trimer, B-triphenyl-N-tri-isobutylborazine, is produced. Contrary to claims in the literature, the pyrolysis does not provide a route to linear boron–nitrogen polymers.

The mean-squared optical anisotropies 〈γ2〉 of four oligomers of polyoxyethylene glycol dimethyl ether have been determined from measurements of depolarized Rayleigh scattering by carbon tetrachloride solutions at 25°C. They have been interpreted using the valence optical scheme and rotational isomeric state theory. The energies of the gauche states relative to trans were taken to be 900 cal mol–1 and –250 cal mol–1 for rotations about C—O and C—C bonds respectively. Gauche states of opposite signs for C—O—C bond pairs were excluded; those for C—C—O bond pairs were assigned an energy of 800 cal mol–1. Bond optical anisotropies were assigned the values ΔαCC= 0.95 A3, ΔαCH= 0.21 A3, and ΔαCO= 0.58 A3. Calculations of 〈γ2〉 carried out with these parameters successfully reproduce the observed values of 〈γ2〉. The foregoing rotational state energies are in close agreement with those deduced previously from the characteristic ratio 〈r2〉0/nl2 for the polymer, from the dipole moments 〈µ2〉 of oligomers and polymer, and from the temperature coefficients of these quantities.