Quadrupolar NMR line-broadening in Al-3d-transition metal alloys

The second moment of the ²⁷Al NMR signal was measured in Al-3d transition metal alloys. A comparison between the line broadening and amplitude reduction suggest no drastic preasymptotic effects in the range of the first order quadrupole effect.     

Identifying a Gaussian signal after a zero-memory filter

We exhibit two large classes of filters which allow for the identification of an incoming Gaussian signal.     

Special-relativistic resolution of Ehrenfest's paradox: Comments on some recent statements by T. E. Phipps,Jr.

It is shown how a consistent kinematic resolution of Ehrenfest's paradox may be given in accordance with the special theory of relativity. Some statements by T. E. Phipps, Jr., connected with these matters, are commented upon. Problems connected with the relation between stress and strain are solved by a manifestly covariant formulation of Hooke's law.     

AC-DC coupling experiments in the spin density wave state of tetramethyltetraselenofulvalene-hexafluorophosphate [(TMTSF)2PF6]

Experiments performed on (TMTSF)₂PF₆ in the spin density wave (SDW) state in the presence of joint ac and dc excitations do not show evidence for coupling between dc and ac response. Irradiation by microwaves does not lead to strong dc nonlinearity, and attempts to resurrect the ESR signal by applied dc currents were also unsuccessful. While the strongly frequency dependent response is indicative of collective effects, the response of the SDW ground state is fundamentally different from that of a charge density wave condensate.     

The 2-homeotoxal tilings of the plane and the 2-sphere

A complete enumeration is obtained of the finite tilings of the 2-sphere and of the infinite tilings of the plane which are normal and admit two transitivity classes of edges under topological automorphisms of the tiling. Every type is found to be representable by a tiling in which the edges form two transitivity classes under isometric symmetries of the tiling.     

Quantenchemische Untersuchung von Protonierungs-und Deprotonierungsgleichgewichten

Zusammenfassung Unter Anwendung der Omega-HMO(Pi + Sigma)-Methode wird die Ladungsverteilung in Carbonsäuren, Alkoholen, Chinuclidinen und Phosphonsäuren berechnet. Die Nettoladung der aciden Wasserstoffatome von Carbonsäuren, Alkoholen und Phosphonsäuren zeigt eine lineare Beziehung zu den pK _a-Werten dieser Verbindungen. Die berechnete Nettoladung am Stickstoff-Atom der Chinuclidine kann zu deren Basizität in Beziehung gesetzt werden.

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Quantum chemical treatment of protonation and deprotonation equilibria

The charge distribution of organic acids, alcohols, chinuclidines and phosphonic acids has been calculated by the Omega-HMO(Pi + Sigma) method. A linear correlation was found between the net charge of the acidic hydrogen atoms of organic acids, alcohols and phosphonic acids and the acidity of these compounds. The calculated net charge of the nitrogen atom of chinuclidines is related to their basicity.

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Mit 4 Abbildungen     

Charge density wave transport in a novel inorganic chain compound, (TaSe4)2I

We report the observation of nonlinear conductivity with a well-defined threshold electric field E_T, and frequency dependent ac conductivity, in a novel linear chain compound, (TaSe₄)₂I. The material undergoes a phase transition to a semiconducting phase at T ～ 260 K, and nonlinear and frequency dependent transport is observed below this temperature. We argue that the material is a new example of collective mode transport provided by a Peierls-Fröhlich charge density wave condensate.