Pyridazines. XLI synthesis of novel pyrido[3,4-d]pyridazine derivatives from 4,5-disubstituted pyridazines

Pyrido[3,4-d]pyridazines 2–5, 21 bearing one, two, or three aryl substituents in the pyridine moiety are shown to be conveniently accessible from 4-aroyl-5-methylpyridazines or 4,5-diaroylpyridazines, respectively, by condensation reactions with appropriate C-N fragments. In addition, the novel pyridazine-annelated pyridones 24, 25 were found to be easily available from ethyl 5-methyl-4-pyridazinecarboxylate.     

Path integrals for the continuous spontaneous localization theory

Path integral expressions are given for the wave function and for the density matrix in a theory which describes state vector reduction. The magnitude of the contribution of each classical path to the propagator is not unity, as in ordinary quantum theory, but depends upon the path.     

A valence-bond diatomics-in-molecules model for the formation of Na+ and Na2+ ions from the interaction of excited sodium atoms with a tungsten surface

Potential energy surfaces for Na(²S, ²P) interacting with a partially covered tungsten surface are computed within the framework of the method of diatomics-in-molecules (DIM). Only two sodium atoms are considered explicitly but the effect of all of the adsorbed sodium is taken into account through its influence on the fragment matrix elements in the DIM formulation. Na₂⁺ wavefunctions are approximated by valence-bond calculations for the ²Σ_g⁺ and ²Σ_u⁺ manifolds. The three lowest potential energy surfaces of the polyatomic system suggest plausible pathways for the production of Na⁺ and Na₂⁺ ions from the interaction of Na(²P) atoms with the metal surface as observed by Auschwitz and Lacmann.     

Upper bounds for growth in the Ryll-Nardzewski function of anω-categorical,ω-stable theory

We establish a sharp upper bound for growth in the sequences _k (T):=the number ofk-types consistent withT, forT ω-categorical andω-stable. This paper forms part of the author’s doctoral dissertation written at the University of Maryland under the direction of David W. Kueker.     

Maximal convex metrics on some classical metric spaces

It is proved that every convex, complete, two-point homogeneous metric for which small spheres are connected has maximal symmetry. This in turn implies that the standard metrics on the classical spaces of geometry are maximally symmetric.     

Steric Crowding in Coordination Compounds: Electron-transfer kinetics of the [Co(tmen)3]3+/2+ couple (tmen = 2,3-dimethylbutane-2,3-diamine)

The [Co(tmen)₃]³⁺ complex ion (tmen = 2,3-dimethylbutane-2,3-diamine) has been synthesized and its redox characteristics compared to those of its parent ion [Co(en)₃]³⁺. The 12 peripheral Me groups significantly affect the properties of the [Co(tmen)₃]³⁺ ion. The ligand-field bands are shifted to lower energies by about 1700 cm^?1 compared to [Co(en)₃]³⁺. The reduction potential for [Co(tmen)₃]³⁺ is +0.28 V (vs. NHE) compared to ?0.18 V for [Co(en)₃]³⁺. The rate of the self-exchange reaction for the [Co(tmen)₃]^3+/2+ couple, k = 8.5 × 10^?8 M^?1·S^?1 was determined by applying the Marcus cross-relation with the reductants Cr²⁺, V²⁺, Eu²⁺, Ru²⁺, and [Co(sepulchrate)]²⁺.     

Slowness surfaces, ray velocity surfaces and phonon focussing in highT c superconductor crystals

This paper reports the results of the study of anisotropy in elastic wave propagation in single crystal superconducting BSCCO. The inverse and group velocities of elastic waves propagating in different directions have been computed and the corresponding slowness and ray velocity surfaces plotted, taking elastic constant data from literature. In addition, the phenomenon of phonon focussing has been investigated in this material by computing the phonon enhancement factor along different directions in spherical polar coordinates. The abnormally high values in phonon enhancement factor exhibited in certain directions for the phonon modes are interpreted as due to caustics occurring in the geometrical acoustics approximation adopted in the computational analysis. The results in LSCO and YBCO are found to be similar to those in BSCCO.     

Polaron defects in a charge density wave: a model for lightly doped BaBiO3

A model for BaBiO₃ was introduced by Rice and Sneddon, which treats this material as a simple three-dimensional version of a Peierls insulator, where the insulating gap is a consequence of the ordered distortion of the oxygen atoms. Charge accumulates on half the atoms and depletes from the other half. Experimentally, when holes are added to BaBiO₃ by doping, it remains insulating until a very large hole concentration is reached, at which point it becomes superconducting. In the Rice-Sneddon model, at large enough electron-phonon coupling, a mechanism for insulating behavior of doped samples is formation of small polarons or bipolarons which trap carriers in bound states in the Peierls gap. A variational calculation of the polaron binding in this model is given, and compared with “exact” numerical results on large clusters with periodic boundary conditions.     

Emission Mössbauer study of the interface between a cobalt substrate and a polyimide coating

The emission Mössbauer technique is used to study the chemical structure of the interphase formed between a cobalt substrate and a polyimide coating. The results are interpreted to indicate that the coating is bonded to the cobalt substrate by means of carboxylate bonds with Co²⁺ ions in the oxide film at the interface.