Ten-fold spin-orbital degeneracy in the true d-electron Hubbard model of the Mott metal-insulator transition

The ten-fold spin-orbital degeneracy of true d-electrons is included in the non-spin-orbitally degenerate Hubbard model treatment theory of the Mott metal-insulator transition of Rice and Brinkman, and Gutzwiller. The Rice-Brinkman and Kohn phase diagrams of the Mott metal-insulator transition are shown to shift due to spin-orbital degeneracy of true d-electrons so as to increase the available phase space in the temperature-“interaction” Mott phase diagram for the formation of the antiferromagnetic insulator, superlattice metal or superlattice insulator states in these phase diagrams.     

Strings with dimension-dependent intercept

By changing the boundary conditions of the relativistics string in extra dimensions, the intercept α(0) is lowered to $\text{1 ?}\text{1}\text{16}\text{(26 ?D}{}_0\text{)}$ in the modified orbital model, where D₀ is the dimensionality of the Poincaré-invariant subspace of space-time. In the modified model of the spinning string, the boson intercept becomes $\text{1}\text{2}\text{?}\text{1}\text{8}\text{(10 ? D}{}_{\mathrm{o}}\text{)}$, while the fermion intercept stays at zero. The projective invariance of the ground state is broken, giving the “photon” mass by a Higgs-like mechanism. Unfortunately, the strings have a negative “G parity”, so the usual, unshifted strings appear as intermediate states in the scattering amplitudes. Also, some of the amplitudes are not dual.     

A biophysical model of an inner hair cell

Whole-cell patch-clamp recordings on isolated inner hair cells (IHCs) of guinea pig cochleae have revealed the presence of voltage-gated potassium channels. A biophysical model of an IHC is presented that indicates activation of slow voltage-gated potassium channels may lead to receptor potentials whose dc component decreases during the stimulus, and membrane potential hyperpolarizes when the stimulus is turned off. Both the decreasing dc and the hyperpolarization are, respectively, consistent with rapid adaptation and suppression of spontaneous rate in the auditory nerve. Receptor potentials recorded in vivo do not show these features, and when a nonspecific leak is included in the model to simulate microelectrode impalement, the model's receptor potentials become similar to those in vivo. The nonspecific leak creates an electrical shunt that masks slow channel activity and allows the cell to depolarize. Both the decreasing dc and the hyperpolarization are sensitive to the resting potential. Because the reported resting potentials in vivo and in vitro differ greatly, the model is used to investigate homeostatic mechanisms responsible for the resting potential. It is found that the voltage-gated potassium channels have the greatest influence on the resting potential, but that the standing transducer current may be sufficient to eliminate the decreasing dc and after-stimulus hyperpolarization.     

Quantum mechanical designs toward planar delocalized cyclooctatetraene: a new target for synthesis.

Ab initio and hybrid density functional quantum mechanical computation are applied to the structure and energetics of a series of annelated cyclooctatetraenes. Tetrakis-cyclobuteno, perfluorocyclobuteno or bicyclo[2.1.1]hexeno annelations result in planar structures with distinct exo and endo valence tautomers of the double bonded cycle. The contribution of each basic annelation to the exo/endo relative energy is estimated. An additivity scheme for approximating the energy of a mixed system is developed and compared to the quantum mechanical prediction. Bis bicyclic annelation to the a and d positions creates "valence tautomeric frustration" and strongly perturbs the molecular structure. This phenomenon leads to a general design for a planar cyclooctatetraenes where the "delocalized" diradicaloid state is the minimum energy form. These compounds are seen as excellent targets for chemical synthesis.     

Synthesis of oligopyridines and their metal complexes as precursors to topological stereoisomers

[structure: see text]. Palladium-based carbon-carbon coupling reactions in sequence with halogen-exchange chemistry on a series of heterocycles lead to an efficient synthetic strategy for oligopyridines that bind metal ions such as ruthenium to form coordination racks. The particular structures are designed to form terpyridine subunits for octahedral binding. Reaction of 4,6-diiodopyrimidine produces a "double-bay" terpyridine from which binuclear coordination complexes have been formed.