Excitonic states in a (Ti6O12)3 nanotube.

The low-lying excited electronic states of a (Ti(6)O(12))(3) nanotube are investigated using ab initio self-consistent field configuration interaction theory. The transition energies and moments are calculated and the nature of the orbitals involved is discussed. Transitions correspond to an excitation from an O(2p) to a nearby Ti(3d) orbital and singlet-singlet transitions vary in excitation energy from 2.1 eV to 4.3 eV, depending on the oxygen site and environment of the titanium site. Two different structures for the three stacked Ti(6)O(12) rings are found. The occluded Ti structure is lower in energy than a staggered structure by 1.25 eV, only 0.02 eV/bond. Excited electronic states are found to correspond to highly localized holes on oxygen and a highly localized electron in a d orbital on a nearest neighbor titanium. The staggered structure has four absorptions that lie within the intense portion of the solar spectrum, at 585 nm, 472 nm, 471 nm, 423 nm; the occluded structure has one strong absorption, at 532 nm.

Silver as an electron source for photodissociation of hydronium.

The photochemistry of a solvated hydronium ion near a silver surface is investigated using ab initio self-consistent field and configuration interaction theory. Photoinduced electron attachment can occur at energies in the range of 1.1-1.2 eV depending upon the initial orientation of the hydronium relative to the silver surface. Rearrangement of solvating waters considerably reduces transition state barriers to dissociation on the excited-state potential energy surface, such that fast dissociation of the neutralized hydronium would occur with no barrier. Both the H and H(2) product channels are exothermic pathways on the excited state surface and in several instances exothermic compared to the energy of the initial structure.

Generation of highly n-type titanium oxide using plasma fluorine insertion.

True n-type doping of titanium oxide without formation of midgap states would expand the use of metal oxides for charge-based devices. We demonstrate that plasma-assisted fluorine insertion passivates defect states and that fluorine acts as an n-type donor in titanium oxide. This enabled us to modify the Fermi level and transport properties of titanium oxide outside the limits of O vacancy doping. The origin of the electronic structure modification is explained by ab initio calculation.

Use of exchange maximization to generate starting vectors for self-consistent field calculations on metal cluster/adsorbate systems.

Localized molecular orbitals (LMOs) derived from exchange maximization with respect to all atom-centered basis functions in the basis set are shown to generate a good starting electronic field for self-consistent field calculations on extended systems such as metal clusters, for which well-defined chemical bonds are not present. Examples studied are a cluster of 20 Ni atoms and the Pt(97)CO, Ag(43)/H(3)CNON, Ag(91)/H(2)CO, and vinylidene/Ni metal cluster plus adsorbate systems. It is also shown that improved starting vectors can be obtained by remixing a subset of the LMOs with the largest exchange eigenvalues through diagonalization of the Fock matrix computed with a null electronic field. Employing only a subset of the exchange-maximized LMOs in the first iterations, and then gradually expanding the space in which the diagonalizations are carried out in succeeding cycles, is shown to be an effective means of guiding the SCF procedure to the converged full-basis solution.

Factor analysis of the continuous performance test and parent-teacher reports of attention deficit disorder.

The relationships between a computerized measure of attention deficit disorder and scores from two commonly used parent-teacher reports were investigated. A factor analysis of the raw omission and commission scores provided by the Continuous Performance Test and Conners' Parent Rating Scale and the ADD-H Comprehensive Teacher Rating Scale indicated that for a sample of 54 children the Continuous Performance Test was most closely associated with measures of impulsivity and hyperactivity provided by the Conners' rating. This finding was congruent with the use of the Continuous Performance Test in the evaluation as a measure of Attention Deficit Hyperactivity Disorder and suggestive of a positive and significant relation between this computerized measure of behavior and parents' perception of behavior. Little association was detected between scores on the teachers' scale and omission and commission scores.

Conformationally restricted analogues of nicotine and anabasine.

A series of conformationally restricted analogues of nicotine has been synthesized and evaluated as agonists of neuronal acetylcholine receptors. Compound 2 (SIB-1663), which selectively activated human recombinant alpha 2 beta 4 and alpha 4 beta 4 nAChRs, was shown to be active in animal models of Parkinson's disease and pain.

Risperidone and hyponatremia: a case report.

A 48 year-old white male not suffering from endocrine disease or polydipsia, not taking diuretics, and suffering from no renal disease was started on risperidone and discharged on no other drug from Western Missiouri Mental Health Center (WMMHC) after an 8-day hospitalization. Seven days later he was admitted to a university medical center with generalized seizures, hyponatremia, respiratory failure, and rhabdomyalysis. He eventually recovered, was transferred back to WMMHC, and stabilized on appropriate medication. A search of the literature indicates no case reports linking risperidone to hyponatremia. It is assumed that the mechanism of hyponatremia is similar to other psychotropic medication in that it is secondary to the syndrome of inappropriate antidiuretic hormone (SIADH).