STM/STS investigation of carbon nanotube junctions

In this paper we present scanning tunneling microscopy/spectroscopy investigations of multiwall carbon nanotube junctions. We concentrated on bent and narrowing junctions, which my be formed by introducing pentagon–heptagon defects into a hexagonal network of a carbon nanotube. It was expected that the defects introduced to the nanotube could cause changes in the local density of states. The scanning tunneling spectroscopy results were used to search for and identify these defects. We also discuss a hypothesis for a combination of a telescope junction and a pentagon–heptagon induced junction. PACS 68.37.Ef; 73.22.–f; 61.46.Fg; 71.20.Tx     

STS investigations of temperature dependence of Au(1 1 1) surface state energy position

High temperature scanning tunneling spectroscopy (HT-STS) was used to investigate the electronic structure of Au(1 1 1) at different temperatures in the energy range 0-1 eV below the Fermi level. We concentrated on the influence of temperature on the Shockley surface state (SS) appearing on noble metals surface due to a surface projected bulk bang gap in [1 1 1] direction. The influence of temperature on the projected band gap edge (BE) was also investigated. The experiment was carried out in the temperature range 294-580 K. As the result of the experiment a delicate shift of the SS and the BE in direction of the Fermi level was reported.     

Computer-aided design of chiral ligands. Part III. A novel ligand for asymmetric allylation designed using computational techniques

[reaction: see text] Computer-aided design protocols to identify new chiral ligands for reactions proceeding through well-defined transition states are outlined. Ligand families are discovered via computational screening of large structural databases such as the Cambridge Structural Database. Using this method, a novel cis-decalin ligand has been identified as a chiral auxiliary for the allylboration of aldehydes. Synthesis, resolution, and evaluation revealed that this new auxiliary provided the aldehyde facial approach upon which the design was predicated.     

Dressed energy of the XXZ chain in the complex plane

We highlight what seems to be a remaining subtlety in the argument for the cancellation of the total anomaly associated with the M5-brane in M-theory. Then, we prove that this subtlety is resolved under the hypothesis that the C-field flux is charge-quantized in the generalized cohomology theory called J-twisted cohomotopy.

     

Controlled sulfur oxygenation of the ruthenium dithiolate (4,7-bis-(2'-methyl-2'-mercaptopropyl)-1-thia-4,7-diazacyclononane)RuPPh(3) under limiting O(2) conditions yields thiolato/sulfinato, sulfenato/sulfinato, and bis-sulfinato derivatives

The ruthenium(II) dithiolate complex (bmmp-TASN)RuPPh(3) (1) reacts with O(2) under limiting conditions to yield isolable sulfur oxygenated derivatives as a function of reaction time. With this approach, a family of sulfur-oxygenates has been prepared and isolated without the need for O-atom transfer agents or column chromatography. Addition of 5 equiv of O(2) to 1 yields the thiolato/sulfinato complex (bmmp-O(2)-TASN)RuPPh(3) (2) in 70% yield within 5 min. Increasing the reaction time to 12 h yields the sulfenato/sulfinato derivative (bmmp-O(3)-TASN)RuPPh(3) (3) in 82% yield. Longer reaction times and/or additional O(2) exposure yield the bis-sulfinato complex (bmmp-O(4)-TASN)RuPPh(3) (4). All products remain in the Ru(II) oxidation state under the conditions employed. Stoichiometric hydrolysis of acetonitrile to acetamide by 2 and 3 is observed in mixed acetonitrile, methanol, PIPES buffer (pH = 7.0) mixtures. The Ru(III)/(II) reduction potential of -0.85 V (versus ferrocenium/ferrocene) for 1 shifts to -0.39 and -0.26 V for 2 and 3, respectively, because of the decreased donor ability of sulfur upon oxygenation. X-ray diffraction studies reveal a decrease in Ru-S bond distances upon oxygenation by 0.045(1) and 0.158(1) ? for the sulfenato and sulfinato donors, respectively. Conversely, sulfur-oxygenation increases the Ru-P bond distance by 0.061(1) ? from 1 to 2 and an additional 0.027(1) ? from 2 to 3. Density functional theory investigations using the BP86 and B3LYP functionals with a LANL2DZ basis set for Ru and the 6-31G(d) basis set for all other atoms reveal a direct correlation between the oxygenation level and the Ru-P distance with an increase of 0.031 ? per O-atom.     

Effctive nonadiabatic calculations on the ground state of the HD+ molecule

The nonadiabatic methodology, which is based on an effective elimination of the center-of-mass motion rather than explicit separation achieved by a coordinate transformation, is applied to the ground state of the HD⁺ molecule. The many-body nonadiabatic wave function is generated in terms of explicitly correlated Gaussian functions. The analytical first and second derivatives of the variational functional with respect to the Gaussian exponents are applied in conjunction with the Newton–Raphson optimization method to find the nonadiabatic energy and the ground–wave function. The numerical results are compared with conventional nonadiabatic calculations. © 1995 John Wiley & Sons, Inc.     

The topology of spaces of coprime polynomials

This article was processed by the author using the LATEX style filepljourlm from Springer-Verlag.