Inelastic electron tunneling spectroscopy of an alkanethiol self-assembled monolayer using scanning tunneling microscopy

We report inelastic electron tunneling spectroscopy (IETS) of a C8 alkanethiol self-assembled monolayer using a scanning tunneling microscope (STM). High-resolution STM IETS spectra show clear features of the C-H bending and C-C stretching modes in addition to the C-H stretching mode, which enables a precise comparison with previously reported vibrational spectroscopy, especially electron energy loss spectroscopy data. Intensity variation of vibrational peaks with tip position is discussed with the STM IETS detection mechanism.     

Weierstrass Semigroups of a Pair of Points Whose First Nongaps are Three

We found all candidates for a Weierstrass semigroup at a pair of Weierstrass points whose first nongaps are three. We prove that such semigroups are actually Weierstrass semigroups by constructing examples.     

Local chemical reaction of benzene on Cu110 via STM-induced excitation

We have investigated the mechanism of the chemical reaction of the benzene molecule adsorbed on Cu(110) surface induced by the injection of tunneling electrons using scanning tunneling microscopy (STM). With the dosing of tunneling electrons of the energy 2-5 eV from the STM tip to the molecule, we have detected the increase of the height of the benzene molecule by 40% in the STM image and the appearance of the vibration feature of the nu(C-H) mode in the inelastic tunneling spectroscopy (IETS) spectrum. It can be understood with a model in which the dissociation of C-H bonds occurs in a benzene molecule that induces a bonding geometry change from flat-lying to up-right configuration, which follows the story of the report of Lauhon and Ho on the STM-induced change of benzene on the Cu(100) surface. [L. J. Lauhon and W. Ho, J. Phys. Chem. A 104, 2463 (2000)]. The reaction probability shows a sharp rise at the sample bias voltage at 2.4 V, which saturates at 3.0 V, which is followed by another sharp rise at the voltage of 4.3 V. No increase of the reaction yield is observed for the negative sample voltage up to 5 eV. In the case of a fully deuterated benzene molecule, it shows the onset at the same energy of 2.4 eV, but the reaction probability is 10(3) smaller than the case of the normal benzene molecule. We propose a model in which the dehydrogenation of the benzene molecule is induced by the formation of the temporal negative ion due to the trapping of the electrons at the unoccupied resonant states formed by the pi orbitals. The existence of the resonant level close to the Fermi level ( approximately 2.4 eV) and multiple levels in less than approximately 5 eV from the Fermi level, indicates a fairly strong interaction of the Cu-pi(*) state of the benzene molecule. We estimated that the large isotope effect of approximately 10(3) can be accounted for with the Menzel-Gomer-Redhead (MGR) model with an assumption of a shallow potential curve for the excited state.     

Induction of Cell Killing, Mutation and umu Gene Expression by 6-Mercaptopurine or 2-Thiouracil with UVA Irradiation

Abstract— When Escherichia coli cells were irradiated by UVA in the presence of 6-mercaptopurine (6-MP) or 2-thiouracil (S²Ura), two kinds of repair-deficient strains of recA ⁻ and uvrA ⁻ were killed more efficiently than the parental wild-type strain having normal repair capacities. In addition, these agents with UVA exposure greatly induced the incidence of mutations in the uvrA ⁻ strain as compared with the wild-type strain but not the uvrA ⁻ strain. Furthermore, the induction of expression of umuDC genes was investigated in two Salmonella typhimurium strains, TA1S35 and TA1538, carrying a pSK1002 plasmid. In these systems, it is easy to measure β-galactosidase activities for the induced activities of SOS responses. These agents with UVA exposure also induced expression of the umuDC genes. These results suggest that 6-MP and S²Ura with UVA induce DNA damage which is repairable by the excision repair mechanism.     

Ammonia adsorption on and diffusion into thin ice films grown on Pt(111)

Ammonia adsorption on and diffusion into thin ice films grown on a Pt(111) surface were studied using Fourier transform infrared spectroscopy (FTIR) and thermal desorption spectroscopy. After exposing the crystalline ice film to ammonia molecules at 45 K (ammonia/ice film), we have detected an intriguing feature at 1470 cm(-1) in the FTIR spectra, which is derived from the adsorption of ammonia on the ice with a characteristic structure which appears in thin film range. The peak intensity of this feature decreases gradually as the thickness of the substrate ice increases. In addition, we have detected a feature at 1260 cm(-1) which appears after annealing the ammonia/ice film. The feature corresponds to the ammonia molecules which reach the ice/Pt(111) interface through the ice film. Intriguingly, the intensity of this feature decreases with the ice thickness and there is a linear relation of the peak intensity of the features at 1470 and 1260 cm(-1). We propose a model in which the solubility of the ammonia molecules is much higher for the thin ice film than that for the ideal ice.     

Structural and Electrochemical Comparison of Copper(II) Complexes with Tripodal Ligands

A series of copper(II) complexes with tripodal polypyridylmethylamine ligands, such as tris(2-pyridylmethyl)amine (tpa), ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Me(1)tpa), bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine (Me(2)tpa), and tris((6-methyl-2-pyridyl)methyl)amine (Me(3)tpa), have been synthesized and characterized by X-ray crystallography. [Cu(H(2)O)(tpa)](ClO(4))(2) (1) crystallized in the monoclinic system, space group P2(1)/a, with a = 15.029(7) ?, b = 9.268(2) ?, c = 17.948(5) ?, beta = 113.80(3) degrees, and Z = 4 (R = 0.061, R(w) = 0.059). [CuCl(Me(1)tpa)]ClO(4) (2) crystallized in the triclinic system, space group P&onemacr;, with a = 13.617(4) ?, b = 14.532(4) ?, c = 12.357(4) ?, alpha = 106.01(3) degrees, beta = 111.96(2) degrees, gamma = 71.61(2) degrees, and Z = 4 (R = 0.054, R(w) = 0.037). [CuCl(Me(2)tpa)]ClO(4) (3) crystallized in the monoclinic system, space group P2(1)/n, with a = 19.650(4) ?, b = 13.528(4) ?, c = 8.55(1) ?, beta = 101.51(5) degrees, and Z = 4 (R = 0.071, R(w) = 0.050). [CuCl(Me(3)tpa)][CuCl(2)(Me(3)tpa)]ClO(4) (4) crystallized in the monoclinic system, space group P2(1)/a, with a = 15.698(6) ?, b = 14.687(7) ?, c = 19.475(4) ?, beta = 97.13(2) degrees, and Z = 4 (R = 0.054, R(w) = 0.038). All the Cu atoms of 1-4 have pentacoordinate geometries with three pyridyl and one tertiary amino nitrogen atoms, and a chloride or aqua oxygen atom. Nitrite ion coordinated to the Cu(II) center of Me(1)tpa, Me(2)tpa, and Me(3)tpa complexes with only oxygen atom to form nitrito adducts. The cyclic voltammograms of [Cu(H(2)O)(Me(n)()tpa)](2+) (n = 0, 1, 2, and 3) in the presence of NO(2)(-) in H(2)O (pH 7.0) revealed that the catalytic activity for the reduction of NO(2)(-) increases in the order Me(3)tpa < Me(2)tpa < Me(1)tpa < tpa complexes.     

The Riemann constant for a non-symmetric Weierstrass semigroup

The zero divisor of the theta function of a compact Riemann surface X of genus g is the canonical theta divisor of Pic\({^{(g-1)}}\) up to translation by the Riemann constant \({\Delta}\) for a base point P of X. The complement of the Weierstrass gaps at the base point P gives a numerical semigroup, called the Weierstrass semigroup. It is classically known that the Riemann constant \({\Delta}\) is a half period, namely an element of \({\frac{1}{2}\Gamma_\tau}\) , for the Jacobi variety \({\mathcal{J}(X)=\mathbb{C}^{g}/\Gamma_\tau}\) of X if and only if the Weierstrass semigroup at P is symmetric. In this article, we analyze the non-symmetric case. Using a semi-canonical divisor D₀, we express the relation between the Riemann constant \({\Delta}\) and a half period in the non-symmetric case. We point out an application to an algebraic expression for the Jacobi inversion problem. We also identify the semi-canonical divisor D₀ for trigonal pointed curves, namely with total ramification at P.