Quenched chiral logarithms in lattice QCD with exact chiral symmetry

We examine quenched chiral logarithms in lattice QCD with overlap Dirac quark. For 100 gauge configurations generated with the Wilson gauge action at $\beta = 5.8$ on the $8^3 \times 24$ lattice, we compute quenched quark propagators for 12 bare quark masses. The pion decay constant is extracted from the pion propagator, and from which the lattice spacing is determined to be 0.147 fm. The presence of quenched chiral logarithm in the pion mass is confirmed, and its coefficient is determined to be $\delta = 0.203 \pm 0.014$, in agreement with the theoretical estimate in quenched chiral perturbation theory. Further, we obtain the topological susceptibility of these 100 gauge configurations by measuring the index of the overlap Dirac operator. Using a formula due to exact chiral symmetry, we obtain the $\eta'$ mass in quenched chiral perturbation theory, $m_{\eta'} = (901 \pm 64)$ Mev, and an estimate of $\delta = 0.197 \pm 0.027$, which is in good agreement with that determined from the pion mass.Comment: 24 pages, 6 EPS figures; v2: some clarifications added, to appear in Physical Review

Acquiring decision rules for predicting ames-negative hepatocarcinogens using chemical-chemical interactions

[[abstract]]Chemical carcinogenicity is an important safety issue for the evaluation of drugs and environmental pollutants. The Ames test is useful for detecting genotoxic hepatocarcinogens. However, the assessment of Ames-negative hepatocarcinogens depends on 2-year rodent bioassays. Alternative methods are desirable for the efficient identification of Ames-negative hepatocarcinogens. This study proposed a decision tree-based method using chemical-chemical interaction information for predicting hepatocarcinogens. It performs much better than that using molecular descriptors with accuracies of 86% and 76% for validation and independent test, respectively. Four important interacting chemicals with interpretable decision rules were identified and analyzed. With the high prediction performances, the acquired decision rules based on chemical-chemical interactions provide a useful prediction method and better understanding of Ames-negative hepatocarcinogens

The structures of (phenylato)(N-2-thiophenecarboxamido-meso-tetra-phenylporphyrinato)mercu ry(II) and bisphenylmercury(II) complex of 21-(4-tert-butyl-benzenesulfonamido)-5,10,15,20-tetraphenylporphyrin

The reaction of PhHgOAc with N-NHCO-2-C4H3S-Htpp (5) and N-p-HNSO2C6H4(tau)Bu-Htpp (4) gave a mercury (11) complex of (phenylato) (N-2-thiophenecarboxamido-meso-tetra phenylporphyrinato)mercury(II) 1.5 methylene chloride solvate [HgPh(N-NHCO2-C4H3S-tpp) center dot CH2Cl2 center dot 0.5C(6)H(14); 6 center dot CH2Cl2 center dot 0.5C(6)H(14)] and a bismercury complex of bisphenylmercury(II) complex of 21-(4-tertbutyl-benzenesulfonamido)-5,10,15,20-tetraphenylporphyrin, [(HgPh)2(N-p-(NSO2C6H4Bu)-Bu-iota-tpp); 7], respectively. The crystal structures of 6 center dot CH2O2 center dot 0.5C(6)H(14) and 7 were determined. The coordination sphere around Hg(1) in 6 center dot CH2O2 center dot 0.5C(6)H(14) and Hg(2) in 7 is a sitting-atop derivative with a seesaw geometry, whereas for the Hg(1) in 7, it is a linear coordination geometry. Both Hg(1) in 6 center dot CH2Cl2 center dot 0.5C(6)H(14) and Hg(2) in 7 acquire 4-coordination with four strong bonds [Hg(1)-N(1) = 2.586(3)angstrom, Hg(1)-N(2) = 2.118(3) angstrom, Hg(1)-N(3) = 2.625(3) angstrom, and Hg(1)-C(50) = 2.049(4) angstrom for 6 center dot CH2Cl2 center dot 0.5C(6)H(14); Hg(2)-N(1) = 2.566(6) angstrom, Hg(2)-N(2) = 2.155(6) angstrom, Hg(2)-N() = 2.583(6) angstrom, and Hg(2)-C(61) = 2.064(7) angstrom for 7]. The plane of the three pyrrole nitrogen atoms [i.e., N(1)-N(3)] strongly bonded to Hg(1) in 6 center dot CH2Cl2 center dot 0.5C(6)H(14) and to Hg(2) in 7 is adopted as a reference plane 3N. For the Hg2+ complex in 6 center dot CH2C12 center dot 0.5C(6)H(14),the pyrrole nitrogen bonded to the 2-thiophenecarboxamido ligand lies in a plane with a dihedral angle of 33.4 degrees with respect to the 3N plane, but for the bismercury(II) complex in 7, the corresponding dihedral angle for the pyrrole nitrogen bonded to the (NSO2C6H4Bu)-Bu-tau group is found to be 42.9 degrees. In the former complex, Hg(1)(2+) and N(5) are located on different sides at 1.47 and -1.29 angstrom from its 3N plane, and in the latter one, Hg(2)(2+) and N(5) are also located on different sides at -1.49 and 1.36 angstrom form its 3N plane. The Hg(1)... Hg(2) distance in 7 is 3.622(6) angstrom. Hence, no metallophilic Hg(II)... Hg(II) interaction may be anticipated. NOE difference spectroscopy, HMQC and HMBC were employed to unambiguous assignment for the H-1 and C-13 NMR resonances of 6 center dot CH2CL2 center dot 0.5C(6)H(14) in CD2Cl2 and 7 in CDCl3 at 20 degrees C. The Hg-199 chemical shift delta for a 0.05 M solution of 7 in CDCl3 solution is observed at -1074 ppm for Hg(2) nucleus with a coordination number of four and at -1191 ppm for Hg(1) nucleus with a coordination number of two. The former resonance is consistent with that chemical shift for a 0.01 M solution of 6 in CD2Cl2 having observed at 1108 ppm for Hg(1) nucleus with a coordination number of four. (C) 2007 Elsevier Ltd. All rights reserved

Scanning tunneling microscopy and atomic force microscopy of Au implanted in highly ordered pyrolytic graphite

Surfaces of highly oriented pyrolytic graphite implanted with gold were studied by both constant current STM, constant force, and tapping mode AFM. Gold colloids were observed by both constant current STM and tapping mode AFM. The surfaces can be modified by applying currents of {plus_minus}4 V and 1 nA. In addition, pyramidal and faceted structures were observed on sample surfaces suggesting the presence of diamond microcrystals