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OBJECTIVES To investigate the transmission process of severe acute respiratory syndrome (SARS) and to evaluate the infectiveness of SARS patients in different periods of disease epidemics. METHODS Standardized questionnaire was used to conduct case investigation and contact tracing by combining the field investigation and telephone interview. Transmission… (More)
A new type of hydrogen-bonding interaction in the diborane (B 2H 6)...pi (benzene C 6H 6, 1,3-cyclopentadiene C 5H 6, and cyclobutadiene C 4H 4) system is identified with the natural bond orbital and atoms-in-molecules analyses based on ab initio calculations. In comparison with the symmetric and asymmetric stretching vibrational modes of the bridging… (More)
Three low-lying conformers of the hydrogen maleate anions (HMAs) regarding cis-HMA(HB) having the O-...HO intramolecular hydrogen bond (HB), cis-HMA(nHB) without the HB, and trans-HMA are studied by density functional theory (B3LYP) combined with natural bond orbital (NBO) and atoms-in-molecules (AIM) analyses. The photoelectron spectra of cis- and… (More)
A thorough theoretical study of phase-transfer quaternary ammonium catalysts designed by the Maruoka group has been performed in an attempt to gain better understanding of the properties and catalytic behavior of the homo- and heterochiral forms of these systems. The conformationally flexible analogue is found to easily undergo interconversion from the… (More)
Graphene nucleation on Ni(111) has been modeled using QM/MD simulations. We demonstrate that graphene precursor nucleation can occur underneath the catalyst surface. In addition, a Ni(111) step-edge is not a static structure, as is often assumed; it is instead highly malleable, being deformed and subsequently healed during graphene nucleation.
Unusual strength: In the complex glycine-BH(4)(-), unconventional dihydrogen bonds are predicted. An ultrashort dihydrogen bond B-H...H-N and a very strong interaction of about -41 kcal mol(-1)) are found in complex 3 (see structures), in which the zwitterionic glycine is stabilized with a big margin.
Quantum chemical molecular dynamics simulations of graphene nucleation on the Ni(111) surface show that graphene creates its own step-edge as it forms. This "step-edge self-assembly" is driven by the formation of thermodynamically favorable Ni-C σ-bonds at the graphene edge. This dynamic aspect of the Ni(111) catalyst is in contrast to the commonly accepted… (More)
Nuclear magnetic resonance (NMR) has been widely used in graphene oxide (GO) structure studies. However, the detailed relationship between its spectroscopic features and the GO structural configuration remains elusive. Based on first principles (13)C chemical shift calculations using the gauge including projector augmented waves method, we provide a… (More)
The origin of higher reactivity in water-accelerated asymmetric aldol reactions with our designed primary amine organocatalyst was elucidated by both computational and experimental methods. As suggested by the calculated transition-state structures for water-promoted imine-enamine isomerization, anti-selective aldol reaction and hemiaminal formation, the… (More)