Browsing by Author "Tsai, SF"

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Adsorption of chlorine on the Si(001)-2 x 1 surface
(2001-08-10)
Pi, TW
;
Tsai, SF
;
Ouyang, CP
;
Wen, JF
;
Wu, RT
It is shown that the room-temperature dissociative adsorption Of Cl-2 on the Si(0 0 1)-2 x 1 surface results in the bonding of Cl atoms to both the up- and down-dimers which then become symmetrical, At saturation coverage the Si 2p core-level spectra exhibit only a single Cl-induced component with emission twice as strong as that from the up-dimer of the clean surface and with a core-level shift of +930 +/- 8 meV. These results were obtained using an analysis in which the intensities of the core-level spectra from the individual Si layers are constrained by an escape depth. It facilitates the identification of components down to the second subsurface layer and yields an inelastic mean free path of 3.4 +/- 0.2 at a photon energy of 140 eV. (C) 2001 Elsevier Science B.V. All rights reserved.
Sequencing and analysis of the large virulence plasmid pLVPK of Klebsiella pneumoniae CG43
(2004-08-04)
Chen, YT
;
Chang, HY
;
Lai, YC
;
Pan, CC
;
Tsai, SF
We have determined the entire DNA sequence of pLVPK, which is a 219-kb virulence plasmid harbored in a bacteremic isolate of Klebsiella pneumoniae. A total of 251 open reading frames (ORFs) were annotated, of which 37% have homologous genes of known function, 31% match the hypothetical genes in the GenBank database, and the remaining 32% are novel sequences. The obvious virulence-associated genes carried by the plasmid are the capsular polysaccharide synthesis regulator rmpA and its homolog rmpA2, and multiple iron-acquisition systems, including iucABCDiutA and iroBCDN siderophore gene clusters, Mesorhizobium loti fepBC ABC-type transporter, and Escherichia coli fecIRA, which encodes a Fur-dependent regulatory system for iron uptake. In addition, several gene clusters homologous with copper, silver, lead, and tellurite resistance genes of other bacteria were also identified. Identification of a replication origin consisting of a repA gene lying in between two sets of iterons suggests that the replication of pLVPK is iteron-controlled and the iterons are the binding sites for the repA to initiate replication and maintain copy number of the plasmid. Genes homologous with E. coli sopA/sopB and parA/parB with nearby direct DNA repeats were also identified indicating the presence of an F plasmid-like partitioning system. Finally, the presence of 13 insertion sequences located mostly at the boundaries of the aforementioned gene clusters suggests that pLVPK was derived from a sequential assembly of various horizontally acquired DNA fragments. (C) 2004 Elsevier B.V. All rights reserved.