Jihyun Jang

Poly(phenanthrenequinone) as a conductive binder for nano-sized silicon negative electrodes

3,6-Poly(phenanthrenequinone) (PPQ) is synthesized and tested as a conductive binder. The PPQ binder, formulated with nano-sized Si powder without conductive carbon, is n-doped by accepting electrons and Li+ ions to become a mixed conductor in the first charging period. The resulting n-doped PPQ binder remains conductive thereafter within the working potential of Si (0.0–0.5 V vs. Li/Li+). Within the composite electrode, the PPQ binder is uniformly dispersed to effectively convey electrons from the current collector to the Si particles. Namely, the PPQ binder by itself plays the roles of conductive carbon and a polymer binder that are loaded in the conventional composite electrodes. Due to the highly conductive nature, the loading of the PPQ binder can be minimized down to 10 wt%, which is close to that used for practical electrode formulation, with reasonable rate and cycle performances of the nano-Si electrode.

Investigation of mutation distribution in DNA gyrase and topoisomerase IV genes in ciprofloxacin-non-susceptible Enterobacteriaceae isolated from blood cultures in a tertiary care university hospital in South Korea, 2005–2010

This study investigated the distribution of mutations in DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE) genes and compared the distribution of these mutations with the distribution of plasmid-mediated quinolone resistance (PMQR) genes and extended-spectrum β-lactamase (ESBL) production in 101 ciprofloxacin-non-susceptible Enterobacteriaceae from blood culture isolates (80 Escherichia coli and 21 Klebsiella pneumoniae) isolated in Kyung Hee University Hospital, a tertiary care university hospital in Seoul, South Korea. Among the 101 isolates, 80 (79.2%) contained PMQR genes and 28 (27.7%) produced ESBL. Mutations in the gyrA and parC genes were observed more frequently than in the gyrB and parE genes as well as more frequently in E. coli than in K. pneumoniae isolates, even in the same ciprofloxacin minimum inhibitory concentration (MIC) range of the two species. In E. coli isolates, the distribution of the codon 529 mutation (Ile→Leu) in parE was increased with an increase in the ciprofloxacin MIC. An increase in high-level resistance to quinolones may occur with double mutations compared with a single mutation in gyrA as well as with additional mutations in parC. However, this finding could not be applied to ciprofloxacin-resistant K. pneumoniae. A higher level of quinolone resistance may be correlated with an additional mutation in parE, especially Ile529→Leu.

A first-cycle coulombic efficiency higher than 100% observed for a Li2MO3 (M = Mo or Ru) electrode.

The lithiation/de-lithiation behavior of a ternary oxide (Li2MO3, where M = Mo or Ru) is examined. In the first lithiation, the metal oxide (MO2) component in Li2MO3 is lithiated by a conversion reaction to generate nano-sized metal (M) particles and two equivalents of Li2O. As a result, one idling Li2O equivalent is generated from Li2MO3. In the de-lithiation period, three equivalents of Li2O react with M to generate MO3. The first-cycle Coulombic efficiency is theoretically 150% since the initial Li2MO3 takes four Li(+) ions and four electrons per formula unit, whereas the M component is oxidized to MO3 by releasing six Li(+) ions and six electrons. In practice, the first-cycle Coulombic efficiency is less than 150% owing to an irreversible charge consumption for electrolyte decomposition. The as-generated MO3 is lithiated/de-lithiated from the second cycle with excellent cycle performance and rate capability.

Characterization of Plasmid-Mediated SHV-11 β-lactamase Gene of Klebsiella pneumoniae Isolated from the Clinical Specimens

In this study, we characterized extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolated from clinical specimens in Korea and found two strains harboring plasmid-mediated blaSHV-11, Klebsiella pneumoniae. First, the isolates were detected using the Vitek system and confirmed by the double-disk synergy test. The classification of gene coding for ESBL was also performed by polymerase chain reactions and followed by DNA sequencing. The transmission of genes was confirmed by transconjugation and transformation. Resistant expression of transformants was determined by broth microdilution minimal inhibitory concentration test. Genotypic analysis revealed that one strain harbored the bla TEM-1 , bla SHV-11 and blaCTX-M-15 and the other strain harbored the bla SHV-11 and bla CTX-M-15 . They showed high resistance to oxyiminocephalosphorins (3rd-generation cephalosporins), while the transformant containing only bla SHV-11 did not show any resistance to the antibiotics.