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A novel high step-up dc-dc converter for a distributed generation system is proposed in this paper. The concept is composed of two capacitors, two diodes, and one coupled inductor. Two capacitors are charged in parallel, and are discharged in series by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stresses on the main switch and output diode are reduced by a passive clamp circuit. Therefore, low resistance R D S (O N ) for the main switch can be adopted to reduce conduction loss. In addition, the reverserecovery problem of the diode is alleviated, and thus, the efficiency can be further improved. The operating principle and steady-state analyses of the voltage gain are also discussed in detail. Finally, a 24-V input voltage, 400-V output voltage, and 400-W output power prototype circuit of the proposed converter are implemented in the laboratory to verify the performance.

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We investigated the mechanisms involved in imipenem resistance in 23 clinical strains of Acinetobacter baumannii. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the presence of a 30-kDa protein in imipenem-intermediate A. baumannii (IIAB) and imipenem-resistant A. baumannii (IRAB) strains; this protein was almost undetectable in imipenem-susceptible A. baumannii (ISAB) strains. The 30-kDa protein was identified as an OXA-51-like carbapenemase using two-dimensional gel electrophoresis and mass spectrometry. Similar to other recent findings, bla OXA-51-like genes were found to exist in all 23 clinical strains; however, the transcript levels of bla OXA-51-like in the IIAB and IRAB were higher than in the ISAB strains using reverse transcriptase PCR (RT-PCR) and real-time RT-PCR assays. This change was due to the presence of an insertion sequence, ISAba1, upstream of bla OXA-51-like in the IIAB and IRAB strains that was not present in the ISAB strains. The introduction of bla OXA-66 (a bla OXA-51-like gene), identified in ISAB ab1254 and IRAB ab1266, into Escherichia coli TOP10 cells resulted in 3.95-fold and 7.90-fold elevations in resistance to imipenem, respectively. Furthermore, when ISAB ab8 and ISAB ab1254 and their in vitro-selected imipenem-resistant mutants ISAB ab8(r) and ISAB ab1254(r) were compared, the results showed no change in the bla OXA-66 /bla OXA-51-like gene sequences, in expression of the gene, and in the outer membrane protein profiles. However, there was a four-to eightfold reduction in imipenem resistance upon adding carbonyl cyanide m-chlorophenylhydrazone. Taken together, these results suggest that the OXA-66/OXA-51-like carbapenemase contributes to intrinsic resistance to imipenem; however, drug export by an efflux pump may be more important and/or occur more frequently in imipenem-resistant A. baumannii. Furthermore, this is the first report of a Taiwanese strain of an OXA-66/OXA-51-like carbapenemase that confers imipenem resistance in A. baumannii.Acinetobacter baumannii accounts for a large percentage of nosocomial infections including pneumonia, bacteremia, skin infections, wound infections, and urinary tract infections (2, 19). Increasingly, multidrug resistance strains of A. baumannii have become common in hospitals worldwide and especially in intensive care units (10, 12, 30) and burn units (2,31,32,40). The types of resistance include many commonly used antibiotics such as aminoglycosides, fluoroquinolones, and ␤-lactams, although carbapenems are the most used antimicrobial drugs. However, an increasing number of recent studies reported the emergence of clinical A. baumannii strains that are resistance to imipenem (7,9,27).The mechanism of resistance to carbapenems in A. baumannii has mostly been ascribed to the acquisition of carbapenemases (1, 26) or to synergistic effects between ␤-lactamases with an ability to hydrolyze carbapenems and decreased expression of certain penicillin-binding proteins (13,14). The carbapenemases in A. baumannii ...

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